Eradication by active specific immunotherapy of established tumor transplants and microscopic lymph node metastases

Guinea pigs, each with an established syngeneic dermal line 10 tumor and microscopic lymph node metastases, were immunized by injection of a mixture of irradiated line 10 tumor cells and an oil-in-water emulsion containing heat-killed cells of Mycobacterium bovis strain Bacillus Calmette-Guérin. Squalane or squalene-in-water emulsions, prepared by ultrasonication and containing mg doses of mycobacterial cells, were effective adjuvants. Immunization eradicated established dermal tumors (about 10 mm in diameter) and prevented growth of microscopic lymph node metastases. Untreated animals, animals treated by intradermal administration of Bacillus Calmette-Guérin cells attached to oil droplets alone or with irradiated tumor cells alone, all died with progressive tumor growth.