ABSTRACT
Glycosylphosphatidylinositol (GPI) anchors and glycoinositolphospholipids (GIPLs) from parasitic protozoa have been shown to exert a wide variety of effects on cells of the host innate immune system. However, the receptor(s) that are triggered by these protozoan glycolipids has not been identified. Here we present evidence that Trypanosoma cruzi-derived GPI anchors and GIPLs trigger CD25 expression on Chinese hamster ovary-K1 cells transfected with CD14 and Toll-like receptor-2 (TLR-2), but not wild-type (TLR-2-deficient) Chinese hamster ovary cells. The protozoan-derived GPI anchors and GIPLs containing alkylacylglycerol and saturated fatty acid chains or ceramide were found to be active in a concentration range of 100 nM to 1 microM. More importantly, the GPI anchors purified from T. cruzi trypomastigotes, which contain a longer glycan core and unsaturated fatty acids in the sn-2 position of the alkylacylglycerolipid component, triggered TLR-2 at subnanomolar concentrations. We performed experiments with macrophages from TLR-2 knockout and TLR-4 knockout mice, and found that TLR-2 expression appears to be essential for induction of IL-12, TNF-alpha, and NO by GPI anchors derived from T. cruzi trypomastigotes. Thus, highly purified GPI anchors from T. cruzi parasites are potent activators of TLR-2 from both mouse and human origin. The activation of TLR-2 may initiate host innate defense mechanisms and inflammatory response during protozoan infection, and may provide new strategies for immune intervention during protozoan infections.
Subject(s)
Drosophila Proteins , Glycosylphosphatidylinositols/physiology , Membrane Glycoproteins/metabolism , Receptors, Cell Surface/metabolism , Trypanosoma cruzi/immunology , Animals , CHO Cells , Cell Line , Cricetinae , Dose-Response Relationship, Immunologic , Glycolipids/physiology , Glycosylphosphatidylinositols/isolation & purification , Inflammation/immunology , Inflammation/parasitology , Macrophages/immunology , Macrophages/metabolism , Membrane Glycoproteins/deficiency , Membrane Glycoproteins/genetics , Membrane Glycoproteins/physiology , Mice , Mice, Knockout , NF-kappa B/physiology , Phospholipids/physiology , Receptors, Cell Surface/deficiency , Receptors, Cell Surface/genetics , Receptors, Cell Surface/physiology , Receptors, Interleukin-2/biosynthesis , Signal Transduction/genetics , Signal Transduction/immunology , Toll-Like Receptor 2 , Toll-Like Receptor 4 , Toll-Like Receptors , Transfection , Trypanosoma cruzi/chemistry , Trypanosoma cruzi/growth & developmentABSTRACT
We serologically tested 140 female prostitutes (mean age, 30 years) from the port city of Callao, Peru, for evidence of infection with human immunodeficiency virus (HIV), Chlamydia trachomatis, Treponema pallidum, herpes simplex viruses (HSV) I and II, and hepatitis B virus. The women had worked as prostitutes for an average of 5 years; one-fourth serviced foreign visitors exclusively, mainly sailors. Only 4 women used condoms, and only 1 woman gave a history of parenteral narcotic abuse, although 53% were regularly exposed to unsterile needles outside the medical setting for injections of vitamins, antibiotics, or steroids; another 29% are thought to probably use unsterile needles. None of the 140 prostitutes screened was seropositive for HIV, despite a very high prevalence of antibody to T. pallidum (24%), C. trachomatis (97%), HSV I and II (100%), and hepatitis B (51%); 5% were HbsAg positive. These data indicate that HIV has not yet been introduced into female prostitutes in the Peruvian port city. We believe that widespread use of unsterile needles in developing countries, such as Peru, represents a serious health threat and will amplify the spread of HIV, once introduced.