Genetic characteristics of influenza Virus A(H3N2)subtype in Kunming City in 2019
Objective The aim of this study was to provide scientific evidence for the prevention and control of the influenza virus by analyzing the genetic characteristics of hemagglutinin(HA)and neuraminidase(NA)genes of seasonal influenza A(H3N2)subtype influenza virus involved in the influenza outbreak in Kunming City.Methods Nineteen strains of A(H3N2)subtype influenza virus were sequenced,isolated from 7 outbreak cases and sentinel hospital monitoring cases in Kunming City from January to December 2019.Homology was analyzed using MegAlign phylogenetic trees were constructed using Jmodeltest and PhyML 3.1,and mutation sites were analyzed using MEGA X.Results The influenza outbreak in Kunming City in 2019 was concentrated in schools during the winter and spring seasons.The strains from the outbreaks and sentinel hospital were highly homologous,both belonging to the clade 3C.2a1b.1b,deviating from the 2019 vaccine strain A/Kansas/14/2017,which belongs to the 3C.3a1 clade.Compared to the vaccine strain,strains isolated from outbreak cases and sentinel hospital monitoring cases showed additional mutation sites T135K,S137F,K144S,S159Y,and K160T in HA1 antigenic sites A and B.Two strains isolated from outbreak cases had an additional mutation site 1140M in antigenic site A,possibly evading antibody recognition.The mutations T135K and S137F in the 130-loop region may alter the virus's binding properties with receptor cells.In antigenic site B,there was an additional glycosylation site 158NYTY that may hinder antibody recognition of the virus.All isolated strains had an additional mutation site T329S in NA antigenic sites.Conclusions The importance of prevention and control of the influenza virus in Kunming City should enhance the surveillance of places where a lot of people gather to discover immune evasion and virulence enhancement mutants in order to update vaccine composition.
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