Mycobacterium vaccae in immunoprophylaxis and immunotherapy of leprosy and tuberculosis.

Both leprosy and tuberculosis present continuing problems in their control, especially in the developing world, despite the availability of drugs effective in producing a bacteriological cure. Improved immunoprophylaxis, and an effective immunotherapy to be used with chemotherapy are urgently required. Intradermal injection of a suspension of killed Mycobacterium vaccae promotes cell-mediated responses to antigens common to all mycobacteria, and switches off the tissue-necrotizing aspects of the Koch phenomenon. These properties led to the use of the suspensions as an improved vaccine, either alone or in combination with BCG. The same properties led to the employment of the suspension in immunotherapy as an adjunct to chemotherapy in the treatment of both leprosy and tuberculosis. The evidence leading to these conclusions is reviewed and discussed.