2012-2015年上海地区成人甲型H3N2流感病毒抗原漂变分析

Antigenic analysis of the human Influenza A （H3N2） virus during 2012-2015 in Shanghai, China

目的 通过分析2012-2015上海地区成年人甲型H3N2流感病毒的分子流行病学及HA抗原漂变情况,从而了解甲型H3N2流感病毒分子流行及变异变迁规律.方法 采集2012-2015年间上海地区三家哨点医院流感样成人病例的呼吸道标本,收集临床资料.提取标本核酸后用实时荧光PCR检测流感病毒,对甲型流感病毒阳性的标本进一步进行基因分型.对H3N2阳性标本扩增血凝素（HA）基因片段、测序和进行基因变异分析.结果 总共收集2 346例病例,甲型流感病毒核酸检测阳性病例331例,其中273例为H3 N2流感病毒阳性,58例为2009 pdmH1N1流感病毒阳性.2012年-2015年期间,上海地区H3N2流感病毒在每年的冬春季流行,但在2014年和2015年均呈现夏季流行高峰.对2012年-2015年间获得的上海地区180个H3N2流感病毒的HA基因全长序列进行系统进化树分析发现：2012-2015年间H3N2流感病毒总共引起了3个主要的流感流行峰,分别是2013年12月-2014年1月、2014年7-8月和2015年7-8月,且分别属于三个不同的基因簇：A/Finland/385/2013类似株,为group 3C.3b;A/Switzerland/9715293/2013类似株（SW13）,为group 3C.3a和A/Hong Kong/5783/2014类似株（HK14）,group 3C.2a分支.比较3个流行峰的甲型H3 N2流感病毒,发现血凝素蛋白氨基酸序列存在一定差异,主要分布于抗原表位和受体结合位点（RBS）.结论 2012-2015年间,上海地区流行的H3N2流感病毒出现明显的2次抗原漂变,可能是导致上海地区近年来H3N2流感流行的原因.

Objective To understand the patterns of emergence and circulation of influenza A （H3N2） virus variants in Shanghai area,we investigated the genetic evolution of the hemagglutinin （HA） gene and epidemic characteristics of the influenza A （H3N2） viruses which were circulated in Shanghai,China,from September 2012 to August 2015.Methods Respiratory clinical samples were collected by clinicians from patients with influenza-like illness from three sentinel hospitals.Extracted RNA from specimens was used for influenza diagnosing and genotyping with real-time RT-PCR.Amplification,sequencing and phylogenetic analysis of HA gene were performed.Results Out of the 2 346 specimens,273 （11.26%）,58 （2.39%） and 75 （2.55%） were positive for influenza A （H3N2） viruses,2009pdmH1N1 viruses and influenza B viruses respectively.We found that influenza activity level in Shanghai increased in summer during 2014 and 2015,and influenza A （H3N2） virus was the main subtype.Phylogenetic analysis based on the full-length HA gene of influenza A （H3N2） virus was carried out.Comparing with the reference sequences,the influenza A （H3N2） viruses predominated during Dec.2013-Jan.2014,Jul.2014-Aug.2014,and Jul.2015-Aug.2015 were classified as genetic clade A/Finland/385/2013-1ike （group 3C.3）,A/Switzerland/9715293/2013-1ike （group 3C.3a） and A/Hong Kong/5783/2014-1ike （group 3C.2a） respectively.And the mutations of amino acid sequences of HA between the three epidemic strains were mainly located in antigenic epitopes and receptor binding site.Conclusion The influenza epidemic in Shanghai caused by H3N2 virus may be due to the antigenic changes of influenza A （H3N2） virus during 2012 to 2015.