HIGHLY PRODUCTIVE ATTENUATED VARIANT OF J APANESE ENCEPHALITIC VIRUS

Attenuated strain of Japanese encephalitis virus (JEV), clone 3, has b een isolated from suckling mouse brain cell cultures chronically infec ted with JEV Nakayama strain, clone 33. Clone 3 actively replicates in 9-day chicken fibroblast cultures and possessed an uncommon for a JE agent capacity of causing cytodestruction of 1-2-day monolayer of chic ken embryo cells, accumulates in these cultures in high titers (9.0 1g PFU/ml and higher), and is characterized by a high antigenic activity and a wide spectrum of antigenic relationships. New biologic properti es acquired by JFV over tile course of its persistence were retained a fter 10 and more passages through suckling mouse brain.