Molecular evolution of HA gene of the influenza A H1N1 pdm09 strain during the consecutive seasons 2009-2011 in Hangzhou, China: several immune-escape variants without positively selected sites.
J Clin Virol, 2012/12;55(4):363-6.
Li J[1], Shao TJ, Yu XF, Pan JC, Pu XY, Wang HQ, Kou Y
Affiliations
PMID: 22921413
Impact factor: 14.481
Abstract
background: Even under immune pressure, the highly active influenza A H1N1 pdm09 variants emerged again in December 2010. Did the variability lead to poor vaccine effectiveness?
objectives: To study the genetic distance and antigenic drift of the influenza A H1N1 pdm09 strains based on the sequence analysis of HA virus gene segments during consecutive seasons 2009-2011 in Hangzhou, China.
study design: 39 Clinical samples from influenza-like-illness patients with culture-confirmed influenza A H1N1 pdm09 infections were collected over seasons in routine influenza surveillance. The HA gene was amplified and sequenced. A perspective analysis of genetic distance, antigenic drift and positively selected sites were conducted.
results: Analyses of human influenza A H1N1 pdm09 strains isolated in Hangzhou revealed that during the seasons 2009-2011, the antigenic drift had occurred, away from the northern hemisphere 2010/2011 influenza vaccine strain A/California/07/2009. The 2010/2011 viruses cluster in two main branches with a significant genetic distance, characterized by either S202T and S468N, or K180T/I, V216A, P288S, I312V and I389F. Interestingly, the epitopes corresponding to the immune-escape characteristic have altered much, but none of the amino acid substitutions in 2010/2011 variants were positively selected.
conclusions: The results of genetic surveillance in this study might account for frequent outbreaks of the influenza A H1N1 pdm09 strains since December 2010 and the disappearance after three months circulation. It facilitates early detection of antigenic sites for the virus to escape immunological restraint in 2010/2011 season. Continuous monitoring of antigenic changes is recommended.
MeSH terms
Antigens, Viral; China; Cluster Analysis; Evolution, Molecular; Hemagglutinin Glycoproteins, Influenza Virus; Humans; Influenza A Virus, H1N1 Subtype; Influenza, Human; Molecular Sequence Data; Mutation, Missense; Phylogeny; RNA, Viral; Sequence Analysis, DNA; Sequence Homology
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