[Genotyping of Japanese encephalitis viruses isolated in Yunnan]

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.

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.

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 1 and 2 strains belonged to genotype 3. The difference between genotype 1 and type 3 were more than 15%. While the difference between 17 strains of genotype 1 which were separated at different time, location and hosts were only 3.8%-5.2%.

The above results suggest that the genotype of the epidemic JEV in Yunnan Province are type 1 and 3 and the latter is the main type.