DEVELOPMENT OF AN IN-VITRO MACROPHAGE SYSTEM TO ASSESS PENICILLIUM-MARNEFFEI GROWTH AND SUSCEPTIBILITY TO NITRIC-OXIDE

We investigated the effect of nitric oxide (NO) and reactive nitrogen intermediates on the in vitro growth of Penicillium marnffei both in a cell-free system and in a novel macrophage culture system. In the cel l-free system, NO that was chemically generated from NaNO2 in acid med ia (pH 4 and 5) markedly inhibited the growth of P. marneffei, On the contrary, inhibition of growth did not occur in neutral medium (pH 7.4 ) in which NO was not produced, P, marneffei conidia were phagocytized by nonstimulated murine J774 macrophages after 2 h of incubation, Dur ing the following 24 h, P, marneffei grew as yeast-like cells replicat ing by fission in the J774 macrophages, The intracellular growth of P. marneffei damaged nonstimulated J774 macrophages, as confirmed by ele ctron microscopy. When 5774 cells were stimulated by gamma interferon and lipopolysaccharide, which led to enhanced production of reactive n itrogen intermediates, the percentage of yeast-like cells was signific antly reduced and P. marneffei conidia were damaged in the J774 macrop hages. The inhibition of NO synthesis by N-monomethyl-L-arginine resto red the intracellular growth of P, marneffei. The inverse correlation between intramacrophage growth and the amount of nitrite detected in c ulture supernatants supports the hypothesis that the L-arginine-depend ent NO pathway plays an important role in the murine macrophage immune response against P. marneffei.