Effect of simultaneous administration of interferon-gamma and chemotherapy against Mycobacterium leprae in experimental infection in nude mice.

The possibility of synergy between immunotherapy with recombinant interferon-gamma (IFN-gamma) and chemotherapy with rifampin (RMP) and dapsone (DDS) against Mycobacterium leprae was examined in nude mice. IFN-gamma alone failed to show any effect on the growth of M. leprae in the nude mouse foot pad. No synergy was demonstrable between DDS, either at 0.0001% or at 0.001%, and IFN-gamma. A subinhibitory level of RMP with IFN-gamma was also ineffective, but RMP at 0.006% with IFN-gamma produced a statistically significant enhancement of killing (26-fold) when compared with RMP at 0.006% only. It should be emphasized, however, that results obtained in the immunodeficient nude mouse model may not be comparable to those which might have been given by lepromatous leprosy patients.