2013-2014年江苏省H3N2亚型流感血凝素分子特征分析

Molecular characteristics of hemagglutinin gene of influenza A （H3N2） virus strains circulating in Jiangsu province, China, 2013-2014

目的 分析2013-2014年江苏省H3N2亚型流感病毒HA基因变异规律及其遗传进化特征. 方法 从2013-2014年江苏省流感病原监测中分离到的季节性H3N2亚型流感毒株中,选取不同时间段、不同地区具有代表性的31株分离毒株,提取病毒RNA,利用自行设计的特异性引物通过RT-PCR扩增HA基因片段,将PCR产物纯化、测序并分析其遗传进化特征. 结果 31株分离株与疫苗株A/Texas/50/2012的核苷酸和氨基酸进化距离分别为0.010 5、 0.012 4,核苷酸与氨基酸的同源性分别为97.9%-99.6%、97.2%-99.3%.遗传进化分析结果表明,分离毒株的HA基因分属不同的进化分支,2013年的3株分离毒株独立形成Group 1;3株2014年江苏省分离株位于Group 2;其余位于Group 3.选择性压力分析通过REL模型得到3个正向压力选择HA氨基酸位点分别是237、366、367.与疫苗株相比,分离毒株分子特征表现为发生N128A/T和P198S/A（去信号肽排列）氨基酸位点变异,均位于B抗原决定簇;分离毒株抗原决定簇上发生变异的位点累计24个;7株分离株出现126NWT糖基化位点,3株分离株糖基化位点45NSS和144NNS消失.流感疫苗的效果评估结果显示,疫苗对江苏省季节性H3N2流感的保护效果不理想. 结论 江苏省2013-2014年H3N2亚型流感病毒的HA基因相较于疫苗毒株发生较大变异,疫苗对病毒的预防效果不理想,使得H3亚型成为当年的优势毒株.

Objective To analyze the genetic characteristics and the evolution of the influenza A （H3N2） virus strains circulating in Jiangsu province between 2013 and 2014.Methods This study analyzed thirty-one representative strains of influenza A （H3N2） virus, which were isolated in different regions of Jiangsu province and during different time periods from 2013 to 2014.Results Genetic distances in nucleic acid and amino acid between a strain used for vaccine production （A/Texas/50/2012） and the 31 strains were 0.010 5 and 0.012 4.Similarities between them in nucleic acid and amino acid sequences were 97.9%-99.6% and 97.2%-99.3%.Phylogenetic analysis showed that the hemagglutinin （HA） genes of the 31 strains were divided into three different groups.Three strains isolated in 2013 and three strains isolated in 2014 belonged to Group 1 and Group 2, respectively, while the others belonged to Group 3.Three positive selection sites （237, 366 and 367） in HA protein were observed by REL model.Compared with the strain used for vaccine production, the 31 strains were characterized by amino acid substitutions （N128A/T and P198S/A） in HA protein and all of the mutations located in B-cell epitopes.The total number of mutation sites reached 24.Compared with the A/Texas/50/2012 strain, seven strains presented the glycosylation site 126NWT, and three strains showed disappeared glycosylation sites of 45NSS and 144NNS.Evaluation of vaccine efficacy for A（H3N2） virus strains showed that the vaccine efficacy was not very well.Conclusion The HA gene of A（H3N2） virus had undergone a greater variation and the vaccine efficacy was not very well in Jiangsu province during 2013 to 2014, which made the influenza A（H3N2） virus become the circulating strain.