Immunogenicity of various mycobacteria and the corresponding levels of cross-protection developed between species.

Seven mycobacterial species were tested for their ability to immunize mice against subsequent tuberculous challenge. The phylogenetic relationships between the vaccine and challenge strains had little direct influence on the level of resistance; a better correlation was found between the ability of the vaccine to survive or multiply in vivo and the immunogenicity of the organism. Mycobacterium tuberculosis, M. bovis (except for an SM(R) variant), M. avium, two of three M. kansasii strains, and one strain of M. intracellulare all survived or multiplied in vivo. They induced an effective resistance against a subsequent M. tuberculosis (Erdman) or BCG challenge. The SM(R) BCG, the Bostrom strain of M. kansasii, M. scrofulaceum, three strains of M. intracellulare, and one of M. terrae and M. fortuitum were unable to survive in vivo and were nonallergenic and nonimmunogenic. No evidence was found for an interference phenomenon between the atypical mycobacteria and the BCG vaccine sufficient to explain the inadequate levels of immunization reported in some field trials.