ORAL IMMUNIZATION WITH RECOMBINANT BCG INDUCES CELLULAR AND HUMORAL IMMUNE-RESPONSES AGAINST THE FOREIGN ANTIGEN

It has been shown recently that BCG can be used as a live recombinant vaccine to stimulate immune responses. Proliferative or cytotoxic T-ce ll responses against several viral proteins such as HIV Gag, Env or Ne f were obtained after parenteral immunization with BCG expressing thes e proteins. Antibody responses were also obtained after immunization o f mice with recombinant BCG strain which expressed lac Z under the con trol of a promoter sequence isolated from Mycobacterium paratuberculos is. We have used this recombinant vaccine in guinea-pigs to investigat e the influence of various routes of immunization on the immunogenicit y of a foreign antigen expressed by recombinant BCG. Guinea-pigs were immunized by oral, respiratory or intradermal routes and proliferative responses, delayed-type hypersensitivity and antibody responses speci fic for beta-galactosidase were followed for 16 weeks. Results demonst rated that humoral and cellular immune responses specific for beta-gal actosidase can be produced in all groups of guinea-pigs. However, the respiratory and especially the oral route of administration induced hi gher local and systemic immune responses than the intradermal route of immunization. Moreover, the oral immunization of mice with this recom binant BCG induced IgA responses which could be detected in both sera and intestinal secretions. Therefore, this study demonstrates for the first time that oral immunization with recombinant BCG can induce stro ng cellular and humoral immune responses.