Amino acid sequences directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases

This application is continuation of U.S. application Ser. No. 15/785,604, filed Oct. 17, 2017, which is a divisional of U.S. application Ser. No. 14/926,381, filed Oct. 29, 2015 and issued as U.S. Pat. No. 9,834,595, which is a divisional of U.S. application Ser. No. 12/996,074, filed Mar. 17, 2011 and issued as U.S. Pat. No. 9,193,780, which is a national stage filing under 35 U.S.C. § 371 of international application PCT/EP2009/056975, filed Jun. 5, 2009, which was published under PCT Article 21(2) in English, and claims the benefit under 35 U.S.C. § 119(e) of U.S. provisional application Ser. No. 61/059,055, filed Jun. 5, 2008, U.S. provisional application Ser. No. 61/092,991, filed Aug. 29, 2008, U.S. provisional application Ser. No. 61/139,130, filed Dec. 19, 2008, U.S. provisional application Ser. No. 61/144,653, filed Jan. 14, 2009, U.S. provisional application Ser. No. 61/172,914, filed Apr. 27, 2009, and U.S. provisional application Ser. No. 61/174,108, filed Apr. 30, 2009, the disclosures of which are incorporated by reference herein in their entireties.

The present invention relates to amino acid sequences that are directed against and/or that can specifically bind to an envelope protein of a virus, as well as to compounds or constructs, and in particular proteins and polypeptides, that comprise or essentially consist of one or more such amino acid sequences (also referred to herein as “amino acid sequences of the invention”, “compounds of the invention”, and “polypeptides of the invention”, respectively).

The invention also relates to nucleic acids encoding such amino acid sequences and polypeptides (also referred to herein as “nucleic acids of the invention” or “nucleotide sequences of the invention”); to methods for preparing such amino acid sequences and polypeptides; to host cells expressing or capable of expressing such amino acid sequences or polypeptides; to compositions, and in particular to pharmaceutical compositions, that comprise such amino acid sequences, polypeptides, nucleic acids and/or host cells; and to uses of such amino acid sequences or polypeptides, nucleic acids, host cells and/or compositions, in particular for prophylactic, therapeutic or diagnostic purposes, such as the prophylactic, therapeutic or diagnostic purposes mentioned herein.

Other aspects, embodiments, advantages and applications of the invention will become clear from the further description herein.

Enveloped viruses assemble by budding at membranes of host cells (Compans et al. In Comprehensive Virology , Fraenkel and Wagner, eds. Plenum Press, New York 4: 179-252 (1975); Choppin and Compans, In Comprehensive Virology , Fraenkel and Wagner, eds. Plenum Press, New York 4: 96-178 (1975); Wagner, In Comprehensive Virology , Fraenkel and Wagner, eds. Plenum Press, New York 4:1-94 (1975)). During this process they acquire an envelope which has a lipid bilayer, whose composition reflects that of the host membrane, glycoproteins that form projections or spikes on the surface of the virus particles, and non-glycosylated M-proteins which are associated with the interior surface of the lipid bilayer of the virus particle. The virion-associated proteins are virus specific.

One of the crucial steps in virus infection is the fusion between the virus membrane and the membrane of the host cell, which is mediated by viral glycoproteins, such as viral attachment proteins and viral fusion proteins.

This virus membrane fusion can take place either at the plasma membrane or at an intracellular location following virus uptake by endocytosis (Earp et al. Curr. Topics Microbiol. Immunol. 285, 25-66 (2005); Smith et al. Science 304, 237-242 (2004)). Viruses belonging to the Retroviridae, Paramyxoviridae, Herpesviridae, and Coronaviridae families typically initiate fusion in a pH-independent manner whereby the virion initially binds to cell surface receptors and subsequently the viral membrane fuses with the plasma membrane of the host cell at neutral pH.

A second, more complex route of entry is characterized by receptor-mediated such as clathrin-dependent, caveola-dependent uptake or non-clathrin-dependent, non-caveola dependent uptake (Smith et al. Science 304, 237-242 (2004); Sieczkarski et al. Curr. Topics Microbiol. Immunol. 285, 1-23 (2005)). Viruses that use such routes frequently have fusion reactions that require exposure to mildly acidic pH within organelles of the endocytic pathway (Helenius et al. J. Cell Biol. 84, 404-420 (1980)). Viruses belonging to the Orthomyxoviridae, Togaviridae, Rhabdoviridae, Bunyaviridae, and Arenaviridae families often require a low-pH-mediated event for efficient fusion of viral and host cellular membranes.

The determination of the atomic structure of complete ectodomains or core regions of many viral fusion proteins in their pre- and/or post-fusion states has revealed a large diversity of conformations. Nevertheless, in all the cases studied so far, the structural transition from a pre- to a post-fusion conformation leads to a stable hairpin conformation resulting in the positioning of the two membrane anchors, the transmembrane and the fusion peptide domains, at the same end of a trimeric elongated rod-like structure. Three different classes of viral fusion proteins have been identified to date based on their common post-fusion structural motifs (Table C-3) (Kielian et al. Nat. Rev. Microbiol. 4: 67-76 (2006); Weissenhom et al. FEBS Lett. 581, 2150-2155 (2007)).

In their final, post-fusion state, class I viral fusion proteins are characterized by the interaction of the membrane-proximal C-terminal regions with the more N-terminal trimeric α-helical coiled-coil domains to form a trimer of hairpins that brings the fusion peptides and transmembrane domains together (Skehel et al. Cell 95: 871-874 (1998)). Importantly, for several class I proteins, peptides containing sequences of these C-terminal or N-interacting regions can bind to the viral fusion protein and inhibit fusion and infection by preventing refolding to the final hairpin conformation (for review see Moore and Doms Proc. Natl. Acad . Sci. USA. 100: 10598-10602 (2003)). The final trimeric hairpin structure is often referred to as a six-helix bundle. The structures of two class I proteins have also been crystallographically determined with respect to their state prior to activation of fusion. For one protein, influenza virus hemagglutinin (HA), this initial state does not exhibit the six-helix bundle (Wilson et al. Nature 289: 366-373 (1981)), whereas for the other, simian parainfluenza virus 5 fusion (F) protein, a six-helix bundle is already present (Yin et al. Proc. Natl. Acad. Sci. USA 102: 9288-9293 (2005)), but this structure is not identical to the final bundle. In both cases, in transiting from their initial to their final state, the proteins undergo changes in secondary structure that cause parts of the protein, notably fusion peptides, to move long distances (Baker et al. Mol. Cell 3: 309-319 (1999). Chen et al. Proc. Natl. Acad. Sci. USA 96: 8967-8972 (1999)). Examples of virus families that express class I fusion proteins are the Orthomyxoviridae, the Paramyxoviridae, the Filoviridae, the Retroviridae and the Coronaviridae.

Viruses that are known to express class II proteins belong to the genus of alphaviruses (family Togaviridae) and to the family of Flaviviridae (Kielian et al. Virology 344: 38-47 (2006)). Alphaviruses and flaviviridae are small, spherical viruses containing plus-strand RNA genomes packaged with a capsid protein. The nucleocapsid is enveloped by a lipid bilayer containing the virus membrane fusion protein (alphavirus E1 or flavivirus E). In mature virions, alphavirus E1 is associated as a heterodimer with the viral E2 protein, whereas the flavivirus E protein is found as an E-E homodimer. Low pH causes a dramatic rearrangement of the fusion protein to the post-fusion conformation, dissociating its dimeric interactions and producing a target membrane-inserted homotrimer that is believed to drive the membrane fusion reaction. Although the alphavirus and flavivirus fusion proteins do not have detectable amino acid sequence similarity, they have remarkably similar secondary and tertiary structures, indicating their evolutionary relationship and leading to their classification as the inaugural members of the class II virus fusion proteins (Lescar et al. Cell 105: 137-148 (2001)). The neutral pH (i.e. pre-fusion) structures of the fusion protein ectodomains have been determined for the alphavirus Semliki Forest virus (SFV; Lescar et al. Cell 105: 137-148 (2001)) and the flaviviruses TBE, DV2, and DV3 (Rey 375: 291-298 (1995); Modis Proc. Natl. Acad. Sci. USA 100: 6986-6991 (2003)). The proteins are elongated molecules composed almost entirely of f-strands and contain three domains: domain I, which is located centrally; domain II, which is located at one side of domain I and contains the target-membrane-interacting fusion peptide loop at its tip; and an Ig-like domain III, which is connected to the other side of domain I. Although not present in the ectodomain structure, in the full-length proteins the stem region and transmembrane anchor are found at the C-terminus of domain III, at the opposite end of the protein from the fusion loop. The fusion proteins are arranged with icosahedral symmetry and lie tangential (almost parallel) to the virus membrane. The conformational changes of class II fusion proteins necessary to transit from the crystallographically determined initial state to the final state do not involve substantial changes in secondary structure. Instead, the domains of class II proteins rotate at “pivot points” so that large-scale movements bring fusion loops and transmembrane domains into proximity, forming trimers of hairpins composed of β-structures.

A third class of fusion proteins forms in its post-fusion state trimers of hairpins by combining two structural elements. Similar to class I fusion proteins, class III fusion proteins display a central α-helical trimeric core; however, each fusion domain exposes two fusion loops located at the tip of an elongated 3-sheet revealing a striking convergence with class II fusion proteins (Roche et al. Science 313: 187-191 (2006); Heldwein et al. Science 313: 217-220 (2006)). Examples of virus families that express class III fusion proteins are the Rhabdoviridae and the Herpesviridae.

Up to now, neutralizing antibodies have been crucial for protection against diseases associated with enveloped viruses. In principle, such antibodies can act against both free virus and against infected cells. The most marked antiviral activity of antibodies and the activity that is most important for antibody-mediated protection is the neutralization of free virus particles. The antiviral activity towards free virus particles can be achieved by binding of the antibody to a specific target on the virion surface, such as an envelope protein which can result in the inhibition of viral infection (neutralization) and/or in the triggering of effector systems that can lead to viral clearance. Antibodies that are specifically directed against infected cells can also mediate several antiviral activities. Fc-mediated effector systems can lead to cell lysis or clearance by antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC). The inhibition of viral replication inside cells by the binding of antibodies to viral molecules that are expressed at the membrane of the cells, presumably through signalling mechanisms, has also been described, particularly for viral infection of neurons (Fujinami et al. Nature 279: 529-530 (1979); Levine et al. Science 254: 856-860 (1991)). Antibodies can also inhibit the release of viruses from infected cells (Gerhard et al. Curr. Top. Microbiol. Immunol. 260: 171-190 (2001)) and the cell-cell transmission of viruses (Pantaleo et al. Eur. J. Immunol. 25: 226-231 (1995); Burioni et al. Proc. Natl. Acad. Sci. USA 91: 355-359 (1994)). Neutralizing antibodies tend to be effective against both infected cells and free virus particles because they bind to envelope molecules that are presented on infected cells as well as on virions. However, non-neutralizing antibodies might also be effective against infected cells by binding to molecules that are expressed on infected cells, but not on virions, for example the M2 protein of influenza virus (Fiers et al. Virus Research 103 (1-2): 173-176 (2004)). Okuno et al. (1993, J. Virol. 67: 2552-2558) describe a monoclonal antibody (MAb C179) that binds to the stem region of HA and inhibits the fusion activity of HA resulting in virus neutralization and inhibition of cell fusion.

Clinically, antibody therapy using polyclonal and monoclonal antibodies (mAbs) is effectively used as prophylaxis against varicella, hepatitis A, hepatitis B, rabies (Montano-Hirose et al. Vaccine 11: 1259-1266 (1993) and Schumacher et al. Vaccine 10: 754-760 (1992)), and respiratory syncytial virus infections (Sawyer Antiviral Res. 47: 57-77 (2000)). Within the last 10 years, two antibodies have been licensed for a viral indication, RespiGam and Synagis®, both for prevention of respiratory syncytial virus infection. RespiGam is a human plasma derived antibody and Synagis® is a humanized monoclonal antibody, the first such antibody to be licensed for an infectious disease indication. CytoGam for prevention of cytomegalovirus infection in kidney transplant patients has recently been granted an expanded indication to include use in lung, liver, pancreas and heart transplant patients. Antibody-based therapy for human patients with influenza is up to now little explored. Nabi-HB is a human plasma derived antibody marketed to treat HBV acute or perinatal exposure. However, it has been shown that specific monoclonal antibodies can confer prophylactic and therapeutic protection against influenza in mice (Smimov et al. Arch Virol. 145: 1733-1741 (2000); Renegar et al. J Immunol. 173: 1978-1986 (2004); Palladino et al. J Virol. 69: 2075-2081 (1995)). Humanized mouse mAbs and equine F(ab′)2 fragments specific for hemagglutinin H5 protein of the influenza virus have also been used for efficacious prophylaxis and therapy in the mouse model (Lu et al. Respir Res. 7: 43 (2006); Hanson et al. Respir Res. 7: 126 (2006)).

Antibody fragments, such as F(ab′)2 fragments, Fab fragments (Lamarre et al. J. Immunol. 154: 3975-3984 (1995); Thullier et al. J. Biotechnol. 69: 183-190 (1999); Schofield et al. J. Gen. Virol. 78: 2431-2439 (1997); Barbas et al. PNAS 89:10164 (1992); Crowe et al. PNAS 91: 1386 (1994); Prince et al. JVI 64: 3091 (1990)) and single chain Fv fragments (Mason et al. Virology 224: 548 (1996)) have also proven to be successful in neutralizing a variety of enveloped viruses both in vitro and in vivo in animal models (predominantly in mice).

Variable domains derived from camelid species heavy chain antibodies have been generated against the nucleoprotein of Marburg virus (Sherwood et al. al. J. Infect. Dis. 196 (2): S213-219 (2007)), against p15 matrix protein of porcine retroviruses (Dekker et al. J Virol. 77 (22): 12132-12139 (2003)), against the HBsAg of human Hepatitis B virus (Serruys et al. 12 th International Symposium on Viral Hepatitis and Liver Disease (2006); Serruys et al. Novel compounds & strategies to combat pathogenic microorganisms ( poster ) (2006); Serruys et al. The Molecular Biology of Hepatitis B Viruses ( poster ) (2007); Serruys New insights in HBV diversity, pathogenesis, diagnosis and treatment ( oral presentation ) (2007); Serruys NBC -12 : Single - domain intrabodies inhibit Hepatitis B virus replication in mice ( oral presentation ) (2008)), against vaccinia virus (Goldman et al. Anal. Chem. 78 (24): 8245-8255 (2006)), and against gp120 of HIV-1 (Forsman et al. Abstract EU - WHO Neut Workshop , Italy, March 2007) in some cases resulting in effective blocking of viral replication or neutralization in vitro and/or in vivo (in a mouse model).

The prior art discussed hereabove clearly indicates that the development of effective and potent antiviral drugs remains a major scientific challenge. Only for a minority of viral infections, there is currently an effective prophylactic and/or therapeutic compound available.

However, these currently existing antiviral drugs, have numerous side-effects, such as nausea, vomiting, skin rashes, migraine, fatigue, trembling, and, more rarely, epileptic seizures.

Also, the mutability and resultant adaptability of viruses present an enormous difficulty to the design of antiviral strategies that are effective over the long term. While drug design has gained from advances in the molecular understanding of viral growth processes, many initially potent drugs lose their efficacy over time because of the emergence of drug-resistant strains. When mutations arise that attenuate or compensate for the inhibitory effect of the drug, virus strains that carry such mutations gain a growth advantage and are subsequently selected for in the viral population.

Hence, for the majority of currently known human viral diseases there is an urgent need for a potent antiviral drugs that can be used for effective treatment and prevention of these diseases. In addition, a need exists for alternative and improved antiviral drugs over the presently existing drugs with regard to efficacy and/or potency (over the long term), overcoming currently encountered disadvantages, such as for instance undesired side-effects and viral evasion/viral escape.

It is an object of the present invention to provide amino acid sequences that are directed against and/or that can specifically bind to an envelope protein of a virus. The amino acid sequences according to the present invention, that are directed against and/or specifically binding to an envelope protein of a virus, can generally be used to modulate, and in particular to inhibit and/or to prevent the viral-mediated biological pathways in which an envelope protein of a virus and/or a viral receptor are involved. In particular, the amino acid sequences of the present invention can be used to neutralize a virus (as defined herein) and/or to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein).

More specifically, the amino acid sequences according to the present invention may neutralize a virus (as defined herein) and/or modulate, reduce and/or inhibit the infectivity of a virus (as defined herein) in the pre-entry phase of viral infection (i.e. before and/or during viral entry in a target host cell has taken place) and/or in the post-entry phase of viral infection (i.e. after viral entry in a target host cell has taken place). Accordingly, amino acid sequences of the present invention that neutralize a virus (as defined herein) and/or modulate, reduce and/or inhibit the infectivity of a virus (as defined herein) in the pre-entry phase of viral infection (i.e. before and/or during viral entry in a target host cell has taken place), are said herein to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell. Furthermore, amino acid sequences of the present invention that neutralize a virus (as defined herein) and/or modulate, reduce and/or inhibit the infectivity of a virus (as defined herein) in the post-entry phase of viral infection (i.e. after viral entry in a target host cell has taken place), are said herein to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell.

Accordingly, the amino acid sequences of the present invention can modulate and in particular inhibit and/or prevent viral entry and/or viral replication in a target host cell by specifically binding to an envelope protein of a virus at any suitable stage of said biological pathway(s); preferably, the amino acid sequences of the present invention can modulate and in particular inhibit and/or prevent viral entry in a target host cell by binding to an envelope protein of a virus, such that virion aggregation is induced and/or virion structure is destabilized and/or virion attachment to a target host cell is modulated, inhibited and/or prevented (for instance by modulating and/or inhibiting and/or preventing the interaction between the envelope protein of a virus and a viral receptor and/or between the envelope protein of a virus and a target host cell or by competing with said envelope protein for binding to said viral receptor and/or said target host cell) and/or viral fusion with said target host cell is modulated, inhibited and/or prevented (for instance at the target host cell membrane or within an endosomal and/or lysosomal compartment of said target host cell), for example by preventing said envelope protein of a virus from undergoing a conformational change. Alternatively, the amino acid sequences of the present invention can modulate and in particular inhibit and/or prevent viral replication (as defined herein) in a target host cell by specifically binding to an envelope protein of a virus at any suitable stage of said biological pathway; preferably, the amino acid sequences of the present invention can modulate and in particular inhibit and/or prevent viral replication in a target host cell by binding to an envelope protein of a virus, such that transcription and/or translation of the viral genome is affected, inhibited and/or prevented and/or viral packaging and/or the formation of functional virions is affected, inhibited and/or prevented and/or budding of nascent virions from the target host cell membrane is reduced, inhibited and/or prevented.

As such, the polypeptides and compositions of the present invention can be used for the prevention and treatment (as defined herein) of viral diseases. Generally, “viral diseases” can be defined as diseases and disorders that are caused by one or more viruses; in particular viral diseases may be diseases that can be prevented and/or treated, respectively, by suitably administering to a subject in need thereof (i.e. having the disease or disorder or at least one symptom thereof and/or at risk of attracting or developing the disease or disorder) of either an amino acid sequence, polypeptide or composition of the invention (and in particular, of a pharmaceutically active amount thereof) and/or of a known anti-viral compound against an envelope protein of a virus or a viral-mediated biological pathway in which an envelope protein of a virus and/or its viral receptor is involved (and in particular, of a pharmaceutically active amount thereof). Examples of such viral diseases will be clear to the skilled person based on the disclosure herein, and for example include the following diseases and disorders (caused by the following viruses): AIDS (caused by HIV), AIDS Related Complex (caused by HIV), Aseptic meningitis (caused by HSV-2), Bronchiolitis (caused by e.g. RSV [RSV virus and diseases caused by RSV are reviewed by Ogra P. Paediatric Respiratory Reviews 5: S119-S126 (2004)]), California encephalitis (caused by California encephalitis virus), Chickenpox (caused by Varicella zoster virus), Colorado tick fever (caused by Colorado tick fever virus), Common cold (caused by e.g. RSV [RSV virus and diseases caused by RSV are reviewed by Ogra P. Paediatric Respiratory Reviews 5: S119-S126 (2004)] or Parainfluenza virus), Conjunctivitis (caused by e.g. Herpes simplex virus), Cowpox (caused by vaccinia virus), Croup (caused by e.g. parainfluenza viruses 1 to 3), Cytomegalovirus Infection (caused by cytomegalovirus), Dengue fever (caused by dengue virus), Eastern equine encephalitis (caused by EEE virus), Ebola hemorrhagic fever (caused by Ebola virus), encephalitis and chronic pneumonitis in sheep (caused by Visna virus), encephalitis (caused by Semliki Forest virus), Gingivostomatitis (caused by HSV-1), Hantavirus hemorrhagic fever/Hantaan-Korean hemorrhagic fever (caused by Hantavirus), Hepatitis (caused by Hepatitis virus), Genital herpes (caused by HSV-2), Herpes labialis (caused by HSV-1), neonatal herpes (caused by HSV-2), Genital HSV (caused by Herpes simplex virus), Infectious mononucleosis (caused by e.g. Epstein-Barr virus), Influenza (Flu) (caused by influenza viruses A, B and C [Influenza viruses, diseases caused by influenza viruses and pharmaceuticals to treat these diseases are reviewed by Subbarao et al. Nat. Rev. Immunol. 7: 267-278 (2007)]), Japanese encephalitis virus (caused by JEE virus), Keratoconjunctivitis (caused by HSV-1), Lassa fever, Leukemia and lymphoma (caused by e.g. Human T cell leukemia virus or Moloney murine leukemia virus), Lower respiratory tract infections (caused by e.g. RSV [RSV virus and diseases caused by RSV are reviewed by Ogra P. Paediatric Respiratory Reviews 5: S119-S126 (2004)] or Sendai virus), Measles (caused by rubeola virus), Marburg hemorrhagic fever (caused by Marburg virus), Molluscum contagiosum (caused by Molluscum), Mononucleosis-like syndrome (caused by CMV), mumps (caused by mumps virus), Newcastle disease (caused by avian paramoxyvirus 1), Norovirus, Orf (caused by Orfvirus), Pharyngitis (caused by e.g. RSV [RSV virus and diseases caused by RSV are reviewed by Ogra P. Paediatric Respiratory Reviews 5: S119-S126 (2004)], Influenza Virus [Influenza viruses, diseases caused by influenza viruses and pharmaceuticals to treat these diseases are reviewed by Subbarao et al. Nat. Rev. Immunol. 7: 267-278 (2007)], Parainfluenza virus and Epstein-Barr virus), Pneumonia (viral) (caused by e.g. RSV [RSV virus and diseases caused by RSV are reviewed by Ogra P. Paediatric Respiratory Reviews 5: S119-S126 (2004)] or CMV), Progressive multifocal leukencephalopathy, Rabies (caused by Rabies virus [rabies virus and diseases caused by rabies are reviewed by Woldehiwet Z. Res. Vet. Sci. 73: 17-25 (2002) and Dietzschold et al. J. Virol. 56: 12-18 (1985)]), Roseola (caused by HHV-6), Rubella (caused by rubivirus), SARS (caused by a human coronavirus), Shingles (caused by Varicella zoster virus), Smallpox (caused by Variola virus), St. Louis encephalitis (caused by SLE virus), Strep Throat (caused by e.g. RSV [RSV virus and diseases caused by RSV are reviewed by Ogra P. Paediatric Respiratory Reviews 5: S119-S126 (2004)], Influenza Virus [Influenza viruses, diseases caused by influenza viruses and pharmaceuticals to treat these diseases are reviewed by Subbarao et al. Nat. Rev. Immunol. 7: 267-278 (2007)], Parainfluenza virus, Epstein-Barr virus), Sindbis fever (Sindbis virus), Temporal lobe encephalitis (caused by HSV-1), Urethritis (caused by Herpes simplex virus), Vesicular stomatitis (caused by vesicular stomatitis virus), Viral encephalitis, Viral gastroenteritis, Viral meningitis, Viral pneumonia, Western equine encephalitis (caused by WEE virus), West Nile disease, Yellow fever (caused by Yellow Fever virus), and Zoster (caused by Varicella zoster virus). The amino acid sequences, polypeptides and compositions according to the invention can be used to treat any of the foregoing viral diseases. Other examples of such viral diseases will be clear to the skilled person; for instance, the amino acid sequences, polypeptides and compositions according to the invention can be used to treat any of the viral diseases that are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, M D; Diane E. Griffin, M D, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, M D; Bernard Roizman, ScD; Stephen E. Straus, M D (ISBN-10: 0781760607; ISBN-13: 9780781760607).

Accordingly, the amino acid sequences, polypeptides and compositions of the present invention can be used for the prevention and treatment of viral diseases which are characterized by viral-mediated biological pathway(s) in which an envelope protein of a virus and/or a viral receptor are involved.

In particular, the amino acid sequences, polypeptides and compositions of the present invention can be used for the prevention and treatment of viral diseases characterized by any viral-mediated biological pathway(s) in which an envelope protein of a virus and/or a viral receptor are involved. However, preferably, the amino acid sequences, polypeptides and compositions of the present invention can be used for the prevention and treatment of viral diseases characterized by viral entry in a target host cell, such as virion attachment to a target host cell and/or viral fusion with a target host cell. Also preferably, the amino acid sequences, polypeptides and compositions of the present invention can be used for the prevention and treatment of viral diseases characterized by viral replication in a target host cell, such as viral transcription and/or viral translation and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane.

Some specific, but non-limiting examples of such uses are:

Amino acid sequences and polypeptide of the invention against hemagglutinin H5, and pharmaceutical compositions comprising the same, may be used in the prevention and treatment of influenza (flu), pharyngitis, strep throat, common cold and respiratory tract infections; Amino acid sequences and polypeptide of the invention against hRSV, and pharmaceutical compositions comprising the same, may be used in the prevention and treatment of lower respiratory tract infections, bronchiolitis, common cold, pharyngitis, viral pneumonia and strep throat; Amino acid sequences and polypeptide of the invention against rabies, and pharmaceutical compositions comprising the same, may be used in the prevention and treatment of rabies, brain inflammation and (acute) encephalitis; Other examples of such uses will be clear to the skilled person based on the disclosure herein.

Thus, without being limited thereto, the amino acid sequences, polypeptides and compositions of the invention can for example be used to prevent and/or to treat all diseases and disorders that are currently being prevented or treated with known anti-viral compounds that can modulate viral-mediated biological pathway(s) in which an envelope protein of a virus and/or a viral receptor are involved, such as those mentioned in the prior art cited above. It is also envisaged that the amino acid sequences, polypeptides and compositions of the invention can be used to prevent and/or to treat all diseases and disorders for which treatment with such anti-viral compounds is currently being developed, has been proposed, or will be proposed or developed in future. In addition, it is envisaged that, because of their favourable properties as further described herein, the amino acid sequences, polypeptides and compositions of the present invention may be used for the prevention and treatment of other diseases and disorders than those for which these known anti-viral compounds are being used or will be proposed or developed; and/or that the amino acid sequences, polypeptides and compositions of the present invention may provide new methods and regimens for treating the diseases and disorders described herein.

Other applications and uses of the amino acid sequences and polypeptides of the invention will become clear to the skilled person from the further disclosure herein.

Generally, it is an object of the invention to provide pharmacologically active agents, as well as compositions comprising the same, that can be used in the diagnosis, prevention and/or treatment of viral diseases and of the further diseases and disorders mentioned herein; and to provide methods for the diagnosis, prevention and/or treatment of such diseases and disorders that involve the administration and/or use of such agents and compositions.

In particular, it is an object of the invention to provide such pharmacologically active agents, compositions and/or methods that have certain advantages compared to the agents, compositions and/or methods that are currently used and/or known in the art. These advantages will become clear from the further description below.

More in particular, it is an object of the invention to provide therapeutic proteins that can be used as pharmacologically active agents, as well as compositions comprising the same, for the diagnosis, prevention and/or treatment of viral diseases and of the further diseases and disorders mentioned herein; and to provide methods for the diagnosis, prevention and/or treatment of such diseases and disorders that involve the administration and/or the use of such therapeutic proteins and compositions.

Accordingly, it is a specific object of the present invention to provide amino acid sequences that are directed against (as defined herein) an envelope protein of a virus, in particular against an envelope protein of a virus that is able to infect a warm-blooded animal, more in particular against an envelope protein of a virus that is able to infect mammalians, and especially against an envelope protein of a virus that is able to infect humans; and to provide proteins and polypeptides comprising or essentially consisting of at least one such amino acid sequence.

In particular, it is a specific object of the present invention to provide such amino acid sequences and such proteins and/or polypeptides that are suitable for prophylactic, therapeutic and/or diagnostic use in a warm-blooded animal, and in particular in a mammal, and more in particular in a human being.

More in particular, it is a specific object of the present invention to provide such amino acid sequences and such proteins and/or polypeptides that can be used for the prevention, treatment, alleviation and/or diagnosis of one or more diseases, disorders or conditions associated with viral entry and/or viral replication and/or mediated by an envelope protein of a virus and/or its viral receptor (such as the diseases, disorders and conditions mentioned herein) in a warm-blooded animal, in particular in a mammal, and more in particular in a human being.

It is also a specific object of the invention to provide such amino acid sequences and such proteins and/or polypeptides that can be used in the preparation of pharmaceutical or veterinary compositions for the prevention and/or treatment of one or more diseases, disorders or conditions associated with viral entry and/or viral replication and/or mediated by an envelope protein of a virus and/or its viral receptor (such as the diseases, disorders and conditions mentioned herein) in a warm-blooded animal, in particular in a mammal, and more in particular in a human being.

In the invention, generally, these objects are achieved by the use of the amino acid sequences, proteins, polypeptides and compositions that are described herein.

In general, the invention provides amino acid sequences that are directed against (as defined herein) and/or can specifically bind (as defined herein) to an envelope protein of a virus; as well as compounds and constructs, and in particular proteins and polypeptides, that comprise at least one such amino acid sequence. Preferably, said envelope protein of a virus against which the amino acid sequences and polypeptides of the invention are directed against and/or specifically bind to may be encoded by the viral genome, i.e. may be a viral-specific envelope protein. Alternatively, said envelope protein of a virus may also not be encoded by the viral genome but may for instance be encoded by the genome of “a target host cell of said virus” (as further defined herein). Furthermore, said envelope protein of a virus is preferably a membrane protein, which is bound to or attached to and/or embedded in and/or crosses the bi-lipid membrane layer of the viral envelope of said virus. In another preferred but non-limiting aspect, said envelope protein of a virus against which the amino acid sequences and polypeptides of the invention are directed and/or which is specifically bound by the amino acid sequences and/or polypeptides of the invention may be a glycoprotein.

Alternatively, said envelope protein may be a non-glycosylated protein.

More in particular, the invention provides amino acid sequences that can bind to an envelope protein of a virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein; as well as compounds and constructs, and in particular proteins and polypeptides, that comprise at least one such amino acid sequence.

In particular, amino acid sequences and polypeptides of the invention are preferably such that they:

bind to an envelope protein of a virus with a dissociation constant (K D ) of 10 −5 to 10 −12 moles/liter or less, and preferably 10 −7 to 10 −12 moles/liter or less and more preferably 10 −8 to 10 −12 moles/liter (i.e. with an association constant (K A ) of 10 5 to 10 12 liter/moles or more, and preferably 10 7 to 10 12 liter/moles or more and more preferably 10 8 to 10 12 liter/moles);

and/or such that they:

bind to an envelope protein of a virus with a k on -rate of between 10 2 M −1 s −1 to about 10 7 M −1 s −1 , preferably between 10 3 M −1 s −1 and 10 7 M −1 s −1 , more preferably between 10 4 M −1 s −1 and 10 7 M −1 s −1 , such as between 10 5 M −1 s −1 and 10 7 M −1 s −1 ;

and/or such that they:

bind to an envelope protein of a virus with a k off rate between 1 s −1 (t 1/2 =0.69 s) and 10 −6 s −1 (providing a near irreversible complex with a t 1/2 of multiple days), preferably between 10 −2 s −1 and 10 −6 s −1 , more preferably between 10 −3 s −1 and 10 −6 s −1 , such as between 10 −4 s −1 and 10 −6 s −1 .

Preferably, a monovalent amino acid sequence of the invention (or a polypeptide that contains only one amino acid sequence of the invention) is preferably such that it will bind to an envelope protein of a virus with an affinity less than 500 nM, preferably less than 200 nM, more preferably less than 10 nM, such as less than 500 pM.

Some preferred IC50 values for binding of the amino acid sequences or polypeptides of the invention to an envelope protein of a virus will become clear from the further description and examples herein.

For binding to an envelope protein of a virus, an amino acid sequence of the invention will usually contain within its amino acid sequence one or more amino acid residues or one or more stretches of amino acid residues (i.e. with each “stretch” comprising two or more amino acid residues that are adjacent to each other or in close proximity to each other, i.e. in the primary or tertiary structure of the amino acid sequence) via which the amino acid sequence of the invention can bind to an envelope protein of a virus, which amino acid residues or stretches of amino acid residues thus form the “site” for binding to an envelope protein of a virus (also referred to herein as the “antigen binding site”).

The amino acid sequences provided by the invention are preferably in essentially isolated form (as defined herein), or form part of a protein or polypeptide of the invention (as defined herein), which may comprise or essentially consist of one or more amino acid sequences of the invention and which may optionally further comprise one or more further amino acid sequences (all optionally linked via one or more suitable linkers). For example, and without limitation, the one or more amino acid sequences of the invention may be used as a binding unit in such a protein or polypeptide, which may optionally contain one or more further amino acid sequences that can serve as a binding unit (i.e. against one or more other targets than the envelope protein of a virus, to which the amino acid sequences of the invention specifically bind to and/or are directed against), so as to provide a monovalent, multivalent or multispecific polypeptide of the invention, respectively, all as described herein. Such a protein or polypeptide may also be in essentially isolated form (as defined herein).

The amino acid sequences and polypeptides of the invention as such preferably essentially consist of a single amino acid chain that is not linked via disulphide bridges to any other amino acid sequence or chain (but that may or may not contain one or more intramolecular disulphide bridges. For example, it is known that NANOBODIES® (V HH sequences)—as described herein—may sometimes contain a disulphide bridge between CDR3 and CDR1 or FR2). However, it should be noted that one or more amino acid sequences of the invention may be linked to each other and/or to other amino acid sequences (e.g. via disulphide bridges) to provide peptide constructs that may also be useful in the invention (for example Fab′ fragments, F(ab′) 2 fragments, ScFv constructs, “diabodies” and other multispecific constructs. Reference is for example made to the review by Holliger and Hudson, Nat Biotechnol. 2005 September; 23(9):1126-36).

Generally, when an amino acid sequence of the invention (or a compound, construct or polypeptide comprising the same) is intended for administration to a subject (for example for therapeutic and/or diagnostic purposes as described herein), it is preferably either an amino acid sequence that does not occur naturally in said subject; or, when it does occur naturally in said subject, in essentially isolated form (as defined herein).

It will also be clear to the skilled person that for pharmaceutical use, the amino acid sequences of the invention (as well as compounds, constructs and polypeptides comprising the same) are preferably directed against an envelope protein of a virus that is able to infect humans; whereas for veterinary purposes, the amino acid sequences and polypeptides of the invention are preferably directed against an envelope protein of a virus that is able to infect the species to be treated, or at least cross-reactive with an envelope protein of a virus that is able to infect the species to be treated.

Furthermore, an amino acid sequence of the invention may optionally, and in addition to the at least one binding site for binding against an envelope protein of a virus, contain one or more further binding sites for binding against other antigens, proteins or targets.

The efficacy of the amino acid sequences and polypeptides of the invention, and of compositions comprising the same, can be tested using any suitable in vitro assay, cell-based assay, in vivo assay and/or animal model known per se, or any combination thereof, depending on the specific disease or disorder involved. Suitable assays and animal models will be clear to the skilled person, and for example include a Biacore assay; epitope mapping e.g. by using monoclonal antibodies which recognize known epitopes; cell based neutralization assays for the different virus strains (e.g. virus neutralization assay for influenza as described in Vanlandschoot et al. Virol. 212: 526-534 (1995) and Vanlandschoot et al. J. Gen. Virol. 79: 1781-1791 (1998) or Rapid Fluorescent Focus Inhibition Test (RFFIT) for rabies as described in Standard procedure from WHO Laboratory Techniques in Rabies, (1996)); in vitro inhibition of cell to cell spread (Dietzschold et al. J. Virol. 56: 12-18 (1985)); cell-cell fusion inhibition assay (Vanlandschoot et al. J. Gen. Virol. 79: 1781-1791 (1998)); plaque assay to examine resistance or sensitivity to antibody (Vanlandschoot et al. J. Gen. Virol. 79: 1781-1791 (1998)); investigate ADEI in macrophage cell lines and primary macrophages and compare infection rates with and without pre-incubation of the virus with antibodies and amino acid sequences and polypeptides of the invention (Tirado et al. Viral Immunol. 16: 69-86 (2003)); retroviral and lentiviral pseudotypes of replication-competent virus to study neutralizing antibody responses to H5N1 viral infection (Temperton et al. Emerg. Infect. Dis. 11: 411-416 (2005)); cotton rat model for studies on RSV (Murphy et al. Virus Res. 11: 1-15 (1988)); in vivo screening of neutralizing capacity of rabies infection by intracerebral inoculation in mice; validation of the use of amino acid sequences and polypeptides according to the invention for post-exposure prophylaxis (Schumacher et al. Vaccine 10: 754-760 (1992)); assessment of the therapeutic potential of amino acid sequences and polypeptides of the invention to treat an ongoing viral brain infection; Ferret model for H5N1 infection (Yen et al. J. Virol. 81: 6890-6898 (2007)); assessment of the prophylactic and therapeutic potential of amino acid sequences and polypeptides of the invention to treat influenza-infected mice (Simmons et al. Plos Medicine 4 (5): 928-936); as well as the assays and animal models used in the experimental part below and in the prior art cited herein.

Also, according to the invention, amino acid sequences and polypeptides that are directed against an envelope protein of a virus that is able to infect a first species of warm-blooded animal may or may not show cross-reactivity with an envelope protein of a virus that is able to infect one or more other species of warm-blooded animal. For example, amino acid sequences and polypeptides directed against an envelope protein of a virus that is able to infect humans may or may not show cross reactivity with an envelope protein of a virus that is able to infect one or more other species of primates (such as, without limitation, monkeys from the genus Macaca (such as, and in particular, cynomolgus monkeys ( Macaca fascicularis ) and/or rhesus monkeys ( Macaca mulatta )) and baboon ( Papio ursinus )) and/or with an envelope protein of a virus that is able to infect one or more species of animals that are often used in animal models for diseases (for example mouse, rat, rabbit, pig or dog), and in particular in animal models for diseases and disorders associated with viral entry and/or viral replication and/or mediated by an envelope protein of a virus and/or its viral receptor (such as the species and animal models mentioned herein). In this respect, it will be clear to the skilled person that such cross-reactivity, when present, may have advantages from a drug development point of view, since it allows the amino acid sequences and polypeptides against an envelope protein of a virus that is able to infect humans to be tested in such disease models.

More generally, amino acid sequences and polypeptides of the invention that are cross-reactive with two or more homologous envelope proteins of a virus that is able to infect multiple species of mammal will usually be advantageous for use in veterinary applications, since it will allow the same amino acid sequence or polypeptide to be used across multiple species. Thus, it is also encompassed within the scope of the invention that amino acid sequences and polypeptides directed against an envelope protein of a virus that is able to infect one species of animal (such as amino acid sequences and polypeptides against an envelope protein of a virus that is able to infect humans) can be used in the treatment of another species of animal, as long as the use of the amino acid sequences and/or polypeptides provide the desired effects in the species to be treated.

The present invention is in its broadest sense also not particularly limited to or defined by a specific envelope protein of a virus or a specific class, category or type of envelope proteins of a virus against which the amino acid sequences and polypeptides of the invention are directed. For example, the amino acid sequences and polypeptides may be directed against any envelope protein of a virus. Virus envelope proteins are known in the art and for example include but are not limited to: the F protein of RSV virus, the G protein of RSV virus, the SH protein of RSV virus, the M protein of RSV virus, the M2 protein of RSV virus, the HA protein of influenza A virus, the gp120 protein of HIV-1 virus, the S1 protein of SARS Corona virus, the gD protein of Herpes simplex 1 virus, the HEF protein of influenza C virus, the 5 F protein of Simian parainfluenza virus, the F protein of Human parainfluenza virus, the F protein of Newcastle disease virus, the F2 protein of measles, the F2 protein of Sendai virus, the gp2 protein of Ebola virus, the TM protein of Moloney murine leukemia virus, the gp41 protein of Human immunodeficiency virus 1, the gp41 protein of Simian immunodeficiency virus, the gp21 protein of Human T cell leukemia virus 1, the TM protein of Human syncytin-2, the TM protein of Visna virus, the S2 protein of Mouse hepatitis virus, the E2 protein of SARS corona virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E protein of Yellow Fever virus, the E protein of West Nile virus, the E1 protein of Semliki forest virus, the E1 protein of Sindbis virus, the G protein of Rabies virus, the G protein of Vesicular stomatitis virus and the gB protein of Herpes simplex virus.

The amino acid sequences and polypeptides of the invention may be directed against any of the foregoing viral envelope proteins. Other examples of viral envelope proteins will be clear to the skilled person; for instance, the amino acid sequences and polypeptides according to the invention may be directed against any of the viral envelope proteins that are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

However, it is generally assumed and preferred that the amino acid sequences and polypeptides of the invention are preferably directed against an envelope protein of a virus, wherein said envelope protein is a viral attachment protein (as further defined herein); and/or a viral fusion protein (as further defined herein); and/or a viral attachment protein and a viral fusion protein (as further defined herein).

Thus, in one preferred, but non-limiting aspect, the amino acid sequences and polypeptides of the invention are directed against and/or specifically bind to an envelope protein of a virus, which is a viral attachment protein (as further defined herein). Viral attachment proteins are known in the art and for example include but are not limited to: the G protein of RSV virus, the HA protein of influenza A virus, the gp120 protein of HIV-1 virus, the S1 protein of SARS Corona virus, the gD protein of Herpes simplex 1 virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E protein of Yellow Fever virus, and the E protein of West Nile virus.

The amino acid sequences and polypeptides of the invention may be directed against any of the foregoing viral attachment proteins. Other examples of viral attachment proteins will be clear to the skilled person; for instance, the amino acid sequences and polypeptides according to the invention may be directed against any of the viral attachment proteins that are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

The structural and functional features and mechanisms of action of a variety of viral attachment proteins are known in the art and are for example described in detail in the following literature: “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

It is assumed to be understood that a particular functional viral attachment protein (as defined herein) can be expressed in its functional form or can be expressed in the form of a (non-active) precursor protein. In the case that said particular functional viral attachment protein is expressed as a (non-active) precursor protein, it may be post-translationally processed and/or modified (for example by cleavage with one or more enzymes, such as proteases) within the target host cell (as defined herein) of the virus (for instance in specialized organelles such as the trans-Golgi compartment), resulting in a functional attachment protein and optionally at least one other main protein moiety. After said functional attachment protein and optionally said at least one other main protein moiety have been formed, these may either remain attached to each other (such as via covalent bounds, for instance by one or more disulfide bridges, or via non-covalent bounds, for instance by forming a protein complex) or these may be separated from each other; in both cases however (remaining attached to each other or being separated from each other) either only the resulting functional attachment protein or both the resulting functional attachment protein and the optionally at least one other main protein moiety may be directly involved in the attachment process between the virion and its target host cell (as defined herein) (for instance by binding to a particular viral receptor that is expressed on the surface of said target host cell). However, it is preferred that only the resulting functional attachment protein is directly involved in the attachment process between the virion and its target host cell (for instance by binding to a particular viral receptor that is expressed on the surface of said target host cell). Examples of such functional attachment proteins that are formed by post-translational modification include but are not limited to the gp120 protein of HIV-1 virus and the HA1 protein of influenza. It is however not excluded that said formed at least one other main protein moiety is involved (either directly or indirectly) in the attachment process between the virion and its target host cell (as defined herein) and/or that said formed at least one other main protein moiety is involved (either directly or indirectly) in another process (such as for instance fusion of said virion with its target host cell) that is part of the process of infection and/or replication of said virion.

In another, non-limiting, preferred aspect, the amino acid sequences and polypeptides of the invention are directed against and/or specifically bind to an envelope protein of a virus, which is a viral fusion protein (as further defined herein).

Viral fusion proteins are known in the art and for example include but are not limited to: the F protein of RSV virus, the HA protein of Influenza A virus, the HEF protein of influenza C virus, the 5 F protein of Simian parainfluenza virus, the F protein of Human parainfluenza virus, the F protein of Newcastle disease virus, the F2 protein of measles, the F2 protein of Sendai virus, the gp2 protein of Ebola virus, the TM protein of Moloney murine leukemia virus, the gp41 protein of Human immunodeficiency virus 1, the gp41 protein of Simian immunodeficiency virus, the gp21 protein of Human T cell leukemia virus 1, the TM protein of Human syncytin-2, the TM protein of Visna virus, the S2 protein of Mouse hepatitis virus, the E2 protein of SARS corona virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E protein of Yellow Fever virus, the E protein of West Nile virus, the E1 protein of Semliki forest virus, the E1 protein of Sindbis virus, the G protein of Rabies virus, the G protein of Vesicular stomatitis virus and the gB protein of Herpes simplex virus.

The amino acid sequences and polypeptides of the invention may be directed against any of the foregoing viral fusion proteins. Other examples of viral fusion proteins will be clear to the skilled person; for instance, the amino acid sequences and polypeptides according to the invention may be directed against any of the viral fusion proteins that are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

The structural and functional features and mechanisms of action of a variety of viral fusion proteins are known in the art and are for example described in detail in the following literature: Baker et al. Mol. Cell 3: 309-319 (1999); Chen et al. Proc. Natl. Acad. Sci. USA 96: 8967-8972 (1999); Earp et al. Curr. Topics Microbiol. Immunol. 285, 25-66 (2005); Heldwein et al. Science 313: 217-220 (2006); Helenius et al. J. Cell Biol. 84, 404-420 (1980); Kielian et al. Nat. Rev. Microbiol. 4: 67-76 (2006); Lescar et al. Cell 105: 137-148 (2001); Modis Proc. Natl. Acad. Sci. USA 100: 6986-6991 (2003); Moore and Doms Proc. Natl. Acad. Sci. USA. 100: 10598-10602 (2003); Rey 375: 291-298 (1995); Roche et al. Science 313: 187-191 (2006); Sieczkarski et al. Curr. Topics Microbiol. Immunol. 285, 1-23 (2005); Smith et al. Science 304, 237-242 (2004); Skehel et al. Cell 95: 871-874 (1998); Weissenhom et al. FEBS Lett. 581, 2150-2155 (2007); Wilson et al. Nature 289: 366-373 (1981) and Yin et al. Proc. Natl. Acad. Sci. USA 102: 9288-9293 (2005); Handbook “Fields Virology ”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

It is assumed to be understood that a particular functional viral fusion protein (as defined herein) can be expressed in its functional form or can be expressed in the form of a (non-active) precursor protein. In the case that said particular functional viral fusion protein is expressed as a (non-active) precursor protein, it may be post-translationally processed and/or modified (for example by cleavage with one or more enzymes, such as proteases) within the target host cell (as defined herein) of the virus (for instance in specialized organelles such as the trans-Golgi compartment), resulting in a functional fusion protein and optionally at least one other main protein moiety. After said functional fusion protein and optionally said at least one other main protein moiety have been formed, these may either remain attached to each other (such as via covalent bounds, for instance by one or more disulfide bridges, or via non-covalent bounds, for instance by forming a protein complex) or these may be separated from each other; in both cases however (remaining attached to each other or being separated from each other) either only the resulting functional fusion protein or both the resulting functional fusion protein and the optionally at least one other main protein moiety may be directly involved in the fusion process between the virion and its target host cell (as defined herein) (for instance by binding to membrane components of said target host cell). However, it is preferred that only the resulting functional fusion protein is directly involved in the fusion process between the virion and its target host cell (for instance by binding to membrane components of said target host cell). Examples of such functional fusion proteins that are formed by post-translational modification include but are not limited to the gp41 protein of HIV-1 virus and the HA2 subunit of HA protein of influenza. It is however not excluded that said at least one other main protein moiety is involved (either directly or indirectly) in the fusion process between the virion and its target host cell and/or that said at least one other main protein moiety is involved (either directly or indirectly) in another process (such as for instance attachment of said virion to its target host cell) that is part of the process of infection and/or replication of said virion.

Also, in another preferred, but non-limiting aspect, the amino acid sequences and polypeptides of the invention are directed against and/or specifically bind to an envelope protein of a virus, which is a viral attachment protein and a viral fusion protein (as further defined herein).

Viral envelope proteins that are both viral attachment proteins and viral fusion proteins are known in the art and for example include but are not limited to: the HA protein of influenza A virus, the E2 protein of SARS corona virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E protein of Yellow Fever virus, the E protein of West Nile virus, the E1 protein of Semliki forest virus, and the E1 protein of Sindbis virus. The amino acid sequences and polypeptides of the invention may be directed against any of the foregoing viral envelope proteins that are both viral attachment proteins and viral fusion proteins. Other examples of viral envelope proteins that are both viral attachment proteins and viral fusion proteins will be clear to the skilled person; for instance, the amino acid sequences and polypeptides according to the invention may be directed against any of the viral envelope proteins that are both viral attachment proteins and viral fusion proteins and are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

The structural and functional features and mechanisms of action of a variety of envelope proteins that are both viral attachment proteins and viral fusion proteins are known in the art and are for example described in detail in the following literature: handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

A particular functional viral envelope protein, which is both an attachment and a fusion protein, can be expressed in its functional form or can be expressed in the form of a (non-active) precursor protein. In the case that said particular functional viral attachment and fusion protein is expressed as a (non-active) precursor protein, it may be post-translationally processed and/or modified (for example by cleavage with one or more enzymes, such as proteases) within the target host cell (as defined herein) of the virus (for instance in specialized organelles such as the trans-Golgi compartment), resulting in a functional viral attachment and fusion protein and optionally at least one other main protein moiety. After said functional viral attachment and fusion protein and optionally said at least one other main protein moiety have been formed, these may either remain attached to each other (such as via covalent bounds, for instance by one or more disulfide bridges, or via non-covalent bounds, for instance by forming a protein complex) or these may be separated from each other; in both cases however (remaining attached to each other or being separated from each other) either only the resulting functional viral attachment and fusion protein or both the resulting functional viral attachment and fusion protein and the optionally at least one other main protein moiety may be directly involved in the fusion process between the virion and its target host cell (for instance by binding to a particular viral receptor that is expressed on the surface of said target host cell and/or to membrane components of said target host cell). However, it is preferred that only the resulting functional viral attachment and fusion protein is directly involved in the fusion process between the virion and its target host cell (for instance by binding to a particular viral receptor that is expressed on the surface of said target host cell and/or to membrane components of said target host cell). It is however not excluded that said at least one other main protein moiety is involved (either directly or indirectly) in the fusion process between the virion and its target host cell (as defined herein) and/or that said at least one other main protein moiety is involved (either directly or indirectly) in another process (such as for instance only attachment of said virion to its target host cell or only fusion of said virion with its target host cell) that is part of the process of infection and/or replication of said virion.

The present invention is not particularly limited to or defined by a specific conformation and/or secondary and/or tertiary and/or quaternary structure of said envelope protein against which the amino acid sequences and polypeptides of the invention are directed. Thus, said envelope protein may be characterized by any conformation and/or secondary and/or tertiary and/or quaternary structure. For example, when an envelope protein of a virus exists in an activated conformation and in an inactive conformation or in a pre-fusion and post-fusion conformation or state, the amino acid sequences and polypeptides of the invention may bind to either one of these conformations, or may bind to both these conformations (i.e. with an affinity and/or specificity which may be the same or different).

Also, for example, the amino acid sequences and polypeptides of the invention may bind to a conformation of an envelope protein of a virus in which it is bound to a binding partner (as further defined herein), may bind to a conformation of an envelope protein of a virus in which it not bound to a binding partner, or may bind to both such conformations (again with an affinity and/or specificity which may be the same or different).

More specifically, said envelope protein may be characterized by a pre-fusion conformational state (as further defined herein) and/or an intermediate conformational state (as further defined herein) and/or a post-fusion conformational state (as further defined herein). In particular, said envelope protein, which is characterized by a pre-fusion conformational state and/or an intermediate conformational state and/or a post-fusion conformational state may be a viral attachment protein; alternatively and more preferably, said envelope protein, which is characterized by a pre-fusion conformational state and/or an intermediate conformational state and/or a post-fusion conformational state may be a viral fusion protein (as defined herein); also, said envelope protein, which is characterized by a pre-fusion conformational state and/or an intermediate conformational state and/or a post-fusion conformational state may be a viral attachment protein and a viral fusion protein.

In cases wherein said at least one fusion protein is characterized by a pre-fusion conformational state, said pre-fusion conformational state may be a fusion protein trimer, such as for example (but not limited to) a trimer of hairpins or a six-helix bundle. When said pre-fusion conformational state of a viral fusion protein is a fusion protein trimer, three protein subunits are comprised in said protein trimer, which are preferably identical but also may be different from each other. Also, a particular protein subunit of said fusion protein trimer can either remain intact or uncleaved before, during and after the fusion process between a virion and its target host cell (as defined herein) or can be cleaved (for instance by one or more enzymes, such as proteases) before, during or after the fusion process to form at least two main protein moieties originating from said subunit of said protein trimer. In the case that said protein subunit of said fusion protein trimer is cleaved as described above, said at least two main protein moieties can either stay attached to each other (such as via covalent bounds, for instance by one or more disulfide bridges, or non-covalent bounds, for instance by forming a protein complex) or can be completely separate protein moieties, originating from the same subunit; in both cases however, either staying attached to each other or being completely separated from each other, it may be that only one, or at least two, or two or more or all of said main proteins moieties (originating from the same subunit of said fusion protein trimer) are directly involved in the fusion process between a virion and its target host cell (as defined herein). However, preferably, only one of said main proteins moieties (originating from the same subunit of said fusion protein trimer) is directly involved in the fusion process between a virion and its target host cell (as defined herein). Examples of such main protein parts that are directly involved in the fusion process between a virion and its target host cell include but are not limited to the F2 protein of RSV virus and the HA2 subunit of HA protein of influenza virus.

Examples of viral fusion proteins that are characterized by a pre-fusion conformational state, which is a fusion protein trimer, such as for example a trimer of hairpins or a six-helix bundle include but are not limited to Influenza A virus HA protein, Influenza C virus HEF protein, Simian parainfluenza virus 5 F protein, Human parainfluenza virus F protein, Newcastle disease virus F protein, Respiratory syncytial virus F protein, Measles F2 protein, Sendai F2 protein, Ebola virus gp2 protein, Moloney murine leukemia virus TM protein, Human immunodeficiency virus 1 gp41 protein, Simian immunodeficiency virus gp41 protein, Human T cell leukemia virus 1 gp21 protein, Human syncytin-2 TM protein, Visna virus TM protein, Mouse hepatitis virus S2 protein and SARS corona virus E2 protein.

Alternatively, said viral fusion protein may be characterized by a pre-fusion conformational state (as defined herein), wherein said pre-fusion conformational state is a protein dimer (comprising two protein subunits), such as for example a fusion protein homodimer (comprising two identical protein subunits) or a protein heterodimer (comprising two different protein subunits). It is assumed to be understood that when said pre-fusion conformational state of a viral fusion protein is a protein dimer, such as a fusion protein homodimer or a protein heterodimer, that in said protein dimer (comprising two protein subunits) either both or only one of the two protein subunits of said protein dimer can be directly involved in the fusion process between a virion and its target host cell (as defined herein). Also, it is assumed to be understood that the two protein subunits of said protein dimer can either be attached to each other (such as for instance via covalent bounds or non-covalent bounds) or can be cleaved (for instance by one or more enzymes, such as proteases) to form two separate protein monomers before, during or after the fusion process between a virion and its target host cell.

Finally, said viral fusion protein may be characterized by a pre-fusion conformational state (as defined herein), wherein said pre-fusion conformational state is a fusion protein monomer.

Examples of viral fusion proteins that are characterized by a pre-fusion conformational state, which is a protein dimer, such as a fusion protein homodimer or a protein heterodimer, or a protein monomer include but are not limited to Tick-borne encephalitis virus E protein, Dengue 2 and 3 virus E2 protein, yellow fever E protein, West Nile virus E protein, Semliki forest virus E1 protein and Sindbis E1 protein.

In cases wherein said at least one fusion protein is characterized by a post-fusion conformational state, said post-fusion conformational state may be a fusion protein trimer, such as for example (but not limited to) a trimer of hairpins or a six-helix bundle. More specifically, said post-fusion conformational state of viral fusion proteins may be a fusion protein trimer, which comprises an α-helical coiled coil and/or β-structures and/or an α-helical coiled coil and β-structures.

Examples of viral fusion proteins that are characterized by a post-fusion conformational state, which is a trimer of hairpins comprising an α-helical coiled coil include but are not limited to Influenza A virus HA protein, Influenza C virus HEF protein, Simian parainfluenza virus 5 F protein, Human parainfluenza virus F protein, Newcastle disease virus F protein, Human respiratory syncytial virus F protein, Measles F2 protein, Sendai F2 protein, Ebola virus gp2 protein, Moloney murine leukemia virus TM protein, Human immunodeficiency virus 1 gp41 protein, Simian immunodeficiency virus gp41 protein, Human T cell leukemia virus 1 gp21 protein, Human syncytin-2 TM protein, Visna virus TM protein, Mouse hepatitis virus S2 protein and SARS corona virus E2 protein.

Examples of viral fusion proteins that are characterized by a post-fusion conformational state, which is a trimer of hairpins comprising β-structures include but are not limited to Tick-borne encephalitis virus E protein, Dengue 2 and 3 virus E2 protein, yellow fever E protein, West Nile virus E protein, Semliki forest virus E1 protein and Sindbis E1 protein.

Examples of viral fusion proteins that are characterized by a post-fusion conformational state, which is a trimer of hairpins comprising an α-helical coiled coil and β-structures include but are not limited to vesicular stomatitis virus G protein, rabies G protein and Herpes simplex virus gB protein.

The present invention thus generally provides amino acid sequences and polypeptides that may be directed to and/or may specifically bind to any conformation and/or secondary and/or tertiary and/or quaternary structure (where applicable) of said envelope protein.

In a first specific aspect, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the pre-fusion conformational state (as defined herein) of an envelope protein, which is a viral attachment protein (as defined herein), such as for example (but not limited to) amino acid sequences and polypeptides that are directed to and/or specifically bind to the pre-fusion conformational state of a viral attachment protein, wherein said pre-fusion conformational state is characterized by a trimer of hairpins or a six-helical bundle; also, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the intermediate conformational state (as defined herein) of an envelope protein, which is a viral attachment protein; finally, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the post-fusion conformational state (as defined herein) of an envelope protein, which is a viral attachment protein, such as for example (but not limited to) amino acid sequences and polypeptides that are directed to and/or specifically bind to the post-fusion conformational state of a viral attachment protein, wherein said post-fusion conformational state is characterized by a trimer of hairpins comprising an α-helical coiled coil or comprising an α-helical coiled coil and β-structures.

In this aspect of the invention, it is also encompassed that the amino acid sequences and polypeptides can be directed to and/or can specifically bind to the pre-fusion conformational state and to the intermediate conformational state of said viral attachment protein; also, the amino acid sequences and polypeptides of the invention can be directed to and/or can specifically bind to the pre-fusion conformational state and to the post-fusion conformational state of said viral attachment protein; furthermore, the amino acid sequences and polypeptides of the invention can be directed to and/or can specifically bind to the intermediate conformational state and to the post-fusion conformational state of said viral attachment protein.

Furthermore, it is encompassed in this specific aspect of the present invention that the amino acid sequences and polypeptides can be directed to and/or can specifically bind to the pre-fusion conformational state and to the intermediate conformational state and to the post-fusion conformational state of said viral attachment protein.

In a second specific and preferable aspect, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the pre-fusion conformational state (as defined herein) of an envelope protein, which is a viral fusion protein (as defined herein), such as for example (but not limited to) amino acid sequences and polypeptides that are directed to and/or specifically bind to the pre-fusion conformational state of a viral fusion protein, wherein said pre-fusion conformational state is characterized by a trimer of hairpins or a six-helical bundle; also, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the intermediate conformational state (as defined herein) of an envelope protein, which is a viral fusion protein; finally, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the post-fusion conformational state (as defined herein) of an envelope protein, which is a viral fusion protein, such as for example (but not limited to) amino acid sequences and polypeptides that are directed to and/or specifically bind to the post-fusion conformational state of a viral fusion protein, wherein said post-fusion conformational state is characterized by a trimer of hairpins comprising an α-helical coiled coil or comprising an α-helical coiled coil and β-structures.

In this aspect of the invention, it is also encompassed that the amino acid sequences and polypeptides can be directed to and/or can specifically bind to the pre-fusion conformational state and to the intermediate conformational state of said viral fusion protein; also, the amino acid sequences and polypeptides of the invention can be directed to and/or can specifically bind to the pre-fusion conformational state and to the post-fusion conformational state of said viral fusion protein; furthermore, the amino acid sequences and polypeptides of the invention can be directed to and/or can specifically bind to the intermediate conformational state and to the post-fusion conformational state of said viral fusion protein.

Furthermore, it is encompassed in this specific aspect of the present invention that the amino acid sequences and polypeptides can be directed to and/or can specifically bind to the pre-fusion conformational state and to the intermediate conformational state and to the post-fusion conformational state of said viral fusion protein.

In a third specific aspect, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the pre-fusion conformational state (as defined herein) of an envelope protein, which is both a viral attachment protein and a viral fusion protein (as defined herein), such as for example (but not limited to) amino acid sequences and polypeptides that are directed to and/or specifically bind to the pre-fusion conformational state of an envelope protein, which is both a viral attachment protein and a viral fusion protein, wherein said pre-fusion conformational state is characterized by a trimer of hairpins or a six-helical bundle; also, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the intermediate conformational state (as defined herein) of an envelope protein, which is both a viral attachment protein and a viral fusion protein; finally, the present invention provides amino acid sequences and polypeptides that are directed to and/or specifically bind to the post-fusion conformational state (as defined herein) of an envelope protein, which is both a viral attachment protein and a viral fusion protein, such as for example (but not limited to) amino acid sequences and polypeptides that are directed to and/or specifically bind to the post-fusion conformational state of an envelope protein, which is both a viral attachment protein and a viral fusion protein, wherein said post-fusion conformational state is characterized by a trimer of hairpins comprising an α-helical coiled coil or comprising an α-helical coiled coil and β-structures.

In this aspect of the invention, it is also encompassed that the amino acid sequences and polypeptides can be directed to and/or can specifically bind to the pre-fusion conformational state and to the intermediate conformational state of said envelope protein, which is both a viral attachment protein and a viral fusion protein; also, the amino acid sequences and polypeptides of the invention can be directed to and/or can specifically bind to the pre-fusion conformational state and to the post-fusion conformational state of said envelope protein, which is both a viral attachment protein and a viral fusion protein; furthermore, the amino acid sequences and polypeptides of the invention can be directed to and/or can specifically bind to the intermediate conformational state and to the post-fusion conformational state of said envelope protein, which is both a viral attachment protein and a viral fusion protein.

Furthermore, it is encompassed in this specific aspect of the present invention that the amino acid sequences and polypeptides can be directed to and/or can specifically bind to the pre-fusion conformational state and to the intermediate conformational state and to the post-fusion conformational state of said envelope protein, which is both a viral attachment protein and a viral fusion protein.

As further described herein, a polypeptide of the invention may be bivalent and/or multivalent (as defined herein) and contain two or more amino acid sequences of the invention that are directed against an envelope protein of a virus. Generally, such polypeptides will bind to an envelope protein of a virus with increased avidity compared to a single amino acid sequence of the invention. It has also been observed that such polypeptides show (synergistically) increased binding, competition, and/or in vitro and/or in vivo neutralization of different genotypes, subtypes, escape mutants and/or strains of a virus.

Such a polypeptide may for example comprise two amino acid sequences of the invention that are directed against the same antigenic determinant, epitope, part, domain, subunit or conformation (where applicable) of an envelope protein of a virus (which may or may not be an interaction site); or such a polypeptide may be biparatopic and/or multiparatopic (as defined herein) and comprise at least one “first” amino acid sequence of the invention that is directed against a first antigenic determinant, epitope, part, domain, subunit or conformation (where applicable) of an envelope protein of a virus (which may or may not be an interaction site); and at least one “second” amino acid sequence of the invention that is directed against a second antigenic determinant, epitope, part, domain, subunit or conformation (where applicable) of said envelope protein of a virus, wherein said second antigenic determinant, epitope, part, domain, subunit or conformation is different from the first (and again may or may not be an interaction site). Preferably, in such “bi- and/or multiparatopic” polypeptides of the invention, at least one amino acid sequence of the invention is directed against an interaction site (as defined herein), although the invention in its broadest sense is not limited thereto.

It is thus also within the scope of the invention that, where applicable, a polypeptide of the invention can bind to two or more antigenic determinants, epitopes, parts, domains, subunits or conformations of an envelope protein of a virus. In such a case, the antigenic determinants, epitopes, parts, domains or subunits of said envelope protein of a virus to which the amino acid sequences and/or polypeptides of the invention bind may be essentially the same (for example, if an envelope protein of a virus contains repeated structural motifs or occurs in a multimeric form) or may be different (and in the latter case, the amino acid sequences and polypeptides of the invention are said to be “bi- and/or multiparatopic” and may bind to such different antigenic determinants, epitopes, parts, domains, subunits of said envelope protein of a virus with an affinity and/or specificity which may be the same or different). Accordingly, bi- or multiparatopic polypeptides of the present invention are directed against and/or specifically bind to at least two epitopes of an envelope protein of a virus, and are for example (but not limited to) polypeptides that are directed against and/or can specifically bind to three or even more epitopes of the same envelope protein of a virus.

For example, and generally, a bivalent polypeptide of the invention may comprise two amino acid sequences of the invention directed against an antigenic determinant, epitope, part or domain of the viral envelope protein which may be suitably linked, for example via a suitable linker as further described herein. Preferably, such a bivalent polypeptide of the invention is further such that, when it binds to the viral envelope protein, it is capable of simultaneously binding to both antigenic determinants, epitopes, parts or domains (i.e. via the two amino acid sequences of the invention capable of binding to said antigenic determinants, epitopes, parts or domains). Examples of such bivalent polypeptides of the invention will become clear from the further description herein. Also, a trivalent polypeptide of the invention may comprise three amino acid sequences of the invention directed against an antigenic determinant, epitope, part or domain of the viral envelope protein, and generally multivalent polypeptides of the invention may contain at least two amino acid sequences of the invention directed against an antigenic determinants, epitopes, parts or domains of the viral envelope protein. Generally, such bivalent, trivalent and multivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent, trivalent and multivalent polypeptides of the invention (for example, these bivalent, trivalent and multivalent polypeptides of the invention preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In one aspect of the invention, the amino acid sequences and (in particular) polypeptides of the invention are capable of binding to two or more antigenic determinants, epitopes, parts, domains of an envelope protein of a virus which are essentially the same. In this context, the amino acid sequences and polypeptides of the invention are also referred to as “multivalent (monospecific)” (such as e.g. “bivalent (monospecific)” or “trivalent (monospecific)”, etc.) amino acid sequences and polypeptides. The multivalent amino acid sequences and polypeptides of the invention can be directed against any antigenic determinants, epitopes, parts, and/or domains of the envelope protein of a virus.

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention bivalent and are directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site II (also referred to as site A) of the RSV F protein as well as against at least one other antigenic determinant, epitope, part or domain on the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 250-275 of the RSV F protein as well as against at least one other antigenic determinant, epitope, part or domain on the RSV F protein.

Generally, such a bivalent polypeptide of the invention may contain two amino acid sequences of the invention that are capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein). Generally, such bivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent polypeptides of the invention (for example, these bivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as Synagis®.

In another preferred, but non-limiting aspect, the amino acid sequences and polypeptides of the invention are bivalent and are directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein, The amino acid sequences and polypeptides of the invention may be directed against antigenic site IV-VI of the RSV F protein as well as against at least one other antigenic determinant on the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 423-436 of the RSV F protein as well as against at least one other antigenic determinant on the RSV F protein.

Generally, such a bivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein). Generally, such bivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent polypeptides of the invention (for example, these bivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the 101F binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as 101F.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus.

Generally, such a bivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such bivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent polypeptides of the invention (for example, these bivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the sialic acid binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus.

Generally, such a bivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such bivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent polypeptides of the invention (for example, these bivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the VN04-2 binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are at least capable, upon binding to the hemagglutinin H5 envelope protein of influenza virus, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as VN04-2.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus.

Generally, such a bivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such bivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent polypeptides of the invention (for example, these bivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb C179 binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are at least capable, upon binding to the hemagglutinin H5 envelope protein of influenza virus, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as MAb C179.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are directed against the mAb 8-2 binding site (and preferably against an epitope located in the antigenic site IIa) on the G envelope protein of rabies and/or capable of competing with mAb 8-2 for binding to the G envelope protein.

Generally, such a bivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the mAb 8-2 binding site (and preferably an epitope located in the antigenic site IIa) on the G envelope protein and/or capable of competing with mAb 8-2 for binding to the G envelope protein. Generally, such bivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these bivalent polypeptides of the invention (for example, these bivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the mAb 8-2 binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are bivalent and are at least capable, upon binding to the G envelope protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as MAb 8-2.

In a preferred aspect, the amino acid sequences and (in particular) polypeptides of the invention are capable of binding to two or more different antigenic determinants, epitopes, parts, domains of an envelope protein of a virus. In this context, the amino acid sequences and polypeptides of the invention are also referred to as “multiparatopic” (such as e.g. “biparatopic” or “triparatopic”, etc.) amino acid sequences and polypeptides. The multiparatopic amino acid sequences and polypeptides of the invention can be directed against any antigenic determinants, epitopes, parts, and/or domains of the envelope protein of a virus.

For example, and generally, a biparatopic polypeptide of the invention may comprise at least one amino acid sequence of the invention directed against a first antigenic determinant, epitope, part or domain of the viral envelope protein and at least one amino acid sequence of the invention directed against a second antigenic determinant, epitope, part or domain of the viral envelope protein different from the first antigenic determinant, epitope, part or domain (in which said amino acid sequences may be suitably linked, for example via a suitable linker as further described herein). Preferably, such a biparatopic polypeptide of the invention is further such that, when it binds to the viral envelope protein, it is capable of simultaneously binding to the first antigenic determinant, epitope, part or domain (i.e. via the at least one amino acid sequence of the invention capable of binding to said first antigenic determinant, epitope, part or domain) and binding to said second antigenic determinant, epitope, part or domain (i.e. via the at least one amino acid sequence of the invention capable of binding to said second antigenic determinant, epitope, part or domain). Examples of such biparatopic polypeptides of the invention will become clear from the further description herein. Also, a triparatopic polypeptide of the invention may comprise at least one further amino acid sequence of the invention directed against a third antigenic determinant, epitope, part or domain of the viral envelope protein (different from both the first and second antigenic determinant, epitope, part or domain), and generally multiparatopic polypeptides of the invention may contain at least two amino acid sequences of the invention directed against at least two different antigenic determinants, epitopes, parts or domains of the viral envelope protein. Generally, such biparatopic, triparatopic and multiparatopic polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic, triparatopic and multiparatopic polypeptides of the invention (for example, these biparatopic, triparatopic and multiparatopic polypeptides of the invention preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein, as well as against at least one other antigenic determinant, epitope, part or domain on the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site II (also referred to as site A) of the RSV F protein as well as against at least one other antigenic determinant, epitope, part or domain on the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 250-275 of the RSV F protein as well as against at least one other antigenic determinant, epitope, part or domain on the RSV F protein.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), as well as at least one further amino acid sequence of the invention that is capable of binding to at least one other antigenic determinant, epitope, part or domain on the RSV F protein. Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the at least one other antigenic determinant, epitope, part or domain on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as Synagis®.

In another preferred, but non-limiting aspect, the amino acid sequences and polypeptides of the invention are biparatopic (or multiparatopic) and are directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein, as well as against at least one other antigenic determinant on the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site IV-VI of the RSV F protein as well as against at least one other antigenic determinant on the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 423-436 of the RSV F protein as well as against at least one other antigenic determinant on the RSV F protein.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein), as well as at least one further amino acid sequence of the invention that is capable of binding to at least one other antigenic determinant, epitope, part or domain on the RSV F protein. Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the 101F binding site and the at least one other antigenic determinant, epitope, part or domain on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as 101F.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic and are at least directed against the Synagis® binding site on the RSV F protein as well as against the 101F binding site on the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site II (also referred to as site A) of the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site IV-VI of the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site II (also referred to as site A) of the RSV F protein as well as against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 250-275 of the RSV F protein. In another preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 250-275 of the RSV F protein as well as against region aa 423-436 of the RSV F protein. In another preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 423-436 of the RSV F protein. In another preferred aspect, the amino acid sequences and polypeptides of the invention are directed against antigenic site II (also referred to as site A) of the RSV F protein as well as against the region aa 423-436 of the RSV F protein. In another preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 250-275 of the RSV F protein as well as against antigenic site IV-VI of the RSV F protein.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), as well as at least one amino acid sequence of the invention that is capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein). Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the 101F binding site on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as Synagis® and 101F.

Again, the above biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the 101F binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic with both paratopes directed against the Synagis® binding site on the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site II (also referred to as site A) of the RSV F protein (one paratope or both paratopes). In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against region aa 250-275 of the RSV F protein (one paratope or both paratopes).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic with both paratopes directed against the 101F binding site on the RSV F protein. The amino acid sequences and polypeptides of the invention may be directed against antigenic site IV-VI of the RSV F protein (one paratope or both paratopes). In a preferred aspect, the amino acid sequences and polypeptides of the invention are directed against the region aa 423-436 of the RSV F protein (one paratope or both paratopes).

Again, the above biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind both binding sites; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as against at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as at least one further amino acid sequence of the invention that is capable of binding to at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the sialic acid binding site and the at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as against at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as at least one further amino acid sequence of the invention that is capable of binding to at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the VN04-2 binding site and the at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are at least capable, upon binding to the hemagglutinin H5 envelope protein of influenza virus, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as VN04-2.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as against at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as at least one further amino acid sequence of the invention that is capable of binding to at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb C179 binding site and the at least one other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are at least capable, upon binding to the hemagglutinin H5 envelope protein of influenza virus, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as MAb C179.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are directed against the MAb 8-2 binding site on the G envelope protein of rabies and/or capable of competing with MAb 8-2 for binding to the G envelope protein, as well as against at least one other antigenic determinant, epitope, part or domain on the G envelope protein.

Generally, such a biparatopic (or multiparatopic) polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the MAb 8-2 binding site on the G envelope protein and/or capable of competing with MAb 8-2 for binding to the G envelope protein, as well as at least one further amino acid sequence of the invention that is capable of binding to at least one other antigenic determinant, epitope, part or domain on the G envelope protein. Generally, such biparatopic (or multiparatopic) polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these biparatopic (or multiparatopic) polypeptides of the invention (for example, these biparatopic and multiparatopic polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb 8-2 binding site and the at least one other antigenic determinant, epitope, part or domain on the G envelope protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are biparatopic (or multiparatopic) and are at least capable, upon binding to the G envelope protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as MAb 8-2.

Also, the polypeptides of the present invention may also be directed against and/or can specifically bind to at least one particular envelope protein of a virus and at least one further epitope of another target, which is different from said at least one particular envelope protein. For example (but not limited to), the polypeptides of the present invention may be directed against and/or can specifically bind to at least one particular envelope protein of a virus and at least one further epitope of a virus, for instance at least one further epitope of a viral protein, such as at least one further epitope of another particular viral envelope protein.

Thus, the polypeptides according to the invention may be directed against and/or may specifically bind to at least two (or even more) epitopes of at least two different envelope proteins. Also, said at least one further epitope of a virus may or may not be involved in one or more of the viral-mediated biological pathways, in which an envelope protein of a virus and/or its viral receptor is involved; more specifically said at least one further epitope of a virus may or may not be involved in viral entry in a target host cell, such as virion attachment to a target host cell and/or viral fusion with a target host cell or said at least one further epitope of a virus may or may not be involved in viral replication in a target host cell, such as viral transcription and/or viral translation and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane.

Generally, bi-, and multivalent (as defined herein), bi-, and multispecific (as defined herein) and bi-, and multiparatopic (as defined herein) polypeptides according to the invention may be useful for the prevention and/or treatment of viral diseases by specifically binding to at least one epitope of an envelope protein of a virus and at least one further epitope (which may or may not be different from said at least one epitope) of a target, wherein said target may or may not be different from said envelope protein.

Preferably, bi-, and multiparatopic polypeptides (as defined herein) according to the invention may be useful for the prevention and/or treatment of viral diseases by specifically binding to at least two (or even more) epitopes (which may be the same or different) on the same envelope protein of a virus.

Alternatively, the polypeptides of the present invention may be directed against and/or can specifically bind to at least one epitope of an envelope protein of a virus and at least one further epitope of another target, which is different from said particular envelope protein and which is for instance a further epitope of a virus, such as a further epitope of a viral protein or a further epitope of another particular viral envelope protein.

In another preferred aspect, the amino acid sequences and (in particular) polypeptides of the invention are capable of binding to three (different) antigenic determinants, epitopes, parts, domains of an envelope protein of a virus. In this context, the amino acid sequences and polypeptides of the invention are also referred to as “trivalent” (such as e.g. “trivalent triparatopic” or “trivalent biparatopic”, “trivalent monoparatopic”, etc.) amino acid sequences and polypeptides. The trivalent amino acid sequences and polypeptides of the invention can be directed against any antigenic determinants, epitopes, parts, and/or domains of the envelope protein of the virus.

For example, and generally, a trivalent polypeptide of the invention may comprise three amino acid sequences of the invention directed against the same antigenic determinant, epitope, part or domain of the viral envelope protein (in which said amino acid sequences may be suitably linked, for example via a suitable linker as further described herein). A trivalent polypeptide of the invention may comprise two amino acid sequences of the invention directed against a first antigenic determinant, epitope, part or domain of the viral envelope protein, and at least one amino acid sequence of the invention directed against a second antigenic determinant, epitope, part or domain of the viral envelope protein different from the first antigenic determinant, epitope, part or domain (in which said amino acid sequences may be suitably linked, for example via a suitable linker as further described herein). Such a trivalent polypeptide of the invention may also be referred to as “trivalent biparatopic”. A trivalent polypeptide of the invention may comprise one amino acid sequence of the invention directed against a first antigenic determinant, epitope, part or domain of the viral envelope protein, at least one amino acid sequence of the invention directed against a second antigenic determinant, epitope, part or domain of the viral envelope protein different from the first antigenic determinant, epitope, part or domain and at least one amino acid sequence of the invention directed against a third antigenic determinant, epitope, part or domain of the viral envelope protein different from the first and the second antigenic determinant, epitope, part or domain (in which said amino acid sequences may be suitably linked, for example via a suitable linker as further described herein). Such a trivalent polypeptide of the invention may also be referred to as “trivalent triparatopic”. A trivalent polypeptide of the invention may comprise two amino acid sequences of the invention directed against a first antigenic determinant, epitope, part or domain of the viral envelope protein, and at least one amino acid sequence of the invention directed against a second antigenic determinant, epitope, part or domain of a viral envelope protein different from the first viral envelope protein. Such a trivalent polypeptide of the invention may also be referred to as “trivalent bispecific”. A trivalent polypeptide of the invention may also comprise one amino acid sequence of the invention directed against a first antigenic determinant, epitope, part or domain of the viral envelope protein, at least one amino acid sequence of the invention directed against a second antigenic determinant, epitope, part or domain of the same viral envelope protein different from the first antigenic determinant, epitope, part or domain and at least one amino acid sequence of the invention directed against a third antigenic determinant, epitope, part or domain of a viral envelope protein different from the first viral envelope protein (in which said amino acid sequences may be suitably linked, for example via a suitable linker as further described herein). Such a trivalent polypeptide of the invention may also be referred to as “trivalent trispecific”. A trivalent polypeptide of the invention may also comprise one amino acid sequence of the invention directed against a first antigenic determinant, epitope, part or domain of the viral envelope protein, at least one amino acid sequence of the invention directed against a second antigenic determinant, epitope, part or domain of a viral envelope protein different from the first viral envelope protein and at least one amino acid sequence of the invention directed against a third antigenic determinant, epitope, part or domain of a viral envelope protein different from the first and the second viral envelope protein (in which said amino acid sequences may be suitably linked, for example via a suitable linker as further described herein). Such a trivalent polypeptide of the invention may also be referred to as “trivalent trispecific”.

Preferably, such a trivalent polypeptide of the invention is further such that, when it binds to the viral envelope protein, it is capable of simultaneously binding to the first antigenic determinant, epitope, part or domain (i.e. via the at least one amino acid sequence of the invention capable of binding to said first antigenic determinant, epitope, part or domain), binding to said second antigenic determinant, epitope, part or domain (i.e. via the at least one amino acid sequence of the invention capable of binding to said second antigenic determinant, epitope, part or domain) and binding to said third antigenic determinant, epitope, part or domain (i.e. via the at least one amino acid sequence of the invention capable of binding to said third antigenic determinant, epitope, part or domain). Examples of such trivalent polypeptides of the invention will become clear from the further description herein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis for binding to the RSV F protein, as well as two amino acid sequences of the invention directed against another antigenic determinant, epitope, part or domain on the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein may be directed against antigenic site II (also referred to as site A) of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein are directed against region aa 250-275 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), as well as two further amino acid sequences of the invention that are capable of binding to two other antigenic determinants, epitopes, parts or domains on the RSV F protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the two other antigenic determinants, epitopes, parts or domains on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis for binding to the RSV F protein, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein may be directed against antigenic site II (also referred to as site A) of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein are directed against region aa 250-275 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), as well as one further amino acid sequence of the invention that is capable of binding to another antigenic determinant, epitope, part or domain on the RSV F protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the other antigenic determinant, epitope, part or domain on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise three amino acid sequences of the invention directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis for binding to the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein may be directed against antigenic site II (also referred to as site A) of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein are directed against region aa 250-275 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain three amino acid sequences of the invention that are capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein). Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as Synagis®.

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein, as well as two amino acid sequences of the invention directed against another antigenic determinant, epitope, part or domain on the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein may be directed against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein are directed against region aa 423-436 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein), as well as two further amino acid sequences of the invention that are capable of binding to two other antigenic determinants, epitopes, parts or domains on the RSV F protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the 101F binding site and the two other antigenic determinants, epitopes, parts or domains on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein may be directed against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein are directed against region aa 423-436 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein), as well as one further amino acid sequence of the invention that is capable of binding to another antigenic determinant, epitope, part or domain on the RSV F protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the 101F binding site and the other antigenic determinant, epitope, part or domain on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise three amino acid sequences of the invention directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein may be directed against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein are directed against region aa 423-436 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain three amino acid sequences of the invention that are capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein). Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the 101F binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as 101F.

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis for binding to the RSV F protein, as well as one amino acid sequence of the invention directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein may be directed against antigenic site II (also referred to as site A) of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein are directed against region aa 250-275 of the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein may be directed against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein are directed against region aa 423-436 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), as well as one further amino acid sequence of the invention that is capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein). Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the 101F binding site on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis for binding to the RSV F protein, as well as two amino acid sequences of the invention directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein may be directed against antigenic site II (also referred to as site A) of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein are directed against region aa 250-275 of the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein may be directed against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein are directed against region aa 423-436 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain one amino acid sequence of the invention that is capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), as well as two further amino acid sequences of the invention that are capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein). Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site and the 101F binding site on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis for binding to the RSV F protein, one amino acid sequence of the invention directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein may be directed against antigenic site II (also referred to as site A) of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the Synagis® binding site on the RSV F protein are directed against region aa 250-275 of the RSV F protein. The amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein may be directed against antigenic site IV-VI of the RSV F protein. In a preferred aspect, the amino acid sequences and polypeptides of the invention that are directed against the 101F binding site on the RSV F protein are directed against region aa 423-436 of the RSV F protein. Generally, such a trivalent polypeptide of the invention will contain one amino acid sequence of the invention that is capable of binding to the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein (and in particular against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein), one further amino acid sequence of the invention that is capable of binding to the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein), as well as one further amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the RSV F protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the Synagis® binding site, the 101F binding site and the other antigenic determinant, epitope, part or domain on the RSV F protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and are at least capable, upon binding to the RSV F protein, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as Synagis® and/or 101F.

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as two amino acid sequences of the invention directed against another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as two further amino acid sequences of the invention that are capable of binding to two other antigenic determinants, epitopes, parts or domains on the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the sialic acid binding site and the two other antigenic determinants, epitopes, parts or domains on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as one further amino acid sequence of the invention that is capable of binding to another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the sialic acid binding site and the other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise three amino acid sequences of the invention directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain three amino acid sequences of the invention that are capable of binding to the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the sialic acid binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as two amino acid sequences of the invention directed against another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as two further amino acid sequences of the invention that are capable of binding to two other antigenic determinants, epitopes, parts or domains on the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the VN04-2 binding site and the two other antigenic determinants, epitopes, parts or domains on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as one further amino acid sequence of the invention that is capable of binding to another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the VN04-2 binding site and the other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise three amino acid sequences of the invention directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain three amino acid sequences of the invention that are capable of binding to the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the VN04-2 binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and are at least capable, upon binding to the hemagglutinin H5 envelope protein of influenza virus, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as VN04-2.

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as two amino acid sequences of the invention directed against another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as two further amino acid sequences of the invention that are capable of binding to two other antigenic determinants, epitopes, parts or domains on the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb C179 binding site and the two other antigenic determinants, epitopes, parts or domains on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as well as one further amino acid sequence of the invention that is capable of binding to another antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb C179 binding site and the other antigenic determinant, epitope, part or domain on the hemagglutinin H5 envelope protein of influenza virus; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise three amino acid sequences of the invention directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such a trivalent polypeptide of the invention will contain three amino acid sequences of the invention that are capable of binding to the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb C179 binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and are at least capable, upon binding to the hemagglutinin H5 envelope protein of influenza virus, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as MAb C179.

In a preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise one amino acid sequence of the invention directed against the MAb 8-2 binding site on the G envelope protein of rabies and/or capable of competing with MAb 8-2 for binding to the G envelope protein, as well as two amino acid sequences of the invention directed against another antigenic determinant, epitope, part or domain on the G envelope protein. Generally, such a trivalent polypeptide of the invention will contain at least one amino acid sequence of the invention that is capable of binding to the MAb 8-2 binding site on the G envelope protein and/or capable of competing with MAb 8-2 for binding to the G envelope protein, as well as two further amino acid sequences of the invention that are capable of binding to two other antigenic determinants, epitopes, parts or domains on the G envelope protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb 8-2 binding site and the two other antigenic determinants, epitopes, parts or domains on the G envelope protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise two amino acid sequences of the invention directed against the MAb 8-2 binding site on the G envelope protein and/or capable of competing with MAb 8-2 for binding to the G envelope protein, as well as one amino acid sequence of the invention directed against another antigenic determinant, epitope, part or domain on the G envelope protein. Generally, such a trivalent polypeptide of the invention will contain two amino acid sequences of the invention that are capable of binding to the MAb 8-2 binding site on the G envelope protein and/or capable of competing with MAb 8-2 for binding to the G envelope protein, as well as one further amino acid sequence of the invention that is capable of binding to another antigenic determinant, epitope, part or domain on the G envelope protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb 8-2 binding site and the other antigenic determinant, epitope, part or domain on the G envelope protein; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and comprise three amino acid sequences of the invention directed against the MAb 8-2 binding site on the G envelope protein and/or capable of competing with MAb 8-2 for binding to the G envelope protein.

Generally, such a trivalent polypeptide of the invention will contain three amino acid sequences of the invention that are capable of binding to the MAb 8-2 binding site on the G envelope protein and/or capable of competing with MAb 8-2 for binding to the G envelope protein. Generally, such trivalent polypeptides of the invention may be as further described herein, and the various preferred aspects of the invention as described herein also apply to these trivalent polypeptides of the invention (for example, these trivalent polypeptides of the invention may comprise suitable linkers; are preferably such that they can simultaneously bind the MAb 8-2 binding site; and preferably comprise single variable domains and more preferably NANOBODIES® (V HH sequences)).

In another preferred, but non-limiting aspect, the amino acid sequences and (in particular) polypeptides of the invention are trivalent and are at least capable, upon binding to the G envelope protein of rabies, to neutralize a virus (as defined herein); to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein); to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell; and/or to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell via the same mechanism of action as MAb 8-2.

Preferred bivalent and trivalent constructs of the invention are given in Tables C-6, Table A-2, Table A-4, Table A-5 and Table A-6.

Preferably, such bi-, tri-, and multivalent, bi-, tri-, and multispecific, and/or bi-, tri-, and multiparatopic polypeptides, as discussed hereabove, will bind to an envelope protein of a virus with increased avidity compared to a single amino acid sequence of the invention.

More specifically, bi-, tri-, and multiparatopic polypeptides and/or bi-, tri-, and multispecific polypeptides according to the invention may be useful in targeting multiple viral receptor binding sites on the same and on different envelope proteins, respectively, which can result in an increased potency of viral neutralization (as defined herein) compared to a single amino acid sequence of the invention. Also, bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be useful in binding different genotypes, different subtypes and/or different strains of a certain virus. Also, bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be useful in preventing viral escape and/or viral evasion.

In a specific aspect of the invention, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H1N1. In another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may bind influenza subtype H5N1 as well as influenza subtype H3N2. In another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may bind influenza subtype H1N1 as well as influenza subtype H3N2. In another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may bind influenza subtype H5N1 as well as influenza subtype H2N2. In another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may bind influenza subtype H5N1, influenza subtype H1N1 as well as influenza subtype H2N2. Yet in another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1 as well as influenza subtype H3N2. Yet in another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H2N2 as well as influenza subtype H3N2. Yet in another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1, influenza subtype H2N2, as well as influenza subtype H3N2. In another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may bind rabies genotype 1 as well as genotype 5. In yet another aspect, the bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be directed against RSV and may bind different escape mutants of RSV (such as e.g. described in Lopez et al. 1998, J. Virol. 72: 6922-6928) and/or one or more escape mutants specific for antigen site II, specific for antigen site IV-VI or specific for the combination of both antigenic sites.

Finally, bi-, tri-, and multivalent, bi-, tri-, and multispecific and/or bi-, tri-, and multiparatopic polypeptides according to the invention may be useful in preventing and/or inhibiting viral infection and/or viral fusion of a virion with its target host cell (as defined herein) or may be useful in neutralizing a virus by inducing virion aggregation of said virus.

Generally, the amino acid sequences according to the present invention can be used to modulate, and in particular inhibit and/or prevent, the interaction between an envelope protein of a virus and a binding partner (e.g. viral receptor, target host cell, a particular cell membrane component or other binding partner, as applicable), and thus to modulate, and in particular inhibit, prevent or modulate viral-mediated biological pathway(s) in which an envelope protein of a virus and/or a viral receptor are involved. Thus, for example, when said envelope protein is part of a binding pair, the amino acid sequences and polypeptides may be such that they compete with the binding partner (e.g. viral receptor or other binding partner, as applicable) for binding to said envelope protein, and/or such that they (fully or partially) neutralize binding of the binding partner to the said envelope protein.

In this context, it is preferred that the amino acid sequences according to the invention can compete with a viral receptor of an envelope protein of a virus and/or with a target host cell for binding to said envelope protein.

When the amino acid sequences according to the invention compete with a target host cell for binding to said envelope protein, said amino acid sequences according to the invention may for example compete with particular cell membrane components of said target host cell, such as viral receptors, phospholipids, proteins, and/or glycoproteins, for binding to said envelope protein.

Viral receptors of enveloped proteins are known in the art and include but are not limited to the following examples: sialic acid, soluble (2,3) sialic acid, (2,6) sialic acid, CD4, CCR5, CXCR4, galactosylceramide, ACE2, HveA, CD155, ICAM-1, CAR, αv integrins, heparin sulphate proteoglycans, JAM-1, the Nicotinic Acetylcholine Receptor (AchR), the Neural Cell Adhesion Molecule (NCAM), and annexin II.

The amino acid sequences and polypeptides of the invention may compete with any of the foregoing viral receptors for binding to the envelope protein. Other examples of viral receptors will be clear to the skilled person; for instance, the amino acid sequences and polypeptides according to the invention may compete for binding to the envelope protein with any of the viral receptors that are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

The amino acid sequences according to the present invention can generally be used to modulate, and in particular inhibit and/or prevent, the interaction between an envelope protein of a virus and a viral receptor and/or the interaction between an envelope protein of a virus and a target host cell.

When the amino acid sequences according to the invention modulate, and in particular inhibit and/or prevent, the interaction between an envelope protein of a virus and a target host cell, said amino acid sequences according to the invention may for example modulate, and in particular inhibit and/or prevent, the interaction between an envelope protein of a virus and particular cell membrane components of said target host cell, such as viral receptors, phospholipids, proteins, and/or glycoproteins, for binding to said envelope protein.

In a preferred aspect, the amino acid sequences according to the present invention can generally be used to modulate, and in particular inhibit and/or prevent, the interaction between an envelope protein of a virus and a viral receptor. The amino acid sequences according to the present invention can generally be used to modulate, and in particular inhibit and/or prevent, the interaction between an envelope protein of a virus and a viral receptor wherein said interaction between an envelope protein and a viral receptor is chosen from the group consisting of the interaction of HA of influenza A virus with sialic acid; (2,3) sialic acid; and/or (2,6) sialic acid; the interaction of gp120 of HIV-1 virus with CD4; CCR5; CXCR4; and/or galactosylceramide; the interaction of S1 of SARS coronavirus with ACE2; the interaction of gD; gB; gC; the interaction of the heterodimer gH/gL of herpes simplex 1 virus and HveA; the interaction of VP1; VP2; VP3 of poliovirus 1 with CD155; the interaction of VP1; VP2; and/or VP3 of rhinovirus 3 with ICAM-1; the interaction of adenovirus 2 fibre with CAR; the interaction of adenovirus 2 penton base with αv integrins; sialic acid; (2,3) sialic acid; (2,6) sialic acid; and/or heparin sulphate proteoglycans; the interaction of σ1 of reovirus 1 with JAM-1; sialic acid; (2,3) sialic acid; and/or (2,6) sialic acid; and the interaction of G-protein of rabies virus with the Nicotinic Acetylcholine Receptor (AchR); and/or the Nueral Cell Adhesion Molecule (NCAM) (Thoulouze et al. 1998, J. Virol. 72: 7181-7190).

The amino acid sequences and polypeptides of the invention may generally be used to modulate, and in particular inhibit and/or prevent any of the foregoing interactions between an envelope protein of a virus and a viral receptor and/or between an envelope protein of a virus and particular cell membrane components of said target host cell, such as viral receptors, phospholipids, proteins, and/or glycoproteins.

Other examples of interactions between an envelope protein of a virus and a viral receptor will be clear to the skilled person; for instance, the amino acid sequences and polypeptides according to the invention may generally be used to modulate, and in particular inhibit and/or prevent any of the interactions between an envelope protein of a virus and a viral receptor that are disclosed in the handbook “Fields Virology”, 5 th edition (2007) by David M. Knipe, PhD; Peter M. Howley, MD; Diane E. Griffin, MD, PhD; Robert A. Lamb, PhD, ScD; Malcolm A. Martin, MD; Bernard Roizman, ScD; Stephen E. Straus, MD (ISBN-10: 0781760607; ISBN-13: 9780781760607).

In this context, the bi-, tri, and multiparatopic polypeptides according to the invention as described above, may compete with at least one, at least two or at least three (or even more) viral receptors of at least one or at least two (or even more) envelope proteins of a virus for binding to said envelope proteins.

Furthermore, the amino acid sequences and polypeptides according to the invention may also compete with at least one binding partner of an envelope protein of a virus (which is different from its natural viral receptor) for binding to said envelope protein. With at least one binding partner of an envelope protein is generally meant any molecule that is directed against and/or specifically binds to said envelope protein. For instance, a binding partner of an envelope protein can be an immunoglobulin, such as an antibody and can more specifically be a monoclonal antibody or any fragment thereof that can specifically bind said envelope protein. In this context, the amino acid sequences and polypeptides according to the invention may compete with a monoclonal antibody that is directed against and/or specifically binds to an envelope protein for binding to said envelope protein. For example, the amino acid sequences and polypeptides according to the invention may compete with the monoclonal antibody Synagis® (Zhao and Sullender J. Virol. 79: 396 (2005)) that is directed against and/or specifically binds to the A-antigenic site and/or amino acids 255 to 280 of the F-protein of RSV virus for binding to said F-protein of RSV virus; and/or the amino acid sequences and polypeptides according to the invention may compete with the monoclonal antibody 9C5 (Krivitskaia et al., Vopr. Virusol. 44: 279 (1999)) that is directed against and/or specifically binds to the F1a site and/or the region comprising amino acid 389 of the F-protein of RSV virus for binding to said F-protein of RSV virus; and/or the amino acid sequences and polypeptides according to the invention may compete with the Fab fragment 101F (Wu et al., J. Gen Virol. 88: 2719 (2007)) that is directed against and/or specifically binds to amino acids 422 to 438 of the F-protein of RSV virus for binding to said F-protein of RSV virus; and/or the amino acid sequences and polypeptides according to the invention may compete with the monoclonal antibody VN04-2 (Hanson et al. Respiratory Research 7: 126 (2006)) that is directed against and/or specifically binds to the sialic acid binding site of the hemagglutinin H5 envelope protein of influenza virus for binding to said hemagglutinin H5 envelope protein; and/or the amino acid sequences and polypeptides according to the invention may compete with the monoclonal antibody C179 (Okkuno et al. J. Virol. 67: 255202558 (1993)) that is directed against and/or specifically binds to the stem region of the hemagglutinin H5 envelope protein of influenza virus for binding to said hemagglutinin H5 envelope protein; and/or the amino acid sequences and polypeptides according to the invention may compete with the monoclonal antibody MAb 8-2 or mAb 8-2 a mouse IgG2alpha (Montaño-Hirose et al. Vaccine 11(12): 1259-1266 (1993)) that is directed against and/or specifically binds to the G envelope protein of rabies virus for binding to said G envelope protein.

In this context, the bi-, tri- and multiparatopic polypeptides according to the invention as described above, may compete with at least one, at least two, at least three (or even more) binding partners of at least one, at least two, at least three (or even more) envelope proteins of a virus for binding to said envelope proteins, wherein said binding partners may be any molecules that are directed against and/or specifically bind to said envelope proteins, such as for instance, an immunoglobulin, such as an antibody and more specifically a monoclonal antibody or any fragment thereof that can specifically bind to said envelope protein. For instance, said bi-, tri- or multiparatopic polypeptides according to the invention may compete with the monoclonal antibody Synagis® (as described above) and/or the monoclonal antibody 9C5 (as described above) and/or the Fab fragment 101F Fab or any suitable combination thereof, for binding to the F-protein of RSV virus. Said bi-, tri- or multiparatopic polypeptides according to the invention may compete with VN04-2 and/or MAb C179 for binding the hemagglutinin H5 envelope protein of influenza virus. Said bi-, tri- or multiparatopic polypeptides according to the invention may compete with MAb 8-2 for binding to the G envelope protein of rabies virus.

The present invention is in its broadest sense also not particularly limited to or defined by a specific antigenic determinant, epitope, part, domain, subunit or conformation (where applicable) of an envelope protein of a virus against which the amino acid sequences and polypeptides of the invention are directed. For example, the amino acid sequences and polypeptides may or may not be directed against an “interaction site” (as defined herein).

However, it is generally assumed and preferred that the amino acid sequences and polypeptides of the invention are preferably directed against an interaction site (as defined herein), and in particular against at least one epitope of an envelope protein of a virus, such that at least one viral-mediated biological pathway in which an envelope protein of a virus and/or a viral receptor are involved is inhibited, prevented and/or modulated.

In particular, it is assumed and preferred that the amino acid sequences, polypeptides and compositions of the present invention are directed against at least one epitope of an envelope protein of a virus, such that viral entry in a target host cell (such as for instance virion attachment to a target host cell and/or viral fusion with a target host cell) and/or viral replication in a target host cell (such as for instance viral transcription and/or viral translation and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane) is inhibited, prevented and/or modulated.

The amino acid sequences and polypeptides may be directed against at least one epitope of an envelope protein of a virus that is surface-exposed or that is located in a cavity or cleft formed by an envelope protein of a virus. The amino acid sequences and polypeptides of the invention may be directed against an interaction site (as defined herein), and in particular against an epitope that is located in a cavity or cleft formed by a trimer of fusion proteins (such as a fusion protein trimer that is a trimer of hairpins or a six-helix bundle) or a dimer of fusion proteins, wherein said fusion proteins can be in their pre-, intermediate, or post-fusion conformational state.

Furthermore, the amino acid sequences and polypeptides of the invention may also be directed against an epitope that is located in the stem region and/or in the neck region and/or in the globular head region of a fusion protein. Preferably, the amino acid sequences and polypeptides of the invention are directed against an epitope that is located in the stem region of a fusion protein, such as for instance against an epitope that is located in the region comprising one or more of the amino acids 318 to 322 of the HA1 subunit of influenza HA and/or the region comprising one or more of the amino acids 47 to 58 of the HA2 subunit of influenza HA; against an epitope that is located in the N-terminal region comprising one or more of the amino acids 1 to 38 of the HA2 subunit of influenza HA; against an epitope that is located in the region comprising one or more of the amino acids 38 to 112 of the HA2 subunit of influenza HA; against an epitope that is located in the region comprising one or more of the amino acids 125 to 175 of the HA2 subunit of influenza HA; or against an epitope that is located in the region comprising one or more of the amino acids 176 to 185 of the HA2 subunit of influenza HA. Alternatively, the amino acid sequences and polypeptides of the invention may be directed against an epitope that is located in the globular head of a fusion protein (wherein said globular head may for example comprise a β-barrel-type structure or an immunoglobulin-type β-sandwich domain and a β-sheet domain).

Also, in particular, the amino acid sequences and polypeptides of the invention may preferably be directed against an interaction site, which is chosen from the group consisting of the A-antigenic site and/or amino acids 255 to 280 of the F-protein of RSV virus, the F1a site and/or the region comprising amino acid 389 of the F-protein of RSV virus, amino acids 422 to 438 of the F-protein of RSV virus, sialic acid binding site of the H5 HA envelope protein of influenza virus, the Nicotinic Acetylcholine Receptor (AchR) and/or the Nueral Cell Adhesion Molecule (NCAM) binding site of the G-protein of rabies virus (Thoulouze et al. 1998, J. Virol. 72: 7181-7190).

In one aspect of the invention the amino acids and polypeptides of the invention are directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein. In particular, they may be directed against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein.

In another aspect of the invention the amino acids and polypeptides of the invention are directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein. In particular, they may be directed against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein.

In yet another aspect of the invention the amino acids and polypeptides of the invention are directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In yet another aspect of the invention the amino acids and polypeptides of the invention are directed against the MAb 179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb 179 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In yet another aspect of the invention the amino acids and polypeptides of the invention are directed against the MAb 8-2 binding site on G envelope protein of rabies virus and/or capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus.

The amino acid sequences and polypeptides of the invention may also be directed against any epitope that is located in the C-terminal region of a fusion protein and/or in the N-terminal domain of a fusion protein and/or in or comprising the fusion peptide of a fusion protein and/or in the transmembrane domain of a fusion protein and/or in a α-helical coiled-coil of a fusion protein and/or in a β-structure of a fusion protein and/or in Domain I of a fusion protein and/or in Domain II of a fusion protein, such as for example in the fusion peptide of Domain II of a fusion protein, and/or in Domain III of a fusion protein, such as for example in the stem region at the C-terminus of Domain III of a fusion protein or in the transmembrane anchor at the C-terminus of Domain III of a fusion protein.

Also, the amino acid sequences and polypeptides of the invention may be directed against any other epitope of an envelope protein of a virus (for instance any other epitope that is close to one of the aforementioned epitopes).

Thus, in one preferred, but non-limiting aspect, the amino acid sequences and polypeptides of the invention are generally directed against any epitope or in particular against one of the above-mentioned epitopes of an envelope protein of a virus, and are as further defined herein. For example, said epitope may be present on an envelope protein of a virus that is chosen from the group consisting of the F protein of RSV virus, the G protein of RSV virus, the SH protein of RSV virus, the M protein of RSV virus, the M2 protein of RSV virus, the HA protein of influenza A virus, the gp120 protein of HIV-1 virus, the S1 protein of SARS Corona virus, the gD protein of Herpes simplex 1 virus, the VP1 and/or VP2 and/or VP3 proteins of Poliovirus 1, the VP1 and/or VP2 and/or VP3 proteins of Rhinovirus 3, fibre and/or penton base of Adenovirus 2, σ1 of Reovirus 1, the HEF protein of influenza C virus, the 5 F protein of Simian parainfluenza virus, the F protein of Human parainfluenza virus, the F protein of Newcastle disease virus, the F2 protein of measles, the F2 protein of Sendai virus, the gp2 protein of Ebola virus, the TM protein of Moloney murine leukemia virus, the gp41 protein of Human immunodeficiency virus 1, the gp41 protein of Simian immunodeficiency virus, the gp21 protein of Human T cell leukemia virus 1, the TM protein of Human syncytin-2, the TM protein of Visna virus, the S2 protein of Mouse hepatitis virus, the E2 protein of SARS corona virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E protein of Yellow Fever virus, the E protein of West Nile virus, the E1 protein of Semliki forest virus, the E1 protein of Sindbis virus, the G protein of Rabies virus, the G protein of Vesicular stomatitis virus and the gB protein of Herpes simplex virus.

Accordingly, the amino acid sequences and polypeptides of the invention may be directed against any epitope that is present on an envelope protein of a virus, which is chosen from the group consisting of the F protein of RSV virus, the G protein of RSV virus, the SH protein of RSV virus, the M protein of RSV virus, the M2 protein of RSV virus, the HA protein of influenza A virus, the gp120 protein of HIV-1 virus, the S1 protein of SARS Corona virus, the gD protein of Herpes simplex 1 virus, the VP1 and/or VP2 and/or VP3 proteins of Poliovirus 1, the VP1 and/or VP2 and/or VP3 proteins of Rhinovirus 3, fibre and/or penton base of Adenovirus 2, al of Reovirus 1, the HEF protein of influenza C virus, the 5 F protein of Simian parainfluenza virus, the F protein of Human parainfluenza virus, the F protein of Newcastle disease virus, the F2 protein of measles, the F2 protein of Sendai virus, the gp2 protein of Ebola virus, the TM protein of Moloney murine leukemia virus, the gp41 protein of Human immunodeficiency virus 1, the gp41 protein of Simian immunodeficiency virus, the gp21 protein of Human T cell leukemia virus 1, the TM protein of Human syncytin-2, the TM protein of Visna virus, the S2 protein of Mouse hepatitis virus, the E2 protein of SARS corona virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E protein of Yellow Fever virus, the E protein of West Nile virus, the E1 protein of Semliki forest virus, the E1 protein of Sindbis virus, the G protein of Rabies virus, the G protein of Vesicular stomatitis virus and the gB protein of Herpes simplex virus.

It is also within the scope of the invention that, where applicable, an amino acid sequence of the invention can bind to two or more antigenic determinants, epitopes, parts, domains, subunits or conformations of said envelope protein of a virus. In such a case, the antigenic determinants, epitopes, parts, domains or subunits of said envelope protein of a virus to which the amino acid sequences and/or polypeptides of the invention bind may be essentially the same (for example, if said envelope protein of a virus contains repeated structural motifs or occurs in a multimeric form) or may be different (and in the latter case, the amino acid sequences and polypeptides of the invention may bind to such different antigenic determinants, epitopes, parts, domains, subunits of said envelope protein of a virus with an affinity and/or specificity which may be the same or different). Also, for example, when said envelope protein of a virus exists in an activated conformation and in an inactive conformation or a pre-fusion and post-fusion conformation or state, the amino acid sequences and polypeptides of the invention may bind to either one of these conformations or states, or may bind to both these conformations or states (i.e. with an affinity and/or specificity which may be the same or different).

It is also expected that the amino acid sequences and polypeptides of the invention will generally bind to all naturally occurring or synthetic analogs, variants, mutants, alleles, parts and fragments of said envelope protein of a virus; or at least to those analogs, variants, mutants, alleles, parts and fragments of said envelope protein of a virus that contain one or more antigenic determinants or epitopes that are essentially the same as the antigenic determinant(s) or epitope(s) to which the amino acid sequences and polypeptides of the invention bind to said envelope protein of a virus (e.g. in wild-type viral envelope proteins). Again, in such a case, the amino acid sequences and polypeptides of the invention may bind to such analogs, variants, mutants, alleles, parts and fragments with an affinity and/or specificity that are the same as, or that are different from (i.e. higher than or lower than), the affinity and specificity with which the amino acid sequences of the invention bind to (wild-type) said envelope protein of a virus. It is also included within the scope of the invention that the amino acid sequences and polypeptides of the invention bind to some analogs, variants, mutants, alleles, parts and fragments of said envelope protein of a virus, but not to others.

In a specific aspect of the invention, the amino acid sequences are multivalent (such as bivalent or trivalent) and show improved affinity and/or improved cross-reactivity for different genotypes, subtypes, viral escape mutants and/or strains of a certain virus compared to the monovalent amino acid sequence. In one aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H1N1. In another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H3N2. In another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H1N1 as well as influenza subtype H3N2. In another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H2N2. Yet in another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1 as well as influenza subtype H3N2. Yet in another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H2N2 as well as influenza subtype H3N2. Yet in another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1 as well as influenza subtype H2N2. Yet in another aspect, the amino acid sequences are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1, influenza subtype H2N2 as well as influenza subtype H3N2. In another aspect, the amino acid sequences are directed against rabies virus and may bind rabies genotype 1 as well as genotype 5. In yet another aspect, the amino acid sequences are directed against RSV and may bind different strains of RSV (such as e.g. Long, A-2 and/or B-1). In yet another aspect, the amino acid sequences are directed against RSV and may bind different escape mutants of RSV (such as e.g. described in Lopez et al. 1998 , J. Virol. 72: 6922-6928) and/or escape mutants specific for antigen site II, antigen site IV-VI or the combination of both antigenic sites.

When said envelope protein of a virus exists in a monomeric form and in one or more multimeric forms, it is within the scope of the invention that the amino acid sequences and polypeptides of the invention only bind to said envelope protein of a virus in monomeric form, only bind to said envelope protein of a virus in multimeric form, or bind to both the monomeric and the multimeric form. Again, in such a case, the amino acid sequences and polypeptides of the invention may bind to the monomeric form with an affinity and/or specificity that are the same as, or that are different from (i.e. higher than or lower than), the affinity and specificity with which the amino acid sequences of the invention bind to the multimeric form.

For example, when the envelope protein of a virus exists in a monomeric form and in a trimeric forms, it is within the scope of the invention that the amino acid sequences and polypeptides of the invention only bind to said envelope protein of a virus in monomeric form, only bind to said envelope protein of a virus in trimeric form, or bind to both the monomeric and the trimeric form. Again, in such a case, the amino acid sequences and polypeptides of the invention may bind to the monomeric form with an affinity and/or specificity that are the same as, or that are different from (i.e. higher than or lower than), the affinity and specificity with which the amino acid sequences of the invention bind to the trimeric form.

Also, when said envelope protein of a virus can associate with other proteins or polypeptides to form protein complexes (e.g. with multiple subunits), it is within the scope of the invention that the amino acid sequences and polypeptides of the invention bind to said envelope protein of a virus in its non-associated state, bind to said envelope protein of a virus in its associated state, or bind to both.

In all these cases, the amino acid sequences and polypeptides of the invention may bind to such multimers or associated protein complexes with an affinity and/or specificity that may be the same as or different from (i.e. higher than or lower than) the affinity and/or specificity with which the amino acid sequences and polypeptides of the invention bind to said envelope protein of a virus in its monomeric and non-associated state.

Also, as will be clear to the skilled person, proteins or polypeptides that contain two or more amino acid sequences directed against said envelope protein of a virus may bind with higher avidity to said envelope protein of a virus than the corresponding monomeric amino acid sequence(s). For example, and without limitation, proteins or polypeptides that contain two or more amino acid sequences directed against different epitopes of said envelope protein of a virus may (and usually will) bind with higher avidity than each of the different monomers, and proteins or polypeptides that contain two or more amino acid sequences directed against said envelope protein of a virus may (and usually will) bind also with higher avidity to a multimer (such as e.g. a trimer) of said envelope protein of a virus.

Generally, amino acid sequences and polypeptides of the invention will at least bind to those forms of said envelope protein of a virus (including monomeric, multimeric and associated forms) that are the most relevant from a biological and/or therapeutic point of view, as will be clear to the skilled person.

It is also within the scope of the invention to use parts, fragments, analogs, mutants, variants, alleles and/or derivatives of the amino acid sequences and polypeptides of the invention, and/or to use proteins or polypeptides comprising or essentially consisting of one or more of such parts, fragments, analogs, mutants, variants, alleles and/or derivatives, as long as these are suitable for the uses envisaged herein. Such parts, fragments, analogs, mutants, variants, alleles and/or derivatives will usually contain (at least part of) a functional antigen-binding site for binding against said envelope protein of a virus; and more preferably will be capable of specific binding to said envelope protein of a virus, and even more preferably capable of binding to said envelope protein of a virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein. Some non-limiting examples of such parts, fragments, analogs, mutants, variants, alleles, derivatives, proteins and/or polypeptides will become clear from the further description herein. Additional fragments or polypeptides of the invention may also be provided by suitably combining (i.e. by linking or genetic fusion) one or more (smaller) parts or fragments as described herein.

In one specific, but non-limiting aspect of the invention, which will be further described herein, such analogs, mutants, variants, alleles, derivatives have an increased half-life in serum (as further described herein) compared to the amino acid sequence from which they have been derived. For example, an amino acid sequence of the invention may be linked (chemically or otherwise) to one or more groups or moieties that extend the half-life (such as PEG), so as to provide a derivative of an amino acid sequence of the invention with increased half-life.

In one specific, but non-limiting aspect, the amino acid sequence of the invention may be an amino acid sequence that comprises an immunoglobulin fold or may be an amino acid sequence that, under suitable conditions (such as physiological conditions) is capable of forming an immunoglobulin fold (i.e. by folding). Reference is inter alia made to the review by Halaby et al. (1999, Protein Eng. 12: 563-71). Preferably, when properly folded so as to form an immunoglobulin fold, such an amino acid sequence is capable of specific binding (as defined herein) to said envelope protein of a virus; and more preferably capable of binding to said envelope protein of a virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein. Also, parts, fragments, analogs, mutants, variants, alleles and/or derivatives of such amino acid sequences are preferably such that they comprise an immunoglobulin fold or are capable for forming, under suitable conditions, an immunoglobulin fold.

In particular, but without limitation, the amino acid sequences of the invention may be amino acid sequences that essentially consist of 4 framework regions (FR1 to FR4 respectively) and 3 complementarity determining regions (CDR1 to CDR3 respectively); or any suitable fragment of such an amino acid sequence (which will then usually contain at least some of the amino acid residues that form at least one of the CDR's, as further described herein).

The amino acid sequences of the invention may in particular be an immunoglobulin sequence or a suitable fragment thereof, and more in particular be an immunoglobulin variable domain sequence or a suitable fragment thereof, such as light chain variable domain sequence (e.g. a V L -sequence) or a suitable fragment thereof; or a heavy chain variable domain sequence (e.g. a V H -sequence) or a suitable fragment thereof. When the amino acid sequence of the invention is a heavy chain variable domain sequence, it may be a heavy chain variable domain sequence that is derived from a conventional four-chain antibody (such as, without limitation, a V H sequence that is derived from a human antibody) or be a so-called V HH -sequence (as defined herein) that is derived from a so-called “heavy chain antibody” (as defined herein).

However, it should be noted that the invention is not limited as to the origin of the amino acid sequence of the invention (or of the nucleotide sequence of the invention used to express it), nor as to the way that the amino acid sequence or nucleotide sequence of the invention is (or has been) generated or obtained. Thus, the amino acid sequences of the invention may be naturally occurring amino acid sequences (from any suitable species) or synthetic or semi-synthetic amino acid sequences. In a specific but non-limiting aspect of the invention, the amino acid sequence is a naturally occurring immunoglobulin sequence (from any suitable species) or a synthetic or semi-synthetic immunoglobulin sequence, including but not limited to “humanized” (as defined herein) immunoglobulin sequences (such as partially or fully humanized mouse or rabbit immunoglobulin sequences, and in particular partially or fully humanized V HH sequences or NANOBODIES® (V HH sequences)), “camelized” (as defined herein) immunoglobulin sequences, as well as immunoglobulin sequences that have been obtained by techniques such as affinity maturation (for example, starting from synthetic, random or naturally occurring immunoglobulin sequences), CDR grafting, veneering, combining fragments derived from different immunoglobulin sequences, PCR assembly using overlapping primers, and similar techniques for engineering immunoglobulin sequences well known to the skilled person; or any suitable combination of any of the foregoing. Reference is for example made to the standard handbooks, as well as to the further description and prior art mentioned herein.

Similarly, the nucleotide sequences of the invention may be naturally occurring nucleotide sequences or synthetic or semi-synthetic sequences, and may for example be sequences that are isolated by PCR from a suitable naturally occurring template (e.g. DNA or RNA isolated from a cell), nucleotide sequences that have been isolated from a library (and in particular, an expression library), nucleotide sequences that have been prepared by introducing mutations into a naturally occurring nucleotide sequence (using any suitable technique known per se, such as mismatch PCR), nucleotide sequence that have been prepared by PCR using overlapping primers, or nucleotide sequences that have been prepared using techniques for DNA synthesis known per se.

The amino acid sequence of the invention may in particular be a domain antibody (or an amino acid sequence that is suitable for use as a domain antibody), a single domain antibody (or an amino acid sequence that is suitable for use as a single domain antibody), a “dAb” (or an amino acid sequence that is suitable for use as a dAb) or a NANOBODY® (V HH sequence) (as defined herein, and including but not limited to a V HH sequence); other single variable domains, or any suitable fragment of any one thereof. For a general description of (single) domain antibodies, reference is also made to the prior art cited above, as well as to EP 0 368 684. For the term “dAb's”, reference is for example made to Ward et al. (Nature 1989 Oct. 12; 341 (6242): 544-6), to Holt et al., Trends Biotechnol., 2003, 21(11):484-490; as well as to for example WO 06/030220, WO 06/003388 and other published patent applications of Domantis Ltd. It should also be noted that, although less preferred in the context of the present invention because they are not of mammalian origin, single domain antibodies or single variable domains can be derived from certain species of shark (for example, the so-called “IgNAR domains”, see for example WO 05/18629).

In particular, the amino acid sequence of the invention may be a NANOBODY® (V HH sequence) (as defined herein) or a suitable fragment thereof. [Note: NANOBODY® (V HH sequence), NANOBODIES® (V HH sequences) and NANOCLONE® are registered trademarks of Ablynx N. V.] Such NANOBODIES® (VHH sequences) directed against an envelope protein of a virus will also be referred to herein as “NANOBODIES® (V HH sequences) of the invention”.

For a general description of NANOBODIES® (VHH sequences), reference is made to the further description below, as well as to the prior art cited herein. In this respect, it should however be noted that this description and the prior art mainly described NANOBODIES® (VHH sequences) of the so-called “V H 3 class” (i.e. NANOBODIES® (VHH sequences) with a high degree of sequence homology to human germline sequences of the V H 3 class such as DP-47, DP-51 or DP-29), which NANOBODIES® (VHH sequences) form a preferred aspect of this invention. It should however be noted that the invention in its broadest sense generally covers any type of NANOBODY® (VHH sequence) directed against an envelope protein of a virus, and for example also covers the NANOBODIES® (VHH sequences) belonging to the so-called “V H 4 class” (i.e. NANOBODIES® (VHH sequences) with a high degree of sequence homology to human germline sequences of the V H 4 class such as DP-78), as for example described in WO 07/118670.

Generally, NANOBODIES® (VHH sequences) (in particular V HH sequences and partially humanized NANOBODIES® (VHH sequences)) can in particular be characterized by the presence of one or more “Hallmark residues” (as described herein) in one or more of the framework sequences (again as further described herein).

Thus, generally, a NANOBODY® (V HH sequence) can be defined as an amino acid sequence with the (general) structure

FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4

in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDR1 to CDR3 refer to the complementarity determining regions 1 to 3, respectively, and in which one or more of the Hallmark residues are as further defined herein.

In particular, a NANOBODY® (V HH sequence) can be an amino acid sequence with the (general) structure

FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4

in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDR1 to CDR3 refer to the complementarity determining regions 1 to 3, respectively, and in which the framework sequences are as further defined herein.

More in particular, a NANOBODY® (V HH sequence) can be an amino acid sequence with the (general) structure

FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4

in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDR1 to CDR3 refer to the complementarity determining regions 1 to 3, respectively, and in which:

i) preferably one or more of the amino acid residues at positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table B-2 below;

and in which:

ii) said amino acid sequence has at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1 to 22, in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences (indicated with X in the sequences of SEQ ID NO's: 1 to 22) are disregarded.

In these NANOBODIES® (VHH sequences), the CDR sequences are generally as further defined herein.

Thus, the invention also relates to such NANOBODIES® (VHH sequences) that can bind to (as defined herein) and/or are directed against an envelope protein of a virus, to suitable fragments thereof, as well as to polypeptides that comprise or essentially consist of one or more of such NANOBODIES® (VHH sequences) and/or suitable fragments.

SEQ ID NO's 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1) give the amino acid sequences of a number of V HH sequences that have been raised against an envelope protein of a virus.

In the above Table A-1, SEQ ID NO's: 126 to 157, 2431 to 2447, 2682 to 2683 and 3064 to 3128 refer to amino acid sequences of the invention that are directed to and/or specifically bind to hemagglutinin H5 of influenza; SEQ ID NO's: 158 to 236, 248 to 407, 2448 and 2574 to 2581 refer to amino acid sequences of the invention that are directed to and/or specifically bind to the F protein of hRSV; and SEQ ID NO's: 237 to 247 and 2684 to 2717 refer to amino acid sequences of the invention that are directed to and/or specifically bind to the G protein of rabies virus.

In particular, the invention in some specific aspects provides:

amino acid sequences that are directed against (as defined herein) an envelope protein of a virus and that have at least 80%, preferably at least 85%, such as 90% or 95% or more sequence identity with at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1); these amino acid sequences may further be such that they neutralize binding of the binding partner (such as the viral receptor) to an envelope protein of a virus; and/or compete with the binding partner (such as the viral receptor) for binding to an envelope protein of a virus; and/or are directed against an interaction site (as defined herein) on an envelope protein of a virus (such as the viral receptor binding site); amino acid sequences that cross-block (as defined herein) the binding of at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1) to an envelope protein of a virus and/or that compete with at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1) for binding to an envelope protein of a virus. Again, these amino acid sequences may further be such that they neutralize binding of the binding partner (such as the viral receptor) to an envelope protein of a virus; and/or compete with the binding partner (such as the viral receptor) for binding to an envelope protein of a virus; and/or are directed against an interaction site (as defined herein) on an envelope protein of a virus (such as the viral receptor binding site);

which amino acid sequences may be as further described herein (and may for example be NANOBODIES® (VHH sequences)); as well as polypeptides of the invention that comprise one or more of such amino acid sequences (which may be as further described herein, and may for example be bispecific and/or biparatopic polypeptides as described herein), and nucleic acid sequences that encode such amino acid sequences and polypeptides. Such amino acid sequences and polypeptides do not include any naturally occurring ligands.

Accordingly, some particularly preferred NANOBODIES® (VHH sequences) of the invention are NANOBODIES® (VHH sequences) which can bind (as further defined herein) to and/or are directed against an envelope protein of a virus and which:

i) have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1), in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences are disregarded. In this respect, reference is also made to Table B-1, which lists the framework 1 sequences (SEQ ID NO's: 408 to 689, 2449 to 2466, 2582 to 2589, 2718 to 2753 and 3129 to 3193), framework 2 sequences (SEQ ID NO's: 972 to 1253, 2485 to 2502, 2598 to 2605, 2790 to 2825 and 3259 to 3323), framework 3 sequences (SEQ ID NO's: 1536 to 1817, 2521 to 2538, 2614 to 2621, 2862 to 2897 and 3389 to 3453) and framework 4 sequences (SEQ ID NO's: 2100 to 2381, 2557 to 2573, 2630 to 2637, 2934 to 2969 and 3519 to 3583) of the NANOBODIES® (V HH sequences) of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1) (with respect to the amino acid residues at positions 1 to 4 and 27 to 30 of the framework 1 sequences, reference is also made to the comments made below. Thus, for determining the degree of amino acid identity, these residues are preferably disregarded);

and in which:

ii) preferably one or more of the amino acid residues at positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table B-2 below.

In these NANOBODIES® (VHH sequences), the CDR sequences are generally as further defined herein.

Again, such NANOBODIES® (VHH sequences) may be derived in any suitable manner and from any suitable source, and may for example be naturally occurring V HH sequences (i.e. from a suitable species of Camelid) or synthetic or semi-synthetic amino acid sequences, including but not limited to “humanized” (as defined herein) NANOBODIES® (VHH sequences), “camelized” (as defined herein) immunoglobulin sequences (and in particular camelized heavy chain variable domain sequences), as well as NANOBODIES® (VHH sequences) that have been obtained by techniques such as affinity maturation (for example, starting from synthetic, random or naturally occurring immunoglobulin sequences), CDR grafting, veneering, combining fragments derived from different immunoglobulin sequences, PCR assembly using overlapping primers, and similar techniques for engineering immunoglobulin sequences well known to the skilled person; or any suitable combination of any of the foregoing as further described herein. Also, when a NANOBODY® (V HH sequence) comprises a V HH sequence, said NANOBODY® (V HH sequence) may be suitably humanized, as further described herein, so as to provide one or more further (partially or fully) humanized NANOBODIES® (VHH sequences) of the invention. Similarly, when a NANOBODY® (V HH sequence) comprises a synthetic or semi-synthetic sequence (such as a partially humanized sequence), said NANOBODY® (V HH sequence) may optionally be further suitably humanized, again as described herein, again so as to provide one or more further (partially or fully) humanized NANOBODIES® (VHH sequences) of the invention.

In particular, humanized NANOBODIES® (VHH sequences) may be amino acid sequences that are as generally defined for NANOBODIES® (VHH sequences) in the previous paragraphs, but in which at least one amino acid residue is present (and in particular, in at least one of the framework residues) that is and/or that corresponds to a humanizing substitution (as defined herein). Some preferred, but non-limiting humanizing substitutions (and suitable combinations thereof) will become clear to the skilled person based on the disclosure herein. In addition, or alternatively, other potentially useful humanizing substitutions can be ascertained by comparing the sequence of the framework regions of a naturally occurring V HH sequence with the corresponding framework sequence of one or more closely related human V H sequences, after which one or more of the potentially useful humanizing substitutions (or combinations thereof) thus determined can be introduced into said V HH sequence (in any manner known per se, as further described herein) and the resulting humanized V HH sequences can be tested for affinity for the target, for stability, for ease and level of expression, and/or for other desired properties. In this way, by means of a limited degree of trial and error, other suitable humanizing substitutions (or suitable combinations thereof) can be determined by the skilled person based on the disclosure herein. Also, based on the foregoing, (the framework regions of) a NANOBODY® (V HH sequence) may be partially humanized or fully humanized.

Some particularly preferred humanized NANOBODIES® (VHH sequences) of the invention are humanized variants of the NANOBODIES® (VHH sequences) of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1), of which the amino acid sequences of SEQ ID NO's: 2999 to 3015 (see Table A-8) are some especially preferred examples.

Thus, some other preferred NANOBODIES® (VHH sequences) of the invention are NANOBODIES (V HH sequences) which can bind (as further defined herein) to an envelope protein of a virus and which:

i) are a humanized variant of one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1); and/or ii) have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1) and/or at least one of the amino acid sequences of SEQ ID NO's: 2999 to 3015 (see Table A-8), in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences are disregarded;

and in which:

iii) preferably one or more of the amino acid residues at positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table B-2 below.

According to another specific aspect of the invention, the invention provides a number of stretches of amino acid residues (i.e. small peptides) that are particularly suited for binding to an envelope protein of a virus. These stretches of amino acid residues may be present in, and/or may be corporated into, an amino acid sequence of the invention, in particular in such a way that they form (part of) the antigen binding site of an amino acid sequence of the invention. As these stretches of amino acid residues were first generated as CDR sequences of heavy chain antibodies or V HH sequences that were raised against an envelope protein of a virus (or may be based on and/or derived from such CDR sequences, as further described herein), they will also generally be referred to herein as “CDR sequences” (i.e. as CDR1 sequences, CDR2 sequences and CDR3 sequences, respectively). It should however be noted that the invention in its broadest sense is not limited to a specific structural role or function that these stretches of amino acid residues may have in an amino acid sequence of the invention, as long as these stretches of amino acid residues allow the amino acid sequence of the invention to bind to an envelope protein of a virus. Thus, generally, the invention in its broadest sense comprises any amino acid sequence that is capable of binding to an envelope protein of a virus and that comprises one or more CDR sequences as described herein, and in particular a suitable combination of two or more such CDR sequences, that are suitably linked to each other via one or more further amino acid sequences, such that the entire amino acid sequence forms a binding domain and/or binding unit that is capable of binding to an envelope protein of a virus. It should however also be noted that the presence of only one such CDR sequence in an amino acid sequence of the invention may by itself already be sufficient to provide an amino acid sequence of the invention that is capable of binding to an envelope protein of a virus; reference is for example again made to the so-called “Expedite fragments” described in WO 03/050531.

Thus, in another specific, but non-limiting aspect, the amino acid sequence of the invention may be an amino acid sequence that comprises at least one amino acid sequence that is chosen from the group consisting of the CDR1 sequences, CDR2 sequences and CDR3 sequences that are described herein (or any suitable combination thereof). In particular, an amino acid sequence of the invention may be an amino acid sequence that comprises at least one antigen binding site, wherein said antigen binding site comprises at least one amino acid sequence that is chosen from the group consisting of the CDR1 sequences, CDR2 sequences and CDR3 sequences that are described herein (or any suitable combination thereof).

Generally, in this aspect of the invention, the amino acid sequence of the invention may be any amino acid sequence that comprises at least one stretch of amino acid residues, in which said stretch of amino acid residues has an amino acid sequence that corresponds to the sequence of at least one of the CDR sequences described herein. Such an amino acid sequence may or may not comprise an immunoglobulin fold. For example, and without limitation, such an amino acid sequence may be a suitable fragment of an immunoglobulin sequence that comprises at least one such CDR sequence, but that is not large enough to form a (complete) immunoglobulin fold (reference is for example again made to the “Expedite fragments” described in WO 03/050531). Alternatively, such an amino acid sequence may be a suitable “protein scaffold” that comprises least one stretch of amino acid residues that corresponds to such a CDR sequence (i.e. as part of its antigen binding site). Suitable scaffolds for presenting amino acid sequences will be clear to the skilled person, and for example comprise, without limitation, to binding scaffolds based on or derived from immunoglobulins (i.e. other than the immunoglobulin sequences already described herein), protein scaffolds derived from protein A domains (such as Affibodies™), tendamistat, fibronectin, lipocalin, CTLA-4, T-cell receptors, designed ankyrin repeats, avimers and PDZ domains (Binz et al., Nat. Biotech 2005, Vol 23:1257), and binding moieties based on DNA or RNA including but not limited to DNA or RNA aptamers (Ulrich et al., Comb. Chem. High Throughput Screen 2006 9(8): 619-32).

Again, any amino acid sequence of the invention that comprises one or more of these CDR sequences is preferably such that it can specifically bind (as defined herein) to an envelope protein of a virus, and more in particular such that it can bind to an envelope protein of a virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein), that is as defined herein.

More in particular, the amino acid sequences according to this aspect of the invention may be any amino acid sequence that comprises at least one antigen binding site, wherein said antigen binding site comprises at least two amino acid sequences that are chosen from the group consisting of the CDR1 sequences described herein, the CDR2 sequences described herein and the CDR3 sequences described herein, such that (i) when the first amino acid sequence is chosen from the CDR1 sequences described herein, the second amino acid sequence is chosen from the CDR2 sequences described herein or the CDR3 sequences described herein; (ii) when the first amino acid sequence is chosen from the CDR2 sequences described herein, the second amino acid sequence is chosen from the CDR1 sequences described herein or the CDR3 sequences described herein; or (iii) when the first amino acid sequence is chosen from the CDR3 sequences described herein, the second amino acid sequence is chosen from the CDR1 sequences described herein or the CDR3 sequences described herein.

Even more in particular, the amino acid sequences of the invention may be amino acid sequences that comprise at least one antigen binding site, wherein said antigen binding site comprises at least three amino acid sequences that are chosen from the group consisting of the CDR1 sequences described herein, the CDR2 sequences described herein and the CDR3 sequences described herein, such that the first amino acid sequence is chosen from the CDR1 sequences described herein, the second amino acid sequence is chosen from the CDR2 sequences described herein, and the third amino acid sequence is chosen from the CDR3 sequences described herein. Preferred combinations of CDR1, CDR2 and CDR3 sequences will become clear from the further description herein. As will be clear to the skilled person, such an amino acid sequence is preferably an immunoglobulin sequence (as further described herein), but it may for example also be any other amino acid sequence that comprises a suitable scaffold for presenting said CDR sequences.

Thus, in one specific, but non-limiting aspect, the invention relates to an amino acid sequence directed against an envelope protein of a virus, that comprises one or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; d) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; g) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518;

or any suitable combination thereof.

When an amino acid sequence of the invention contains one or more amino acid sequences according to b) and/or c):

i) any amino acid substitution in such an amino acid sequence according to b) and/or c) is preferably, and compared to the corresponding amino acid sequence according to a), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to b) and/or c) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to a);

and/or

iii) the amino acid sequence according to b) and/or c) may be an amino acid sequence that is derived from an amino acid sequence according to a) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to e) and/or f):

i) any amino acid substitution in such an amino acid sequence according to e) and/or f) is preferably, and compared to the corresponding amino acid sequence according to d), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to e) and/or f) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to d);

and/or

iii) the amino acid sequence according to e) and/or f) may be an amino acid sequence that is derived from an amino acid sequence according to d) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Also, similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to h) and/or i):

i) any amino acid substitution in such an amino acid sequence according to h) and/or i) is preferably, and compared to the corresponding amino acid sequence according to g), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to h) and/or i) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to g);

and/or

iii) the amino acid sequence according to h) and/or i) may be an amino acid sequence that is derived from an amino acid sequence according to g) by means of affinity maturation using one or more techniques of affinity maturation known per se.

It should be understood that the last preceding paragraphs also generally apply to any amino acid sequences of the invention that comprise one or more amino acid sequences according to b), c), e), f), h) or i), respectively.

In this specific aspect, the amino acid sequence preferably comprises one or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; ii) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; and iii) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518;

or any suitable combination thereof.

Also, preferably, in such an amino acid sequence, at least one of said stretches of amino acid residues forms part of the antigen binding site for binding against an envelope protein of a virus.

In a more specific, but again non-limiting aspect, the invention relates to an amino acid sequence directed against an envelope protein of a virus, that comprises two or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; d) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; g) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518;

such that (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b) or c), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e), f), g), h) or i); (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e) or f), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), g), h) or i); or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to g), h) or i), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), d), e) or f).

In this specific aspect, the amino acid sequence preferably comprises two or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; ii) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; and iii) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518;

such that, (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388, or of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258 or of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258 or of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388.

Also, in such an amino acid sequence, the at least two stretches of amino acid residues again preferably form part of the antigen binding site for binding to an envelope protein of a virus.

In an even more specific, but non-limiting aspect, the invention relates to an amino acid sequence directed against an envelope protein of a virus, that comprises three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258;

the second stretch of amino acid residues is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388;

and the third stretch of amino acid residues is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518.

Preferably, in this specific aspect, the first stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; the second stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; and the third stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518.

Again, preferably, in such an amino acid sequence, the at least three stretches of amino acid residues forms part of the antigen binding site for binding to an envelope protein of a virus.

Preferred combinations of such stretches of amino acid sequences will become clear from the further disclosure herein.

Preferably, in such amino acid sequences the CDR sequences have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1). This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (see Table A-1), in which the amino acid residues that form the framework regions are disregarded. Also, such amino acid sequences of the invention can be as further described herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to an envelope protein of a virus; and more in particular bind to an envelope protein of a virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

When the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258;

and/or

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388;

and/or

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518.

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; and/or CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; and/or CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518.

In particular, when the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258;

and

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388;

and

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518; or any suitable fragment of such an amino acid sequence

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 690 to 971, 2467 to 2484, 2590 to 2597, 2754 to 2789 and 3194 to 3258; and CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1254 to 1535, 2503 to 2520, 2606 to 2613, 2826 to 2861 and 3324 to 3388; and CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1818 to 2099, 2539 to 2556, 2622 to 2629, 2898 to 2933 and 3454 to 3518.

Again, preferred combinations of CDR sequences will become clear from the further description herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to an envelope protein of a virus; and more in particular bind to an envelope protein of a virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

In one preferred, but non-limiting aspect, the invention relates to an amino acid sequence that essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which the CDR sequences of said amino acid sequence have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128. This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128, in which the amino acid residues that form the framework regions are disregarded. Such amino acid sequences of the invention can be as further described herein.

In a more specific, but again non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the F-protein of human RSV virus, that comprises one or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; d) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; g) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629;

or any suitable combination thereof.

When an amino acid sequence of the invention contains one or more amino acid sequences according to b) and/or c):

i) any amino acid substitution in such an amino acid sequence according to b) and/or c) is preferably, and compared to the corresponding amino acid sequence according to a), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to b) and/or c) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to a);

and/or

iii) the amino acid sequence according to b) and/or c) may be an amino acid sequence that is derived from an amino acid sequence according to a) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to e) and/or f):

i) any amino acid substitution in such an amino acid sequence according to e) and/or f) is preferably, and compared to the corresponding amino acid sequence according to d), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to e) and/or f) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to d);

and/or

iii) the amino acid sequence according to e) and/or f) may be an amino acid sequence that is derived from an amino acid sequence according to d) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Also, similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to h) and/or i):

i) any amino acid substitution in such an amino acid sequence according to h) and/or i) is preferably, and compared to the corresponding amino acid sequence according to g), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to h) and/or i) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to g);

and/or

iii) the amino acid sequence according to h) and/or i) may be an amino acid sequence that is derived from an amino acid sequence according to g) by means of affinity maturation using one or more techniques of affinity maturation known per se.

It should be understood that the last preceding paragraphs also generally apply to any amino acid sequences of the invention that comprise one or more amino acid sequences according to b), c), e), f), h) or i), respectively.

In this specific aspect, the amino acid sequence preferably comprises one or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; ii) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; and iii) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629;

or any suitable combination thereof.

Also, preferably, in such an amino acid sequence, at least one of said stretches of amino acid residues forms part of the antigen binding site for binding the F-protein of human RSV virus.

In a more specific, but again non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the F-protein of human RSV virus, that comprises two or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971. 2484 and 2590 to 2597; d) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; g) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629;

such that (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b) or c), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e), f), g), h) or i); (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e) or f), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), g), h) or i); or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to g), h) or i), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), d), e) or f).

In this specific aspect, the amino acid sequence preferably comprises two or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; ii) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; and iii) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629;

such that, (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613 or of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597 or of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556, and 2622 to 2629, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484, and 2590 to 2597 or of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613.

Also, in such an amino acid sequence, the at least two stretches of amino acid residues again preferably form part of the antigen binding site for binding to the F-protein of human RSV virus.

In an even more specific, but non-limiting aspect, the invention relates to an amino acid sequence directed against the F-protein of human RSV virus, that comprises three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597

the second stretch of amino acid residues is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613;

and the third stretch of amino acid residues is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629.

Preferably, in this specific aspect, the first stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; the second stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; and the third stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629.

Again, preferably, in such an amino acid sequence, the at least three stretches of amino acid residues form part of the antigen binding site for binding to the F-protein of human RSV virus.

Preferred combinations of such stretches of amino acid sequences will become clear from the further disclosure herein.

Preferably, in such amino acid sequences the CDR sequences have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 158 to 236, 248 to 407, 2448 and 2574 to 2581 (see Table A-1). This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 158 to 236, 248 to 407, 2448, and 2574 to 2581 (see Table A-1), in which the amino acid residues that form the framework regions are disregarded. Also, such amino acid sequences of the invention can be as further described herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to the F-protein of human RSV virus; and more in particular bind to the F-protein of human RSV virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

When the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597;

and/or

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613;

and/or

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629.

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; and/or CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; and/or CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629.

In particular, when the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597;

and

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613;

and

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629; or any suitable fragment of such an amino acid sequence

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 722 to 800, 812 to 971, 2484 and 2590 to 2597; and CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1286 to 1364, 1376 to 1535, 2520 and 2606 to 2613; and CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1850 to 1928, 1940 to 2099, 2556 and 2622 to 2629.

Again, preferred combinations of CDR sequences will become clear from the further description herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to at least one epitope of the F-protein of human RSV virus; and more in particular bind to the F-protein of human RSV virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

In one preferred, but non-limiting aspect, the invention relates to an amino acid sequence that essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which the CDR sequences of said amino acid sequence have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 158 to 236, 248 to 407, 2448 and 2574 to 2581. This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 158 to 236, 248 to 407, 2448 and 2574 to 2581, in which the amino acid residues that form the framework regions are disregarded. Such amino acid sequences of the invention can be as further described herein.

In another specific, but again non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the hemagglutinin of influenza virus.

In particular, the invention relates to an amino acid sequence directed against the hemagglutinin H5 protein of influenza virus that comprises one or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; d) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; g) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518;

or any suitable combination thereof.

When an amino acid sequence of the invention contains one or more amino acid sequences according to b) and/or c):

i) any amino acid substitution in such an amino acid sequence according to b) and/or c) is preferably, and compared to the corresponding amino acid sequence according to a), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to b) and/or c) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to a);

and/or

iii) the amino acid sequence according to b) and/or c) may be an amino acid sequence that is derived from an amino acid sequence according to a) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to e) and/or f):

i) any amino acid substitution in such an amino acid sequence according to e) and/or f) is preferably, and compared to the corresponding amino acid sequence according to d), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to e) and/or f) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to d);

and/or

iii) the amino acid sequence according to e) and/or f) may be an amino acid sequence that is derived from an amino acid sequence according to d) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Also, similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to h) and/or i):

i) any amino acid substitution in such an amino acid sequence according to h) and/or i) is preferably, and compared to the corresponding amino acid sequence according to g), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to h) and/or i) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to g);

and/or

iii) the amino acid sequence according to h) and/or i) may be an amino acid sequence that is derived from an amino acid sequence according to g) by means of affinity maturation using one or more techniques of affinity maturation known per se.

It should be understood that the last preceding paragraphs also generally apply to any amino acid sequences of the invention that comprise one or more amino acid sequences according to b), c), e), f), h) or i), respectively.

In this specific aspect, the amino acid sequence preferably comprises one or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; ii) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; and iii) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518;

or any suitable combination thereof.

Also, preferably, in such an amino acid sequence, at least one of said stretches of amino acid residues forms part of the antigen binding site for binding the hemagglutinin H5 protein of influenza virus.

In a more specific, but again non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the hemagglutinin H5 protein of influenza virus, that comprises two or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; d) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; g) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518;

such that (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b) or c), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e), f), g), h) or i); (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e) or f), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), g), h) or i); or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to g), h) or i), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), d), e) or f).

In this specific aspect, the amino acid sequence preferably comprises two or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258 ii) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; and iii) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518;

such that, (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388 or of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258 or of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258 or of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388.

Also, in such an amino acid sequence, the at least two stretches of amino acid residues again preferably form part of the antigen binding site for binding to the hemagglutinin H5 protein of influenza virus.

In an even more specific, but non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the hemagglutinin H5 protein of influenza virus, that comprises three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258;

the second stretch of amino acid residues is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388;

and the third stretch of amino acid residues is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518.

Preferably, in this specific aspect, the first stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 690 to 721 and 2467 to 2483; the second stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; and the third stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518.

Again, preferably, in such an amino acid sequence, the at least three stretches of amino acid residues forms part of the antigen binding site for binding to the hemagglutinin H5 protein of influenza virus.

Preferred combinations of such stretches of amino acid sequences will become clear from the further disclosure herein.

Preferably, in such amino acid sequences the CDR sequences have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 126 to 157, 2431 to 2447, 2682 to 2683 and 3064 to 3128 (see Table A-1). This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 126 to 157, 2431 to 2447, 2682 to 2683 and 3064 to 3128 (see Table A-1), in which the amino acid residues that form the framework regions are disregarded. Also, such amino acid sequences of the invention can be as further described herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to the hemagglutinin H5 protein of influenza virus; and more in particular bind to the hemagglutinin H5 protein of influenza virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

When the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258;

and/or

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388;

and/or

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518.

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; and/or CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; and/or CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518.

In particular, when the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258;

and

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388;

and

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518; or any suitable fragment of such an amino acid sequence.

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 690 to 721, 2467 to 2483, 2754 to 2755 and 3194 to 3258; and CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1254 to 1285, 2503 to 2519, 2826 to 2827 and 3324 to 3388; and CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1818 to 1849, 2539 to 2555, 2898 to 2899 and 3454 to 3518.

Again, preferred combinations of CDR sequences will become clear from the further description herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to the hemagglutinin H5 protein of influenza virus; and more in particular bind to the hemagglutinin H5 protein of influenza virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

In one preferred, but non-limiting aspect, the invention relates to an amino acid sequence that essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which the CDR sequences of said amino acid sequence have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 126 to 157, 2431 to 2447, 2682 to 2683 and 3064 to 3128. This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 126 to 157, 2431 to 2447, 2682 to 2683 and 3064 to 3128, in which the amino acid residues that form the framework regions are disregarded. Such amino acid sequences of the invention can be as further described herein.

In particular, the invention relates to an amino acid sequence directed against at least one epitope of the G-protein of rabies virus that comprises one or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; d) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; g) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933;

or any suitable combination thereof.

When an amino acid sequence of the invention contains one or more amino acid sequences according to b) and/or c):

i) any amino acid substitution in such an amino acid sequence according to b) and/or c) is preferably, and compared to the corresponding amino acid sequence according to a), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to b) and/or c) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to a);

and/or

iii) the amino acid sequence according to b) and/or c) may be an amino acid sequence that is derived from an amino acid sequence according to a) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to e) and/or f):

i) any amino acid substitution in such an amino acid sequence according to e) and/or f) is preferably, and compared to the corresponding amino acid sequence according to d), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to e) and/or f) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to d);

and/or

iii) the amino acid sequence according to e) and/or f) may be an amino acid sequence that is derived from an amino acid sequence according to d) by means of affinity maturation using one or more techniques of affinity maturation known per se.

Also, similarly, when an amino acid sequence of the invention contains one or more amino acid sequences according to h) and/or i):

i) any amino acid substitution in such an amino acid sequence according to h) and/or i) is preferably, and compared to the corresponding amino acid sequence according to g), a conservative amino acid substitution, (as defined herein);

and/or

ii) the amino acid sequence according to h) and/or i) preferably only contains amino acid substitutions, and no amino acid deletions or insertions, compared to the corresponding amino acid sequence according to g);

and/or

iii) the amino acid sequence according to h) and/or i) may be an amino acid sequence that is derived from an amino acid sequence according to g) by means of affinity maturation using one or more techniques of affinity maturation known per se.

It should be understood that the last preceding paragraphs also generally apply to any amino acid sequences of the invention that comprise one or more amino acid sequences according to b), c), e), f), h) or i), respectively.

In this specific aspect, the amino acid sequence preferably comprises one or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; ii) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; and iii) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; or any suitable combination thereof.

Also, preferably, in such an amino acid sequence, at least one of said stretches of amino acid residues forms part of the antigen binding site for binding the G-protein of rabies virus.

In a more specific, but again non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the G-protein of rabies virus, that comprises two or more stretches of amino acid residues chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; d) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; g) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933;

such that (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b) or c), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e), f), g), h) or i); (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to d), e) or f), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), g), h) or i); or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences according to g), h) or i), the second stretch of amino acid residues corresponds to one of the amino acid sequences according to a), b), c), d), e) or f).

In this specific aspect, the amino acid sequence preferably comprises two or more stretches of amino acid residues chosen from the group consisting of:

i) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; ii) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; and iii) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; such that, (i) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861 or of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; (ii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789 or of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; or (iii) when the first stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933, the second stretch of amino acid residues corresponds to one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789 or of SEQ ID NO's: 1365 to 1375 and 2828 to 2861.

Also, in such an amino acid sequence, the at least two stretches of amino acid residues again preferably form part of the antigen binding site for binding to the G-protein of rabies virus.

In an even more specific, but non-limiting aspect, the invention relates to an amino acid sequence directed against at least one epitope of the G-protein of rabies virus, that comprises three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789;

the second stretch of amino acid residues is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; e) f) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; g) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861;

and the third stretch of amino acid residues is chosen from the group consisting of:

h) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; i) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; j) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933.

Preferably, in this specific aspect, the first stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; the second stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; and the third stretch of amino acid residues is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933.

Again, preferably, in such an amino acid sequence, the at least three stretches of amino acid residues forms part of the antigen binding site for binding to the G-protein of rabies virus.

Preferred combinations of such stretches of amino acid sequences will become clear from the further disclosure herein.

Preferably, in such amino acid sequences the CDR sequences have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 237 to 247 and 2684 to 2717 (see Table A-1). This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 237 to 247 and 2684 to 2717 (see Table A-1), in which the amino acid residues that form the framework regions are disregarded. Also, such amino acid sequences of the invention can be as further described herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to the G-protein of rabies virus; and more in particular bind to the G-protein of rabies virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

When the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789;

and/or

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861;

and/or

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933.

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; and/or CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; and/or CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933.

In particular, when the amino acid sequence of the invention essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), the amino acid sequence of the invention is preferably such that:

CDR1 is chosen from the group consisting of:

a) the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; b) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; c) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789;

and

CDR2 is chosen from the group consisting of:

d) the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; e) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; f) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861;

and

CDR3 is chosen from the group consisting of:

g) the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; h) amino acid sequences that have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; i) amino acid sequences that have 3, 2, or 1 amino acid difference with at least one of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933; or any suitable fragment of such an amino acid sequence.

In particular, such an amino acid sequence of the invention may be such that CDR1 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 801 to 811 and 2756 to 2789; and CDR2 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1365 to 1375 and 2828 to 2861; and CDR3 is chosen from the group consisting of the amino acid sequences of SEQ ID NO's: 1929 to 1939 and 2900 to 2933.

Again, preferred combinations of CDR sequences will become clear from the further description herein.

Also, such amino acid sequences are preferably such that they can specifically bind (as defined herein) to the G-protein of rabies virus; and more in particular bind to the G-protein of rabies virus with an affinity (suitably measured and/or expressed as a K D -value (actual or apparent), a K A -value (actual or apparent), a k on -rate and/or a k off -rate, or alternatively as an IC 50 value, as further described herein) that is as defined herein.

In one preferred, but non-limiting aspect, the invention relates to an amino acid sequence that essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which the CDR sequences of said amino acid sequence have at least 70% amino acid identity, preferably at least 80% amino acid identity, more preferably at least 90% amino acid identity, such as 95% amino acid identity or more or even essentially 100% amino acid identity with the CDR sequences of at least one of the amino acid sequences of SEQ ID NO's: 237 to 247 and 2684 to 2717. This degree of amino acid identity can for example be determined by determining the degree of amino acid identity (in a manner described herein) between said amino acid sequence and one or more of the sequences of SEQ ID NO's: 237 to 247 and 2684 to 2717, in which the amino acid residues that form the framework regions are disregarded. Such amino acid sequences of the invention can be as further described herein.

In such an amino acid sequence of the invention, the framework sequences may be any suitable framework sequences, and examples of suitable framework sequences will be clear to the skilled person, for example on the basis the standard handbooks and the further disclosure and prior art mentioned herein.

The framework sequences are preferably (a suitable combination of) immunoglobulin framework sequences or framework sequences that have been derived from immunoglobulin framework sequences (for example, by humanization or camelization). For example, the framework sequences may be framework sequences derived from a light chain variable domain (e.g. a V L -sequence) and/or from a heavy chain variable domain (e.g. a V H -sequence). In one particularly preferred aspect, the framework sequences are either framework sequences that have been derived from a V HH -sequence (in which said framework sequences may optionally have been partially or fully humanized) or are conventional V H sequences that have been camelized (as defined herein).

The framework sequences are preferably such that the amino acid sequence of the invention is a domain antibody (or an amino acid sequence that is suitable for use as a domain antibody); is a single domain antibody (or an amino acid sequence that is suitable for use as a single domain antibody); is a “dAb” (or an amino acid sequence that is suitable for use as a dAb); or is a NANOBODY® (V HH sequence) (including but not limited to V HH sequence). Again, suitable framework sequences will be clear to the skilled person, for example on the basis the standard handbooks and the further disclosure and prior art mentioned herein.

In particular, the framework sequences present in the amino acid sequences of the invention may contain one or more of Hallmark residues (as defined herein), such that the amino acid sequence of the invention is a NANOBODY® (V HH sequence). Some preferred, but non-limiting examples of (suitable combinations of) such framework sequences will become clear from the further disclosure herein.

Again, as generally described herein for the amino acid sequences of the invention, it is also possible to use suitable fragments (or combinations of fragments) of any of the foregoing, such as fragments that contain one or more CDR sequences, suitably flanked by and/or linked via one or more framework sequences (for example, in the same order as these CDR's and framework sequences may occur in the full-sized immunoglobulin sequence from which the fragment has been derived). Such fragments may also again be such that they comprise or can form an immunoglobulin fold, or alternatively be such that they do not comprise or cannot form an immunoglobulin fold.

In one specific aspect, such a fragment comprises a single CDR sequence as described herein (and in particular a CDR3 sequence), that is flanked on each side by (part of) a framework sequence (and in particular, part of the framework sequence(s) that, in the immunoglobulin sequence from which the fragment is derived, are adjacent to said CDR sequence. For example, a CDR3 sequence may be preceded by (part of) a FR3 sequence and followed by (part of) a FR4 sequence). Such a fragment may also contain a disulphide bridge, and in particular a disulphide bridge that links the two framework regions that precede and follow the CDR sequence, respectively (for the purpose of forming such a disulphide bridge, cysteine residues that naturally occur in said framework regions may be used, or alternatively cysteine residues may be synthetically added to or introduced into said framework regions). For a further description of these “Expedite fragments”, reference is again made to WO 03/050531, as well as to WO 08/068280.

In another aspect, the invention relates to a compound or construct, and in particular a protein or polypeptide (also referred to herein as a “compound of the invention” or “polypeptide of the invention”, respectively) that comprises or essentially consists of one or more amino acid sequences of the invention (or suitable fragments thereof), and optionally further comprises one or more other groups, residues, moieties or binding units. As will become clear to the skilled person from the further disclosure herein, such further groups, residues, moieties, binding units or amino acid sequences may or may not provide further functionality to the amino acid sequence of the invention (and/or to the compound or construct in which it is present) and may or may not modify the properties of the amino acid sequence of the invention.

For example, such further groups, residues, moieties or binding units may be one or more additional amino acid sequences, such that the compound or construct is a (fusion) protein or (fusion) polypeptide. In a preferred but non-limiting aspect, said one or more other groups, residues, moieties or binding units are immunoglobulin sequences. Even more preferably, said one or more other groups, residues, moieties or binding units are chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, “dAb” 's, amino acid sequences that are suitable for use as a dAb, or NANOBODIES® (VHH sequences).

Alternatively, such groups, residues, moieties or binding units may for example be chemical groups, residues, moieties, which may or may not by themselves be biologically and/or pharmacologically active. For example, and without limitation, such groups may be linked to the one or more amino acid sequences of the invention so as to provide a “derivative” of an amino acid sequence or polypeptide of the invention, as further described herein.

Also within the scope of the present invention are compounds or constructs, that comprises or essentially consists of one or more derivatives as described herein, and optionally further comprises one or more other groups, residues, moieties or binding units, optionally linked via one or more linkers. Preferably, said one or more other groups, residues, moieties or binding units are amino acid sequences.

In the compounds or constructs described above, the one or more amino acid sequences of the invention and the one or more groups, residues, moieties or binding units may be linked directly to each other and/or via one or more suitable linkers or spacers. For example, when the one or more groups, residues, moieties or binding units are amino acid sequences, the linkers may also be amino acid sequences, so that the resulting compound or construct is a fusion (protein) or fusion (polypeptide).

As will be clear from the further description above and herein, this means that the amino acid sequences of the invention can be used as “building blocks” to form polypeptides of the invention, i.e. by suitably combining them with other groups, residues, moieties or binding units, in order to form compounds or constructs as described herein (such as, without limitations, the bi-, tri-, multiparatopic, bi-, tri-, multivalent and bi-, tri-, multispecific polypeptides of the invention described herein) which combine within one molecule one or more desired properties or biological functions.

The compounds or polypeptides of the invention can generally be prepared by a method which comprises at least one step of suitably linking the one or more amino acid sequences of the invention to the one or more further groups, residues, moieties or binding units, optionally via the one or more suitable linkers, so as to provide the compound or polypeptide of the invention. Polypeptides of the invention can also be prepared by a method which generally comprises at least the steps of providing a nucleic acid that encodes a polypeptide of the invention, expressing said nucleic acid in a suitable manner, and recovering the expressed polypeptide of the invention. Such methods can be performed in a manner known per se, which will be clear to the skilled person, for example on the basis of the methods and techniques further described herein.

The process of designing/selecting and/or preparing a compound or polypeptide of the invention, starting from an amino acid sequence of the invention, is also referred to herein as “formatting” said amino acid sequence of the invention; and an amino acid of the invention that is made part of a compound or polypeptide of the invention is said to be “formatted” or to be “in the format of” said compound or polypeptide of the invention. Examples of ways in which an amino acid sequence of the invention can be formatted and examples of such formats will be clear to the skilled person based on the disclosure herein; and such formatted amino acid sequences form a further aspect of the invention.

In one specific aspect of the invention, a compound of the invention or a polypeptide of the invention may have an increased half-life, compared to the corresponding amino acid sequence of the invention. Some preferred, but non-limiting examples of such compounds and polypeptides will become clear to the skilled person based on the further disclosure herein, and for example comprise amino acid sequences or polypeptides of the invention that have been chemically modified to increase the half-life thereof (for example, by means of pegylation); amino acid sequences of the invention that comprise at least one additional binding site for binding to a serum protein (such as serum albumin); or polypeptides of the invention that comprise at least one amino acid sequence of the invention that is linked to at least one moiety (and in particular at least one amino acid sequence) that increases the half-life of the amino acid sequence of the invention. Examples of polypeptides of the invention that comprise such half-life extending moieties or amino acid sequences will become clear to the skilled person based on the further disclosure herein; and for example include, without limitation, polypeptides in which the one or more amino acid sequences of the invention are suitable linked to one or more serum proteins or fragments thereof (such as (human) serum albumin or suitable fragments thereof) or to one or more binding units that can bind to serum proteins (such as, for example, domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, “dAb”'s, amino acid sequences that are suitable for use as a dAb, or NANOBODIES® (VHH sequences) that can bind to serum proteins such as serum albumin (such as human serum albumin), serum immunoglobulins such as IgG, or transferrin; reference is made to the further description and references mentioned herein); polypeptides in which an amino acid sequence of the invention is linked to an Fc portion (such as a human Fc) or a suitable part or fragment thereof; or polypeptides in which the one or more amino acid sequences of the invention are suitable linked to one or more small proteins or peptides that can bind to serum proteins (such as, without limitation, the proteins and peptides described in WO 91/01743, WO 01/45746, WO 02/076489 and in WO 08/068280.

Generally, the compounds or polypeptides of the invention with increased half-life preferably have a half-life that is at least 1.5 times, preferably at least 2 times, such as at least 5 times, for example at least 10 times or more than 20 times, greater than the half-life of the corresponding amino acid sequence of the invention per se.

In a preferred, but non-limiting aspect of the invention, such compounds or polypeptides of the invention have a serum half-life that is increased with more than 1 hours, preferably more than 2 hours, more preferably more than 6 hours, such as more than 12 hours, or even more than 24, 48 or 72 hours, compared to the corresponding amino acid sequence of the invention per se.

In another preferred, but non-limiting aspect of the invention, such compounds or polypeptides of the invention exhibit a serum half-life in human of at least about 12 hours, preferably at least 24 hours, more preferably at least 48 hours, even more preferably at least 72 hours or more. For example, compounds or polypeptides of the invention may have a half-life of at least 5 days (such as about 5 to 10 days), preferably at least 9 days (such as about 9 to 14 days), more preferably at least about 10 days (such as about 10 to 15 days), or at least about 11 days (such as about 11 to 16 days), more preferably at least about 12 days (such as about 12 to 18 days or more), or more than 14 days (such as about 14 to 19 days).

In another aspect, the invention relates to a nucleic acid that encodes an amino acid sequence of the invention or a polypeptide of the invention (or a suitable fragment thereof). Such a nucleic acid will also be referred to herein as a “nucleic acid of the invention” and may for example be in the form of a genetic construct, as further described herein.

In another aspect, the invention relates to a host or host cell that expresses (or that under suitable circumstances is capable of expressing) an amino acid sequence of the invention and/or a polypeptide of the invention; and/or that contains a nucleic acid of the invention. Some preferred but non-limiting examples of such hosts or host cells will become clear from the further description herein.

The invention further relates to a product or composition containing or comprising at least one amino acid sequence of the invention, at least one polypeptide of the invention (or a suitable fragment thereof), at least one compound of the invention and/or at least one nucleic acid of the invention, and optionally one or more further components of such compositions known per se, i.e. depending on the intended use of the composition. Such a product or composition may for example be a pharmaceutical composition (as described herein), a veterinary composition or a product or composition for diagnostic use (as also described herein). Some preferred but non-limiting examples of such products or compositions will become clear from the further description herein.

The invention also relates to the use of an amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention, or of a composition comprising the same, in (methods or compositions for) modulating viral entry and/or viral replication and/or for modulating the biological pathways that are mediated by an envelope protein of a virus (and/or its viral receptor) either in vitro (e.g. in an in vitro or cellular assay) or in vivo (e.g. in an a single cell or in a multicellular organism, and in particular in a mammal, and more in particular in a human being, such as in a human being that is at risk of or suffers from a viral disease).

The invention also relates to methods for modulating viral entry and/or viral replication and/or for modulating the biological pathways that are mediated by an envelope protein of a virus (and/or its viral receptor) either in vitro (e.g. in an in vitro or cellular assay) or in vivo (e.g. in an a single cell or multicellular organism, and in particular in a mammal, and more in particular in a human being, such as in a human being that is at risk of or suffers from a viral disease), which method comprises at least the step of contacting an envelope protein of a virus with at least one amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention, or with a composition comprising the same, in a manner and in an amount suitable to modulate viral entry and/or viral replication and/or to modulate the biological pathways that are mediated by an envelope protein of a virus and/or its viral receptor, with at least one amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention.

The invention also relates to the use of an one amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention in the preparation of a composition (such as, without limitation, a pharmaceutical composition or preparation as further described herein) for modulating viral entry and/or viral replication and/or for modulating the biological pathways that are mediated by an envelope protein of a virus (and/or its viral receptor), either in vitro (e.g. in an in vitro or cellular assay) or in vivo (e.g. in an a single cell or multicellular organism, and in particular in a mammal, and more in particular in a human being, such as in a human being that is at risk of or suffers from a viral disease.

In the context of the present invention, “modulating” or “to modulate” generally means either reducing, preventing or inhibiting viral entry and/or viral replication and/or reducing, preventing or inhibiting the biological pathways that are mediated by an envelope protein of a virus and/or its viral receptor, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, “modulating” or “to modulate” may mean either reducing, preventing or inhibiting viral entry and/or viral replication and/or reducing, preventing or inhibiting the biological pathways that are mediated by an envelope protein of a virus and/or its viral receptor as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral entry and/or viral replication and/or normal (i.e. naturally occurring) biological pathways that are mediated by an envelope protein of a virus and/or its viral receptor in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention.

As will be clear to the skilled person, “modulating” may also involve effecting a change (which may either be an increase or a decrease) in binding specificity and/or selectivity of an envelope protein of a virus for one or more of its binding partners; and/or effecting a change (which may either be an increase or a decrease) in the sensitivity of an envelope protein of a virus for one or more conditions in the medium or surroundings in which an envelope protein of a virus is present (such as pH, ion strength, the presence of co-factors, etc.), compared to the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention. As will be clear to the skilled person, this may again be determined in any suitable manner and/or using any suitable assay known per se, such as the assays described herein or in the prior art cited herein.

“Modulating” may also mean effecting a change with respect to one or more biological or physiological mechanisms, effects, responses, functions, pathways or activities in which an envelope protein of a virus (or in which its binding partners or pathway(s) are involved) is involved. Again, as will be clear to the skilled person this may be determined in any suitable manner and/or using any suitable (in vitro and usually cellular or in assay) assay known per se, such as the assays described herein or in the prior art cited herein. In particular, with respect to one or more biological or physiological mechanisms, effects, responses, functions, pathways or activities in which an envelope protein of a virus and/or its viral receptor is involved, effecting a change can mean a change by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to the biological or physiological mechanisms, effects, responses, functions, pathways or activities in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), compound or polypeptide of the invention.

Modulating may for example involve reducing, preventing or inhibiting the binding of an envelope protein of a virus to one of its binding partners and/or competing with a natural binding partner for binding to an envelope protein of a virus. Modulating may be reversible or irreversible, but for pharmaceutical and pharmacological purposes will usually be in a reversible manner.

Accordingly, the present invention also relates to amino acid sequences and polypeptides that can be used to modulate, and in particular to inhibit and/or to prevent the viral-mediated biological pathways in which an envelope protein of a virus and/or a viral receptor are involved. In particular, the amino acid sequences and polypeptides of the present invention can be used to neutralize a virus (as defined herein) and/or to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein).

More specifically, the amino acid sequences and polypeptides according to the present invention may neutralize a virus (as defined herein) and/or modulate, reduce and/or inhibit the infectivity of a virus (as defined herein) in the pre-entry phase of viral infection (i.e. before and/or during viral entry in a target host cell has taken place) and/or in the post-entry phase of viral infection (i.e. after viral entry in a target host cell has taken place). Accordingly, the amino acid sequences and polypeptides of the present invention that neutralize a virus (as defined herein) and/or modulate, reduce and/or inhibit the infectivity of a virus (as defined herein) in the pre-entry phase of viral infection (i.e. before and/or during viral entry in a target host cell has taken place), are said herein to modulate and in particular inhibit and/or prevent viral entry (as further defined herein) in a target host cell. Furthermore, the amino acid sequences and polypeptides of the present invention that neutralize a virus (as defined herein) and/or modulate, reduce and/or inhibit the infectivity of a virus (as defined herein) in the post-entry phase of viral infection (i.e. after viral entry in a target host cell has taken place), are said herein to modulate and in particular inhibit and/or prevent viral replication (as further defined herein) in a target host cell.

In a specific aspect, the present invention relates to multivalent (such as bivalent, biparatopic, bispecific, trivalent, triparatopic, trispecific, as further defined herein) amino acid sequences and polypeptides that modulate, and in particular to inhibit and/or to prevent the viral-mediated biological pathways in which an envelope protein of a virus and/or a viral receptor are involved. In particular, the multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides of the present invention can neutralize a virus (as defined herein) and/or to modulate, reduce and/or inhibit the infectivity of a virus (as defined herein). In one aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against hemagglutinint H5 envelope protein of influenza and show increased in vitro and/or in vivo neutralization of influenza virus (as e.g. measured by a pseudotype neutralization assay such as described herein) compared to the corresponding monovalent amino acid sequence. The neutralization may be increased by at least 2 times, preferably at least 3 times, such as at least 5 times or at least 10 times, for example by at least 15 times, at least 20 times, at least 30 times, at least 50 times, or 100 times or more, compared to the neutralization in the same assay under the same conditions by the corresponding monovalent amino acid sequence. In another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against the G envelope protein of rabies and show increased in vitro and/or in vivo neutralization of rabies (as e.g. measured by a RFITT assay such as described herein) compared to the corresponding monovalent amino acid sequence. The neutralization may be increased by at least 2 times, preferably at least 3 times, such as at least 5 times or at least 10 times, for example by at least 15 times, at least 20 times, at least 30 times, at least 50 times, or 100 times or more, compared to the neutralization in the same assay under the same conditions by the corresponding monovalent amino acid sequence. In another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against F-protein of RSV and show increased in vitro and/or in vivo neutralization of RSV compared to the corresponding monovalent amino acid sequence. The neutralization may be increased by at least 2 times, preferably at least 3 times, such as at least 5 times or at least 10 times, for example by at least 15 times, at least 20 times, at least 30 times, at least 50 times, or 100 times or more, compared to the neutralization in the same assay under the same conditions by the corresponding monovalent amino acid sequence. In yet another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against hemagglutinin H5 envelope protein of influenza and show increased competition with sialic acid for binding hemagglutinint H5 envelope protein of influenza compared to the corresponding monovalent amino acid sequence. The competition may be increased by at least 2 times, preferably at least 3 times, such as at least 5 times or at least 10 times, for example by at least 15 times, at least 20 times, at least 30 times, at least 50 times, or 100 times or more, compared to the competition in the same assay under the same conditions by the corresponding monovalent amino acid sequence. In yet another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides show increased cross reactivity and/or neutralization of different genotypes, subtypes, escape mutants and/or strains of a certain virus. In one aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against the G envelope protein of rabies and may show cross reactivity and/or neutralization of different genotypes of rabies (such as e.g. genotype 1 and 5). In another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against hemagglutinin H5 envelope protein of influenza and show cross reactivity and/or neutralization of different subtypes and/or strains of influenza virus (such as e.g. H5N1 and H1N1; H3N2 and H1N1; H5N1 and H3N2; H5N1 and H2N2; H5N1, H1N1 and H3N2; H5N1, H2N2 and H3N2; H5N1, H1N1 and H2N2; H5N1, H1N1, H2N2 and H3N2). In yet another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against F protein of RSV and show cross reactivity and/or neutralization of different strains (such as e.g. Long and A-2, Long and B-1, A-2 and B-1, Long, A-2 and B-1) of RSV. In yet another aspect, these multivalent (preferably bivalent, more preferably trivalent) amino acid sequences and polypeptides are directed against F protein of RSV and show cross reactivity and/or neutralization of different escape mutants of RSV (such as e.g. escape mutants in antigenic site II, escape mutants in antigenic site IV-VI, and/or escape mutants in both antigenic site II and antigenic site IV-VI).

Accordingly, the amino acid sequences and (multivalent) polypeptides of the present invention can modulate and in particular inhibit and/or prevent viral entry and/or viral replication in a target host cell by specifically binding to an envelope protein of a virus at any suitable stage of said biological pathway(s); preferably, the amino acid sequences and polypeptides of the present invention can modulate and in particular inhibit and/or prevent viral entry in a target host cell by binding to an envelope protein of a virus, such that virion aggregation is induced and/or virion structure is destabilized and/or virion attachment to a target host cell is modulated, inhibited and/or prevented (for instance by modulating and/or inhibiting and/or preventing the interaction between the an envelope protein of a virus and a viral receptor on a target host cell and/or the interaction between the an envelope protein of a virus and a target host cell or by competing with said envelope protein for binding to said viral receptor or said target host cell) and/or viral fusion with said target host cell is modulated, inhibited and/or prevented (for instance at the target host cell membrane or within an endosomal and/or lysosomal compartment of said target host cell), for example by preventing said envelope protein of a virus from undergoing a conformational change.

Alternatively, the amino acid sequences and polypeptides of the present invention can modulate and in particular inhibit and/or prevent viral replication (as defined herein) in a target host cell by specifically binding to an envelope protein of a virus at any suitable stage of said biological pathway; preferably, the amino acid sequences of the present invention can modulate and in particular inhibit and/or prevent viral replication in a target host cell by binding to an envelope protein of a virus, such that transcription and/or translation of the viral genome is affected, inhibited and/or prevented and/or viral packaging and/or the formation of functional virions is affected, inhibited and/or prevented and/or budding of nascent virions from the target host cell membrane is reduced, inhibited and/or prevented.

Also according to this aspect, bi- and multivalent (as defined herein), bi- and multispecific (as defined herein) and bi- and multiparatopic (as defined herein) polypeptides according to the invention may be useful for the prevention and/or treatment of viral diseases by specifically binding to at least one epitope of an envelope protein of a virus and at least one further epitope (which may or may not be different from said at least one epitope) of a target, wherein said target may or may not be different from said envelope protein.

Accordingly, the present invention also relates to biparatopic amino acid sequences and polypeptides according to the invention or compositions comprising the same, that combine two different modes of action, for example reducing, preventing and/or inhibiting viral entry (such for example at the stage of viral attachment, viral fusion, etc.) and/or viral replication (such for example at the stage of transcription, translation, viral packaging, budding, etc.), each mediated by one of the binding units of the biparatopic amino acid sequence and/or polypeptide of the invention, wherein each binding unit binds to a different site of said envelope protein of a virus.

Furthermore, the present invention also relates to triparatopic amino acid sequences and polypeptides according to the invention or compositions comprising the same, that combine two or three different modes of action, such as reducing, preventing and/or inhibiting viral entry (such for example at the stage of viral attachment, viral fusion, etc.) and/or viral replication (such for example at the stage of transcription, translation, viral packaging, budding, etc.), each mediated by one of the binding units of the triparatopic amino acid sequence and/or polypeptide of the invention, wherein each binding unit binds to a different site of said envelope protein of a virus.

More generally, the present invention relates to multiparatopic amino acid sequences and polypeptides according to the invention or compositions comprising the same, that combine two or more different modes of action, such as reducing, preventing and/or inhibiting viral entry (such for example at the stage of viral attachment, viral fusion, etc.) and/or viral replication (such for example at the stage of transcription, translation, viral packaging, budding, etc.), each mediated by one of the binding units of the multiparatopic amino acid sequence and/or polypeptide of the invention, wherein each binding unit binds to a different site of said envelope protein of a virus.

The invention further relates to methods for preparing or generating the amino acid sequences, polypeptides, nucleic acids, host cells, products and compositions described herein. Some preferred but non-limiting examples of such methods will become clear from the further description herein.

Generally, these methods may comprise the steps of:

a) providing a set, collection or library of amino acid sequences; and

b) screening said set, collection or library of amino acid sequences for amino acid sequences that can bind to and/or have affinity for an envelope protein of a virus; and

c) isolating the amino acid sequence(s) that can bind to and/or have affinity for an envelope protein of a virus.

In such a method, the set, collection or library of amino acid sequences may be any suitable set, collection or library of amino acid sequences. For example, the set, collection or library of amino acid sequences may be a set, collection or library of immunoglobulin sequences (as described herein), such as a naïve set, collection or library of immunoglobulin sequences; a synthetic or semi-synthetic set, collection or library of immunoglobulin sequences; and/or a set, collection or library of immunoglobulin sequences that have been subjected to affinity maturation.

Also, in such a method, the set, collection or library of amino acid sequences may be a set, collection or library of heavy chain variable domains (such as V H domains or V HH domains) or of light chain variable domains. For example, the set, collection or library of amino acid sequences may be a set, collection or library of domain antibodies or single domain antibodies, or may be a set, collection or library of amino acid sequences that are capable of functioning as a domain antibody or single domain antibody.

In a preferred aspect of this method, the set, collection or library of amino acid sequences may be an immune set, collection or library of immunoglobulin sequences, for example derived from a mammal that has been suitably immunized with an envelope protein of a virus or with a suitable antigenic determinant based thereon or derived therefrom, such as an antigenic part, fragment, region, domain, loop or other epitope thereof. In one particular aspect, said antigenic determinant may be an extracellular part, region, domain, loop or other extracellular epitope(s).

In the above methods, the set, collection or library of amino acid sequences may be displayed on a phage, phagemid, ribosome or suitable micro-organism (such as yeast), such as to facilitate screening. Suitable methods, techniques and host organisms for displaying and screening (a set, collection or library of) amino acid sequences will be clear to the person skilled in the art, for example on the basis of the further disclosure herein. Reference is also made to the review by Hoogenboom in Nature Biotechnology, 23, 9, 1105-1116 (2005).

In another aspect, the method for generating amino acid sequences comprises at least the steps of:

a) providing a collection or sample of cells expressing amino acid sequences; b) screening said collection or sample of cells for cells that express an amino acid sequence that can bind to and/or have affinity for an envelope protein of a virus;

and

c) either (i) isolating said amino acid sequence; or (ii) isolating from said cell a nucleic acid sequence that encodes said amino acid sequence, followed by expressing said amino acid sequence.

For example, when the desired amino acid sequence is an immunoglobulin sequence, the collection or sample of cells may for example be a collection or sample of B-cells. Also, in this method, the sample of cells may be derived from a mammal that has been suitably immunized with an envelope protein of a virus or with a suitable antigenic determinant based thereon or derived therefrom, such as an antigenic part, fragment, region, domain, loop or other epitope thereof. In one particular aspect, said antigenic determinant may be an extracellular part, region, domain, loop or other extracellular epitope(s).

The above method may be performed in any suitable manner, as will be clear to the skilled person. Reference is for example made to EP 0 542 810, WO 05/19824, WO 04/051268 and WO 04/106377. The screening of step b) is preferably performed using a flow cytometry technique such as FACS. For this, reference is for example made to Lieby et al., Blood, Vol. 97, No. 12, 3820 (2001).

In another aspect, the method for generating an amino acid sequence directed against an envelope protein of a virus may comprise at least the steps of:

a) providing a set, collection or library of nucleic acid sequences encoding amino acid sequences; b) screening said set, collection or library of nucleic acid sequences for nucleic acid sequences that encode an amino acid sequence that can bind to and/or has affinity for an envelope protein of a virus;

and

c) isolating said nucleic acid sequence, followed by expressing said amino acid sequence.

In such a method, the set, collection or library of nucleic acid sequences encoding amino acid sequences may for example be a set, collection or library of nucleic acid sequences encoding a naïve set, collection or library of immunoglobulin sequences; a set, collection or library of nucleic acid sequences encoding a synthetic or semi-synthetic set, collection or library of immunoglobulin sequences; and/or a set, collection or library of nucleic acid sequences encoding a set, collection or library of immunoglobulin sequences that have been subjected to affinity maturation.

Also, in such a method, the set, collection or library of nucleic acid sequences may encode a set, collection or library of heavy chain variable domains (such as V H domains or V HH domains) or of light chain variable domains. For example, the set, collection or library of nucleic acid sequences may encode a set, collection or library of domain antibodies or single domain antibodies, or a set, collection or library of amino acid sequences that are capable of functioning as a domain antibody or single domain antibody.

In a preferred aspect of this method, the set, collection or library of amino acid sequences may be an immune set, collection or library of nucleic acid sequences, for example derived from a mammal that has been suitably immunized with an envelope protein of a virus or with a suitable antigenic determinant based thereon or derived therefrom, such as an antigenic part, fragment, region, domain, loop or other epitope thereof. In one particular aspect, said antigenic determinant may be an extracellular part, region, domain, loop or other extracellular epitope(s).

The set, collection or library of nucleic acid sequences may for example encode an immune set, collection or library of heavy chain variable domains or of light chain variable domains. In one specific aspect, the set, collection or library of nucleotide sequences may encode a set, collection or library of V HH sequences.

In the above methods, the set, collection or library of nucleotide sequences may be displayed on a phage, phagemid, ribosome or suitable micro-organism (such as yeast), such as to facilitate screening. Suitable methods, techniques and host organisms for displaying and screening (a set, collection or library of) nucleotide sequences encoding amino acid sequences will be clear to the person skilled in the art, for example on the basis of the further disclosure herein. Reference is also made to the review by Hoogenboom in Nature Biotechnology, 23, 9, 1105-1116 (2005).

In another aspect, the method for generating an amino acid sequence directed against an envelope protein of a virus may comprise at least the steps of:

a) providing a set, collection or library of nucleic acid sequences encoding amino acid sequences; b) screening said set, collection or library of nucleic acid sequences for nucleic acid sequences that encode an amino acid sequence that can bind to and/or has affinity for an envelope protein of a virus and that is cross-blocked or is cross blocking a NANOBODY® (V HH sequence) of the invention, e.g. one of SEQ ID NO's: 126 to 407, 2431 to 2448, 2574 to 2581, 2682 to 2717 and 3064 to 3128 (Table A-1), or a humanized version of a NANOBODY® (V HH sequence) of the invention, e.g. SEQ ID NO: 2999 to 3015 (see Table A-8), or a polypeptide or construct of the invention comprising at least one NANOBODY® (V HH sequence) of the invention, e.g. one of SEQ ID NO's: 2382 to 2415, 2423 to 2430, 2641 to 2659, 2663 to 2681, 2978 to 2998, 3016 to 3056 and 3584 to 3591 (see Table A-2, Table A-4, Table A-5, Table A-6, Table A-9 and Table A-10); and c) isolating said nucleic acid sequence, followed by expressing said amino acid sequence.

The invention also relates to amino acid sequences that are obtainable and/or obtained by the above methods, or alternatively by a method that comprises the one of the above methods and in addition at least the steps of determining the nucleotide sequence or amino acid sequence of said immunoglobulin sequence; and of expressing or synthesizing said amino acid sequence in a manner known per se, such as by expression in a suitable host cell or host organism or by chemical synthesis.

Also, following the steps above, one or more amino acid sequences of the invention may be suitably humanized (or alternatively camelized); and/or the amino acid sequence(s) thus obtained may be linked to each other or to one or more other suitable amino acid sequences (optionally via one or more suitable linkers) so as to provide a polypeptide of the invention. Also, a nucleic acid sequence encoding an amino acid sequence of the invention may be suitably humanized (or alternatively camelized) and suitably expressed; and/or one or more nucleic acid sequences encoding an amino acid sequence of the invention may be linked to each other or to one or more nucleic acid sequences that encode other suitable amino acid sequences (optionally via nucleotide sequences that encode one or more suitable linkers), after which the nucleotide sequence thus obtained may be suitably expressed so as to provide a polypeptide of the invention.

Also encompassed within the present invention are methods for preparing and generating multivalent (such as e.g. bivalent, trivalent, etc.), multiparatopic (such as e.g. biparatopic, triparatopic, etc.) and/or multispecific (such as e.g. bispecific, trispecific, etc.) amino acids of the invention.

A method for preparing multivalent, multiparatopic and/or multispecific amino acids or constructs of the invention may comprise at least the steps of linking two or more monovalent amino acid sequences or monovalent constructs of the invention and for example one or more linkers together in a suitable manner. The monovalent constructs (and linkers) can be coupled by any method known in the art and as further described herein. Preferred techniques include the linking of the nucleic acid sequences that encode the monovalent constructs (and linkers) to prepare a genetic construct that expresses the multivalent, multiparatopic and/or multispecific amino acid or construct. Techniques for linking amino acid sequences or nucleic acid sequences will be clear to the skilled person, and reference is again made to the standard handbooks, such as Sambrook et al. and Ausubel et al., mentioned above, as well as the Examples below.

Accordingly, the present invention also relates to the use of a monovalent construct (which may comprise or essentially consists of an amino acid sequence of the invention such as a domain antibody, an amino acid sequence that is suitable for use as a domain antibody, a single domain antibody, an amino acid sequence that is suitable for use as a single domain antibody, a “dAb”, an amino acid sequences that is suitable for use as a dAb, or a NANOBODY® (V HH sequence)) in providing and/or preparing a multivalent (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) compound or construct. The monovalent construct is then used as a binding domain or binding unit in providing and/or preparing the multivalent (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct comprising two (e.g. in a bivalent and/or biparatopic construct), three (e.g. in a trivalent and/or triparatopic construct) or more (e.g. in a multivalent and/or multiparatopic construct) binding units. In this respect, the monovalent construct may be used as a binding domain or binding unit in providing and/or preparing a multivalent and preferably bivalent or trivalent (such as multiparatopic, and preferably biparatopic or triparatopic) construct of the invention comprising two, three or more binding units.

In one aspect, the invention relates to multivalent polypeptides directed against the F-protein of RSV, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein.

In another aspect, the invention relates to multivalent polypeptides directed against the F-protein of RSV, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the RSV F protein. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) as well as the other antigenic determinant, epitope, part or domain of the RSV F protein, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as a binding domain or binding unit in providing and/or preparing a multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct, wherein the binding domains or binding units are linked via a linker such that the multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In yet another aspect, the invention relates to multivalent polypeptides directed against the F-protein of RSV, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein.

In yet another aspect, the invention relates to multivalent polypeptides directed against the F-protein of RSV, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the RSV F protein. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) as well as the other antigenic determinant, epitope, part or domain of the RSV F protein, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, as a binding domain or binding unit in providing and/or preparing a multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct, wherein the binding domains or binding units are linked via a linker such that the multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In yet another aspect, the invention relates to multivalent polypeptides directed against the F-protein of RSV, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein; and at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) as well as the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, and a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a multiparatopic (such as a biparatopic) construct, wherein the binding domains or binding units are linked via a linker such that the multiparatopic (such as biparatopic) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the RSV F protein. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) as well as the other antigenic determinant, epitope, part or domain of the RSV F protein, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as a binding domain or binding unit in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the RSV F protein. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) as well as the other antigenic determinant, epitope, part or domain of the RSV F protein, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, as a binding domain or binding unit in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein; and at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) as well as the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, and a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred bivalent polypeptides of the invention, at least two monovalent constructs of the invention (and in particular at least two NANOBODIES® (V HH sequences)) are used that are directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that are capable of competing with Synagis® for binding to the RSV F protein. In such a preferred bivalent construct of the invention, the linker is most preferably such that the bivalent construct of the invention is capable of (simultaneously) binding to two Synagis® binding sites on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of two monovalent constructs comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a bivalent construct, wherein the binding domains or binding units are linked via a linker such that the bivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred bivalent polypeptides of the invention, at least two monovalent construct of the invention (and in particular at least two NANOBODIES® (V HH sequences)) are used that are directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that are capable of competing with 101F for binding to the RSV F protein. In such a preferred bivalent construct of the invention, the linker is most preferably such that the bivalent construct of the invention is capable of (simultaneously) binding to two 101F binding sites on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of two monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a bivalent construct, wherein the binding domains or binding units are linked via a linker such that the bivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the RSV F protein. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) as well as the other antigenic determinant, epitope, part or domain of the RSV F protein, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as a binding domain or binding unit in providing and/or preparing a trivalent, biparatopic or triparatopic construct, wherein the binding domains or binding units are linked via a linker such that the trivalent or triparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the RSV F protein. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) construct of the invention is capable of (simultaneously) binding to both the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) as well as the other antigenic determinant, epitope, part or domain of the RSV F protein, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, as a binding domain or binding unit in providing and/or preparing a trivalent, biparatopic or triparatopic construct, wherein the binding domains or binding units are linked via a linker such that the trivalent, biparatopic or triparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein; and at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) construct of the invention is capable of (simultaneously) binding to both the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) as well as the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, and a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a trivalent (biparatopic or triparatopic) construct, wherein the binding domains or binding units are linked via a linker such that the trivalent (biparatopic or triparatopic) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least three monovalent constructs of the invention (and in particular at least three NANOBODIES® (VHH sequences)) are used that are directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that are capable of competing with Synagis® for binding to the RSV F protein. In such a preferred trivalent construct of the invention, the linker is most preferably such that the trivalent construct of the invention is capable of (simultaneously) binding to three Synagis® binding sites on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of three monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the Synagis® binding site on the RSV F protein (and in particular against antigenic site II of the RSV F protein, and more in particular against the region aa 250-275 of the RSV F protein) and/or that is capable of competing with Synagis® for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a trivalent construct, wherein the binding domains or binding units are linked via a linker such that the trivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least three monovalent constructs of the invention (and in particular at least three NANOBODIES® (VHH sequences)) are used that are directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein) and/or that are capable of competing with 101F for binding to the RSV F protein. In such a preferred trivalent construct of the invention, the linker is most preferably such that the trivalent construct of the invention is capable of (simultaneously) binding to three 101F binding sites on the RSV F protein (and in particular against antigenic site IV-VI of the RSV F protein, and more in particular against region aa 423-436 of the RSV F protein), again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of three monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the 101F binding site on the RSV F protein (and in particular against antigenic site IV of the RSV F protein, and more in particular against the region aa 423-436 of the RSV F protein) and/or that is capable of competing with 101F for binding to the RSV F protein, as binding domains or binding units in providing and/or preparing a trivalent construct, wherein the binding domains or binding units are linked via a linker such that the trivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In another aspect, the invention relates to multivalent polypeptides directed against the hemagglutinin H5 envelope protein of influenza virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus.

In another aspect, the invention relates to multivalent polypeptides directed against the hemagglutinin H5 envelope protein of influenza virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct, wherein the binding domains or binding units are linked via a linker such that the multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In yet another aspect, the invention relates to multivalent polypeptides directed against the hemagglutinin H5 envelope protein of influenza virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In yet another aspect, the invention relates to multivalent polypeptides directed against the hemagglutinin H5 envelope protein of influenza virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct, wherein the binding domains or binding units are linked via a linker such that the multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In yet another aspect, the invention relates to multivalent polypeptides directed against the hemagglutinin H5 envelope protein of influenza virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In yet another aspect, the invention relates to multivalent polypeptides directed against the hemagglutinin H5 envelope protein of influenza virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C1792 for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct, wherein the binding domains or binding units are linked via a linker such that the multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred bivalent polypeptides of the invention, at least two monovalent constructs of the invention (and in particular at least two NANOBODIES® (VHH sequences)) are used that are directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that are capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus. In such a preferred bivalent construct of the invention, the linker is most preferably such that the bivalent construct of the invention is capable of (simultaneously) binding to two sialic acid binding sites on the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of two monovalent constructs comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as binding domains or binding units in providing and/or preparing a bivalent construct, wherein the binding domains or binding units are linked via a linker such that the bivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred bivalent polypeptides of the invention, at least two monovalent construct of the invention (and in particular at least two NANOBODIES® (VHH sequences)) are used that are directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that are capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus. In such a preferred bivalent construct of the invention, the linker is most preferably such that the bivalent construct of the invention is capable of (simultaneously) binding to two VN04-2 binding sites on the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of two monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as binding domains or binding units in providing and/or preparing a bivalent construct, wherein the binding domains or binding units are linked via a linker such that the bivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred bivalent polypeptides of the invention, at least two monovalent construct of the invention (and in particular at least two NANOBODIES® (VHH sequences)) are used that are directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that are capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus. In such a preferred bivalent construct of the invention, the linker is most preferably such that the bivalent construct of the invention is capable of (simultaneously) binding to two MAb C179 binding sites on the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of two monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as binding domains or binding units in providing and/or preparing a bivalent construct, wherein the binding domains or binding units are linked via a linker such that the bivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) construct of the invention is capable of (simultaneously) binding to the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a trivalent, biparatopic or triparatopic construct, wherein the binding domains or binding units are linked via a linker such that the trivalent or triparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) construct of the invention is capable of (simultaneously) binding to both the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a trivalent, biparatopic or triparatopic construct, wherein the binding domains or binding units are linked via a linker such that the trivalent, biparatopic or triparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) construct of the invention is capable of (simultaneously) binding to both the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus as well as the other antigenic determinant, epitope, part or domain of the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as a binding domain or binding unit in providing and/or preparing a trivalent, biparatopic or triparatopic construct, wherein the binding domains or binding units are linked via a linker such that the trivalent, biparatopic or triparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least three monovalent constructs of the invention (and in particular at least three NANOBODIES® (VHH sequences)) are used that are directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that are capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus. In such a preferred trivalent construct of the invention, the linker is most preferably such that the trivalent construct of the invention is capable of (simultaneously) binding to three sialic acid binding sites on the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of three monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the sialic acid binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with sialic acid for binding to the hemagglutinin H5 envelope protein of influenza virus, as binding domains or binding units in providing and/or preparing a trivalent construct, wherein the binding domains or binding units are linked via a linker such that the trivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least three monovalent constructs of the invention (and in particular at least three NANOBODIES® (VHH sequences)) are used that are directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that are capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus. In such a preferred trivalent construct of the invention, the linker is most preferably such that the trivalent construct of the invention is capable of (simultaneously) binding to three VN04-2 binding sites on the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of three monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus, as binding domains or binding units in providing and/or preparing a trivalent construct, wherein the binding domains or binding units are linked via a linker such that the trivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least three monovalent constructs of the invention (and in particular at least three NANOBODIES® (V HH sequences)) are used that are directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that are capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus. In such a preferred trivalent construct of the invention, the linker is most preferably such that the trivalent construct of the invention is capable of (simultaneously) binding to three MAb C179 binding sites on the hemagglutinin H5 envelope protein of influenza virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of three monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or that is capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus, as binding domains or binding units in providing and/or preparing a trivalent construct, wherein the binding domains or binding units are linked via a linker such that the trivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In another aspect, the invention relates to multivalent polypeptides directed against the G envelope protein of rabies virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus.

In another aspect, the invention relates to multivalent polypeptides directed against the G envelope protein of rabies virus, in which at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the G envelope protein of rabies virus. In such a preferred multiparatopic construct of the invention, the linker is most preferably such that the multiparatopic construct of the invention is capable of (simultaneously) binding to both the MAb 8-2 binding site on the G envelope protein of rabies virus as well as the other antigenic determinant, epitope, part or domain of the G envelope protein of rabies virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus, as a binding domain or binding unit in providing and/or preparing a multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct, wherein the binding domains or binding units are linked via a linker such that the multivalent or multiparatopic (such as multispecific, multiparatopic, and preferably trivalent, bivalent, triparatopic, biparatopic, trispecific, bispecific, etc.) construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred biparatopic polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the G envelope protein of rabies virus. In such a preferred biparatopic construct of the invention, the linker is most preferably such that the biparatopic construct of the invention is capable of (simultaneously) binding to both the MAb 8-2 binding site on the G envelope protein of rabies virus as well as the other antigenic determinant, epitope, part or domain of the G envelope protein of rabies virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus, as a binding domain or binding unit in providing and/or preparing a biparatopic construct, wherein the binding domains or binding units are linked via a linker such that the biparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred bivalent polypeptides of the invention, at least two monovalent constructs of the invention (and in particular at least two NANOBODIES® (VHH sequences)) are used that are directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that are capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus. In such a preferred bivalent construct of the invention, the linker is most preferably such that the bivalent construct of the invention is capable of (simultaneously) binding to two MAb 8-2 binding sites on the G envelope protein of rabies virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of two monovalent constructs comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus, as binding domains or binding units in providing and/or preparing a bivalent construct, wherein the binding domains or binding units are linked via a linker such that the bivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus.

In some of the most preferred trivalent (biparatopic or triparatopic) polypeptides of the invention, at least one monovalent construct of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus; and at least one amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) is used that is directed against another antigenic determinant, epitope, part or domain of the G envelope protein of rabies virus. In such a preferred trivalent (biparatopic or triparatopic) construct of the invention, the linker is most preferably such that the trivalent (biparatopic or triparatopic) construct of the invention is capable of (simultaneously) binding to the MAb 8-2 binding sites on the G envelope protein of rabies virus as well as the other antigenic determinant, epitope, part or domain of the G envelope protein of rabies virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of a monovalent construct comprising an amino acid of the invention (and in particular a NANOBODY® (V HH sequence)) that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus, as a binding domain or binding unit in providing and/or preparing a trivalent, biparatopic or triparatopic construct, wherein the binding domains or binding units are linked via a linker such that the trivalent or triparatopic construct preferably exhibits intramolecular binding compared to intermolecular binding.

In some of the most preferred trivalent polypeptides of the invention, at least three monovalent constructs of the invention (and in particular at least three NANOBODIES® (VHH sequences)) are used that are directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that are capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus. In such a preferred trivalent construct of the invention, the linker is most preferably such that the trivalent construct of the invention is capable of (simultaneously) binding to three MAb 8-2 binding sites on the G envelope protein of rabies virus, again most preferably so as to allow binding with increased avidity and also intramolecular binding and/or recognition.

Accordingly, also encompassed in the present invention is the use of three monovalent construct comprising an amino acid sequence of the invention (and in particular at least one NANOBODY® (V HH sequence)) that is directed against the MAb 8-2 binding site on the G envelope protein of rabies virus and/or that is capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus, as binding domains or binding units in providing and/or preparing a trivalent construct, wherein the binding domains or binding units are linked via a linker such that the trivalent construct preferably exhibits intramolecular binding compared to intermolecular binding.

The invention further relates to applications and uses of the amino acid sequences, compounds, constructs, polypeptides, nucleic acids, host cells, products and compositions described herein, as well as to methods for the prevention and/or treatment for diseases and disorders associated with viral entry and/or viral replication and/or mediated by an envelope protein of a virus and/or its viral receptor. Some preferred but non-limiting applications and uses will become clear from the further description herein.

The invention also relates to the amino acid sequences, compounds, constructs, polypeptides, nucleic acids, host cells, products and compositions described herein for use in therapy.

In particular, the invention also relates to the amino acid sequences, compounds, constructs, polypeptides, nucleic acids, host cells, products and compositions described herein for use in therapy of a disease or disorder that can be prevented or treated by administering, to a subject in need thereof, of (a pharmaceutically effective amount of) an amino acid sequence, compound, construct or polypeptide as described herein.

More in particular, the invention relates to the amino acid sequences, compounds, constructs, polypeptides, nucleic acids, host cells, products and compositions described herein for use in therapy of viral diseases.

Other aspects, embodiments, advantages and applications of the invention will also become clear from the further description herein, in which the invention will be described and discussed in more detail with reference to the NANOBODIES® (VHH sequences) of the invention and polypeptides of the invention comprising the same, which form some of the preferred aspects of the invention.

As will become clear from the further description herein, NANOBODIES® (VHH sequences) generally offer certain advantages (outlined herein) compared to “dAb's” or similar (single) domain antibodies or immunoglobulin sequences, which advantages are also provided by the NANOBODIES® (VHH sequences) of the invention. However, it will be clear to the skilled person that the more general aspects of the teaching below can also be applied (either directly or analogously) to other amino acid sequences of the invention.

In the present description, examples and claims:

a) Unless indicated or defined otherwise, all terms used have their usual meaning in the art, which will be clear to the skilled person. Reference is for example made to the standard handbooks mentioned in paragraph a) on page 46 of WO 08/020079. b) Unless indicated otherwise, the terms “immunoglobulin sequence”, “sequence”, “nucleotide sequence” and “nucleic acid” are as described in paragraph b) on page 46 of WO 08/020079 c) Unless indicated otherwise, all methods, steps, techniques and manipulations that are not specifically described in detail can be performed and have been performed in a manner known per se, as will be clear to the skilled person. Reference is for example again made to the standard handbooks and the general background art mentioned herein and to the further references cited therein; as well as to for example the following reviews Presta, Adv. Drug Deliv. Rev. 2006, 58 (5-6): 640-56; Levin and Weiss, Mol. Biosyst. 2006, 2(1): 49-57; Irving et al., J. Immunol. Methods, 2001, 248(1-2), 31-45; Schmitz et al., Placenta, 2000, 21 Suppl. A, S106-12, Gonzales et al., Tumour Biol., 2005, 26(1), 31-43, which describe techniques for protein engineering, such as affinity maturation and other techniques for improving the specificity and other desired properties of proteins such as immunoglobulins. d) Amino acid residues will be indicated according to the standard three-letter or one-letter amino acid code. Reference is made to Table A-2 on page 48 of the International application WO 08/020079 of Ablynx N.V. entitled “Amino acid sequences directed against IL-6R and polypeptides comprising the same for the treatment of diseases and disorders associated with 11-6 mediated signalling”. e) For the purposes of comparing two or more nucleotide sequences, the percentage of “sequence identity” between a first nucleotide sequence and a second nucleotide sequence may be calculated or determined as described in paragraph c) on page 49 of WO 08/020079 (incorporated herein by reference), such as by dividing [the number of nucleotides in the first nucleotide sequence that are identical to the nucleotides at the corresponding positions in the second nucleotide sequence] by [the total number of nucleotides in the first nucleotide sequence] and multiplying by [100%], in which each deletion, insertion, substitution or addition of a nucleotide in the second nucleotide sequence—compared to the first nucleotide sequence—is considered as a difference at a single nucleotide (position); or using a suitable computer algorithm or technique, again as described in paragraph c) on pages 49 of WO 08/020079 (incorporated herein by reference). f) For the purposes of comparing two or more amino acid sequences, the percentage of “sequence identity” between a first amino acid sequence and a second amino acid sequence (also referred to herein as “amino acid identity”) may be calculated or determined as described in paragraph f) on pages 49 and 50 of WO 08/020079 (incorporated herein by reference), such as by dividing [the number of amino acid residues in the first amino acid sequence that are identical to the amino acid residues at the corresponding positions in the second amino acid sequence] by [the total number of amino acid residues in the first amino acid sequence] and multiplying by [100%], in which each deletion, insertion, substitution or addition of an amino acid residue in the second amino acid sequence—compared to the first amino acid sequence—is considered as a difference at a single amino acid residue (position), i.e. as an “amino acid difference” as defined herein; or using a suitable computer algorithm or technique, again as described in paragraph f) on pages 49 and 50 of WO 08/020079 (incorporated herein by reference).

Also, in determining the degree of sequence identity between two amino acid sequences, the skilled person may take into account so-called “conservative” amino acid substitutions, as described on page 50 of WO 08/020079. Any amino acid substitutions applied to the polypeptides described herein may also be based on the analysis of the frequencies of amino acid variations between homologous proteins of different species developed by Schulz et al., Principles of Protein Structure, Springer-Verlag, 1978, on the analyses of structure forming potentials developed by Chou and Fasman, Biochemistry 13: 211, 1974 and Adv. Enzymol., 47: 45-149, 1978, and on the analysis of hydrophobicity patterns in proteins developed by Eisenberg et al., Proc. Natl. Acad Sci. USA 81: 140-144, 1984; Kyte & Doolittle; J Molec. Biol. 157: 105-132, 198 1, and Goldman et al., Ann. Rev. Biophys. Chem. 15: 321-353, 1986, all incorporated herein in their entirety by reference. Information on the primary, secondary and tertiary structure of NANOBODIES® (VHH sequences) is given in the description herein and in the general background art cited above. Also, for this purpose, the crystal structure of a V HH domain from a llama is for example given by Desmyter et al., Nature Structural Biology, Vol. 3, 9, 803 (1996); Spinelli et al., Natural Structural Biology (1996); 3, 752-757; and Decanniere et al., Structure, Vol. 7, 4, 361 (1999). Further information about some of the amino acid residues that in conventional V H domains form the V H /V L interface and potential camelizing substitutions on these positions can be found in the prior art cited above.

g) Amino acid sequences and nucleic acid sequences are said to be “exactly the same” if they have 100% sequence identity (as defined herein) over their entire length; h) When comparing two amino acid sequences, the term “amino acid difference” refers to an insertion, deletion or substitution of a single amino acid residue on a position of the first sequence, compared to the second sequence; it being understood that two amino acid sequences can contain one, two or more such amino acid differences; i) When a nucleotide sequence or amino acid sequence is said to “comprise” another nucleotide sequence or amino acid sequence, respectively, or to “essentially consist of” another nucleotide sequence or amino acid sequence, this has the meaning given in paragraph i) on pages 51-52 of WO 08/020079. j) The term “in essentially isolated form” has the meaning given to it in paragraph j) on pages 52 and 53 of WO 08/020079. k) The terms “domain” and “binding domain” have the meanings given to it in paragraph k) on page 53 of WO 08/020079. l) The terms “antigenic determinant” and “epitope”, which may also be used interchangeably herein. have the meanings given to it in paragraph 1) on page 53 of WO 08/020079. m) As further described in paragraph m) on page 53 of WO 08/020079, an amino acid sequence (such as a NANOBODY® (V HH sequence), an antibody, a polypeptide of the invention, or generally an antigen binding protein or polypeptide or a fragment thereof) that can (specifically) bind to, that has affinity for and/or that has specificity for a specific antigenic determinant, epitope, antigen or protein (or for at least one part, fragment or epitope thereof) is said to be “against” or “directed against” said antigenic determinant, epitope, antigen or protein. n) The term “specificity” has the meaning given to it in paragraph n) on pages 53-56 of WO 08/020079; and as mentioned therein refers to the number of different types of antigens or antigenic determinants to which a particular antigen-binding molecule or antigen-binding protein (such as a NANOBODY® (V HH sequence) or a polypeptide of the invention) molecule can bind. The specificity of an antigen-binding protein can be determined based on affinity and/or avidity, as described on pages 53-56 of WO 08/020079 (incorporated herein by reference), which also describes some preferred techniques for measuring binding between an antigen-binding molecule (such as a NANOBODY® (V HH sequence) or polypeptide of the invention) and the pertinent antigen. Typically, antigen-binding proteins (such as the amino acid sequences, NANOBODIES® (VHH sequences) and/or polypeptides of the invention) will bind to their antigen with a dissociation constant (K D ) of 10 −5 to 10 −12 moles/liter or less, and preferably 10 −7 to 10 −12 moles/liter or less and more preferably 10 −8 to 10 −12 moles/liter (i.e. with an association constant (K A ) of 10 5 to 10 12 liter/moles or more, and preferably 10 7 to 10 12 liter/moles or more and more preferably 10 8 to 10 12 liter/moles). Any K D value greater than 10 4 mol/liter (or any K A value lower than 10 4 M −1 ) liters/mol is generally considered to indicate non-specific binding. Preferably, a monovalent immunoglobulin sequence of the invention will bind to the desired antigen with an affinity less than 500 nM, preferably less than 200 nM, more preferably less than 10 nM, such as less than 500 pM. Specific binding of an antigen-binding protein to an antigen or antigenic determinant can be determined in any suitable manner known per se, including, for example, Scatchard analysis and/or competitive binding assays, such as radioimmunoassays (RIA), enzyme immunoassays (EIA) and sandwich competition assays, and the different variants thereof known per se in the art; as well as the other techniques mentioned herein. As will be clear to the skilled person, and as described on pages 53-56 of WO 08/020079, the dissociation constant may be the actual or apparent dissociation constant. Methods for determining the dissociation constant will be clear to the skilled person, and for example include the techniques mentioned on pages 53-56 of WO 08/020079. o) The half-life of an amino acid sequence, compound or polypeptide of the invention can generally be defined as described in paragraph o) on page 57 of WO 08/020079 and as mentioned therein refers to the time taken for the serum concentration of the amino acid sequence, compound or polypeptide to be reduced by 50%, in vivo, for example due to degradation of the sequence or compound and/or clearance or sequestration of the sequence or compound by natural mechanisms. The in vivo half-life of an amino acid sequence, compound or polypeptide of the invention can be determined in any manner known per se, such as by pharmacokinetic analysis. Suitable techniques will be clear to the person skilled in the art, and may for example generally be as described in paragraph o) on page 57 of WO 08/020079. As also mentioned in paragraph o) on page 57 of WO 08/020079, the half-life can be expressed using parameters such as the t½-alpha, t½-beta and the area under the curve (AUC). Reference is for example made to the Experimental Part below, as well as to the standard handbooks, such as Kenneth, A et al: Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists and Peters et al, Pharmacokinetic analysis: A Practical Approach (1996). Reference is also made to “Pharmacokinetics”, M Gibaldi & D Perron, published by Marcel Dekker, 2nd Rev. edition (1982). The terms “increase in half-life” or “increased half-life” as also as defined in paragraph o) on page 57 of WO 08/020079 and in particular refer to an increase in the t½-beta, either with or without an increase in the t½-alpha and/or the AUC or both. p) In the context of the present invention, “modulating” or “to modulate” generally means either reducing or inhibiting the activity of, or alternatively increasing the activity of, a target or antigen, as measured using a suitable in vitro, cellular or in vivo assay. In particular, “modulating” or “to modulate” may mean either reducing or inhibiting the activity of, or alternatively increasing a (relevant or intended) biological activity of, a target or antigen, as measured using a suitable in vitro, cellular or in vivo assay (which will usually depend on the target or antigen involved), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to activity of the target or antigen in the same assay under the same conditions but without the presence of the construct of the invention.

As will be clear to the skilled person, “modulating” may also involve effecting a change (which may either be an increase or a decrease) in affinity, avidity, specificity and/or selectivity of a target or antigen for one or more of its binding partners, partners for association into a homomultimeric or heteromultimeric form; and/or effecting a change (which may either be an increase or a decrease) in the sensitivity of the target or antigen for one or more conditions in the medium or surroundings in which the target or antigen is present (such as pH, ion strength, the presence of co-factors, etc.), compared to the same conditions but without the presence of the construct of the invention. As will be clear to the skilled person, this may again be determined in any suitable manner and/or using any suitable assay known per se, depending on the target or antigen involved. “Modulating” may also mean effecting a change (i.e. an activity as an agonist, as an antagonist or as a reverse agonist, respectively, depending on the target or antigen and the desired biological or physiological effect) with respect to one or more biological or physiological mechanisms, effects, responses, functions, pathways or activities in which the target or antigen (or in which its binding partners or pathway(s) are involved, such as its signalling pathway or metabolic pathway and their associated biological or physiological effects) is involved. Again, as will be clear to the skilled person, such an action as an agonist or an antagonist may be determined in any suitable manner and/or using any suitable (in vitro and usually cellular or in assay) assay known per se, depending on the target or antigen involved. In particular, an action as an agonist or antagonist may be such that an intended biological or physiological activity is increased or decreased, respectively, by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to the biological or physiological activity in the same assay under the same conditions but without the presence of the construct of the invention. Modulating may for example also involve allosteric modulation of the target or antigen; and/or reducing or inhibiting the binding of the target or antigen to one of its binding partners and/or competing with a natural binding partner for binding to the target or antigen. Modulating may also involve activating the target or antigen or the mechanism or pathway in which it is involved. Modulating may for example also involve effecting a change in respect of the folding or conformation of the target or antigen, or in respect of the ability of the target or antigen to fold, to change its conformation (for example, upon binding of a binding partner), to associate with other (sub)units, or to disassociate. Modulating may for example also involve effecting a change in the ability of the target or antigen to transport other compounds or to serve as a channel for other compounds (such as ions). Modulating may be reversible or irreversible, but for pharmaceutical and pharmacological purposes will usually be in a reversible manner.

q) In respect of a target or antigen, the term “interaction site” on the target or antigen means a site, epitope, antigenic determinant, part, domain or stretch of amino acid residues on the target or antigen that is a site for binding to a receptor or other binding partner, a catalytic site, a cleavage site, a site for allosteric interaction, a site involved in multimerisation (such as homomerization or heterodimerization) of the target or antigen; or any other site, epitope, antigenic determinant, part, domain or stretch of amino acid residues on the target or antigen that is involved in a biological action or mechanism of the target or antigen. More generally, an “interaction site” can be any site, epitope, antigenic determinant, part, domain or stretch of amino acid residues on the target or antigen to which an amino acid sequence or polypeptide of the invention can bind such that the target or antigen (and/or any pathway, interaction, signalling, biological mechanism or biological effect in which the target or antigen is involved) is modulated (as defined herein). r) An amino acid sequence or polypeptide is said to be “specific for” a first target or antigen compared to a second target or antigen when is binds to the first antigen with an affinity (as described above, and suitably expressed as a K D value, K A value, K off rate and/or K on rate) that is at least 10 times, such as at least 100 times, and preferably at least 1000 times, and up to 10.000 times or more better than the affinity with which said amino acid sequence or polypeptide binds to the second target or polypeptide. For example, the first antigen may bind to the target or antigen with a K D value that is at least 10 times less, such as at least 100 times less, and preferably at least 1000 times less, such as 10.000 times less or even less than that, than the K D with which said amino acid sequence or polypeptide binds to the second target or polypeptide. Preferably, when an amino acid sequence or polypeptide is “specific for” a first target or antigen compared to a second target or antigen, it is directed against (as defined herein) said first target or antigen, but not directed against said second target or antigen. s) The terms “cross-block”, “cross-blocked” and “cross-blocking” are used interchangeably herein to mean the ability of an amino acid sequence or other binding agent (such as a polypeptide of the invention) to interfere with the binding of other amino acid sequences or binding agents of the invention to a given target. The extend to which an amino acid sequence or other binding agents of the invention is able to interfere with the binding of another to the target, and therefore whether it can be said to cross-block according to the invention, can be determined using competition binding assays. One particularly suitable quantitative cross-blocking assay uses a Biacore machine which can measure the extent of interactions using surface plasmon resonance technology. Another suitable quantitative cross-blocking assay uses an ELISA-based approach to measure competition between amino acid sequences or other binding agents in terms of their binding to the target.

The following generally describes a suitable Biacore assay for determining whether an amino acid sequence or other binding agent cross-blocks or is capable of cross-blocking according to the invention. It will be appreciated that the assay can be used with any of the amino acid sequences or other binding agents described herein. The Biacore machine (for example the Biacore 3000) is operated in line with the manufacturer's recommendations. Thus in one cross-blocking assay, the target protein is coupled to a CM5 Biacore chip using standard amine coupling chemistry to generate a surface that is coated with the target. Typically 200-800 resonance units of the target would be coupled to the chip (an amount that gives easily measurable levels of binding but that is readily saturable by the concentrations of test reagent being used). Two test amino acid sequences (termed A* and B*) to be assessed for their ability to cross-block each other are mixed at a one to one molar ratio of binding sites in a suitable buffer to create the test mixture. When calculating the concentrations on a binding site basis the molecular weight of an amino acid sequence is assumed to be the total molecular weight of the amino acid sequence divided by the number of target binding sites on that amino acid sequence. The concentration of each amino acid sequence in the test mix should be high enough to readily saturate the binding sites for that amino acid sequence on the target molecules captured on the Biacore chip. The amino acid sequences in the mixture are at the same molar concentration (on a binding basis) and that concentration would typically be between 1.00 and 1.5 micromolar (on a binding site basis). Separate solutions containing A* alone and B* alone are also prepared. A* and B* in these solutions should be in the same buffer and at the same concentration as in the test mix. The test mixture is passed over the target-coated Biacore chip and the total amount of binding recorded. The chip is then treated in such a way as to remove the bound amino acid sequences without damaging the chip-bound target. Typically this is done by treating the chip with 30 mM HCl for 60 seconds. The solution of A* alone is then passed over the target-coated surface and the amount of binding recorded. The chip is again treated to remove all of the bound amino acid sequences without damaging the chip-bound target. The solution of B* alone is then passed over the target-coated surface and the amount of binding recorded. The maximum theoretical binding of the mixture of A* and B* is next calculated, and is the sum of the binding of each amino acid sequence when passed over the target surface alone. If the actual recorded binding of the mixture is less than this theoretical maximum then the two amino acid sequences are cross-blocking each other. Thus, in general, a cross-blocking amino acid sequence or other binding agent according to the invention is one which will bind to the target in the above Biacore cross-blocking assay such that during the assay and in the presence of a second amino acid sequence or other binding agent of the invention the recorded binding is between 80% and 0.1% (e.g. 80% to 4%) of the maximum theoretical binding, specifically between 75% and 0.1% (e.g. 75% to 4%) of the maximum theoretical binding, and more specifically between 70% and 0.1% (e.g. 70% to 4%) of maximum theoretical binding (as just defined above) of the two amino acid sequences or binding agents in combination. The Biacore assay described above is a primary assay used to determine if amino acid sequences or other binding agents cross-block each other according to the invention. On rare occasions particular amino acid sequences or other binding agents may not bind to a target coupled via amine chemistry to a CM5 Biacore chip (this usually occurs when the relevant binding site on the target is masked or destroyed by the coupling to the chip). In such cases cross-blocking can be determined using a tagged version of the target, for example a N-terminal His-tagged version. In this particular format, an anti-His amino acid sequence would be coupled to the Biacore chip and then the His-tagged target would be passed over the surface of the chip and captured by the anti-His amino acid sequence. The cross blocking analysis would be carried out essentially as described above, except that after each chip regeneration cycle, new His-tagged target would be loaded back onto the anti-His amino acid sequence coated surface. In addition to the example given using N-terminal His-tagged target, C-terminal His-tagged target could alternatively be used. Furthermore, various other tags and tag binding protein combinations that are known in the art could be used for such a cross-blocking analysis (e.g. HA tag with anti-HA antibodies; FLAG tag with anti-FLAG antibodies; biotin tag with streptavidin). The following generally describes an ELISA assay for determining whether an amino acid sequence or other binding agent directed against a target cross-blocks or is capable of cross-blocking as defined herein. It will be appreciated that the assay can be used with any of the amino acid sequences (or other binding agents such as polypeptides of the invention) described herein. The general principal of the assay is to have an amino acid sequence or binding agent that is directed against the target coated onto the wells of an ELISA plate. An excess amount of a second, potentially cross-blocking, anti-target amino acid sequence is added in solution (i.e. not bound to the ELISA plate). A limited amount of the target is then added to the wells. The coated amino acid sequence and the amino acid sequence in solution compete for binding of the limited number of target molecules. The plate is washed to remove excess target that has not been bound by the coated amino acid sequence and to also remove the second, solution phase amino acid sequence as well as any complexes formed between the second, solution phase amino acid sequence and target. The amount of bound target is then measured using a reagent that is appropriate to detect the target. An amino acid sequence in solution that is able to cross-block the coated amino acid sequence will be able to cause a decrease in the number of target molecules that the coated amino acid sequence can bind relative to the number of target molecules that the coated amino acid sequence can bind in the absence of the second, solution phase, amino acid sequence. In the instance where the first amino acid sequence, e.g. an Ab-X, is chosen to be the immobilized amino acid sequence, it is coated onto the wells of the ELISA plate, after which the plates are blocked with a suitable blocking solution to minimize non-specific binding of reagents that are subsequently added. An excess amount of the second amino acid sequence, i.e. Ab-Y, is then added to the ELISA plate such that the moles of Ab-Y target binding sites per well are at least 10 fold higher than the moles of Ab-X target binding sites that were used, per well, during the coating of the ELISA plate. Target is then added such that the moles of target added per well are at least 25-fold lower than the moles of Ab-X target binding sites that were used for coating each well. Following a suitable incubation period the ELISA plate is washed and a reagent for detecting the target is added to measure the amount of target specifically bound by the coated anti-target amino acid sequence (in this case Ab-X). The background signal for the assay is defined as the signal obtained in wells with the coated amino acid sequence (in this case Ab-X), second solution phase amino acid sequence (in this case Ab-Y), target buffer only (i.e. without target) and target detection reagents. The positive control signal for the assay is defined as the signal obtained in wells with the coated amino acid sequence (in this case Ab-X), second solution phase amino acid sequence buffer only (i.e. without second solution phase amino acid sequence), target and target detection reagents. The ELISA assay may be run in such a manner so as to have the positive control signal be at least 6 times the background signal. To avoid any artefacts (e.g. significantly different affinities between Ab-X and Ab-Y for the target) resulting from the choice of which amino acid sequence to use as the coating amino acid sequence and which to use as the second (competitor) amino acid sequence, the cross-blocking assay may to be run in two formats: 1) format 1 is where Ab-X is the amino acid sequence that is coated onto the ELISA plate and Ab-Y is the competitor amino acid sequence that is in solution and 2) format 2 is where Ab-Y is the amino acid sequence that is coated onto the ELISA plate and Ab-X is the competitor amino acid sequence that is in solution. Ab-X and Ab-Y are defined as cross-blocking if, either in format 1 or in format 2, the solution phase anti-target amino acid sequence is able to cause a reduction of between 60% and 100%, specifically between 70% and 100%, and more specifically between 80% and 100%, of the target detection signal {i.e. the amount of target bound by the coated amino acid sequence) as compared to the target detection signal obtained in the absence of the solution phase anti-target amino acid sequence (i.e. the positive control wells).

t) An amino acid sequence is said to be “cross-reactive” for two different antigens or antigenic determinants (such as e.g. serum albumin from two different species of mammal, such as e.g. human serum albumin and cyno serum albumin, such as e.g. the same envelop proteins of different strains of a virus, such as e.g. the same envelope proteins of different genotypes of a virus) if it is specific for (as defined herein) both these different antigens or antigenic determinants. u) By binding that is “essentially independent of the pH” is generally meant herein that the association constant (K A ) of the amino acid sequence with respect to the serum protein (such as serum albumin) at the pH value(s) that occur in a cell of an animal or human body (as further described herein) is at least 5%, such as at least 10%, preferably at least 25%, more preferably at least 50%, even more preferably at least 60%, such as even more preferably at least 70%, such as at least 80% or 90% or more (or even more than 100%, such as more than 110%, more than 120% or even 130% or more, or even more than 150%, or even more than 200%) of the association constant (K A ) of the amino acid sequence with respect to the same serum protein at the pH value(s) that occur outside said cell. Alternatively, by binding that is “essentially independent of the pH” is generally meant herein that the k off rate (measured by Biacore) of the amino acid sequence with respect to the serum protein (such as serum albumin) at the pH value(s) that occur in a cell of an animal or human body (as e.g. further described herein, e.g. pH around 5.5, e.g. 5.3 to 5.7) is at least 5%, such as at least 10%, preferably at least 25%, more preferably at least 50%, even more preferably at least 60%, such as even more preferably at least 70%, such as at least 80% or 90% or more (or even more than 100%, such as more than 110%, more than 120% or even 130% or more, or even more than 150%, or even more than 200%) of the k off rate of the amino acid sequence with respect to the same serum protein at the pH value(s) that occur outside said cell, e.g. pH 7.2 to 7.4. By “the pH value(s) that occur in a cell of an animal or human body” is meant the pH value(s) that may occur inside a cell, and in particular inside a cell that is involved in the recycling of the serum protein. In particular, by “the pH value(s) that occur in a cell of an animal or human body” is meant the pH value(s) that may occur inside a (sub)cellular compartment or vesicle that is involved in recycling of the serum protein (e.g. as a result of pinocytosis, endocytosis, transcytosis, exocytosis and phagocytosis or a similar mechanism of uptake or internalization into said cell), such as an endosome, lysosome or pinosome. v) As further described herein, the total number of amino acid residues in a NANOBODY® (V HH sequence) can be in the region of 110-120, is preferably 112-115, and is most preferably 113. It should however be noted that parts, fragments, analogs or derivatives (as further described herein) of a NANOBODY® (V HH sequence) are not particularly limited as to their length and/or size, as long as such parts, fragments, analogs or derivatives meet the further requirements outlined herein and are also preferably suitable for the purposes described herein; w) As further described in paragraph q) on pages 58 and 59 of WO 08/020079 (incorporated herein by reference), the amino acid residues of a NANOBODY® (V HH sequence) are numbered according to the general numbering for V H domains given by Kabat et al. (“Sequence of proteins of immunological interest”, US Public Health Services, NIH Bethesda, Md., Publication No. 91), as applied to V HH domains from Camelids in the article of Riechmann and Muyldermans, J. Immunol. Methods 2000 Jun. 23; 240 (1-2): 185-195 (see for example FIG. 2 of this publication), and accordingly FR1 of a NANOBODY® (V HH sequence) comprises the amino acid residues at positions 1-30, CDR1 of a NANOBODY® (V HH sequence) comprises the amino acid residues at positions 31-35, FR2 of a NANOBODY® (V HH sequence) comprises the amino acids at positions 36-49, CDR2 of a NANOBODY® (V HH sequence) comprises the amino acid residues at positions 50-65, FR3 of a NANOBODY® (V HH sequence) comprises the amino acid residues at positions 66-94, CDR3 of a NANOBODY® (V HH sequence) comprises the amino acid residues at positions 95-102, and FR4 of a NANOBODY® (V HH sequence) comprises the amino acid residues at positions 103-113. x) In the context of the present invention “target host cell (of a virus)” generally refers to a particular cell, which is or is derived from a living subject, being susceptible to infection with said virus. y) The term “infectivity of a virus”, as used herein, refers to the proportion of living subjects that, when exposed to said virus, actually become infected by said virus. z) The term “neutralization of a virus”, as used herein, refers to the modulation and/or reduction and/or prevention and/or inhibition of the infectivity (as defined herein) of a virus by binding of a neutralizing compound to the virion, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, “neutralizing (a virus)” or “to neutralize (a virus)” may mean either modulating, reducing, preventing or inhibiting the infectivity (as defined herein) of a virus, which can be mediated by an envelope protein of a virus and/or its viral receptor as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) infectivity (as defined herein) of a virus, which is mediated by an envelope protein of a virus and/or its viral receptor in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence) or polypeptide of the invention. aa) The term “viral attachment protein”, as used herein, is any protein that is present on the virion surface and that is able to directly (for example by interacting with a viral receptor) or indirectly (for example by mediating the interaction of one or more other proteins or molecules to a viral receptor) mediate viral attachment to a target host cell. bb) The term “viral fusion protein”, as used herein, is any protein that is present on the virion surface and that is able to directly (for example by interacting with membrane compounds of the target host cell) or indirectly (for example by mediating the interaction of one or more other proteins or molecules with membrane compounds of the target host cell) mediate viral fusion to a target host cell. cc) The term “viral attachment and viral fusion protein”, as used herein is any protein that is present on the virion surface and that is able to directly (for example by interacting with a viral receptor and/or membrane compounds of the target host cell) or indirectly (for example by mediating the interaction of one or more other proteins or molecules to a viral receptor and/or one or more other proteins or molecules with membrane compounds of the target host cell) mediate viral attachment and viral fusion to a target host cell. dd) The term “pre-fusion conformational state (of a viral (attachment, fusion, or both attachment and fusion) protein)”, as used herein, refers to the primary and/or secondary and/or tertiary and/or quaternary conformational state of a viral (attachment, fusion, or both attachment and fusion) protein before and/or during the fusion process of a virion with its target host cell, wherein said virion has said viral (attachment, fusion, or both attachment and fusion) protein exposed on its surface. ee) The term “intermediate fusion conformational state (of a viral (attachment, fusion, or both attachment and fusion) protein)”, as used herein, refers to the primary and/or secondary and/or tertiary and/or quaternary conformational state of a viral (attachment, fusion, or both attachment and fusion) protein during the fusion process of a virion with its target host cell, wherein said virion has said viral (attachment, fusion, or both attachment and fusion) protein exposed on its surface. ff) The term “post-fusion conformational state (of a viral (attachment, fusion, or both attachment and fusion) protein)”, as used herein, refers to the primary and/or secondary and/or tertiary and/or quaternary conformational state of a viral (attachment, fusion, or both attachment and fusion) protein during and/or after the fusion process of a virion with its target host cell, wherein said virion has said viral (attachment, fusion, or both attachment and fusion) protein exposed on its surface. gg) The term “viral receptor”, as used herein, refers to a specific molecular component of the cell, which is capable of recognizing and interacting with a virus, and which, after binding to said virus, is capable of generating a signal that initiates a chain of events leading to a biological response. hh) The term “viral entry” used herein encompasses any viral-mediated biological pathway that is needed to accomplish virion attachment to a target host cell and/or viral fusion with a target host cell. It is encompassed in the present invention that viral entry, which may be any viral-mediated biological pathway that is needed to accomplish virion attachment to a target host cell and/or viral fusion with a target host cell, can be modulated and/or reduced and/or prevented and/or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, viral entry, which can be mediated by an envelope protein of a virus and/or its viral receptor, can be modulated, reduced, prevented or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral entry (as defined herein), which can be mediated by an envelope protein of a virus and/or its viral receptor in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), polypeptide and/or compound of the invention. Thus, it is also encompassed that that viral attachment and/or viral fusion can be modulated and/or reduced and/or prevented and/or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, viral attachment and/or viral fusion, which can be mediated by an envelope protein of a virus and/or its viral receptor, can be modulated, reduced, prevented or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral attachment and/or viral fusion, which can be mediated by an envelope protein of a virus and/or its viral receptor in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), polypeptide and/or compound of the invention. ii) The term “viral replication” used herein encompasses any viral-mediated biological pathway that is needed to accomplish transcription and/or translation of the viral genome and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane. It is encompassed in the present invention that viral replication, which may be any viral-mediated biological pathway that is needed to accomplish transcription and/or translation of the viral genome and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane, can be modulated and/or reduced and/or prevented and/or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, viral replication, which can be mediated by an envelope protein of a virus and/or its viral receptor, can be modulated, reduced, prevented or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral replication (as defined herein), which can be mediated by an envelope protein of a virus and/or its viral receptor, in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), polypeptide and/or compound of the invention. Thus, it is also encompassed that transcription and/or translation of the viral genome and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane can be modulated and/or reduced and/or prevented and/or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, transcription and/or translation of the viral genome and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane, which can be mediated by an envelope protein of a virus and/or its viral receptor, can be modulated, reduced, prevented or inhibited by specific binding of the amino acid sequences, NANOBODIES® (VHH sequences), polypeptides and/or compounds of the invention to an envelope protein of a virus, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) transcription and/or translation of the viral genome and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane, which can be mediated by an envelope protein of a virus and/or its viral receptor in the same assay under the same conditions but without the presence of the amino acid sequence, NANOBODY® (V HH sequence), polypeptide and/or compound of the invention. jj) In the context of the present invention “a virus” may be any virus that is generally known in the art. In particular, said virus may be chosen from the group consisting of a DNA virus (such as but not limited to a dsDNA virus or a ssDNA virus), an RNA virus (such as but not limited to a dsRNA virus, a positive-sense ssRNA virus or a negative-sense ssRNA virus) and a Reverse Transcriptase (RT) virus (such as but not limited to dsDNA-RT virus and a ssRNA-RT virus. For example, said virus may belong to a viral family chosen from the group consisting of Orthomyxoviridae, Paramyxoviridae, Filoviridae, Retroviridae, Coronaviridae, Togaviridae and Flaviviridae, Rhabdoviridae, Herpesviridae, Arenaviridae, Bornaviridae, Bunyaviridae, Hepadnaviridae and Poxviridae; and said virus may for instance belong to a viral genus chosen from the group consisting of Alphaviruses and Flaviviruses. Accordingly, amino acid sequences, polypeptides and compositions according to the invention may be directed against at least one epitope of an envelope protein of any of the foregoing viruses, chosen from the group consisting of a DNA virus (such as but not limited to a ds DNA virus or a ssDNA virus), an RNA virus (such as but not limited to a dsRNA virus, a positive-sense ssRNA virus or a negative-sense ssRNA virus) and a Reverse Transcriptase (RT) virus (such as but not limited to dsDNA-RT virus and a ssRNA-RT virus. For example, said virus may belong to a viral family chosen from the group consisting of Orthomyxoviridae, Paramyxoviridae, Filoviridae, Retroviridae, Coronaviridae, Togaviridae and Flaviviridae, Rhabdoviridae, Herpesviridae, Arenaviridae, Bornaviridae, Bunyaviridae, Hepadnaviridae and Poxviridae; and in particular said virus may for instance belong to a viral genus chosen from the group consisting of Alphaviruses and Flaviviruses. kk) The Figures, Sequence Listing and the Experimental Part/Examples are only given to further illustrate the invention and should not be interpreted or construed as limiting the scope of the invention and/or of the appended claims in any way, unless explicitly indicated otherwise herein.

For a general description of heavy chain antibodies and the variable domains thereof, reference is inter alia made to the prior art cited herein, as well as to the prior art mentioned on page 59 of WO 08/020079 and to the list of references mentioned on pages 41-43 of the International application WO 06/040153, which prior art and references are incorporated herein by reference.

In accordance with the terminology used in the art (see the above references), the variable domains present in naturally occurring heavy chain antibodies will also be referred to as “V HH domains”, in order to distinguish them from the heavy chain variable domains that are present in conventional 4-chain antibodies (which will be referred to hereinbelow as “V H domains”) and from the light chain variable domains that are present in conventional 4-chain antibodies (which will be referred to hereinbelow as “V L domains”).

As mentioned in the prior art referred to above, V HH domains have a number of unique structural characteristics and functional properties which make isolated V HH domains (as well as NANOBODIES® (VHH sequences) based thereon, which share these structural characteristics and functional properties with the naturally occurring V HH domains) and proteins containing the same highly advantageous for use as functional antigen-binding domains or proteins. In particular, and without being limited thereto, V HH domains (which have been “designed” by nature to functionally bind to an antigen without the presence of, and without any interaction with, a light chain variable domain) and NANOBODIES® (VHH sequences) can function as a single, relatively small, functional antigen-binding structural unit, domain or protein. This distinguishes the V HH domains from the V H and V L domains of conventional 4-chain antibodies, which by themselves are generally not suited for practical application as single antigen-binding proteins or domains, but need to be combined in some form or another to provide a functional antigen-binding unit (as in for example conventional antibody fragments such as Fab fragments; in ScFv's fragments, which consist of a V H domain covalently linked to a V L domain).

Because of these unique properties, the use of V HH domains and NANOBODIES® (VHH sequences) as single antigen-binding proteins or as antigen-binding domains (i.e. as part of a larger protein or polypeptide) offers a number of significant advantages over the use of conventional V H and V L domains, scFv's or conventional antibody fragments (such as Fab- or F(ab′) 2 -fragments), including the advantages that are listed on pages 60 and 61 of WO 08/020079.

In a specific and preferred aspect, the invention provides NANOBODIES® (VHH sequences) against an envelope protein of a virus, and in particular NANOBODIES® (VHH sequences) against an envelope protein of a virus that is able to infect a warm-blooded animal, and more in particular NANOBODIES® (VHH sequences) against an envelope protein of a virus that is able to infect a mammal, and especially NANOBODIES® (VHH sequences) against an envelope protein of a human virus; as well as proteins and/or polypeptides comprising at least one such NANOBODY® (V HH sequence).

In particular, the invention provides NANOBODIES® (VHH sequences) against an envelope protein of a virus, and proteins and/or polypeptides comprising the same, that have improved therapeutic and/or pharmacological properties and/or other advantageous properties (such as, for example, improved ease of preparation and/or reduced costs of goods), compared to conventional antibodies against an envelope protein of a virus or fragments thereof, compared to constructs that could be based on such conventional antibodies or antibody fragments (such as Fab′ fragments, F(ab′)2 fragments, ScFv constructs, “diabodies” and other multispecific constructs (see for example the review by Holliger and Hudson, Nat. Biotechnol. 2005 September; 23(9): 1126-36)), and also compared to the so-called “dAb's” or similar (single) domain antibodies that may be derived from variable domains of conventional antibodies. These improved and advantageous properties will become clear from the further description herein, and for example include, without limitation, one or more of:

increased affinity and/or avidity for an envelope protein of a virus, either in a monovalent format, in a multivalent format (for example in a bivalent or trivalent format) and/or in a multispecific format (for example one of the multispecific formats described herein); better suitability for formatting in a multivalent format (for example in a bivalent or trivalent format); better suitability for formatting in a multispecific format (for example one of the multispecific formats described herein); improved suitability or susceptibility for “humanizing” substitutions (as defined herein); less immunogenicity, either in a monovalent format, in a multivalent format (for example in a bivalent or trivalent format) and/or in a multispecific format (for example one of the multispecific formats described herein); increased stability, either in a monovalent format, in a multivalent format (for example in a bivalent or trivalent format) and/or in a multispecific format (for example one of the multispecific formats described herein); increased specificity towards an envelope protein of a virus, either in a monovalent format, in a multivalent format (for example in a bivalent or trivalent format) and/or in a multispecific format (for example one of the multispecific formats described herein); decreased or where desired increased cross-reactivity with an envelope protein of a virus from different species;

and/or

one or more other improved properties desirable for pharmaceutical use (including prophylactic use and/or therapeutic use) and/or for diagnostic use (including but not limited to use for imaging purposes), either in a monovalent format, in a multivalent format (for example in a bivalent or trivalent format) and/or in a multispecific format (for example one of the multispecific formats described hereinbelow).

As generally described herein for the amino acid sequences of the invention, the NANOBODIES® (VHH sequences) of the invention are preferably in essentially isolated form (as defined herein), or form part of a protein or polypeptide of the invention (as defined herein), which may comprise or essentially consist of one or more NANOBODIES® (VHH sequences) of the invention and which may optionally further comprise one or more further amino acid sequences (all optionally linked via one or more suitable linkers). For example, and without limitation, the one or more amino acid sequences of the invention may be used as a binding unit in such a protein or polypeptide, which may optionally contain one or more further amino acid sequences that can serve as a binding unit (i.e. against one or more other targets than an envelope protein of a virus), so as to provide a monovalent, multivalent or multispecific polypeptide of the invention, respectively, all as described herein. In particular, such a protein or polypeptide may comprise or essentially consist of one or more NANOBODIES® (VHH sequences) of the invention and optionally one or more (other) NANOBODIES® (VHH sequences) (i.e. directed against other targets than an envelope protein of a virus), all optionally linked via one or more suitable linkers, so as to provide a monovalent, multivalent or multispecific NANOBODY® (V HH sequence) construct, respectively, as further described herein. Such proteins or polypeptides may also be in essentially isolated form (as defined herein).

In a NANOBODY® (V HH sequence) of the invention, the binding site for binding against an envelope protein of a virus is preferably formed by the CDR sequences. Optionally, a NANOBODY® (V HH sequence) of the invention may also, and in addition to the at least one binding site for binding to an envelope protein of a virus, contain one or more further binding sites for binding against other antigens, proteins or targets. For methods and positions for introducing such second binding sites, reference is for example made to Keck and Huston, Biophysical Journal, 71, October 1996, 2002-2011; EP 0 640 130; and WO 06/07260.

As generally described herein for the amino acid sequences of the invention, when a NANOBODY® (V HH sequence) of the invention (or a polypeptide of the invention comprising the same) is intended for administration to a subject (for example for prophylactic, therapeutic and/or diagnostic purposes as described herein), it is preferably directed against an envelope protein of a virus that is able to infect humans; whereas for veterinary purposes, it is preferably directed against an envelope protein of a virus that is able to infect the species to be treated. Also, as with the amino acid sequences of the invention, a NANOBODY® (V HH sequence) of the invention may or may not be cross-reactive (i.e. directed against two or more homologous envelope proteins of a virus that is able to infect two or more species of mammal, such as against two or more homologous envelope proteins of a virus that is both able to infect humans and at least one of the species of mammal mentioned herein).

A NANOBODY® (V HH sequence) of the invention may or may not be cross-reactive for two or more different genotypes, subtypes, viral escape mutants and/or strains of a certain virus. In this respect, the present invention provides multivalent NANOBODIES® (VHH sequences) or polypeptides which show increased cross-reactivity for different genotypes, subtypes, viral escape mutants and/or strains of a certain virus compared to the corresponding monovalent NANOBODY® (V HH sequence). In one aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H1N1. In another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H3N2. In another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H1N1 as well as influenza subtype H3N2. In another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1 as well as influenza subtype H2N2. Yet in another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1 as well as influenza subtype H3N2. Yet in another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H2N2 as well as influenza subtype H3N2. Yet in another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1 as well as influenza subtype H2N2. Yet in another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against influenza virus and may bind influenza subtype H5N1, influenza subtype H1N1, influenza subtype H2N2 as well as influenza subtype H3N2. In another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against rabies virus and may bind rabies genotype 1 as well as genotype 5. In yet another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against RSV and may bind different strains of RSV (such as e.g. Long, A-2 and/or B-1). In yet another aspect, the (multivalent) NANOBODIES® (VHH sequences) are directed against RSV and may bind different escape mutants of RSV (such as e.g. described in Lopez et al. 1998 , J. Virol. 72: 6922-6928) and/or escape mutants specific for antigen site II, antigen site IV-VI or the combination of both antigenic sites.

Also, again as generally described herein for the amino acid sequences of the invention, the NANOBODIES® (VHH sequences) of the invention may generally be directed against any antigenic determinant, epitope, part, domain, subunit or conformation (where applicable) of an envelope protein of a virus.

However, it is generally assumed and preferred that the NANOBODIES® (VHH sequences) and polypeptides of the invention are preferably directed against an interaction site (as defined herein), and in particular against at least one epitope of an envelope protein of a virus, such that at least one viral-mediated biological pathway in which an envelope protein of a virus and/or a viral receptor are involved is inhibited, prevented and/or modulated.

In particular, it is assumed and preferred that the NANOBODIES® (VHH sequences), polypeptides and compositions of the present invention are directed against at least one epitope of an envelope protein of a virus, such that viral entry in a target host cell (such as for instance virion attachment to a target host cell and/or viral fusion with a target host cell) and/or viral replication in a target host cell (such as for instance viral transcription and/or viral translation and/or viral packaging and/or the formation of functional virions and/or budding of nascent virions from the target host cell membrane) is inhibited, prevented and/or modulated.

The NANOBODIES® (VHH sequences) and polypeptides may be directed against at least one epitope of an envelope protein of a virus that is surface-exposed or that is located in a cavity or cleft formed by an envelope protein of a virus. Preferably, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against an interaction site (as defined herein), and in particular against an epitope that is located in a cavity or cleft formed by a trimer of fusion proteins (such as a fusion protein trimer that is a trimer of hairpins or a six-helix bundle) or a dimer of fusion proteins, wherein said fusion proteins can be in their pre-, intermediate, or post-fusion conformational state.

Furthermore, the NANOBODIES® (VHH sequences) and polypeptides of the invention may also be directed against an epitope that is located in the stem region and/or in the neck region and/or in the globular head region of a fusion protein. Preferably, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against an epitope that is located in the stem region of a fusion protein, such as for instance against an epitope that is located in the region comprising one or more of the amino acids 318 to 322 of the HA1 subunit of influenza HA and/or the region comprising one or more of the amino acids 47 to 58 of the HA2 subunit of influenza HA; against an epitope that is located in the N-terminal region comprising one or more of the amino acids 1 to 38 of the HA2 subunit of influenza HA; against an epitope that is located in the region comprising one or more of the amino acids 38 to 112 of the HA2 subunit of influenza HA; against an epitope that is located in the region comprising one or more of the amino acids 125 to 175 of the HA2 subunit of influenza HA; or against an epitope that is located in the region comprising one or more of the amino acids 176 to 185 of the HA2 subunit of influenza HA. Alternatively, the NANOBODIES® (VHH sequences) and polypeptides of the invention may be directed against an epitope that is located in the globular head of a fusion protein (wherein said globular head may for example comprise a β-barrel-type structure or an immunoglobulin-type β-sandwich domain and a β-sheet domain).

Also, in particular, the NANOBODIES® (VHH sequences) and polypeptides of the invention may preferably be directed against an interaction site, which is chosen from the group consisting of the A-antigenic site and/or amino acids 255 to 280 of the F-protein of RSV virus, the F1a site and/or the region comprising amino acid 389 of the F-protein of RSV virus, amino acids 422 to 438 of the F-protein of RSV virus, sialic acid binding site of the H5 HA envelope protein of influenza virus, the Nicotinic Acetylcholine Receptor (AchR) and/or the Nueral Cell Adhesion Molecule (NCAM) binding site of the G-protein of rabies virus (Thoulouze et al. 1998, J. Virol. 72: 7181-7190).

Finally, the NANOBODIES® (VHH sequences) and polypeptides of the invention may be directed against any epitope that is located in the C-terminal region of a fusion protein and/or in the N-terminal domain of a fusion protein and/or in or comprising the fusion peptide of a fusion protein and/or in the transmembrane domain of a fusion protein and/or in a α-helical coiled-coil of a fusion protein and/or in a β-structure of a fusion protein and/or in Domain I of a fusion protein and/or in Domain II of a fusion protein, such as for example in the fusion peptide of Domain II of a fusion protein, and/or in Domain III of a fusion protein, such as for example in the stem region at the C-terminus of Domain III of a fusion protein or in the transmembrane anchor at the C-terminus of Domain III of a fusion protein.

In one aspect, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against the Synagis® binding site on the RSV F protein and/or capable of competing with Synagis® for binding to the RSV F protein. In particular, they may be directed against antigenic site II (also referred to as site A) of the RSV F protein and more preferably against region aa 250-275 of the RSV F protein.

In another aspect, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against the 101F binding site on the RSV F protein and/or capable of competing with 101F for binding to the RSV F protein. In particular, they may be directed against antigenic site IV-VI of the RSV F protein and more preferably against region aa 423-436 of the RSV F protein.

In yet another aspect, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against the VN04-2 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with VN04-2 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In yet another aspect, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against the MAb C179 binding site on the hemagglutinin H5 envelope protein of influenza virus and/or capable of competing with MAb C179 for binding to the hemagglutinin H5 envelope protein of influenza virus.

In yet another aspect, the NANOBODIES® (VHH sequences) and polypeptides of the invention are directed against the MAb 8-2 binding site on G envelope protein of rabies virus and/or capable of competing with MAb 8-2 for binding to the G envelope protein of rabies virus.

Also, the NANOBODIES® (VHH sequences) and polypeptides of the invention may be directed against any other epitope of an envelope protein of a virus (for instance any other epitope that is close to one of the aforementioned epitopes).

Thus, in one preferred, but non-limiting aspect, the NANOBODIES® (VHH sequences) and polypeptides of the invention are generally directed against any epitope or in particular against one of the above-mentioned epitopes of an envelope protein of a virus, and are as further defined herein. For example, said epitope may be present on an envelope protein of a virus that is chosen from the group consisting of the F protein of RSV virus, the G protein of RSV virus, the SH protein of RSV virus, the M protein of RSV virus, the M2 protein of RSV virus, the HA protein of influenza A virus, the gp120 protein of HIV-1 virus, the S1 protein of SARS Corona virus, the gD protein of Herpes simplex 1 virus, the VP1 and/or VP2 and/or VP3 proteins of Poliovirus 1, the VP1 and/or VP2 and/or VP3 proteins of Rhinovirus 3, fibre and/or penton base of Adenovirus 2, al of Reovirus 1, the HEF protein of influenza C virus, the 5 F protein of Simian parainfluenza virus, the F protein of Human parainfluenza virus, the F protein of Newcastle disease virus, the F2 protein of measles, the F2 protein of Sendai virus, the gp2 protein of Ebola virus, the TM protein of Moloney murine leukemia virus, the gp41 protein of Human immunodeficiency virus 1, the gp41 protein of Simian immunodeficiency virus, the gp21 protein of Human T cell leukemia virus 1, the TM protein of Human syncytin-2, the TM protein of Visna virus, the S2 protein of Mouse hepatitis virus, the E2 protein of SARS corona virus, the E protein of Tick-borne encephalitis virus, the E2 protein of Dengue 2 and 3 virus, the E prote