title: Toll-like receptor 9-dependent macrophage activation by Entamoeba histolytica DNA.
abstract: Activation of the innate immune system by bacterial DNA and DNA of other invertebrates represents a pathogen recognition mechanism. In this study we investigated macrophage responses to DNA from the intestinal protozoan parasite Entamoeba histolytica. E. histolytica genomic DNA was purified from log-phase trophozoites and tested with the mouse macrophage cell line RAW 264.7. RAW cells treated with E. histolytica DNA demonstrated an increase in levels of tumor necrosis factor alpha (TNF-alpha) mRNA and protein production. TNF-alpha production was blocked by pretreatment with chloroquine or monensin. In fact, an NF-kappaB luciferase reporter assay in HEK cells transfected with human TLR9 demonstrated that E. histolytica DNA signaled through Toll-like receptor 9 (TLR9) in a manner similar to that seen with CpG-ODN. Immunofluorescence assays confirmed NF-kappaB activation in RAW cells, as seen by nuclear translocation of the p65 subunit. Western blot analysis demonstrated mitogen-activated protein kinase activation by E. histolytica DNA. E. histolytica DNA effects were abolished in MYD88-/- mouse-derived macrophages. In the context of disease, immunization with E. histolytica DNA protected gerbils from an E. histolytica challenge infection. Taken together, these results demonstrate that E. histolytica DNA is recognized by TLR9 to activate macrophages and may provide an innate defense mechanism characterized by the induction of the inflammatory mediator TNF-alpha.
authors.affiliation: Faculty of Medicine, Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Centre, 3330 Hospital Dr. NW, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Catherine P A
authors.initials: CP
authors.lastname: Ivory
authors.forename: Michael
authors.initials: M
authors.lastname: Prystajecky
authors.forename: Christian
authors.initials: C
authors.lastname: Jobin
authors.forename: Kris
authors.initials: K
authors.lastname: Chadee
mesh_terms: D000562:Amebiasis / Q000276:immunology; D000818:Animals; D002478:Cells, Cultured; D016054:DNA, Protozoan / Q000494:pharmacology*; D004748:Entamoeba histolytica / Q000235:genetics*; D017353:Gene Deletion; D015870:Gene Expression; D005786:Gene Expression Regulation; D005849:Gerbillinae; D006801:Humans; D007113:Immunity, Innate; D007371:Interferon-gamma / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D016054:DNA, Protozoan; D008070:Lipopolysaccharides; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D012333:RNA, Messenger; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D020928:Mitogen-Activated Protein Kinases