BCG-immunotherapy of L2C guinea pig leukemia.

In different experiments 46 guinea pigs of inbred strain 2 were inoculated intradermally with a lethal dose of about 10(5) gelatine purified L2C leukocytes per animal in mixture with 10(7) colony forming units (CFU) of BCG Copenhagen 1331. From these animals 58% showed a significant (p = 0.05) delay of death from leukemia in comparison to 38 animals not treated with BCG all perishing of leukemia with an average life time of 22.7 days (+/- 4.1 S.D.) after tumor cell inoculation. In 15% of the animals BCG caused long term survivors, still alive more than three months after L2C application. Twelve of them were challenged with nearly 10(5) L2C leukocytes; nine animals remained healthy demonstrating strong acquired resistance against L2C leukemia. Fresh submers cultured and lyophilized pellicle grown preparations of BCG Copenhagen 1331 were equally effective in antitumor activity. Using the same CFU dosage the lyophilized Copenhagen 1331 preparation was compared with two other commercial BCG vaccines and was found equivalent or better in efficacy against L2C leukemia.