TgCyp18 stimulated IL-12 production in macrophages [13] and DCs [12]. Therefore, macrophages and DCs both play click here a role in IL-12 production in the present study. Further investigations are required to distinguish the relative contributions made by these cells. These results suggest that CCR5-independent accumulation of inflammatory cells at the site of infection might produce higher levels of pro-inflammatory cytokines in CCR5−/−

mice. The ability of T. gondii to attract, invade, and survive inside immune cells (T cells, DCs and macrophages), along with the migratory properties of DCs and macrophages that allow parasite dissemination around the host see more have been reported previously [7, 24]*[26]. Our results revealed that while T. gondii could infect CD3+, CD11c+, and CD11b+ cells, it exhibited a preference for CD11b+. We observed enhanced recruitment of CD11b+ cells after infection with RH-OE. This chemotactic effect of TgCyp18 was correlated with the ability of RH-OE to increase CCR5 expression levels. Thus, overproduction of TgCyp18 during RH-OE infection enhanced cellular recruitment. Recruitment of CD11b+ cells in CCR5−/− mice infected with RH-OE was also higher than that in RH-GFP-infected mice.

Additionally, there was no significant difference in the recruitment of CD11b+ cells between WT and CCR5−/− mice that were infected peritoneally with RH-GFP tachyzoites. Recently, our group demonstrated that recombinant TgCyp18 controlled the in vitro migration during of macrophages and lymphocytes in CCR5-dependent and -independent ways [14]. Therefore, the results presented here suggest that the TgCyp18-induced cell migration occurred in a CCR5-independent way in our in vivo experimental

model. Migration of macrophages and lymphocytes to the site of infection would enhance T. gondii invasion into these cells, after which the parasite-infected cells, such as CD11b+ leukocytes, are transported to other organs [7]. Our quantitative PCR analyses revealed that infection with RH-OE resulted in an increased parasitic load in the liver compared with RH-GFP infection. These results suggest that cells recruited by TgCyp18 are used to shuttle the parasite to other organs. In general, chemokines and their receptors play an important role in the migration of immune cells. A previous study showed that an early burst of CCR5 ligand production occurred in the tissue of WT and CCR5−/− mice by day 5 after oral infection with T. gondii strain 76 k cysts [27]. Our present study showed that recombinant TgCyp18 increased the expression levels of CCL5 in macrophages. In addition, significantly higher levels of CCL5 were detected in the peritoneal fluids of CCR5−/− mice infected RH-OE.