[Properties of the tick-borne encephalitis virus persisting for a long time in a chronically infected cell culture].

The biological properties of tick-borne encephalitis virus (Sof K) produced by chronically infected HEp-2-Sof cells at late stages of the cultivation were studied. The Sof K virus was infective for mice of different ages upon intracerebral and subcutaneous inoculation, had high immunogenicity and was completely neutralized by antiserum to the parental strain. The Sof K virus had the small-plaque phenotype and replicated with similar intensity in pig embryo cell cultures (SPEC) at 36 degrees, 42 degrees and 31 degrees C.