Molecular characteristics of hemagglutinin gene of influenza A(H3N2)virus in Quzhou, 2015-2017

Objective To understand the molecular evolutional characteristics of hemagglutinin (HA)gene of influenza A (H3N2)virus in Quzhou,Zhejiang province,from 2015 to 2017 and provide scientific evidence for the prevention and control of influenza. Methods A total of 18 influenza A (H3N2)virus strains isolated in Quzhou from 2015 to 2017 were selected. The full-length of HA genes were amplified by RT-PCR and sequenced. Bioinformatics software was used to analyze the sequences. Results The homologies of nucleotide and amino acid of 18 influenza A (H3N2)strains were 97.36%-100.00% and 96.76%-100.00%,respectively. The average genetic distances of the HA genes between the vaccine strains and the isolated strains were 0.008 2,0.007 1 and 0.011 2 at nucleotide levels,and 0.009 2,0.003 1 and 0.010 0 at amino acid levels,respectively. The HA genetic clades of the isolated strains had transformed from 3C. 3a to 3C. 2a. The amino acid sites of the isolated strains had changed compared with the vaccine strain A/Switzerland/9715293/2013 and A/Hong Kong/4801/2014,there were 5 antigenic epitopes (A,B,C,D and E regions),2 receptor binding sites (T131K,T135N/K) and 6 potential glycosylation sites (122NES,126NWT,133NGT,135NSS,144NSS,158NYT)involved. Conclusion The results revealed that the antigenic drift might occur in influenza A (H3N2)virus strains isolated in Quzhou from 2015 to 2017,suggesting that the efficacy of the vaccine strain A/Hong Kong/4801/2014 need to be re-evaluated.