Potentiation of L1210 murine leukemia vaccine in vivo by levamisole.

Intraperitoneal inoculation of either levamisole or 2 x 10(6) cells of concanavalin-A (Con-A)-bound L1210 leukemia vaccine produced no cured mice after subsequent ip inoculation of 10(3) live L1210 cells. Combined inocluation of levamisole and Con-A-bound vaccine produced about 20% cure incidence but no prolongation of life span of tumor-bearing mice after inoculation of live L1210 cells. Combined inoculation of levamisole and Con A-free vaccine did not induce detectable immune resistance in mice. These results suggest that levamisole enhanced host response to cell-bound Con-A associated with immunogenic potency of the vaccine. Levamisole given intravenously and orally was as effective as that inoculated intraperitoneally in enhancing the induction of resistance in mice by Con-A-bound vaccine. Dose of levamisole was very critical for this enhancement, being effective at 0.38 mg/kg but not either at 0.75 or 0.19 mg/kg. Furthermore, levamisole restored immune resistance induced by a larger inoculum of Con-A-bound vaccine cells (10(7)) and impaired by cyclophosphamide.