Abstract
Infection of macrophages with the protozoan parasite Toxoplasma gondii results in inhibition of a large panel of LPS-responsive cytokines, including TNF-alpha, while leaving others such as IL-10 intact. Recent studies provide evidence that the parasite interferes with chromatin remodeling at the TNF-alpha promoter that is normally associated with LPS stimulation, but that is not required for TLR4 induction of IL-10. Here, we examined the effect of Toxoplasma on IL-10 induced by simultaneous signaling through TLR4 and FcgammaR, a combined stimulus that triggers histone H3 covalent modification at the IL-10 promoter resulting in high level IL-10 cytokine production. We show that the parasite inhibits high level IL-10 production and prevents histone H3 Ser(10) phosphorylation and Lys(9/14) acetylation at the IL-10 promoter. These results provide compelling evidence that T. gondii targets the host cell chromatin remodeling machinery to down-regulate cytokine responses in infected macrophages.