A Leishmania protein that modulates interleukin (IL)‐12, IL‐10 and tumor necrosis factor‐α production and expression of B7‐1 in human monocyte‐derived antigen‐presenting cells

Abstract

LeIF, a gene homologue of the eukaryotic initiation factor 4A was first described as a leishmanial antigen that induced a Th1-type T cell response in peripheral blood mononuclear cells (PBMC) from leishmaniasis patients. Moreover, the interferon (IFN)-gamma production by PBMC was found to be interleukin (IL)-12 dependent. Herein, we characterize the effects of LeIF on cytokine production and expression of surface molecules by normal human monocytes as well as by monocyte-derived macrophages and dendritic cells (MoDC). LeIF was a strong inducer of IL-12 and, to a lesser extent, of IL-10 and tumor necrosis factor (TNF)-alpha in macrophages and MoDC. IL-12 production did not require CD40 triggering, confirming that the ability of LeIF to induce IL-12 was not mediated through an effect on T cells. However, addition of soluble CD40 ligand (L) synergistically augmented IL-12 production in macrophages and MoDC. The cytokine-inducing activity of LeIF is located in the N-terminal portion of the molecule and was both proteinase K sensitive and polymyxin B resistant. LeIF, lipopolysaccharide and fixed Staphylococcus aureus all induced comparable amounts of IL-12, validating the potent cytokine-inducing effects of LeIF. Moreover, of these stimuli, LeIF had the highest IL-12/IL-10 and IL-12/TNF-alpha ratio demonstrating the preference of LeIF for IL-12 induction. Studies investigating the expression of surface molecules showed that LeIF up-regulated B7-1 and CD54 (ICAM-1) on macrophages and MoDC. To our knowledge this is the first report describing IL-12 production, up-regulation of co-stimulatory and intercellular adhesion molecules by monocytic antigen-presenting cells in response to a protein from a pathogenic microorganism. These immunomodulatory characteristics of LeIF might be excellent properties for a Th1-type adjuvant.

Dendritic Cell (DC)-Based Protection Against an Intracellular Pathogen Is Dependent Upon DC-Derived IL-12 and Can Be Induced by Molecularly Defined Antigens

“…LeIF has been revealed to be a unique candidate vaccine Ag because it bridges the innate immune system with adaptive responses. It is able to induce IFN-␥ production by NK cells (43) and stimulates macrophages and DC to produce IL-12 and IL-18, thus favoring the expansion of LeIFspecific Th1 cells (37,41). On the basis of these observations, LeIF has been proposed to serve as an adjuvant for the induction of Th1 responses.…”

“…DC have been shown to release IL-12 in response to activation by microbial Ag (7,18,19,41,42). Furthermore, our previous findings demonstrated that DC pulsing with L. major lysate induces IL-12 expression (20).…”

Immunization with a Recombinant Stage-Regulated Surface Protein fromLeishmania donovaniInduces Protection Against Visceral Leishmaniasis

“…However, rapid decay in IL-12 production, reaching baseline levels within 24 h of STAg administration, results from the induction of a state of DC paralysis, rather than death (38). Among leishmanial Ags, LeIF has been shown to be a potent inducer of IL-12 from monocyte-derived human DC (39) and from murine macrophages (40) in vitro. It remains to be determined whether LeIF directly stimulates murine DC, either in vitro or in vivo.…”

Structure-Activity Relationship of Synthetic Toll-like Receptor 4 Agonists

“…Monocyte-derived macrophages were generated from adherent peripheral blood mononuclear cells as described previously (18). On the 5th day of culture, the medium was replaced with fresh medium supplemented with the indicated AGP concentrations.…”