[Effect of vaccination of mice with endogenous retrovirus on the development of tumors induced by gamma-irradiation or 7,12-dimethylbenz[a]anthracene].

Mouse vaccination with alive endogenous N-tropic virus OA-3 inhibited and decreased the development of the Rauscher leukemia in C57B1/6 mice (B-type) and SWR mice (N-type) as well as the development 7,12-dimethyl benzanthracene (DMBA)-induced tumours in mouse hybrids (neither N-, nor B-types). The effect of vaccination was DMBA- or MLV-P-dose-dependent. Vaccination with the same virus did not affect the incidence of gamma-irradiation-induced leukemia in CBA mice (N-type) and C57B1/6 mice while it increased twice the incidence of radiation leukemia in DBA mice (N-type). However, the incidence of thymomas lowered in radiation leukemia-bearing vaccinated mice of all the 3 strains, which may result from inhibition of murine thymotropic endogenous virus reproduction. The data obtained indicate the participation of murine own endogenous viruses in DMBA- or gamma-irradiation induced carcinogenesis.