| Budget Amount *help |
¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2004: ¥1,000,000 (Direct Cost: ¥1,000,000)
|
|---|
| Research Abstract |
Japanese encephalitis virus (JEV)
Japanese encephalitis virus (JEV) has been classified into 4 subtypes (G1-4) based on the molecular phylogenetic analysis of the C-prM gene region (240 base) and the location of isolation. The subtype of Japanese strains was believed to be G3. But, we found that since around 1994, the dominant strain had shifted from G3 to G1, which belonged to the northern Thailand subgroup. It is suggested that these G1 strains might be introduced into Japan from abroad. Phylogenetic analyses based on the C-prM gene region of 23 JEV strains isolated at Nagasaki, Okinawa, Osaka, Ishikawa and Tokyo during 1965-2001 indicated that G3 strains were further divided into 6 clusters (A, B, C, D, E1 and E2), each one of which became dominant during 1935-1994. Antigenic difference among the strains belong to different genetic clusters was examined by 50% plaque-reduction neutralization (NT) test. Six JEV strains and 20 swine sera naturally infected with JEV were used. The results indicated that NT reactivity showed significant difference (P<0.05) (1)between the JEV strains isolated in 1981 and 1989 ; (2)between the strains isolated in 1989 and 1995 ; and (3)between the two strains isolated in 1995. However, NT reactivity was not significantly different between strains isolated in 1981 and 1995. The results indicate that there is a possibility of introduction of antigenically distinct JEV strains into Japan. Continuous JEV surveillance is necessary.
|
