Studies on Japanese B Encephalitis Virus

Characteristics of mouse-adapted and hamster kidney (HK) adapted Japanese B encephalitis virus on chick embryo cell cultures have been studied by the plaque method, and the following results obtained: Plaques produced by mouse virus appeared faster than the plaques produced by HK virus. After 4 days of cultivation, mouse virus plaques were clear and 2 to 3 mm in diameter. In contrast, HK virus plaques were hazy and 1 to 2 mm in diameter.Using mouse and HK viruses, a strict linearity of response between plaque count and virus concentration was obtained over a 16-fold range.Maximal adsorption of mouse virus was obtained by 90 min incubation at 36°C, and that of HK virus by 120 minutes. Particles of mouse virus, unadsorbed at the time of agar overlay, subsequently diffused through the agar and produced plaques. In contrast, unadsorbed HK virus was unable to produce plaques.Using mouse and HK viruses, the titers obtained by plaque assay were as high or higher than the LD50 titers in mice or the TCD50 titers in HK cells.