Immunotherapy of experimental cancer by intralesional injection of emulsified nonliving mycobacteria: comparison of Mycobacterium bovis (BCG), Mycobacterium phlei, and Mycobacterium smegmatis

Mycobacterium bovis (BCG), Mycobacterium phlei, and Mycobacterium smegmatis were each tested in emulsified form for their potency to cause regression of transplants of a syngeneic murine fibrosarcoma and of a syngeneic guinea pig hepatoma. On a weight basis, M. phlei and M. smegmatis were as effective as BCG in causing tumor regression. M. phlei and M. smegmatis were comparable to BCG in provoking delayed cutaneous hypersensitivity reactions in guinea pigs sensitized to M. phlei or M. smegmatis. In BCG-sensitized guinea pigs, M. phlei and M. smegmatis provoked weaker delayed cutaneous hypersensitivity reactions than did BCG. Purified protein derivative of M. tuberculosis was more active in eliciting delayed cutaneous hypersensitivity in BCG-sensitized guinea pigs than in animals sensitized with M. phlei or M. smegmatis.