title: Structures of complexes formed by H5 influenza hemagglutinin with a potent broadly neutralizing human monoclonal antibody.
abstract: H5N1 avian influenza viruses remain a threat to public health mainly because they can cause severe infections in humans. These viruses are widespread in birds, and they vary in antigenicity forming three major clades and numerous antigenic variants. The most important features of the human monoclonal antibody FLD194 studied here are its broad specificity for all major clades of H5 influenza HAs, its high affinity, and its ability to block virus infection, in vitro and in vivo. As a consequence, this antibody may be suitable for anti-H5 therapy and as a component of stockpiles, together with other antiviral agents, for health authorities to use if an appropriate vaccine was not available. Our mutation and structural analyses indicate that the antibody recognizes a relatively conserved site near the membrane distal tip of HA, near to, but distinct from, the receptor-binding site. Our analyses also suggest that the mechanism of infectivity neutralization involves prevention of receptor recognition as a result of steric hindrance by the Fc part of the antibody. Structural analyses by EM indicate that three Fab fragments are bound to each HA trimer. The structure revealed by X-ray crystallography is of an HA monomer bound by one Fab. The monomer has some similarities to HA in the fusion pH conformation, and the monomer's formation, which results from the presence of isopropanol in the crystallization solvent, contributes to considerations of the process of change in conformation required for membrane fusion.
authors.affiliation: Mill Hill Laboratory, The Francis Crick Institute, London NW7 1AA, United Kingdom;
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Xiong
authors.affiliation: Institute for Research in Biomedicine, 6500 Bellinzona, Switzerland;
authors.forename: Davide
authors.initials: D
authors.lastname: Corti
authors.affiliation: Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China;
authors.forename: Junfeng
authors.initials: J
authors.lastname: Liu
authors.affiliation: Institute for Research in Biomedicine, 6500 Bellinzona, Switzerland;
authors.forename: Debora
authors.initials: D
authors.lastname: Pinna
authors.affiliation: Institute for Research in Biomedicine, 6500 Bellinzona, Switzerland;
authors.forename: Mathilde
authors.initials: M
authors.lastname: Foglierini
authors.affiliation: Mill Hill Laboratory, The Francis Crick Institute, London NW7 1AA, United Kingdom;
authors.forename: Lesley J
authors.initials: LJ
authors.lastname: Calder
authors.affiliation: Structural Biology Science Technology Platform, Mill Hill Laboratory, The Francis Crick Institute, The Ridgeway, London NW7 1AA, United Kingdom;
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Martin
authors.affiliation: Mill Hill Laboratory, The Francis Crick Institute, London NW7 1AA, United Kingdom;
authors.forename: Yi Pu
authors.initials: YP
authors.lastname: Lin
authors.affiliation: Structural Biology Science Technology Platform, Mill Hill Laboratory, The Francis Crick Institute, The Ridgeway, London NW7 1AA, United Kingdom;
authors.forename: Philip A
authors.initials: PA
authors.lastname: Walker
authors.affiliation: Mill Hill Laboratory, The Francis Crick Institute, London NW7 1AA, United Kingdom;
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Collins
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, 35020 Padua, Italy;
authors.forename: Isabella
authors.initials: I
authors.lastname: Monne
authors.affiliation: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Amorsolo L
authors.initials: AL
authors.lastname: Suguitan
authors.affiliation: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Celia
authors.initials: C
authors.lastname: Santos
authors.affiliation: Viral Pseudotype Unit, University of Kent, Kent ME4 4TB, United Kingdom.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Temperton
authors.affiliation: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892;
authors.forename: Kanta
authors.initials: K
authors.lastname: Subbarao
authors.affiliation: Institute for Research in Biomedicine, 6500 Bellinzona, Switzerland;
authors.forename: Antonio
authors.initials: A
authors.lastname: Lanzavecchia
authors.affiliation: Mill Hill Laboratory, The Francis Crick Institute, London NW7 1AA, United Kingdom;
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Gamblin
authors.affiliation: Mill Hill Laboratory, The Francis Crick Institute, London NW7 1AA, United Kingdom; John.Skehel@crick.ac.uk.
authors.forename: John J
authors.initials: JJ
authors.lastname: Skehel
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D057134:Antibodies, Neutralizing / Q000737:chemistry; D000914:Antibodies, Viral / Q000737:chemistry; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000737:chemistry; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry*; D006388:Hemagglutinins / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007128:Immunoglobulin Fragments / Q000737:chemistry; D007074:Immunoglobulin G / Q000737:chemistry; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D009500:Neutralization Tests; D011485:Protein Binding; D011487:Protein Conformation; D012997:Solvents / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000939:Epitopes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006388:Hemagglutinins; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G; D007252:Influenza Vaccines; D012997:Solvents; C109963:hemagglutinin, avian influenza A virus
keywords: H5N1; influenza virus; neutralizing antibody