2013-2018年北京市怀柔区甲型H3N2流感病毒HA基因分子特征分析

Molecular characteristics of the hemagglutinin gene of influenza A(H3N2) virus in the Huairou District, Beijing from 2013-2018

目的分析怀柔区2013-2018年甲型H3N2流感病毒血凝素(HA)基因的遗传变异特征。方法选取怀柔区2013年9月-2018年8月50株甲型H3N2流感病毒,进行HA基因扩增和测序,运用MEGA6.0软件分析HA的分子特征,并构建系统进化树。结果怀柔区2013-2018年甲型H3N2流感病毒优势流行株分别为3c.3系(2013年9月-2014年8月)、3c.3a系(2013年9月-2015年8月)和3c.2a系(2015年9月-2018年8月)。系统进化树分析显示,同一监测年度的流行株基本呈现集中分布,各监测年度流行株与当年推荐流感疫苗株距离均较远。分子特征显示HA蛋白5个抗原决定簇均发生变异,有29处氨基酸位点发生变异,变异频率逐年增加;受体结合位点发生N225D、T131K和T135K/N变异;糖基化位点自2015年9月-2018年8月变化增加,144NSS消失,部分流行株新增了142NSS、158NYT和135NSS。结论怀柔区2013-2018年甲型H3N2流感病毒HA基因不断发生突变,变异频率增加,可能出现了抗原漂移,与当年推荐疫苗株匹配程度降低,近期应加强对流感病毒分子变异的监测。

Objectives To analyze mutations in the hemagglutinin(HA)gene of influenza A(H3 N2)virus from 2013 to 2018 in Huairou District in order to determine its molecular characteristics.Methods Fifty strains that were identified as a subtype of influenza A(H3 N2)virus in Huairou District from September 2013 to August 2018 were selected.Sequences of the HA gene were obtained using RT-PCR and sequencing.The software MEGA6.0 was used to analyze the molecular characteristics of the HA gene,and a phylogenetic tree was constructed using the neighbor-joining method.Results Endemic strains of influenza A(H3 N2)virus in the Huairou District were clade 3 c.3(from September 2013 to August 2014),3 c.3 a(from September 2014 to August 2015),and 3 c.2 a(from September 2015 to August 2018).Phylogenetic analysis indicated that the HA gene of strains isolated in the same year were closely clustered on the phylogenetic tree far from recommended influenza vaccine strains in the same year.Molecular characteristics indicated that amino acid substitutions had occurred in 5 epitopes of the HA protein.Mutations occurred in 29 amino acids,and the frequency of mutation increased each year.The mutations N225 D,T131 K,and T135 K/N occurred at receptor binding sites.Mutations in glycosylation sites increased from September 2015 to August 2018,and 144 NSS disappeared,though the mutations 142 NSS,158 NYT,and 135 NSS were found in some endemic strains.Conclusion The HA gene of influenza A H3 N2 virus in the Huairou District continued to mutate from 2013 to 2018,and the frequency of mutation increased.The influenza virus may exhibit antigenic drift,resulting in a mismatch with the recommended vaccine strains.Monitoring of molecular variation in the influenza virus should be enhanced in the near future.