title: Leishmania pifanoi proteoglycolipid complex P8 induces macrophage cytokine production through Toll-like receptor 4.
abstract: The P8 proteoglycolipid complex (P8 PGLC) is a glyconjugate expressed by Leishmania mexicana complex parasites. We previously have shown that vaccination with P8 PGLC provides protection against cutaneous leishmaniasis in susceptible BALB/c mice. However, the biological importance of this complex remains unknown. Here we show that P8 PGLC localizes to the surface of Leishmania pifanoi amastigotes and that upon exposure to macrophages, P8 PGLC binds and induces inflammatory cytokine and chemokine mRNAs such as tumor necrosis factor alpha and RANTES early after stimulation. Our studies indicate that cytokine and chemokine induction is dependent upon Toll-like receptor 4 (TLR4). Interestingly, key inflammatory cytokines and chemokines (such as interleukin-6 [IL-6], macrophage inflammatory protein 1beta, and beta interferon [IFN-beta]) that can be induced through TLR4 activation were not induced or only slightly upregulated by P8 PGLC. Activation by P8 PGLC does not occur in the presence of TLR4 alone and requires both CD14 and myeloid differentiation protein 2 for signaling; this requirement may be responsible for the limited TLR4 response. This is the first characterization of a TLR4 ligand for Leishmania. In vitro experiments indicate that L. pifanoi amastigotes induce lower levels of cytokines in macrophages in the absence of TLR4; however, notably higher IL-10/IFN-gamma ratios were found for TLR4-deficient mice than for BALB/c mice. Further, increased levels of parasites persist in BALB/c mice deficient in TLR4. Taken together, these results suggest that TLR4 recognition of Leishmania pifanoi amastigotes is important for the control of infection and that this is mediated, in part, through the P8 PGLC.
authors.affiliation: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Shanta M
authors.initials: SM
authors.lastname: Whitaker
authors.forename: Maria
authors.initials: M
authors.lastname: Colmenares
authors.forename: Karen Goldsmith
authors.initials: KG
authors.lastname: Pestana
authors.forename: Diane
authors.initials: D
authors.lastname: McMahon-Pratt
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology; D000818:Animals; D002452:Cell Count; D002460:Cell Line; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007891:Leishmania / Q000737:chemistry / Q000276:immunology*; D007896:Leishmaniasis / Q000276:immunology / Q000469:parasitology; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D051218:Lymphocyte Antigen 96; D017737:Macrophages, Peritoneal / Q000276:immunology* / Q000469:parasitology*; D008565:Membrane Proteins / Q000032:analysis / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011510:Proteolipids / Q000032:analysis / Q000276:immunology* / Q000302:isolation & purification; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016207:Cytokines; D018950:Lipopolysaccharide Receptors; C411728:Ly96 protein, mouse; D051218:Lymphocyte Antigen 96; D008565:Membrane Proteins; D011510:Proteolipids; D051197:Toll-Like Receptor 4; C024374:proteoglycolipids