2007—2011年青岛地区H3N2流感病毒全基因组进化特征分析

Analysis of evolution features of whole genome of influenza virus H3N2 in Qingdao between year 2007 and 2011

目的了解2007-2011年青岛地区流行的H3N2流感病毒的全基因组进化特征。方法选取2007--2011年青岛地区流行的H3N2流感病毒58株，提取病毒RNA，应用RT—PCR扩增各基因片段，并进行序列测定；用Sequencher软件完成序列拼接。选取GenBank收录的全球同期氨基酸数大于300的H3N2流感病毒589株，以其血凝素重链区（HAl）序列作为参照，用Mega5．0软件对各基因片段进行系统发育分析及分子特征分析。结果2007--2011年青岛地区流行的H3N2流感病毒血凝素（HA）基因在进化树上形成单一主干，每一流行季毒株的起源均晚于上一季；全基因组进化分析发现，2009--2010流行季存在重配病毒株，而2010—2011流行季同时存在簇Ⅰ和簇Ⅱ两系毒株流行，该季病毒呈现复杂的重配现象。病毒HA1蛋白与疫苗株比较，2007--2011年各监测季分别有8、6、6、8、11处氨基酸变异，涉及13个抗原位点。M2蛋白氨基酸序列分析表明，分离到的H3N2流感病毒31位氨基酸均发生丝氨酸→天冬酰胺（$31N）突变。2007--2011年青岛地区分离的H3N2流感病毒HA1基因在进化树上与全球同期H3N2流感毒株处于同一主要分支。序列比对及抗原性分析显示，毒株A／Qingdao／F521／2011存在H3N2与甲型H1N1流感病毒共感染现象。结论2007—2011年青岛地区流行的H3N2流感病毒各基因片段呈现复杂的进化特征。

Objective To investigate the evolution features of whole-genome of influenza virus H3N2 prevalent in Qingdao from year 2007 to 2011. Methods The RNA of 58 strains of influenza virus H3N2 prevalent in Qingdao between 2007 and 2011 was extracted and all segments amplified by RT-PCR. The sequence was then detected and assembled by software Sequencher. A total of 589 strains of influenza virus H3N2 with more than 300 amino acid recorded by GenBank were selected. The phylogeny and molecular features of all gene segments were analyzed by software Mega 5.0, referred by the heavy chain of hemagglutinin （ HA1 ）. Results Hemagglutinin （HA） genes of influenza virus H3N2 prevalent in Qingdao between year 2007 and 2011 formed a single trunk of phylogenetic tree. Every prevalent strain originated in last season. The analysis of the evolution of whole genome found that reassortment virus strains were prevalent between year 2009 and 2010, but between 2010 and 2011 there were two series of prevalent strains, which showed complicated reassortment. Compared with the vaccine strains, the variant amino acids of protein of virus HA1 between year 2007 and 2011 were 8,6,6,8 and 11, involving 13 antigenic sites. The sequence analysis of M2 protein showed that the isolated influenza virus H3N2 mutated in amino acid site 31, from serine to asparagine （$31N）. HA1 gene of influenza virus H3N2 isolated in Qingdao between 2007 and 2011 shared the similar phylogenetic tree with the globally prevalent strain. The comparison of the sequence and the analysis of the antigenicity found co-infection between H3N2 and A/H1N1 in the strain A/Qingdao/F521/2011. Conclusion The evolution features of all segments of influenza virus H3N2 prevalent in Qingdao between year 2007 and 2011 were complicated.