Evolution and variation of the genes encoding hemagglutinin of H3N2 influenza virus strains prevalent in Guangdong during 2011-2015

Abstract

Objective To study the evolution and variation of the genes encoding hemagglutinin (HA) proteins of H3N2 influenza virus strains prevalent in Guangdong during 2011-2015. Methods Forty-eight H3N2 influenza virus strains prevalent in Guangdong during 2011-2015 were recruited in this study by using time-space sampling. The nucleotide sequences of HA genes of those strains were sequenced and compared with those of the H3N2 influenza virus strains prevalent worldwide. The mutations and antigenic variations in HA genes of Guangdong strains were analyzed by MEGA 5.05, BEAST v1.7.0 and BioEdit7.1.3. Results The 48 H3N2 influenza virus strains prevalent in Guangdong shared 96.4%-100.00% homologies in nucleotide sequences. The Guangdong strains isolated during 2013-2015 shared 97.8%-98.7% homologies in nucleotide sequences with the southern hemisphere vaccine strain A/Switzerland/9715293/2013. Phylogenetic analysis showed that the evolution was upward along the main branch over time. The Guangdong strains mainly distributed in clade 3C.3a with some of the 2015 strains in clade 3C.2a. A total of 330 nucleotide mutations were detected in the HA genes of H3N2 influenza virus strains prevalent during 2011-2015 as compared with the HA gene of the vaccine strain A/Texas/50/2012, resulting in 116 amino acid mutations with 12 of them associating with 4 epitope mutations. The N241D (N225D) and K192C mutations located in the receptor binding sites (RBS) and the 190 helix of RBS, respectively. Conclusion Amino acid mutations occurred in the antigenic epitopes of HA proteins of H3N2 influenza virus strains prevalent in Guangdong province during 2011-2015, which might give rise to antigenic drift resulting in the outbreak of influenza. Thus, it is necessary to strengthen the surveillance for influenza pathogens. Key words: Influenza virus; H3N2 subtype; Hemagglutinin; Evolution