RNA interference reveals a role for TLR2 and TLR3 in the recognition of Leishmania donovani promastigotes by interferon-gamma-primed macrophages.
Leishmania donovani promastigotes evade the induction of a proinflammatory response during their invasion of naive macrophages. However, their entry into IFN-gamma-primed macrophages is accompanied by the secretion of nitric oxide (NO) and proinflammatory cytokines. In the present study, we addressed the hypothesis that priming with IFN-gamma induces the expression of a receptor that enables mouse macrophages to recognize L. donovani promastigotes. We observed that in IFN-gamma-primed macrophages, L. donovani promastigotes stimulated Interleukin-1 receptor-associated kinase-1 (IRAK-1) activity. We next showed that Toll-like receptor (TLR)3 is barely detectable in naive macrophages but is expressed in IFN-gamma-treated macrophages. Silencing of TLR3, TLR2, IRAK-1 and myeloid differentiation factor 88 (MyD88) expression by RNA interference revealed that both TLR are involved in the secretion of NO and TNF-alpha induced by L. donovani promastigotes. Using L. donovani mutants, we showed that TLR2-mediated responses are dependent on Galbeta1,4Manalpha-PO(4)-containing phosphoglycans, whereas TLR3-mediated responses are independent of these glycoconjugates. Furthermore, our data indicate a participation of TLR2 and TLR3 in the phagocytosis of L. donovani promastigotes and a role for TLR3 in the leishmanicidal activity of the IFN-gamma-primed macrophages. Collectively, our data are consistent with a model where recognition of L. donovani promastigotes depends on the macrophage activation status and requires the expression of TLR3.
Flandin
Jean-Frédéric
JF
INRS- Institut Armand-Frappier and Centre for host-parasite interactions, Laval QC, Canada H7V 1B7.
Chano
Frédéric
F
Descoteaux
Albert
A
D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology; D000818:Animals; D000970:Antineoplastic Agents / Q000276:immunology / Q000494:pharmacology*; D002460:Cell Line; D007249:Inflammation / Q000235:genetics / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology / Q000494:pharmacology*; D053592:Interleukin-1 Receptor-Associated Kinases; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000276:immunology; D007893:Leishmania donovani / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000235:genetics / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000469:parasitology; D051379:Mice; D053594:Myeloid Differentiation Factor 88; D009569:Nitric Oxide / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology; D034622:RNA Interference / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000276:immunology*; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000276:immunology*
D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D047908:Intracellular Signaling Peptides and Proteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D034741:RNA, Small Interfering; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D009569:Nitric Oxide; D007371:Interferon-gamma; D053592:Interleukin-1 Receptor-Associated Kinases; D017346:Protein Serine-Threonine Kinases