Tobin Magle Crystal, Pittman Kelly J, Moser Lindsey A, Boldon Kyle M, Knoll Laura J
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Infect Immun. 2014 Feb;82(2):618-25. doi: 10.1128/IAI.00444-13. Epub 2013 Nov 25.
Toxoplasma gondii is an obligate intracellular parasite that forms a lifelong infection within the central nervous system of its host. The T. gondii genome encodes six members of the patatin-like phospholipase family; related proteins are associated with host-microbe interactions in bacteria. T. gondii patatin-like protein 1 (TgPL1) was previously determined to be necessary for parasites to suppress nitric oxide and prevent degradation in activated macrophages. Here, we show that in the rapidly replicating tachyzoite stage, TgPL1 is localized within vesicles inside the parasite that are distinct from the dense granules; however, in the encysted bradyzoite stage, TgPL1 localizes to the parasitophorous vacuole (PV) and cyst wall. While we had not previously seen a defect of the TgPL1 deletion mutant (ΔTgPL1) during acute and early chronic infection, the localization change of TgPL1 in bradyzoites caused us to reevaluate the ΔTgPL1 mutant during late chronic infection and in a toxoplasmic encephalitis (TE) mouse model. Mice infected with ΔTgPL1 are more resistant to TE and have fewer inflammatory lesions than mice infected with the wild type and ΔTgPL1 genetically complemented with TgPL1. This increased resistance to TE could result from several contributing factors. First, we found that ΔTgPL1 bradyzoites did not convert back to tachyzoites readily in tissue culture. Second, a subset of cytokine levels were higher in ΔTgPL1-infected mice, including gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and monocyte chemotactic protein 1 (MCP-1). These studies suggest that TgPL1 plays a role in the maintenance of chronic T. gondii infection.
刚地弓形虫是一种专性细胞内寄生虫，可在其宿主的中枢神经系统内形成终身感染。刚地弓形虫基因组编码六个类马铃薯Patatin磷脂酶家族成员；相关蛋白在细菌中与宿主-微生物相互作用有关。先前已确定刚地弓形虫类马铃薯Patatin样蛋白1（TgPL1）是寄生虫抑制一氧化氮并防止其在活化巨噬细胞中降解所必需的。在此，我们表明，在快速复制的速殖子阶段，TgPL1定位于寄生虫内部与致密颗粒不同的囊泡中；然而，在包囊缓殖子阶段，TgPL1定位于寄生泡（PV）和囊壁。虽然我们之前在急性和早期慢性感染期间未发现TgPL1缺失突变体（ΔTgPL1）有缺陷，但TgPL1在缓殖子中的定位变化促使我们在慢性感染后期和弓形虫性脑炎（TE）小鼠模型中重新评估ΔTgPL1突变体。与感染野生型和用TgPL1进行基因互补的ΔTgPL1的小鼠相比，感染ΔTgPL1的小鼠对TE更具抵抗力，炎症病变也更少。对TE抵抗力的增强可能由几个因素共同导致。首先，我们发现ΔTgPL1缓殖子在组织培养中不易转化回速殖子。其次，在感染ΔTgPL1的小鼠中，一部分细胞因子水平较高，包括γ干扰素（IFN-γ）、肿瘤坏死因子α（TNF-α）、白细胞介素6（IL-6）和单核细胞趋化蛋白1（MCP-1）。这些研究表明TgPL1在维持刚地弓形虫慢性感染中起作用。
