Autophagy and ocular toxoplasmosis

描述(申请人提供)：弓形虫是世界上最常见的视网膜脉络膜炎病因。尽管使用了抗生素，眼弓形体病仍会复发，并且仍然是导致视力丧失的重要原因，特别是在患有先天性感染的儿童以及老年人和免疫抑制者中。不幸的是，我们对预防眼弓形体病的机制的了解还不是很清楚。巨噬细胞、小胶质细胞和T细胞是眼弓形体病细胞浸润的主要成分。在这些细胞之间相互作用的一个重要事件是刺激巨噬细胞/小胶质细胞上表达的CD40。我们确定了一种新的范式，免疫系统通过CD40杀死弓形虫。CD40可诱导巨噬细胞和视网膜小胶质细胞的弓形体杀伤活性。这依赖于自噬，这是一个以寄生虫为目标的溶酶体降解过程。这一发现可能是眼弓形虫病的关键，因为在体内控制这种疾病需要CD40。因此，研究CD40诱导的自噬的调节可能会为根除弓形虫和治疗眼弓形虫病确定新的分子靶点，有望防止这种疾病的复发。这项应用的目的是了解巨噬细胞和视网膜小胶质细胞中的CD40信号如何控制眼弓形体病，以及弓形虫如何颠覆这些信号。这项研究的中心假设是，CD40通过激活蛋白激酶和诱导自噬来调节眼睛对弓形虫病的抵抗力。相反，弓形虫和由寄生虫触发的细胞因子使用一种策略来破坏自噬的最佳激活所需的信号，从而使寄生虫逃避根除。这一假说将通过免疫化学研究以及阻止特定囊泡运输分子的遗传方法进行验证。在第一个特定目标中，我们将确定CD40诱导的自噬和蛋白激酶激活是否介导了对眼弓形虫病的抵抗。在第二个目标中，我们将确定细胞因子阻止自噬的最佳诱导的细胞内事件，并测试这些事件的抑制是否改善了眼弓形虫病的控制。这项拟议的工作可能导致基于调制自噬和/或CD40信号的新策略来根除弓形虫和治疗眼弓形虫病。公共卫生相关性：眼弓形体病是一种复发性疾病，也是导致视力丧失的主要原因。目前可用的治疗方案不能防止这种疾病的复发。我们计划进行研究，希望能识别出可以用来提高免疫系统控制眼弓形虫病能力的分子。

DESCRIPTION (provided by applicant): Toxoplasma gondii is the most common cause of retinochoroiditis in the world. Ocular toxoplasmosis relapses despite the use of antibiotics and remains an important cause of loss of visual acuity especially in children with congenital infection as well as the elderly and the immunosuppressed. Unfortunately, our understanding of the mechanisms of protection against ocular toxoplasmosis is fragmentary. Macrophages, microglia and T cells are the major components of the cell infiltrates in ocular toxoplasmosis. An important event in the interaction between these cells is the stimulation of CD40 expressed on macrophages/microglia. We identified a new paradigm by which the immune system through CD40 kills T. gondii. CD40 induces toxoplasmacidal activity in macrophages and retinal microglia. This is dependent on autophagy, a process that targets the parasite to lysosomal degradation. This finding is likely key to ocular toxoplasmosis because in vivo control of this disease requires CD40. Thus, studying the regulation of CD40-induced autophagy will likely identify new molecular targets for eradication of T. gondii and for therapy of ocular toxoplasmosis that will hopefully prevent relapse of this disease. The objective of this application is to understand how CD40 signaling in macrophages and retinal microglia controls ocular toxoplasmosis and how T. gondii subverts these signals. The central hypothesis for the proposed research is that, CD40 mediates resistance against toxoplasmosis in the eye through protein kinase activation and induction of autophagy. In contrast, T. gondii and cytokines triggered by the parasite use a strategy to impair the signaling needed for optimal activation of autophagy allowing the parasite to evade eradication. This hypothesis will be tested using immunochemical studies as well as genetic approaches that block specific vesicular trafficking molecules. In the first specific aim we will determine if autophagy and protein kinase activation induced by CD40 mediate resistance to ocular toxoplasmosis. In the second aim, we will identify the intracellular events by which cytokines prevent optimal induction of autophagy and test whether inhibition of these events improves control of ocular toxoplasmosis. The proposed work may lead to new strategies to eradicate T. gondii and treat ocular toxoplasmosis based on modulation autophagy and/or CD40 signaling. PUBLIC HEALTH RELEVANCE: Toxoplasmosis of the eye is a relapsing disease and a major cause of visual loss. Currently available therapeutic regimens do not prevent relapse of this disease. We plan studies that will hopefully identify molecules that can be used to boost the ability of the immune system to control ocular toxoplasmosis.