西藏自治区1999～2002年儿童埃柯病毒7型分子流行病学分析

目的研究西藏自治区1999~2002年≤5岁儿童埃柯病毒7型(ECHO7)VP1区编码基因特征及其分子流行病学特点。方法选取1999~2002年从西藏自治区<15岁急性弛缓性麻庳(AFP)病例和≤5岁到儿童医院就诊儿童及部分健康儿童的659份粪便标本中分离的16株ECHO7病毒,进行核糖核酸(RNA)提取,VP1编码区逆转录-聚合酶链反应(RT-PCR),PCR产物的核苷酸序列测定和分析。结果1999年的标本分离到9株,2000年分离到7株,VP1区核苷酸序列测定结果证实,此16株经血清中和试验定型的病毒全部为ECHO7病毒。其它年份未分离到ECHO7病毒。16株ECHO7病毒VP1区基因全长都是876bp,翻译的氨基酸全长292aa。所测16株ECHO7病毒序列之间同源性为86.73~100.00%。所测序列和ECHO7原型株——Wallace株相比,同源性为77.85%~78.99%;和引起致死性脑脊髓炎的ECHO7变异株——UMMC株相比,同源性为81.67%~83.79%。所构建的ECHO7病毒遗传进化树将已知的ECHO7病毒划分为4个基因型,西藏自治区分离的ECHO7病毒独自形成1个基因型(D基因型)。结论首次报告的西藏自治区1999、2000年儿童中流行的ECHO7病毒为一个新的基因型(D基因型)。16株D基因型病毒划分为2个基因亚型D1、D2。1999年流行的为D1;2000年流行的为D2。西藏自治区1999、2000年ECHO7流行为不同的病毒亚型引起。2001~2002年未发现ECHO7的持续流行。

Analysis on the Molecular Characteristics of ECHO7 Virus in Tibet

Objective To study the molecular characterization of ECHO7 virus in Tibet. Methods To isolate the enteroviruses from stool specimens of AFP cases and other children in Tibet in 1999-2002,and identify them by neutralization test using the RIVM antiserum;then determine the complete nucleotide sequence of VP1 region of ECHO7 viruses,and analyze the results. Results A total of 16 strains of ECHO7 virus were isolated from the stool specimens and identified.The complete nucleotide sequence of VP1 region of these ECHO7 viruses was 876nt coding 292 amino acids.To compare with the sequences of Wallace strain,the homogeneity of nucleotide sequence were 77.85%-78.99%;while they were 81.67%-83.79% compared with UMMC strain.The phylogenetic tree of ECHO7 viruses showed 4 genotypes,and the isolates from Tibet formed 1 independent genotype. Conclusion The deduction is that the 16 ECHO7 virus strains are proposed one new genotype of ECHO7 virus.