The effect of pretreatment with Corynebacterium parvum on the growth of a chemical induced transplanted murine tumor.

Unspecific immunostimulation with or without specific tumor immunotherapy may well contribute to the control of minimal residual cancer. Corynebacterium parvum (C.p.) has been shown to raise the level of immunocompetence in tumor bearing animals. Experiments are reported, which aim at an evaluation of optimal conditions for an immunostimulation with C.p. prior to the transplantation of BALB/c Meth A ascitis. Using different dosages, routes of injection and schedules of vaccination it was found, that the highest non-toxic dose of C.p. per mouse yielded the optimal inhibition of tumor growth, the longest survival of tumor bearing hosts and the highest number of tumor rejections as compared to untreated controls. If the vaccine was distributed to at least 4 sites of injection, the s.c. route appeared superior to i.p. application. The intravenous route appeared to be most effective. The oral route seemed to inhibit tumor growth, if not less than 4 mg/mouse were fed daily for five days. The mechanism of action of C.p. in the model system used is discussed and correlated with an appropriate timing of both C.p. sensitization and tumor challenge.