Abstract
Summary
Japanese B encephalitis virus on hamster kidney cell cultures has been studied by the plaque method, and the following results obtained. 1. The effect of some environmental variables on plating efficiency: a. Maximum adsorption was obtained by 120 minutes incubation at 35°C. b. Optimal conditions for initiating plaques were obtained by seeding the virus in a small volume of lactalbumin medium containing bovine albumin. c. Cations were required for maximum virus adsorption but plaques were produced in the absence of added Ca++ and Mg++. d. Washing cultures with phosphate-buffered saline (pH 7.0) before and after exposure to virus was not required, and it was shown that plaques developed only from virus adsorbed on cells before agar was applied. 2. The titers obtained by plaque assay were in almost all instances similar to those of the tube culture method and varied with the mouse titer as might be expected on the basis of the passage level in mice or in HKC. 3. Hamster kidney cells proved slightly more sensitive for plaque assay than chick embryo cells, when HKC adapted virus was used.
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