IFN Immune Effector Mechanisms in Cerebral Toxoplasmosis

描述（由申请人提供）：刚地弓形虫是一种普遍存在的细胞内原生动物寄生虫，是免疫功能低下个体的主要机会性感染，是新生儿先天性弓形虫病的原因，最近被确定为潜在的生物恐怖主义制剂（清单B）。细胞因子在弓形虫在中枢神经系统的调控中起重要作用。干扰素- γ (IFN)是控制脑内弓形虫复制的主要细胞因子。研究者之前的研究确定IFNgamma显著抑制弓形虫在星形胶质细胞中的复制。研究发现，星形胶质细胞中ifnγ的作用机制独立于所有已知的抗弓形虫效应机制。然而，研究者最近确定IFNgamma介导的星形胶质细胞抑制在缺乏GTP结合蛋白IGTP （deltaIGTP）的星形胶质细胞中被逆转。IGTP的功能尚不清楚，但它被认为参与了囊泡运输途径的调节。星形胶质细胞中IFNgamma诱导基因表达的初步微阵列研究表明，IFNgamma处理的星形胶质细胞改变了宿主细胞胆固醇代谢。弓形虫最近被证明需要从宿主细胞摄取胆固醇。影响脂质和胆固醇运输到寄生液泡可能是ifnγ抑制星形胶质细胞的机制。由于IFNgamma依赖机制在控制脑内弓形虫中发挥重要作用，了解这些机制仍然是了解疾病发病机制的重要挑战。本项目将研究IFNgamma诱导星形胶质细胞抑制的机制。本研究的具体目的是：1)通过微阵列分析确定野生型和IGTP敲除（deltaIGTP）星形胶质细胞中IFNgamma的应答基因；2)表征IFNgamma对星形胶质细胞寄生液泡建立的影响；3)研究IFNgamma抑制是通过影响寄生液泡的囊泡运输和/或胆固醇运输介导的，并且IGTP参与了这种运输的调节。

DESCRIPTION (provided by the applicant): Toxoplasma gondii is a ubiquitous intracellular protozoan parasite that is a major opportunistic infection in immunocompromised individuals, the cause of congenital toxoplasmosis in newborns and recently has been identified as a potential bioterrorism agent (list B). Cytokines play an important role in the regulation of T. gondii in the central nervous system. Interferon-gamma (IFN() is the main cytokine controlling replication of T. gondii in the brain. The investigator's previous studies defined that IFNgamma significantly inhibits the replication of T. gondii in astrocytes. The mechanism of IFNgamma in astrocytes was found to be independent of all of the known anti-Toxoplasma effector mechanisms. However, the investigator recently determined that IFNgamma mediated inhibition in astrocytes was reversed in astrocytes deficient in the GTP binding protein, IGTP (deltaIGTP). The function of IGTP is not known but it is thought to be involved in regulation of the vesicular trafficking pathway. Preliminary microarray studies of IFNgamma induced gene expression in astrocytes indicate that host cell cholesterol metabolism is altered in IFNgamma treated astrocytes. T. gondii has recently been shown to require cholesterol uptake from the host cell. Effects on lipid and cholesterol trafficking to the parasitophorous vacuole may be the mechanism of IFNgamma inhibition in astrocytes. As IFNgamma dependent mechanism(s) play a major role in controlling T. gondii in the brain, understanding these mechanism(s) remains an important challenge in understanding disease pathogenesis. In this project the mechanism(s) of IFNgamma induced inhibition in astrocytes will be investigated. The specific aims of this proposal are: 1) Identify the IFNgamma response genes in wild type and IGTP knockout (deltaIGTP) astrocytes via microarray analysis, 2) Characterize the effect of IFNgamma on the establishment of the parasitophorous vacuole in astrocytes and 3) Investigate the hypothesis that IFNgamma inhibition is mediated by affecting vesicular trafficking and/or cholesterol trafficking to the parasitophorous vacuole and that IGTP is involved in regulating this trafficking.