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.

NK1.1+ cells mediate the antitumor effects of a dual Toll-like receptor 7/8 agonist in the disseminated B16-F10 melanoma model.

Innate immune stimulation with Toll-like receptor (TLR) agonists is a proposed modality for immunotherapy of melanoma. Here, a TLR7/8 agonist, 3M-011, was used effectively as a single systemic agent against disseminated mouse B16-F10 melanoma. The investigation of the mechanism of antitumor action revealed that the agonist had no direct cytotoxic effects on tumor cells tested in vitro. In addition, 3M-011 retained its effectiveness in scid/B6 mice and scid/NOD mice, eliminating the requirement for T and B cells, but lost its activity in beige (bg/bg) and NK1.1-immunodepleted mice, suggesting a critical role for natural killer (NK) cells in the antitumor response. NK cytotoxicity was enhanced in vivo by the TLR7/8 agonist; this activation was long lasting, as determined by sustained expression of the activation marker CD69. Also, in human in vitro studies, 3M-011 potentiated NK cytotoxicity. TLR7/8-mediated NK-dependent antitumor activity was retained in IFN-alpha/beta receptor-deficient as well as perforin-deficient mice, while depletion of IFN-gamma significantly decreased the ability of 3M-011 to delay tumor growth. Thus, IFN-gamma-dependent functions of NK cell populations appear essential for cancer immunotherapy with TLR7/8 agonists.