Induction of delayed-type hypersensitivity to Mycobacterium leprae in healthy individuals.

Delayed-type hypersensitivity (DTH) to a soluble Mycobacterium leprae skin test antigen (SML) was successfully induced in healthy volunteers following immunization with 2 X 10(8) killed armadillo-derived M. leprae. No better sensitization was obtained by a mixture of live BCG and killed M. leprae. The relative specificity of the DTH reaction to SML has been demonstrated in this study, since little cross-reactivity was observed to PPD, after immunization with BCG ro M, leprae alone, or combined. Moreover, armadillo-derived M. leprae readily induced a specific hypersensitivity with the time course DTH response associated with protective immunity suggesting that this bacterial preparation may be a candidate for an effective anti-leprosy vaccine.