贵州省麻疹疫苗强化免疫后麻疹野病毒基因特征分析

Genetic characteristic of the wild-type measles virus strains isolated after measles vaccine campaign immunization activities in Guizhou Province

目的了解贵州省麻疹疫苗强化免疫后麻疹野病毒的基因型特征,为麻疹消除提供科学依据。方法将收集的咽拭子或尿液标本接种到单层Vero/SLAM细胞,获取阳性分离物后提取其病毒RNA,用逆转录-聚合酶链反应(RT-PCR)对麻疹病毒核蛋白(N)基因羧基(COOH)末端676个核苷酸片段进行扩增,对扩增产物进行核苷酸序列测定和分析。以C末端456个核苷酸片段构建基因亲缘性关系树,分析毒株间相互关系。结果2007年贵州省共分离到11株麻疹野病毒,与H1a参考株China 9344的核苷酸差异为0.9%～1.4%,同属于H1a基因亚型。分离的麻疹野病毒包括2个亚支(即GZ07-1与GZ07-3,GZ07-6～12),分属不同的病毒传播链。GZ-06～12为相同麻疹野毒株引起的传播,GZ07-1、GZ07-3和GZ04-5是来源于一个祖先病毒的传播,为同一麻疹野毒株不同年份的传播。结论贵州省麻疹强化免疫后流行的麻疹野病毒为H1a基因亚型,与中国的优势株保持一致,未见强化免疫前存在的H1b基因亚型流行。存在相同麻疹野毒株引起的传播和同一麻疹野毒株不同年份的传播,需加强麻疹疫苗覆盖率和病毒分子流行病学监测。

Objective To investigate the genetic characteristic of wild - type measles virus strains isolated after the provincial measles vaccine（MV） campaign immunization, and to provide scientific evidence for elimination measles. Methods The throat swabs or urine specimens from the measles patients of outbreak and prevalence in some areas of the province in 2007 were collected and measles viruses were isolated with Vero/ SLAM cell. RNAs of positive isolates were extracted, and the 676 nucleotide sequence of the C - terminus of the nucleoprotein （N） gene of the virus genome were amplified by reverse transcription polymerase chain reaction（RT - PCR） , the nucleotide sequences of amplified products were determined and analyzed. The phylogenetic analysis based on the 456 C - terminal nucleotide sequence of N gene was carried out. Results 11 measles virus strains were isolated, and were determined to be genotype Hla strains, compared with the Chinese measles vaccine strain 9344, the nucleotide diversity varied from 0.9% to 1.4%. These wild - type measles viruses were separated into two branches （that is GZ07- 1, GZ07- 3 and GZ07 - 6- 12）, which belonged to different virus transmission chain. GZ07 - 6- 12 was one transmission from same wild - type measles virus strain. GZ07 - 1, GZ07 - 3 and GZ04 - 5 viruses had the same ancestor, and were different year transmission of the same virus strain. Conclusion After MV campaign immunization in Guizhou Province, the prevalent wild - type measles virus was Hla genotype, in accordance with China predominant virus strain. And Hlb genotype which existed before campaign wasn＇ t found. There were the same wild - type measles virus strain transmission chain and different year transmission of one wild - type measles virus strain. It is very necessary to improve measles vaccine coverage and strengthen viral molecular epidemiological surveillance.