云浮市首例麻疹野病毒的血清学和分子生物学研究

STUDY ON SEROLOGY AND MOLECULAR BIOLOGY OF THE FIRST WILD MEASLES VIRUS IN YUNFU CITY OF GUANGDONG PROVINCE

目的：实验室诊断麻疹疑似病例和进行病原学分析。方法：收集2005年3月广东省云浮市1例麻疹病例流行病学资料，并收集病例急性期血清和咽拭子各1份，进行血清学检测，病毒分离和中和实验；通过RT-PCR扩增麻疹N基因碳末端589个核苷酸。并进行测序和种系分析。结果：该麻疹疑似病例确诊为麻疹病例，并分离出1株麻疹病毒，该麻疹流行株不同于中国疫苗株（S-191），鉴定为H1基因型；和目前国外流行株相比在核苷酸水平变异最大可达12．8％。和目前广东省H1流行株相比在核苷酸水平变异在1．1％-3．7％；中和实验表明麻疹疫苗免疫后血清能够中和该野病毒，但其中和的滴度比中和疫苗株低2至4倍。结论：云浮市存在麻疹病毒野毒株，病毒基因发生变异，现在使用麻疹疫苗免疫对易感人群仍然具有保护作用。

Objective： Pathogenic analysis and laboratory diagnosis on suspected measles cases. Methods： The epidemic dates in march 2005, a throat swab and a acute serum sample were collected. Then, a serial of tests were performed, including serologic antibody test, pathogenic isolation and neutralization test. Finally, a 589bp fragment of the C- terminal of the nucleoprotein （N） gene was amplified by RT - PCR and subjected to sequence and phylogenetic analysis by bioinformatic tools.Results： The suspected measles case was confimed , and a wild measles virus was isolated .This virus was distinct from the vaccine strain （S-191） and grouped into the clade HI. Comparison current abroad strains, the most divergence was 12.8% at the nucleotide level, and the divergence ranged 1.1% - 3.7 % when compared with other measles viruses in Guangdong . Neutralization test showed that the serum vaccinated with S - 191 could neutralize Yunfu strain with titers 2 - 4 times lower than vaccine virus.Conclusion： There is wild measles virus epidemic in Yunfu, the mutation in Yunfu strain had occurred, but current measles vaccines are still effective.