[Neuromorphological and immunofluorescence study of experimental infection caused by the attenuated strain of tick-borne encephalitis virus].

In Syrian hamsters inoculated subcutaneously with an attenuated strain of tick-borne encephalitis virus the infection runs an asymptomatic course in all the animals, some of which, however, develop within 4 weeks some changes in nerve cells and hypertrophy of astrocytes. The viral antigen is detected by Coons' method in nerve cells and spleen cells. An intensive treatment of the hamsters with cyclophosphane 106 days after virus inoculation provoked no morphological lesions in the brain which could have been associated with virus activation. No virus antigen could be found in brain impression smears either. However, in both untreated animals and those treated with the immunosuppressant drug the viral antigen was found in mononuclear cells of the spleen.