IFN Immune Effector Mechanisms in Cerebral Toxoplasmosis

描述(申请人提供)：弓形虫是一种普遍存在的细胞内原生动物寄生虫，是免疫受损个体的一种主要机会性感染，是新生儿先天性弓形虫病的原因，最近已被确定为潜在的生物恐怖主义因素(清单B)。细胞因子在弓形虫中枢神经系统的调控中起着重要作用。干扰素是控制弓形虫在脑内复制的主要细胞因子。这位研究人员之前的研究确定，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，研究人员最近发现，在缺乏GTP结合蛋白IGTP(DeltaIGTP)的星形胶质细胞中，IFNGamma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)。这一建议的具体目的是：1)通过微阵列分析确定野生型和IGTP敲除(DeltaIGTP)星形胶质细胞中的IFNGamma反应基因；2)表征IFNGamma在星形胶质细胞中建立寄生虫空泡的作用；3)研究IFNGamma抑制是通过影响囊泡运输和/或胆固醇运输到寄生虫液泡的假说，以及IGTP参与调节这种运输。

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.