Lepromin conversion in repeatedly lepromin negative BL/LL patients after immunization with autoclaved Mycobacterium w

Thirty-two clinically, histopathologically confirmed cases of BL/LL leprosy were rendered bacteriologically negative by prolonged chemotherapy. All of them were negative to Mitsuda and Dharmendra lepromin at the start of study. They were immunized with a single intradermal injection of 5 X 10(7) autoclaved Mycobacterium w and were retested for lepromin reaction 4-6 weeks later. Twenty subjects gave at this time a positive reaction with both Dharmendra and Mitsuda lepromins. The histology of biopsies from converted cases showed mononuclear infiltration in all and granuloma formation in 12 of the 20 positive cases. The stability of the conversion of the patients' lepromin positivity was investigated 6-11 months after immunization with Mycobacterium w. Patients who were earlier converted to a positivity status remained positive in the skin test response to M. leprae. The leukocytes of these patients produced lymphokines on culture with lepromin, causing leukocyte migration inhibition. Patients who did not convert earlier continued to remain anergic to lepromin. These results suggest a conversion, stable for several months, to lepromin positivity caused by immunization with Mycobacterium w in about 60% of BL/LL leprosy patients.