Friday, July 02, 2010

Virulence of Toxoplasma gondii Is Associated with Distinct Dendritic Cell Responses and Reduced Numbers of Activated CD8+ T Cells

J Immunol. 2010 Jun 30. [Epub ahead of print]

Virulence of Toxoplasma gondii Is Associated with Distinct Dendritic Cell Responses and Reduced Numbers of Activated CD8+ T Cells

Tait ED, Jordan KA, Dupont CD, Harris TH, Gregg B, Wilson EH, Pepper M, Dzierszinski F, Roos DS, Hunter CA.

Department of Pathobiology and.

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.

PMID: 20592284 [PubMed - as supplied by publisher]