Propagation of Japanese B Encephalitis Virus in the Developing Chick Embryo

Abstract

The Japanese B encephalitis virus was cultivated through 37 generations in the developing chick embryo by yolk sac passage. No changes in the virulence of the virus for mice occurred as result of such cultivation. The virus apparently increased best at incubation temperatures of 35.5–36 C. The virus was present throughout the egg, with the highest concentration being found in the embryo. The LD₅₀ titer of embryo suspension remained within the range of 10^−7.20 to 10^−8.00, with the maximum reached in chick embryos approximately 48 hours after inoculation. Chick embryos were as susceptible to the virus as were mice; comparative titrations of virus in both gave LD⁵⁰ titers which were practically identical. The possibilities of using infected chick embryo as material for the preparation of formalin inactivated vaccine are discussed.