2016-2019年北京市GII.2[P16]型诺如病毒全长基因组系统进化分析

Phylogenetic analysis of complete genomes of GII.2[P16]noroviruses in Beijing,2016-2019

目的对2016—2019年北京市GII.2[P16]诺如病毒全长基因组进行系统进化分析。方法收集2016—2019年北京市GII.2[P16]诺如病毒毒株,采用一步法RT-PCR对基因组全长进行分段扩增,应用BioEdit软件分析核苷酸相似性和氨基酸变异情况,采用BEAST软件分别构建衣壳蛋白(major capsid protein,VP1)区和RNA聚合酶(RNA-dependent RNA polymerase,RdRp)区全长序列的贝叶斯进化树,结合流行病学资料对毒株进化特征进行分析。结果测得44个毒株的全基因组序列,其VP1和RdRp基因分型一致。进化分析显示北京市2017年5月以后毒株形成新亚群并分为两个分支,分别以2017—2018年和2018—2019年毒株为主。该亚群毒株在VP1区均存在Val256Ile点突变,但RdRp区没有发现氨基酸变异位点。流行病学数据表明,北京市GII.2[P16]型诺如病毒从2016年10月输入,2017年3月至6月为暴发高峰,2017年7月以后暴发数量明显降低,但2018年底暴发又有所增加。结论北京市GII.2[P16]诺如病毒新变异株2017年5月之后基因特征有所改变,暴发强度降低,但仍具有传播风险。

Objective To perform phylogenetic analysis of complete genomes of GII.2[P16]noroviruses in Beijing,2016-2019.Methods GII.2[P16]noroviruses detected during 2016 and 2019 were collected,and the segments of norovirus complete genome were amplified by one-step RT-PCR.The nucleotide sequence similarity and amino acid substitutions were analyzed by BioEdit software.Bayesian phylogenetic trees of the complete sequences of major capsid protein(VP1)and RNA-dependent RNA polymerase(RdRp)genes were constructed using BEAST software,respectively.The genetic characteristics of these strains were analyzed along with the epidemiological data.Results The complete genome sequences of 44 strains were obtained.The genotyping results by VP1 and RdRp genes were consistent.Phylogenetic analysis showed that strains detected in Beijing between May 2017 and November 2019 formed a new subclade,which further clustered into two branches of the strains mainly detected in 2017-2018 and 2018-2019 respectively.Val256Ile mutation in VP1 was observed in all strains of this new subclade,while no amino acid substitution in the RdRp was found.The epidemiological data showed that the first GII.2[P16]norovirus outbreak was reported in October 2016 in Beijing.The peak of outbreaks was observed during March and June 2017 followed by a dramatic decline after July 2017 and a slight increment during October and December 2018.Conclusions The genetic characteristics of new GII.2[P16]variants in Beijing had changed after May 2017 with decreased number of outbreaks,but there is still risk of spreading.