title: Antigenic mapping of an H9N2 avian influenza virus reveals two discrete antigenic sites and a novel mechanism of immune escape.
abstract: H9N2 avian influenza virus is a major cause of poultry production loss across Asia leading to the wide use of vaccines. Efficacy of vaccines is often compromised due to the rapid emergence of antigenic variants. To improve the effectiveness of vaccines in the field, a better understanding of the antigenic epitopes of the major antigen, hemagglutinin, is required. To address this, a panel of nine monoclonal antibodies were generated against a contemporary Pakistani H9N2 isolate, which represents a major Asian H9N2 viral lineage. Antibodies were characterized in detail and used to select a total of 26 unique 'escape' mutants with substitutions across nine different amino acid residues in hemagglutinin including seven that have not been described as antigenic determinants for H9N2 viruses before. Competition assays and structural mapping revealed two novel, discrete antigenic sites "H9-A" and "H9-B". Additionally, a second subset of escape mutants contained amino acid deletions within the hemagglutinin receptor binding site. This constitutes a novel method of escape for group 1 hemagglutinins and could represent an alternative means for H9N2 viruses to overcome vaccine induced immunity. These results will guide surveillance efforts for arising antigenic variants as well as evidence based vaccine seed selection and vaccine design.
authors.affiliation: The Pirbright Institute, Pirbright, Woking, UK.|Imperial College London, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Peacock
authors.affiliation: The Pirbright Institute, Pirbright, Woking, UK.
authors.forename: Kolli
authors.initials: K
authors.lastname: Reddy
authors.affiliation: The Pirbright Institute, Pirbright, Woking, UK.|Imperial College London, UK.
authors.forename: Joe
authors.initials: J
authors.lastname: James
authors.affiliation: The Pirbright Institute, Pirbright, Woking, UK.
authors.forename: Beata
authors.initials: B
authors.lastname: Adamiak
authors.affiliation: Imperial College London, UK.
authors.forename: Wendy
authors.initials: W
authors.lastname: Barclay
authors.affiliation: The Pirbright Institute, Pirbright, Woking, UK.
authors.forename: Holly
authors.initials: H
authors.lastname: Shelton
authors.affiliation: The Pirbright Institute, Pirbright, Woking, UK.
authors.forename: Munir
authors.initials: M
authors.lastname: Iqbal
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000737:chemistry; D057134:Antibodies, Neutralizing / Q000737:chemistry; D000914:Antibodies, Viral / Q000097:blood / Q000737:chemistry*; D000956:Antigens, Viral / Q000737:chemistry / Q000276:immunology*; D002645:Chickens / Q000276:immunology / Q000821:virology; D003429:Cross Reactions; D018604:Epitope Mapping; D006801:Humans; D006825:Hybridomas; D057131:Immune Evasion; D007106:Immune Sera / Q000737:chemistry; D053127:Influenza A Virus, H9N2 Subtype / Q000737:chemistry / Q000276:immunology*; D005585:Influenza in Birds / Q000276:immunology / Q000821:virology; D007251:Influenza, Human / Q000276:immunology / Q000821:virology; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008958:Models, Molecular; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000956:Antigens, Viral; D007106:Immune Sera; D047908:Intracellular Signaling Peptides and Proteins; C513679:WDFY2 protein, human