2013年北京市朝阳区柯萨奇A6型病毒分子流行病学研究

Molecular epidemiology of coxsackievirus A6 associated with hand- foot-mouth disease in Chaoyang district,Beijing in 2013

目的了解2013年北京市朝阳区柯萨奇A6型（Coxsackievirus A6,CVA6）病毒的流行特点及其基因特征。方法对2013年收集的795份手足口病患者的咽拭子样本进行肠道病毒检测,对非EV71、非CVA16型病毒阳性样本进行CVA6荧光定量PCR检测,选取CVA6阳性样本进行VP1片段（794bp）序列扩增与测序,运用Clustalx软件和MEGA4.0软件对本地区CVA6的VP1片段序列与从NCBI下载的CVA6的VP1参考序列进行聚类分析。结果肠道病毒通用型核酸阳性样本共计382例（48.1%,382/795）,其中非EV71、非CVA16型病毒236例（61.8%,236/382）;非EV71、非CVA16型病毒阳性样本中有CVA6型病毒样本185例（78.4%,185/236）。基于VP1片段的聚类分析,结果显示2013年该地区的CVA6型病毒与中国地区的参考序列明显聚为一类;CVA6在系统进化树中形成A、B和C等3个基因型,C基因型又可分为C1和C2两个基因亚型;两个基因亚型间的核苷酸序列差异度为10.8%-13.2%。朝阳区所有的CVA6都位于C基因型,C1亚型包括了大部分该地区序列。结论 2013年该地区的CVA6已经超过了EV71和CVA16,首次成为北京市朝阳区手足口病的主要病原体。该地区存在CVA6的C1和C2两个基因亚型的共循环,其中C1亚型对该地区2013年CVA6的暴发流行起关键作用。

Objective In order to determine the epidemiologic features of coxsackievirus A6（ CVA6） associated with hand-foot-mouth disease（ HFMD） in Chaoyang district,Beijing in 2013. Methods The enterovirus was detected in 795 throat swabs of hand-foot-mouth disease cases in 2013. Samples which were CVA6 strains positive were detected by real-time PCR from enterovirus strains positive for neither enterovirus A71（ EV71） nor CVA16. The partial sequences of VP1 genes were amplified and sequenced. The phylogenetic analysis was performed using clustalx and MEGA 4. 0. Results 382 specimens were detected as enterovirus positive from 795 samples in 2013. 236 specimens were identified as non-EV71,non-CVA16 enterovirus positive by real-time PCR. CVA6 accounted for 78. 4% of the non-EV71,non-CVA16 samples. Based on the phylogenetic analysis,all the strains in 2013 were grouped together with reference strains from China. The CVA6 strains could be classified into three genotypes in the phylogenetic tree,designated A,B,and C（ including C1 and C2 subgenotypes）. The two subgenotypes shared nucleotide diversity ranging 10. 8% - 13. 2%. All the strains were grouped in C genotype,and C1 subgenotype contains most of strains detected in Chaoyang district. Conclusion CVA6 strains were the major pathogen associated with HFMD in Chaoyang district,Beijing in 2013. HFMD epidemics had primarily been associated with CVA16 or EV71 infections in the past few years.Phylogenetic analysis based on VP1 nucleotide sequences revealed that two CVA6 subgenotypes co-circulated in Chaoyang district,and C1 was the key subgenotype accounted for the wide spread of CVA6 strains around Chaoyang district,Beijing in 2013.