贵州2起麻疹暴发疫情病毒分离株基因特征分析

Genetic characteristics of measles virus strains causing two outbreaks in Guizhou province

目的对2014年11月—2015年3月贵州发生的2起麻疹暴发疫情病毒分离株进行基因特征分析。方法采集暴发麻疹病例咽拭子标本，经Vero/SLAM细胞分离培养，从阳性培养物中提取病毒RNA，用逆转录-聚合酶链反应（RT-PCR）扩增麻疹病毒核蛋白（N）基因，对扩增产物进行测序与分析。结果2起麻疹暴发共分离到11株麻疹病毒野毒株，均为H1基因型中的H1a基因亚型；进化树分析有2个明显的分支。11株暴发麻疹病毒与H1a基因亚型参考株Chin9322的核苷酸和氨基酸遗传距离差异分别为1.1%～1.6%和0.7%～3.4%。推导出氨基酸序列与参考株Chin9322及近年来贵州流行株比较，结果显示有6株在主要位点[47（G-S）、82（S-G）、122（R-K）]发生变异；2株在位点98（P-L）发生变异。结论H1a基因亚型麻疹病毒是引起2014—2015年贵州省2起麻疹疫情的主要病原，也是贵州省以及全国本土流行的优势基因亚型；且多个不同的H1a基因亚型病毒传播链在贵州省持续流行。本研究为贵州省麻疹的控制和消除提供了一定的基础资料。

ObjectiveTo analyze the genetic characteristics of measles virus strains causing two outbreaks in Guizhou province from November 2014 to March 2015.MethodsThroat swab samples collected from measles cases in two outbreaks were inoculated into Vero/SLAM cells. Viral RNAs were extracted from positive cultures. Nucleoprotein genes were amplified by using reverse transcription-polymerase chain reaction （RT-PCR） and the PCR products were sequenced and analyzed.ResultsEleven strains of wild-type measles virus were isolated from the two measles outbreaks and all of them belonged to H1a sub-genotype. Phylogenetic analysis showed that those strains were clustered into two distinct branches. Differences in nucleotide and amino acid genetic distances between the 11 strains of measles virus and the WHO reference strain of H1a sub-genotype （Chin9322） were 1.1%-1.6% and 0.7%-3.4%, respectively. Compared with the reference strain Chin9322 and Guizhou epidemic strains in recent years, six strains showed amino acid sequence mutations in 47 （G to S）, 82 （S to G） and 122 （R to K） sites and two strains had a mutation in 98 （P-L） site.ConclusionH1a sub-genotype measles virus was the predominant pathogen causing two measles outbreaks in Guizhou province during 2014 to 2015. Moreover, it was also a predominant sub-genotype circulating in China and Guizhou province. Different measles virus strains of H1a sub-genotype continued to be prevalent in Guizhou province. This study provided some scientific data for the control and elimination of measles in Guizhou province.