Assessing Antigenic Drift of Seasonal Influenza A(H3N2) and A(H1N1)pdm09 Viruses

PLoS One. 2015 Oct 6;10(10):e0139958. doi: 10.1371/journal.pone.0139958. eCollection 2015.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigenic Variation / genetics*
  • Antigens, Viral / immunology*
  • Epitopes / genetics
  • Epitopes / immunology*
  • Evolution, Molecular
  • Humans
  • Influenza A Virus, H1N1 Subtype / immunology*
  • Influenza A Virus, H3N2 Subtype / immunology*
  • Influenza Vaccines
  • Influenza, Human / virology*
  • Seasons
  • Thailand

Substances

  • Antigens, Viral
  • Epitopes
  • Influenza Vaccines

Grants and funding

This work was supported by The National Research University Project, Office of Higher Education Commission (WCU001-HR-57, WCU007-HR-57, and WCU-58-006-HR), The National Research Council of Thailand (NRCT), The Research Chair Grant from the National Science and Technology Development Agency, Chulalongkorn University Centenary Academic Development Project (CU56-HR01), Ratchadaphiseksomphot Endowment Fund of Chulalongkorn University (RES560530093), The Outstanding Professor of Thailand Research Fund (DPG5480002), Siam Cement Group, and MK Restaurant Company Limited. The authors thank the 100th anniversary Chulalongkorn University Fund for doctoral scholarship awarded to Nipaporn Tewawong. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.