Influence of the Host Cell Molecular Environment on Toxoplasma Development

描述（由申请方提供）：弓形虫是一种人畜共患的原生动物，每年感染约150万人，感染可能对胎儿、接受化疗或器官移植的患者以及艾滋病患者造成危险。缓殖子的发育是永久感染的原因，而复发到溶解性速殖子阶段是临床弓形虫病发病机制的基础。导致缓殖子发育的特定宿主-寄生虫相互作用的分子基础大多是未知的，但有证据表明，在长寿命的终末分化细胞如肌肉和脑选择细胞中的优先发育可以由不同的、可定义的宿主和寄生虫特异性因素的相互作用决定。我们已经证明了用三取代的吡咯（命名为化合物1）处理宿主细胞，诱导新的宿主细胞基因表达和早期缓殖子发育。在化合物1改变的细胞中表达的一种宿主mRNA，称为细胞分裂自身抗原1（CDA 1），当在单独的感染的宿主细胞中过表达时，能够诱导寄生虫发育。我们的假设是，增加CDA 1是一个分子环境的一部分，在主机的“信号”，或可以“采取行动”，寄生虫启动缓殖子的发展。这种改变的环境和宿主或寄生虫特异性分子诱导发育的分子元素将有重要意义的理解慢性弓形虫感染的发病机制。为了鉴定这些关键分子并为将来的实验提供基础，以了解导致动物中天然缓殖子发育的相关相互作用，我们将（1）完成结构功能研究，以鉴定CDA 1蛋白中对诱导缓殖子发育至关重要的序列元件和（2）鉴定寄生虫对化合物1改变的宿主细胞环境易感性的遗传元件。弓形虫是艾滋病中常见的机会致病菌。我们已经发现寄生虫可以从宿主细胞中获得线索，建立永久感染。这些研究将寻求使用宿主和寄生虫特异性方法来表征宿主细胞对发育的影响，以了解影响感染和疾病发病机制的关键分子相互作用。

DESCRIPTION (provided by applicant): Toxoplasma gondii is a zoonotic protozoan that infects an estimated 1.5 million human subjects annually, and infection can be dangerous to the unborn, to patients undergoing chemotherapy or organ transplant, and to people with AIDS. Bradyzoite development is responsible for permanent infection and recrudescence to the lytic tachyzoite stage underlies the pathogenesis of clinical toxoplasmosis. The molecular basis for specific host-parasite interaction leading to bradyzoite development is mostly unknown, but evidence suggests that preferential development in long-lived, terminally differentiated cells like muscle and select cells of the brain can be dictated by the interaction of distinct, definable host- and parasite-specific factors. We have demonstrated treatment of the host cell with a trisubstituted pyrrole, designated Compound 1, induces new host cell gene expression and early bradyzoite development. One host mRNA expressed in the Compound 1-altered cell, called cell division autoantigen 1 (CDA1), is able to induce parasite development when over-expressed in the infected host cell alone. Our hypothesis is that increased CDA1 is one part of a molecular environment in the host that 'signals', or can be 'acted on' by, the parasite to initiate bradyzoite development. The molecular elements of this altered environment and the host- or parasite-specific molecules pertinent to induced development will have significant implications for understanding the pathogenesis of chronic Toxoplasma infection. To identify these key molecules and provide a basis for future experiments to understand the relevant interactions leading to natural bradyzoite development in the animal, we will (1) We will complete structure function studies to identify sequence elements in the CDA1 protein critical to induction of bradyzoite development and (2) identify the genetic elements that underlie parasite susceptibility to the Compound 1-altered host cell environment. PUBLIC HEALTH RELEVANCE Toxoplasma is a common opportunistic pathogen in AIDS. We have found the parasite can take cues from the host cell to establish permanent infection. These studies will seek to characterize the host cell influence on development using both host- and parasite-specific approaches to understand key molecular interactions that influence the pathogenesis of infection and disease.