Effect of 3M-003, an imidazoquinoline, on phagocyte candidacidal activity directly and via induction of peripheral blood mononuclear cell cytokines.

3M-003, like related imidazoquinoline immunomodulators, interacts with Toll-like receptor-7 (TLR-7) and TLR-8. TLRs are important in the defense against fungal pathogens. The effect of 3M-003 on killing of Candida was evaluated on mouse (BALB/c) effector cell lineages: monocytes, neutrophils, and macrophages. After direct application, 3M-003 (1-80 microg mL(-1)) enhanced (P<0.05-0.01) macrophage killing, comparable to killing by interferon-gamma-activated macrophages. 3M-003 did not directly enhance the candidacidal activity of monocytes or neutrophils. To test an effect mediated by leukocytes, BALB/c peripheral blood mononuclear cells (PBMC) were stimulated in vitro with 3M-003 to generate cytokine-containing supernatants. 3M-003 at 1 or 3 microM was optimal for the stimulation of PBMC to produce tumor necrosis factor-alpha and interleukin-12p40 in 24 h. For indirect tests, monolayers were treated with supernatants for 18 h, the supernatants were removed, and effector cells were tested; the supernatants enhanced (P<0.05-0.01) killing, in 2-4-h assays, by neutrophils from 42% to 73%, macrophages from 0% to 23%, and monocytes from 0% to 20%. 3M-003, presumably through TLRs, acts directly on macrophages to enhance fungal killing and stimulates PBMC to produce soluble factors that enhance killing by neutrophils, macrophages, and monocytes. 3M-003 could be a candidate for antifungal immunotherapy.