ABSTRACT
Studies were caried out to determine the effect of intra-dermal injections of recombinant human interferon-gamma (rIFNy) on the viability of Mycobacterium leprae. Twenty-three untreated and 4 treated multibacillary patients, 12 with lepromatous leprosy (LL) and 15 with bordeline lepromatous leprosy (BL), were selected for intradermal administration of rIFNy or PPD. Treated patients (LL and BL) had received multi-drug therapy according to the recommendations of the World Health Organization, i. e., rifampicxin (600 mg/month), dapsone (100 mg/day) and clofazimine (50 mg/day and 300 mg/month) for 1-4 months. Three daily doses of 10 or 30 ug rIFNy induced local induration and mononuclear leucocyte accumulation. Bacteria isolated from a punch biopsy of the site 21 days after lymphokine administration were injected into mouse foot pads and evaluated for viability and growth. The local response to rIFN (specific activity 2 x 10 7 units/mg protein) induced a delay or total inhibition of M. leprae growth in the mouse foot pad, ,indicating that the cellular response to the antigen reduced local M. leprae viability. The extent of reduction in viability depended on the dose of rIFNy injected and the extent of local induration induced by the lymphokine. With a vigorous cell-mediated immune response growth was fully inhibited. A similar but less extensive effect on M. leprae viability was observed in resapo0nse to the local injection of 5 units in 0.1 ml of purified protein derivative of tuberculin (PPD)