[Changes in the organs of the immune system of Syrian hamsters infected by the tick-borne encephalitis virus with various degrees of virulence].

On the model of Syrian hamsters inoculated intracerebrally with 9 tick-borne encephalitis (TBE) virus strains varying in virulence, the specific involvement of the organs of the immune system (spleen and lymph nodes) was established and morphological features of the process described. The most severe destructive changes of these organs were found in the hamsters inoculated with highly virulent strains which appeared to be one of the factors leading to 100% death of the animals. In hamsters inoculated with strains of low virulence, the destructive changes in immunogenesis organs were less marked, but active migration and proliferative processes developed in them. The above-described differences in the involvement of the immune system organs should be taken into consideration in the interpretation of TBE pathogenesis and evaluation of the degree of virulence of the virus strains.