Effect of Bacillus firmus on antibody formation after mucosal and parenteral immunization in mice

Immunostimulatory properties of B. firmus, a nontoxic, nonpathogenic G+ bac terium of external environment, were described previously. Antiinfectious a nd antitumor activity, macrophage activation and strong polyclonal stimulat ion of B lymphocytes were proved in human, mice and rats. The adjuvant effe ct of B. firmus On specific antibody response to ovalbumin in BALB/c mice i s the topic of the present study. Against our expectation, B. firmus exerts more suppressive than stimulatory effect on specific antibody response. Fo rmolized B. firmus decreased anti-ovalbumin response after subcutaneous imm unization and only slightly increased serum antibodies after intraperitonea l immunization. After mucosal immunization, both oral and rectal, ovalbumin itself did not cause a significant systemic response but induced IgA anti- ovalbumin response in the intestine. B. firmus applied together with ovalbu min increased systemic serum response but absolutely eliminated intestinal response. The rectal route of antigen administration has been found less co nvenient because of less precise dosing of antigen in this mode of immuniza tion. (C) 1998 Elsevier Science B.V. All rights reserved.