Evolution and mutation of H1N1pdm virus hemagglutinin genes in Guangdong

Objective To reveal hemagglutinin gene (HA) characteristics and variability of Guangdong H1N1 pandemic viruses (H1Nlpdm) during 2009-2011.Methods Using time-space sampling,the nucleotide sequences of twenty-four HA genes of Guangdong H1Nlpdm influenza viruses isolated between 2009-2011 were sequenced and compared with forty-four HA sequences in GenBank.The mutations and antigenic variation were analyzed and phylodynamics MCMC tree was established.Results Phylogenetic tree of all 68 HA genes was divided into at least 6 branches.In 2011,Guangdong H1N1 strains clustered into 2 major clades (Ⅴ and Ⅵ) with local strain characteristics.The amino acid sites 391,467,202 and 214 were highly variable while the positive selective sites located at 8,145 and 391 aa.The epitope mutations of HA genes among Guangdong strains occurred in S145L/P,L2081,Q240R,S160G and G187R.Guangdong Ⅰ genotyping emerged in 2009 might be spread to Asia,Europe and Australia in 2010.Conclusion Guangdong H1N1pdm virus HA gene mutations showed propagation (Ⅰ) and regional(Ⅵ) characteristics.The mutations occurred in epitope Ca,Sa and Sb particularly with high variable rate in 145 aa and other sites indicated the existence of the positive immunological pressure. Key words: H1N1pdm; Hemagglutinin (HA); Epitope; Evolution; Mutation