[Persistence of the tick-borne encephalitis and Langat viruses in mouse thymocytes in experimental infection against a background of cyclophosphane-induced immunodepression].

The intensity of infection of immunocompetent organ cells with tick-borne encephalitis and Langat viruses in mice with temporary immunodeficiency induced by cyclophosphane is characterized. Using the method of infectious centres it was shown that at various stages of the infectious process splenocytes, bone marrow cells and thymocytes may be target cells for both viruses tested. The viruses persist for over 6 weeks in brain and thymocytes of clinically normal mice if at the time of inoculation the animals had a temporary immunodeficiency after a single administration of 200 mg/kg cyclophosphane). The asymptomatic persistence of the viruses, however, was 2-3 times more frequently detected in thymus cells than in the central nervous system. By the set of surface markers, the infected thymocytes were classified as a population of T lymphocytes. We failed to demonstrate the presence on the surface of the infected thymus cells of virus-specific antigens detectable by the complement-dependent immune cytolysis test. The role of virus-infected thymocytes as a reservoir of the agent in chronic forms of flavivirus infections is discussed.