CROSS-REACTIVE IMMUNE-RESPONSES AGAINST MYCOBACTERIUM-BOVIS BCG IN MICE INFECTED WITH NONTUBERCULOUS MYCOBACTERIA BELONGING TO THE MAIS-GROUP

Two bacillus Calmette-Guerin (BCG)-susceptible mouse strains, BALB/c a nd C57BL/6, were infected intravenously with Mycobacterium intracellul are, M. avium or M. scrofulaceum and monitored during 3 months for myc obacterial replication and antibody and Th1-type cytokine production i n response to cytoplasmic and secreted antigens from M. bovis BCG. Whe reas initial colony-forming unit (CFU) counts of M. intracellulare and M. avium were higher in lungs than in spleen, the opposite was observ ed for M. scrofulaceum. Mycobacterium intracellulare was the most viru lent species and its replication could not be controlled in either mou se strain. It also induced the strongest antibody response. Mycobacter ium avium was eliminated in both mouse strains and M. scofulaceum fina lly was eliminated in C57BL/6 but multiplied in spleen from BALB/c mic e. Significant sustained interleukin-2 and interferon-gamma production towards BCG antigens was only found in M. scrofulaceum infection. As in BCG-vaccination, M. scrofulaceum-infected C57BL/6 mice demonstrated a higher response towards whole BCG culture filtrate, BCG extract and purified antigen 85 complex (Ag85) from BCG than did BALB/c mice. The data suggest that the presence of M. scrifulaceum in the environment may possibly interfere in genetically predisposed subjects with BCG va ccine and its protective efficacy against M. tuberculosis.