title: Characterization of an enhanced antigenic change in the pandemic 2009 H1N1 influenza virus haemagglutinin.
abstract: Murine hybridomas producing neutralizing mAbs specific to the pandemic influenza virus A/California/07/2009 haemagglutinin (HA) were isolated. These antibodies recognized at least two different but overlapping new epitopes that were conserved in the HA of most Spanish pandemic isolates. However, one of these isolates (A/Extremadura/RR6530/2010) lacked reactivity with the mAbs and carried two unique mutations in the HA head (S88Y and K136N) that were required simultaneously to eliminate reactivity with the murine antibodies. This unusual requirement directly illustrates the phenomenon of enhanced antigenic change proposed previously for the accumulation of simultaneous amino acid substitutions at antigenic sites of the influenza A virus HA during virus evolution (Shih et al., Proc Natl Acad Sci USA, 104 , 6283-6288, 2007). The changes found in the A/Extremadura/RR6530/2010 HA were not found in escape mutants selected in vitro with one of the mAbs, which contained instead nearby single amino acid changes in the HA head. Thus, either single or double point mutations may similarly alter epitopes of the new antigenic site identified in this work in the 2009 H1N1 pandemic virus HA. Moreover, this site is relevant for the human antibody response, as shown by competition of mAbs and human post-infection sera for virus binding. The results are discussed in the context of the HA antigenic structure and challenges posed for identification of sequence changes with possible antigenic impact during virus surveillance.
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Blanca
authors: B
authors: García-Barreno
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Teresa
authors: T
authors: Delgado
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Sonia
authors: S
authors: Benito
authors: National Influenza Centre at Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.|Virus Respiratorios & Gripe, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Inmaculada
authors: I
authors: Casas
authors: National Influenza Centre at Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.|Virus Respiratorios & Gripe, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Francisco
authors: F
authors: Pozo
authors: National Influenza Centre at Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.|Virus Respiratorios & Gripe, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: María Teresa
authors: MT
authors: Cuevas
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Vicente
authors: V
authors: Mas
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: Alfonsina
authors: A
authors: Trento
authors: Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain.|CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.
authors: Ariel
authors: A
authors: Rodriguez-Frandsen
authors: Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain.|CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.
authors: Ana
authors: A
authors: Falcón
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain.
authors: Juan
authors: J
authors: Ortín
authors: Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain.|CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.
authors: Amelia
authors: A
authors: Nieto
authors: CIBER de Enfermedades Respiratorias, Mallorca, Illes Baleares, Spain.|Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
authors: José A
authors: JA
authors: Melero
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D000956:Antigens, Viral / Q000235:genetics* / Q000276:immunology*; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics* / Q000276:immunology*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification; D007251:Influenza, Human / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000235:genetics / Q000276:immunology; D020125:Mutation, Missense; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D013030:Spain
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D050505:Mutant Proteins; D012367:RNA, Viral