Immunogenicity of recombinant BCG vaccine strains overexpressing components of the antigen 85 complex of Mycobacterium tuberculosis.

The components of antigen 85 complex of Mycobacterium tuberculosis (Ag 85A, Ag 85B and Ag 85C), due to their immunodominant and secretory nature, represent promising protective antigen candidates and have been used in numerous vaccine preparations. We have used recombinant Bacille Calmette Guerin (BCG) strains overexpressing Ag 85A and Ag 85C to immunize BALB/c mice to investigate the immunogenicity of these strains. Mice immunized with recombinant BCG strains exhibited an increased humoral immune response when compared to mice immunized with wild-type BCG. The recombinant BCG strain overexpressing Ag 85A also induced an increased Th1-like response, characterized by elevated levels of IFN-gamma in antigen stimulated splenocyte cultures and a strong IgG2a antibody response, when compared to wild-type BCG. Immunization with recombinant BCG strain overexpressing Ag 85C, on the other hand did not elicit increased IFN-gamma secretion on restimulation of splenocytes in vitro.