SYNERGIC INHIBITORY ACTIVITY OF AMPHOTERICIN-B AND GAMMA-INTERFERON AGAINST INTRACELLULAR CRYPTOCOCCUS-NEOFORMANS IN MURINE MACROPHAGES

Cryptococcus neoformans is responsible for pulmonary and meningal infe ctions in HIV patients. The lack of effective cellular cooperation cau sed by the low level of CD4(+) cells, and the resistance of C. neoform ans to phagocytosis allows growth and persistence of the yeast in the host. We describe here an in-vitro model of intracellular replication of C. neoformans inside J774-A.1 macrophages, and the determination of the intracellular antifungal activity of amphotericin B and fluconazo le alone or in association with IFN-gamma. The maximum inhibitory effe ct was observed with one MIC of amphotericin B and 100 or 1000 IU/mL o f IFN-gamma. amphotericin B alone (at 1 x MIC), or either 1 x or 50 x MIC of fluconazole in normal or IFN-gamma activated macrophages, did n ot eradicate the ingested yeast. A potential underlying mechanism of t he synergy of amphotericin B in IFN-gamma primed macrophages was inves tigated by measurement of nitrite level and by use of the NO synthase competitive inhibitor, N-G-monomethyl L-arginine (NMMA). One MIC of am photericin B was able to activate the synthesis of nitrogen reactive i ntermediates in IFN gamma-primed macrophages. NMMA treated infected ma crophages responded less well to IFN-gamma priming, resulting in a mod erate inhibition in subsequent amphotericin B exposure.