2008～2009年南宁市季节性H1N1亚型流感病毒血凝素HA1基因变异分析

Analysis of the genetic variation of HA1 gene of human seasonal influenza H1N1 virus in Nanning during 2008-2009

目的分析南宁市2008～2009年度流行性感冒的病原学监测结果,探讨其季节性H1N1亚型流感病流行情况和HA1基因变异规律及进化趋势。方法根据流感病原学监测和疫情挑选2008～2009年中分离到的季节性H1N1亚型毒株20株(每年10株),提取病毒RNA,采用RT-PCR扩增病毒HA基因后进行核苷酸序列测定,利用VectorNTI 9.0分析处理,并与WHO推荐疫苗株进行比对,用Mage 4.1构建系统进化树。结果 2008～2009年南宁市季节性流感流行主要集中在夏秋季节,H1N1成为2008年度的优势毒株。进化树分析表明,南宁市2008～2009年毒株被分为2个分支(Ⅰ和Ⅱ),A/Solomon/3/2006和A/Brisbane/59/2007分别分布在分支Ⅰ和Ⅱ内。对H1N1HA1氨基酸序列分析表明,20份毒株二硫键和糖基化位点比较保守,受体结合位点(RBS)和抗原决定簇位点相对活跃,其中RBS 188、189、222、224均发生了不同程度的变异。与A/Solomon/3/2006相比,2008年毒株抗原决定簇存在4个氨基酸的替换并且分布在两个抗原决定簇区域,2009年毒株除A/nanning/473/2009外,抗原决定簇区氨基酸变异未达到4个。结论南宁市2009年H1N1流感病毒HA1基因特性与A/Brisbane/59/2007疫苗株接近,2008年毒株与两疫苗株相比变异较大,这可能是导致2008年南宁市H1N1亚型流感病毒流行强度明显增加的原因。

Objective To analyze the data of influenza surveillance and discuss the epidemic situation,genetic variation and evolution characteristics of HA1 gene of human influenza H1N1 viruses circulating in Nanning City during 2008-2009.Methods 20 H1N1 strains（10 strains each year） isolated in influenza surveillance and epidemic situation during 2008-2009 were selected.RNAs were extracted,their HA genes were amplified by RT-PCR and then sequenced.The data obtained were compared with the vaccine strains recommended by WHO with the software VectorNTI 9.0.Genetic distance and phylogenetic tree of these strains were constructed by using Mega 4.1.Results Seasonal influenza epidemics mainly occurred in the summer and autumn in Nanning during 2008-2009.The HA1 phylogenetic tree constructed and showed that the strains were divided into two branch,both vaccine strains A/Solomon /3/2006 and A/Brisbane/59/2007 were located in branchⅠand Ⅱ,analysis of the H1N1 HA1 amino acid sequence showed that 20 strains disulfide bonds and glycosylation sites were more conserved,but the receptor binding site（RBS） and the antigenic sites were relatively active,including the RBS 188,189,222,224 occurred in distinct variation.Compared to the vaccine strains A/Solomon /3/2006,the strains in 2008 showed four amino acid substitution which located in two antigenic sites.Except to A/nanning/473/2009,all strains that isolated in 2009 showed less than 4 variation in antigenic sites.Conclusion The genetic characteristics of HA1 gene of influenza H1N1 virus isolated in Nanning in 2009 was similar to A/Brisbane/59/2007.More genetic variation occurred in 2008 strains compared with two vaccine strains recommended,which may lead to human seasonal influenza epidemics in 2008.