Morphological characteristics of the infection of animals with tick-borne encephalitis virus persisting for a long time in cell cultures.

The pathogenicity of the Soph-K strain of tick-borne encephalitis (TBE) virus produced by the persistently infected HEp-2-Soph cell culture was investigated in monkeys, white mice and hamsters. The persistent infection of this culture with TBE virus has been maintained for 17 years. The Soph-K strain was shown to retain its pathogenic properties for mice of different ages and hamsters. Morphological examinations of the brains and spinal cords of these animals infected with the Soph-K strain revealed acute and subacute forms of encephalitis. Monkeys inoculated with the Soph-K strain intracerebrally showed an asymptomatic infection with the pathomorphological picture of subacute disseminated meningoencephalitis with a progredient course for 3 months of observation. This chronic TBE infection in monkeys offers an interesting model for investigations on progressive degenerative disease of the nervous system.