title: Virulence of Toxoplasma gondii is associated with distinct dendritic cell responses and reduced numbers of activated CD8+ T cells.
abstract: The Toxoplasma gondii population consists of multiple strains, defined by genotype and virulence. Previous studies have established that protective immunity to this organism is mediated by IL-12, which drives T cells to produce IFN-gamma. Paradoxically, although type I and type II strains of T. gondii both induce IL-12 and IFN-gamma in the mouse, type I parasites are lethal, whereas type II strains establish chronic infection. The cellular basis for these strain-dependent differences remains unclear. To better understand these events, the CD8(+) T cell and dendritic cell (DC) responses to transgenic, OVA-expressing type I RH (RH OVA) and type II Prugniuad (Pru OVA) parasites were examined. Pru OVA-infected mice developed a robust DC response at the site of infection and the draining lymph node and generated a population of endogenous OVA-specific CD8(+) T cells. In contrast, RH OVA-infected mice had fewer DCs and OVA-specific CD8(+) T cells. RH OVA-infected mice given preactivated OVA-specific CD8(+) T cells were protected, suggesting that reduced DC-derived signals contributed to the low OVA-specific CD8(+) T cell numbers observed during type I infection. Indeed, DC depletion prior to Pru OVA infection resulted in a failure to generate activated OVA-specific CD8(+) T cells, and IL-12p70 treatment during RH OVA infection modestly increased the number of Ag-specific cells. Together, these data are consistent with a model of immunity to T. gondii in which strain-dependent DC responses shape the generation of Ag-specific CD8(+) T cells and determine the outcome of infection.
authors.affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Room H310F Hill Pavilion, 380 South University Avenue, Philadelphia, PA 19104, USA.
authors.forename: Elia D
authors.initials: ED
authors.lastname: Tait
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Jordan
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Dupont
authors.forename: Tajie H
authors.initials: TH
authors.lastname: Harris
authors.forename: Beth
authors.initials: B
authors.lastname: Gregg
authors.forename: Emma H
authors.initials: EH
authors.lastname: Wilson
authors.forename: Marion
authors.initials: M
authors.lastname: Pepper
authors.forename: Florence
authors.initials: F
authors.lastname: Dzierszinski
authors.forename: David S
authors.initials: DS
authors.lastname: Roos
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Hunter
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000469:parasitology / Q000473:pathology; D049109:Cell Proliferation; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology* / Q000469:parasitology* / Q000473:pathology; D018984:Epitopes, T-Lymphocyte / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D005260:Female; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology*; D018655:Lymphocyte Count; D008231:Lymphopenia / Q000235:genetics / Q000276:immunology / Q000469:parasitology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000008:administration & dosage / Q000096:biosynthesis / Q000235:genetics; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D014124:Toxoplasmosis, Animal / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D014774:Virulence / Q000276:immunology
chemical_list: D018984:Epitopes, T-Lymphocyte; D010047:Ovalbumin