IFN Inhibition of Toxoplasma gondii in Astrocytes

描述（申请人提供）：刚地弓形虫是一种普遍存在于细胞内的原生动物寄生虫，是艾滋病患者和其他免疫功能低下个体的常见感染，也是先天性弓形虫病的病因。在艾滋病患者和其他免疫功能低下的宿主中，感染是由于大脑中潜伏感染的重新激活，导致严重且通常是致命的坏死性脑炎。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 (IFNgamma)是控制脑内弓形虫复制的主要细胞因子。我之前的研究确定ifn - γ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，我们最近确定IFN？在缺乏GTP结合蛋白IGTP （AIGTP）的星形胶质细胞中，介导的抑制作用被逆转。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。本提案的具体目的是：1)对野生型与IGTP敲除（deltaIGTP）星形胶质细胞中IFNgamma应答基因进行微阵列分析；2)研究IFNgamma影响到寄生液泡的囊泡运输（Aim 2A）或IFNgamma影响到寄生液泡的胆固醇运输（Aim 2B），以及IGTP参与调节这种运输的假设。

DESCRIPTION (provided by applicant): Toxoplasma gondii is a ubiquitous intracellular protozoan parasite that is a common infection in AIDS patients and other immunocompromised individuals as well as the cause congenital toxoplasmosis. In AIDS patients and other immunocompromised hosts infection is due to reactivation of a latent infection in the brain that results in a severe and often fatal necrotizing encephalitis. Cytokines play an important role in the regulation of T. gondii in the central nervous system. Interferon-gamma (IFNgamma) is the main cytokine controlling replication of T. gondii in the brain. My previous studies defined that IFN-gamma 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, we recently determined that IFN? mediated inhibition in astrocytes was reversed in astrocytes deficient in the GTP binding protein, IGTP (AIGTP). 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) To perform a microarray analysis of IFNgamma response genes in wildtype vs. IGTP knockout (deltaIGTP) astrocytes and 2) Investigate the hypothesis that IFNgamma affects vesicular trafficking to the parasitophorous vacuole (Aim 2A) or that IFNgamma affects cholesterol trafficking to the parasitophorous vacuole (Aim 2B) and that IGTP is involved in regulating this trafficking .