2010-2012年长沙市流感流行情况及B型流感病毒基因特性分析

Analysis of influenza epidemics and molecular characteristics of influenza B virus in Changsha in 2010-2012

目的分析2010-2012年长沙市流感流行情况,并探讨B型流感病毒分离株血凝素（HA）和神经氨酸酶（NA）基因的分子流行病学特征。方法采集长沙市流感网络监测哨点医院及暴发点流感样病例（ILI）咽拭子样本,狗肾传代细胞（MDCK）进行病毒分离,血凝和血凝抑制实验进行型别和亚型鉴定;提取B型流感病毒核酸,一步法RT-PCR扩增HA和NA基因片段,双向测定扩增产物核苷酸序列,对基因序列和氨基酸序列进行分析。结果 2010-2012年间,长沙市甲型H1N1、H3N2、B型流感交替流行,流行高峰为冬春季。3年间共分离到B型流感病毒78株,其中79.5%为Victoria系,20.5%为Yamagata系,以Victoria系为主。与WHO推荐疫苗株B/Brisbane/60/2008相比,HA基因的同源性在87.2%~98.4%之间,NA基因的同源性在94.5%~97.5%之间。氨基酸序列分析发现,与疫苗株相比,HA蛋白主要存在单个氨基酸的突变;种系进化分析发现,所有毒株HA和NA蛋白位于相应的谱系内,无抗原重排发生。结论 2010-2012年间长沙市甲型H1N1、H3N2、B型流感交替流行,B型流感病毒HA基因出现抗原漂移,但无重组毒株的出现。

Objective To understand the situation of influenza epidemics in Changsha from 2010to 2012,and to analyze the molecular characteristics of hemagglutinin（HA）and neuraminidase（NA）genes of influenza B virus.Methods Throat swab specimens were collected from patients with influenza-like illness（ILI）from whistle hospital and outbreak sites and influenza virus were isolated in MDCK cells.The serotype and subtype of influenza virus were determined by hemagglutination and hemagglutination inhibition test.Fragments of HA and NA genes of influenza B virus were amplified by one-step RT-PCR and then sequenced.The nucleic acid and amino acid sequences were analyzed.Results During the year of 2010to 2012,influenza A H1N1,H3N2and influenza B virus prevailed in Changsha alternatively with the peak season of winter and spring.78 strains of influenza B virus were isolated during this period,and 79.5% were found to be Victoria lineage and the rest were Yamagata lineage.Compared to the vaccine strains B/Brisbane/60/2008recommended by WHO,the homology of HA gene and NA gene ranged from 87.2%to 98.4%and from 94.5%to 97.5%.Amino acid sequence alignment analysis showed single amino acid mutation in HA gene.Meanwhile,the phylogenetic tree analysis showed that HA and NA molecules of all isolated strains were in the corresponding lineage and there was no antigen rearrangment.Conclusions The influenza A H1N1,H3N2and influenza B virus prevail alternatively in Changsha from 2010to 2012,although antigen drift appears in the HA gene of isolated influenza B strains,no antigen rearrangement shows up.