中文摘要：

目的对近30年来云南省分离的19株乙脑病毒进行PrM基因核苷酸序列测定，以确定病毒基因分型。方法乙脑病毒接种3日龄乳鼠，取发病濒死的乳鼠脑组织经研磨制成上清液。提取核酸，通过RT-PCR扩增PrM-C基因片段，用病毒PrM-C（456．695）区核苷酸序列与国内外不同年代分离的72株各基因型乙脑病毒相应序列作比较，用Woan-Ru Chen建立的方法进行基因型分析。结果云南省分离的乙脑病毒均可引起3日龄乳鼠在78h之内死亡；核酸序列分析结果显示，19株乙脑病毒中，17株属基因Ⅲ型，2株属基因I型，其中M28分离自1977年；两株I型病毒与17株Ⅲ型病毒间核苷酸序列的差异大于15％。分离自不同地区、不同时间、不同宿主的Ⅲ型乙脑病毒核苷酸间仅存在3.8％-5.2％的差异。结论云南省广泛存在基因Ⅲ型和I型乙型脑炎病毒流行，Ⅲ型为主要流行型。

英文摘要：

Objective To explore the genotype of the epidemic Japanese encephalitis virus （JEV） in Yunnan Province from molecular level and to understand the molecular differences of the virus isolated from Yunnan at different time, locality and host. Methods Three-day suckling mice were inoculated with viruses continuously and when the disease developed and the mice were dying, the brain was taken and DNA was extracted from the supernatants of the brain after grinding; then the gene fragments of Prm-C region were amplified by RT-PCR. The viral gene sequences were compared with those of other 72 strains of JEV originated from both China and abroad at different times. Finally the genotypes were analyzed with the method which was established by Woan-Ru Chen. Results All the 3-day suckling mice which were inoculated with the virus died within 78 h. The results of the nucleic acid-sequence analysis showed that 17 strains of the experimental virus belonged to genotype Ⅲ and 2 strains belonged to genotype I. The difference between genotype Ⅲ and type I were more than 15% . While the difference between 17 strains of genotype Ⅲ which were separated at different time, location and hosts were only 3.8%-5.2%. Conclusion The above results suggest that the genotype of the epidemic JEV in Yunnan Province are type I and Ⅲ and the latter is the main type.