Abstract
Objective To analyze the genetic characteristics of influenza A (H1N1) in winter and spring in 2015 and 2016. Methods A total of 35 strains of influenza A (H1N1) isolated from Changning district influenza network laboratory from December, 2015 to April, 2016 were selected. Full length hemagglutinin (HA) and neuraminidase (NA) genes were amplified by RT-PCR and were sequenced. MEGA software was used to calculate the gene similarity. MegAlign software was used to analyze related antigens and resistance sites. NetNGlyc 1.0 was used for online prediction of glycosylation sites. Results The results of phylogenetic analysis for HA gene showed that the 35 strains belonged to clade 6B.1, 6B.2 and 6C with clade 6B.1 as the main branch. Comparing to A/California/07/2009, the recommended vaccine strain for northern hemisphere in 2015-2016 and 2016-2017, the strains showed 96.7%-99.0% and 96.7%-98.2% similarity in nucleotide sequence and amino acid sequences, respectively. The similarity of nucleiotide and amino acid sequences between strains and the vaccine strain of 2017-2018, A/Michigan/45/2015, were 97.2%-99.3% and 97.5%-99.5%, respectively. Comparing to vaccine strain A/California/07/2009, all 35 strains had S185T (Sb antigenic site) and S203T (Cb antigenic site) mutations, while 33 strains had K163Q mutation and 7 strains had Q223R mutation. No mutation occurred in the receptor binding sites and glycosylation sites. Analysis of 9 sites related to resistance on NA genes of the 35 strains showed 1 strain had the H274Y mutation. Conclusions Mutations on HA and NA genes of influenza A (H1N1) predominant in Shanghai during 2015-2016 winter season might be responsible for the high epidemic peak. Key words: Influenza A virus; H1N1 subtype; Hemagglutinins; Neuraminidase; Gene characteristic analysis
Published Version
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