Influence of the Host Cell Molecular Environment on Toxoplasma Development

描述(申请人提供)：弓形虫是一种人畜共患原虫，估计每年感染150万人，感染对未出生的人、接受化疗或器官移植的患者以及艾滋病患者可能是危险的。慢殖子的发育是导致永久性感染和复发至溶血性速殖子阶段的原因，是临床弓形虫病发病的基础。宿主-寄生虫相互作用导致慢体发育的分子基础大多尚不清楚，但有证据表明，肌肉和大脑的特定细胞等长期、终末分化的细胞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吡咯处理宿主细胞，命名为化合物1，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(CDA1)，当仅在感染的宿主细胞中过度表达时，能够诱导寄生虫的发展。我们的假设是，增加的CDA1是宿主分子环境的一部分，该分子环境‘发出’信号‘，或’作用于‘寄生虫，以启动缓殖子的发育。这种改变环境的分子成分以及与诱导发育相关的宿主或寄生虫特异性分子将对理解慢性弓形虫感染的发病机制具有重要意义。为了确定这些关键分子，并为未来的实验提供基础，以了解导致动物体内自然缓体发育的相关相互作用，我们将(1)完成结构功能研究，以确定CDA1蛋白中对诱导缓体发育至关重要的序列元件，以及(2)鉴定导致寄生虫对化合物1改变的宿主细胞环境易感性的遗传元件。与公共卫生相关弓形虫是艾滋病常见的机会性病原体。我们已经发现这种寄生虫可以从宿主细胞中获得线索来建立永久感染。这些研究将寻求利用宿主和寄生虫特异性的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.