2019-2020年山东省H3N2流感病毒抗原性及血凝素基因特征分析

Analysis of antigenicity and hemagglutinin genetic characteristics of the H3N2 influenza virus in Shandong during 2019-2020

目的了解2019-2020年流感监测年度山东省分离的H3N2亚型流感病毒抗原性及血凝素(hemagglutinin,HA)基因遗传进化规律与氨基酸变异情况。方法用免疫雪貂后的抗血清进行红细胞凝集抑制试验,对2019年4月至2020年3月山东省分离的40株H3N2亚型流感毒株进行抗原性分析,并对其中19株待检病毒的HA基因进行序列测定及分析。结果抗原性分析结果显示检测的H3N2亚型流感病毒中仅仅35%(14/40)与疫苗株A/Kansas/14/2017抗原性类似。系统进化树显示,19株H3N2亚型流感病毒分离株血凝素基因在进化树上全部属于3C.2a分支,与处于3C.3a分支的疫苗株A/Kansas/14/2017亲缘关系较远;与疫苗株相比,所有待检毒株A抗原决定簇有3个位点,B抗原决定簇有2个位点发生改变;受体结合位点均发生T135K位和S137F位变异;19株分离株全部发生133位糖基化位点缺失。结论抗原性分析及HA基因序列分析结果显示,WHO推荐的2019—2020年疫苗株保护效果有可能不理想。应继续密切关注H3N2亚型流感病毒的流行与基因变异情况,为流感病毒疫苗株推荐及防控提供科学依据。

This study aimed to analyze the antigenicity,genetic evolution and amino acid variation of the hemagglutinin(HA)gene of the influenza H3 N2 virus circulating in Shandong during the 2019-2020 influenza surveillance year.The antigenic characteristics of 40 influenza H3 N2 viruses were assessed with post-infection ferret antisera in hemagglutination inhibition assays.The HA genes of the 19 viruses were sequenced and analyzed.Only 35%(14/40)of the detected influenza H3 N2 viruses during the 2019-2020 influenza season were antigenically similar to the vaccine virus A/Kansas/14/2017.Phylogenetic tree analysis showed that the HA genes of 19 H3 N2 strains belonged to the 3 c.2 a1 clade and were distant from the vaccine strain A/Kansas/14/2017 in 3 c.3 a.In the analysis of amino acid variation of epitopes,three sites in the A epitope and two sites in the B epitope were found to be mutated among all tested strains.The mutations T135 K and S137 F affected the receptor binding sites of all strains.The glycosylation site 133 had been lost in the 19 analyzed strains.The results of antigenicity analysis and HA gene sequence analysis showed that the protective effects of the vaccine strains recommended by the WHO from 2019 to 2020 may not be ideal.Greater attention should be paid to H3 N2 subtype influenza virus epidemic status and genetic variation,to provide scientific evidence supporting vaccine strain recommendations and influenza virus prevention.