Interrogating the Interaction between Toxoplasma Secreted Factors and the Host Im

描述（由申请人提供）：刚地弓形虫是一种专性细胞内病原体，具有非常广泛的宿主范围；它几乎能够感染任何温血动物的任何有核细胞。众所周知，弓形虫会对发育中的胎儿造成损害，但它已成为艾滋病毒/艾滋病和淋巴瘤患者以及正在接受免疫抑制治疗的器官移植患者的严重机会性病原体。在人类和小鼠中，不同的弓形虫菌株可导致不同的疾病结果。我已经确定分泌的弓形虫假激酶ROP5是一个主要的毒力因子。这个K22奖将为我提供资源、时间和培训，使我能够建立一个独立的研究项目，以确定ROP5对疾病结局的深刻影响的分子机制。这项工作将为病原体与哺乳动物免疫系统之间的相互作用提供急需的调查，使弓形虫病的新疗法得以开发。我发现，与野生型寄生虫相比，缺乏ROP5的寄生虫对小鼠的毒力完全减弱，并且在感染早期引起更强的促炎反应。此外，我已经解决了ROP5的伪激酶结构域的晶体结构，并发现与菌株特异性毒力差异相关的多态性在底物结合域附近形成一个表面。这让我假设ROP5通过在其伪激酶结构域结合宿主信号分子来破坏宿主免疫系统，从而导致免疫信号网络失调。我将在以下补充目标中验证这一假设：1)确定ROP5调节的特定免疫细胞类型和信号网络；2)确定ROP5在被感染宿主细胞中的物理相互作用以及ROP5对毒力产生深远影响的生化机制。

DESCRIPTION (provided by applicant): Toxoplasma gondii is an obligate intracellular pathogen with a remarkably broad host range; it is able to infect virtually any nucleated cell of almost any warm-blooded animal. While well-known for the damage Toxoplasma can cause to a developing fetus, it has become a serious opportunistic pathogen in HIV/AIDS and lymphoma patients, as well as in organ transplant patients who are undergoing immunosuppressive therapy. Different strains of Toxoplasma can lead to different disease outcomes, both in humans and in mice. I have identified the secreted Toxoplasma pseudokinase ROP5 as a dominant virulence factor. This K22 award will provide the resources, time, and training to allow me to build an independent research program to determine molecular mechanism of ROP5's profound effect on disease outcome. This work will provide a much-needed interrogation of the interactions between a pathogen and the mammalian immune system, enabling the development of new therapies for toxoplasmosis. I have found that parasites deficient in ROP5 are completely attenuated in their virulence to mice and elicit a stronger pro-inflammatory response during early infection than do wild-type parasites. Furthermore, I have solved the crystal structure of ROP5's pseudokinase domain and found that polymorphisms correlated with strain-specific differences in virulence form a surface near the substrate binding domain. This has led me to hypothesize that ROP5 subverts the host immune system by binding host signaling molecules in its pseudokinase domain, which leads to dysregulation of immune signaling networks. I will test this hypothesis in the following complementary aims: 1) Identify the specific immune cell types and signaling networks modulated by ROP5; 2) Determine the physical interactions ROP5 makes in infected host cells and the biochemical mechanism of ROP5's profound effect on virulence.