Molecular epidemiological studies on Japanese encephalitis and dengue viruses in Asia

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The study was performed to clarify the unsolved problem of overwintering of Japanese encephalitis; whether the virus persists in the temperate climate or it is introduced from tropical area during the summer time, by using molecular epidemiological studies, which is quite different from those to find out the virus during interepidemic season. The study also aimed to obtain informations on the possible role of virus virulence factor in the pathogenesis of dengue haemorrhagic fever, which has been a major viral disease in Southeast Asian Countries since the first outbreak in 1953.The strains of Japanese encephalitis virus isolated from 1935 to 1983 in Japan as well as in foreign countires was used for the analysis. Dengue virus type 3 and 4 were used in the studies. These viruses were grown in Aedes albopictus clone C6/36 cells in mass culture and the virus was concentrated and purified from the infected fluid by polyethylene glycol precipitation and ultracentrifugation. Viral RNA was ph … More enol-extracted from the pelleted virus, and purified by the sucrose gradient sedimentation to obtain 42S virion RNA. The RNA was digested by T1-RNase and labeled by polynucleotide kinase and <r^(32)> P-ATP. The labeled nucleotides were analyzed by 2-dimensional gel electrophoresis and revealed by the autoradiography.The fingerprints of Japanese encephalitis virus isolated in Japan were quite different from those of southeast Asian isolates after 1980. The finding was in favour of the hypothesis that the virus persists somewhere in Japan during winter season.The fingerprint pattern of type 3 dengue virus isolated in the Philippines was quite distinct from those of the Indonesian isolates. The fingerprints of these isolates were also different from those of Thailand. The fingerprints of the Philippine isolates were rather similar even when the year of isolation showed 10 years difference, so were the Indoensian isolates. There were 11 spots difference between the type 3 dengue virus isolated from severe haemorrhagic fever case from the strain isolated from mild case in the same epidemic season in the Indonesia. Less