Influence of BCG vaccination on the primary and transplantable hamster tumors induced by SV40 and on the specific SV40 virus-induced antitumor immunity.

The main purpose of the study was the estimation of the effect of BCG vaccination and BCG in the combination with the specific immunization with SV40 on the incidence of primary and growth of transplantable SV40-induced tumors in Syrian hamsters. Different BCG vaccine preparations containing 60--100 millions of viable Mycobacteries per 1 mg were used. It has been demonstrated that one and two intradermal injections of BCG (0.25 mg per animal) during the latent period in Syrian hamsters inoculated with SV40 when newborn had no influence on the incidence of primary SV40-induced tumors. Repeated six injections of BCG during the latent period increased the frequency of tumors in one of two experiments. The subsequent was concern with investigation of the effect of BCG vaccination and its different combinations with specific immunization with SV40 on the growth of transplantable SV40-induced tumors in adult Syrian hamsters. Experimental data have shown that different preparations of BCG were varying in the capacity to increase nonspecific antitumor resistance; some preparations were nonimmunogeneic. Injections of a mixture of BCG and SV40 as well as BCG followed with SV40 14 and 20 days later did not lead to summation of effects of immunization, even when immunogenic preparations of BCG were used. Moreover inoculation of SV40 followed with BCG injection 4, 14 or 20 days later completely or partly declined the effect of SV40 specific immunization. Possible mechanisms of the negative effect of BCG on specific antitumor resistance are discussed.