IFN Inhibition of Toxoplasma gondii in Astrocytes

描述(申请人提供)：弓形虫是一种普遍存在的细胞内原虫寄生虫，是艾滋病患者和其他免疫功能低下者的常见感染，也是先天性弓形虫病的原因。在艾滋病患者和其他免疫功能受损的宿主中，感染是由于大脑中的潜伏感染重新激活，导致严重的、往往是致命的坏死性脑炎。细胞因子在弓形虫中枢神经系统的调控中起着重要作用。干扰素-γ是控制弓形虫在脑内复制的主要细胞因子。我之前的研究表明，干扰素-伽马能显著抑制弓形虫在星形胶质细胞中的复制。星形胶质细胞中的干扰素-γ机制被发现独立于所有已知的抗弓形虫效应机制。然而，我们最近确定了干扰素？在GTP结合蛋白IGTP(AIGTP)缺陷的星形胶质细胞中，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。对干扰素-γ诱导星形胶质细胞基因表达的微阵列初步研究表明，在干扰素-γ处理的星形胶质细胞中，宿主细胞的胆固醇代谢发生改变。最近发现弓形虫需要从宿主细胞摄取胆固醇。抑制星形胶质细胞中干扰素-γ的作用可能是影响脂质和胆固醇向寄生虫空泡的转运。由于干扰素γ依赖机制(S)在控制脑内弓形虫中起着重要作用，了解这些机制(S)仍然是理解疾病发病机制的一个重要挑战。在本项目中，我们将研究干扰素-γ抑制星形胶质细胞的机制(S)。这项建议的具体目的是：1)对野生型与IGTP基因敲除(DeltaIGTP)星形胶质细胞中的IFNGamma反应基因进行微阵列分析；2)研究IFNGamma影响囊泡向寄生虫液泡的运输(Aim 2A)或IFNGamma影响胆固醇向寄生虫液泡的运输(Aim 2B)以及IGTP参与调节这种运输的假说。

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 .