In hamsters inoculated with tubercle bacilli of the Calmette-Guérin strain (BCG) a week after birth and later with polyoma virus, the incidence of malignant changes was reduced and survival was considerably prolonged; hemagglutination-inhibiting, complement-fixing, and neutralizing antibodies against the virus were augmented. However, in controls given polyoma virus but no BCG, animals with higher titers of antibodies died earlier and had more neoplastic lesions than those with low titers. This suggests the presence of other types of antibodies, which would also be stimulated by BCG and would be responsible for protection against neoplasia.

In mice inoculated with the virus at birth and with BCG later, the incidence of tumors was not changed, but other results were similar to those seen in hamsters (prolonged life, increased antibodies), although less significant.

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This work was supported by grants from the National Cancer Institute of Canada.

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