Antitumor and Immunological Adjuvant Effect of Bifidobacterium infantis in Mice

Intraregional repeated injections of living or killed Bifidobacterium infantis inhibited the growth of established Meth-A tumor cells transplanted subcutaneousl y into syngeneic BALB/c mice (regression) . When tumor cells mixed with B infantis were inoculated subcutaneously into mice, tumors did not develop in the majority of the recipient mice (suppression) . Water-insoluble cell walls which were obtained b y sonication f k ll ed B. infantis induced suppression of tumor development but failed to induce regression of tumor growth when these preparations were injected intra regionally after tumor implantation . In contrast, although the water-soluble supernatant fractions of sonicated killed B. infantis did not exhibit tumor suppression , ef-f ective regression of established tumors followed intraregional injection of these frac tions. The immunological adjuvant effects of B. infantis or its components were also studied. These bacterial preparations potentiated both tumor tra nsplantation i mmunity and the delayed-type hypersensitivity response against sheep erythrocytes in mice.