title: Assessing Antigenic Drift of Seasonal Influenza A(H3N2) and A(H1N1)pdm09 Viruses.
abstract: Under selective pressure from the host immune system, antigenic epitopes of influenza virus hemagglutinin (HA) have continually evolved to escape antibody recognition, termed antigenic drift. We analyzed the genomes of influenza A(H3N2) and A(H1N1)pdm09 virus strains circulating in Thailand between 2010 and 2014 and assessed how well the yearly vaccine strains recommended for the southern hemisphere matched them. We amplified and sequenced the HA gene of 120 A(H3N2) and 81 A(H1N1)pdm09 influenza virus samples obtained from respiratory specimens and calculated the perfect-match vaccine efficacy using the pepitope model, which quantitated the antigenic drift in the dominant epitope of HA. Phylogenetic analysis of the A(H3N2) HA1 genes classified most strains into genetic clades 1, 3A, 3B, and 3C. The A(H3N2) strains from the 2013 and 2014 seasons showed very low to moderate vaccine efficacy and demonstrated antigenic drift from epitopes C and A to epitope B. Meanwhile, most A(H1N1)pdm09 strains from the 2012-2014 seasons belonged to genetic clades 6A, 6B, and 6C and displayed the dominant epitope mutations at epitopes B and E. Finally, the vaccine efficacy for A(H1N1)pdm09 (79.6-93.4%) was generally higher than that of A(H3N2). These findings further confirmed the accelerating antigenic drift of the circulating influenza A(H3N2) in recent years.
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Nipaporn
authors.initials: N
authors.lastname: Tewawong
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Slinporn
authors.initials: S
authors.lastname: Prachayangprecha
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Preeyaporn
authors.initials: P
authors.lastname: Vichiwattana
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Sumeth
authors.initials: S
authors.lastname: Korkong
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Sirapa
authors.initials: S
authors.lastname: Klinfueng
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Sompong
authors.initials: S
authors.lastname: Vongpunsawad
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Thanunrat
authors.initials: T
authors.lastname: Thongmee
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Apiradee
authors.initials: A
authors.lastname: Theamboonlers
authors.affiliation: Center of Excellence in Clinical Virology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Yong
authors.initials: Y
authors.lastname: Poovorawan
mesh_terms: D000940:Antigenic Variation / Q000235:genetics*; D000956:Antigens, Viral / Q000276:immunology*; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D019143:Evolution, Molecular; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology*; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000821:virology*; D012621:Seasons; D013785:Thailand
chemical_list: D000956:Antigens, Viral; D000939:Epitopes; D007252:Influenza Vaccines