BCG-INDUCED MUCOSAL IMMUNE-RESPONSES

The induction of mucosal immune responses is particularly important fo r protection against diseases for which entry and pathogenesis are cle arly related to the mucosal system, such as salmonellosis, AIDS or tub erculosis. We investigated the immune responses in guinea-pigs vaccina ted by BCG via the respiratory compared to the intradermal route. The results demonstrate that the aerogenic BCG induced a better activation of broncho-alveolar macrophages and a substantially improved protecti ve effect against a virulent challenge with Mycobacterium tuberculosis . We also used a DNA recombinant BCG expressing LacZ gene to investiga te the influence of various routes of administration on the immunogeni city of the beta-galactosidase, a foreign antigen expressed by the Lac Z-BCG recombinant. Thus, lymph-node proliferative responses, delayed t ype hypersensitivity and antibody responses specific for beta-galactos idase can be produced in guinea-pigs immunized orally, respiratorily a nd intradermally. The respiratory and especially the oral route of adm inistration produced higher mucosal and systemic immune responses comp ared with the intradermal route of immunization. Moreover, the oral im munization of mice with recombinant BCG induced IgA responses which ca n be detected both in sera and in intestinal secretions. In conclusion , BCG recombinants may be of potential use as an adjuvant vaccine.