Effect of BCG vaccination on Mycobacterium lepraemurium infection in a highly susceptible inbred mouse strain.

Upon infection with Mycobacterium lepraemurium (MLM) C3H mice develop a disease that has features in common with lepromatous leprosy in man. Intraperitoneal vaccination with a single dose of BCG four weeks before inoculation with MLM in the footpad significantly reduced the total bacillary load of the animals. In vaccinated animals there was a delay in the dissemination of bacilli to the popliteal lymph node, liver, and spleen. The growth rate of MLM in the footpad and the popliteal lymph node was not altered by BCG vaccination. Reduced dissemination of the bacilli seems to be a sensitive parameter of resistance in murine leprosy. The mechanism of the resistance observed is discussed mainly in relation to non-specific macrophage activation and T-cell mediated responses to cross-reactive antigens.