Influence of type of oil and surfactant concentration on the efficacy of emulsified Mycobacterium bovis BCG cell walls to induce tumor regression in guinea pigs.

The influence of mineral ol, squalane, squalene, hexadecane, or peanut oil and of the concentration of Tween 80 on the immunotherapeutic capability of emulsified Mycobacterium bovis Bacillus Calmette-Guérin (BCG) cell walls was studied in guinea pigs, each with an established dermal transplant of a syngeneic hepatocarcinoma and tumor cells in the draining lymph node. Immunotherapy consisted of an intratumoral injection of emulsified cell walls. Conditions were established under which therapeutically effective emulsions could be made with mineral oil, squalane, squalene, or hexadecane. Emulsions made with peanut oil failed to cause tumor regression. Emulsions of squalene or hexadecane were effective substitutes for mineral oil as carriers of cell walls in the absence of added Tween or at a Tween concentration one-hundredth of that used to stabilize the mineral oil-containing emulsions. Cell wall emulsions made with squalane were therapeutically effective over the same range of Tween concentrations used to prepare emulsions containing mineral oil. Cell wall emulsions made without added Tween demonstrated effective antitumor activity even after autoclaving. Emulsions made with Tween separated after autoclaving. Emulsions of whole killed BCG were immunotherapeutically as active as those made with cell walls.