Immune response to BCG-Moreau (Rio de Janeiro) strain. Spectrum of delayed hypersensitivity in genetically defined mice

Generation of delayed hypersensitivity (DTH) in genetically defined mice immunized with Mycobacterium bovis BCG of the Moreau (Rio de Janeiro) strain was studied. This vaccine strain has been reported as the most virulent and able to induce strong tuberculin sensitivity. Mice were selected by the expression of Bcg gene trait, by responsiveness to mycobacterial antigens and H2 haplotype. DTH was evaluated by the ear-swelling test of mice immunized subcutaneously with live BCG at doses ranging from 1 microgram to 1000 micrograms. A survey of inbred strains of mice showed H2b and H2q mice as high responders, H2d as an intermediate responder, H2k as a low responder and H2a as a non-responder. Study of H2-congenic pairs of high and non-responder strains showed significant DTH in all mice independently of the genetic background and H2 haplotype. A mouse strain expressing Bcg (r) trait displayed DTH superior to a Bcg (s) strain. Comparison of DTH response of strains expressing Bcg (r) or (s) trait showed no relationship between the Bcg locus and DTH to mycobacteria. These data suggest DTH is under polygenic control including the major histocompatibility complex but excluding the Bcg locus.