[Changes in the synthesis of the virion antigen of the tick-borne encephalitis virus after passage through ixodid ticks and small mammals].

Large-plaque strains of tick-borne encephalitis (TBE) virus possess a high peripheral activity, and in acute infection in continuous pig embryo kidney cells (PEK) synthesize a virion antigen (VA) whose subpopulations differ in their mobility in agarose gel electrophoresis: the bulk portion of VA moves towards the cathode and a small one towards the anode. After long-term passages of these strains in Ixodid ticks they lose their peripheral activity and produce only small plaques. In reproduction in PEK cells the amount of the infectious virus remains the same but VA synthesis changes significantly. There is almost no synthesis of VA moving towards the cathode and that of VA moving towards the anode remains unchanged or decreases insignificantly. The decrease in the synthesis of the major portion of VA is accompanied by the reduction of the hemagglutinating properties of the strains and retention of the nonvirion antigen production. Reversion to the initial properties of the strains passaged in ticks occurs after their inoculation into natural hosts of tick-borne encephalitis virus: small mammals (bank vole and common vole).