[A highly-productive attenuated variant of Japanese encephalitis virus].

Attenuated strain of Japanese encephalitis virus (JEV), clone 3, has been isolated from suckling mouse brain cell cultures chronically infected 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 chicken embryo cells, accumulates in these cultures in high titers (9.0 lg PFU/ml and higher), and is characterized by a high antigenic activity and a wide spectrum of antigenic relationships. New biologic properties acquired by JEV over the course of its persistence were retained after 10 and more passages through suckling mouse brain.