Interrogating the Interaction between Toxoplasma Secreted Factors and the Host Im

描述(申请人提供)：弓形虫是一种专性细胞内病原体，宿主范围非常广泛；它能够感染几乎任何温血动物的任何有核细胞。虽然弓形虫对发育中的胎儿造成的损害是众所周知的，但它已经成为艾滋病毒/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。不同的弓形虫菌株会导致不同的疾病结果，无论是在人类还是在老鼠身上。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奖项将提供资源、时间和培训，使我能够建立一个独立的研究计划，以确定ROP5‘S对疾病结局的深刻影响的分子机制。这项工作将提供急需的病原体和哺乳动物免疫系统之间的相互作用的询问，使开发新的弓形虫病治疗方法成为可能。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，并在早期感染时引发更强的促炎反应。此外，我还解开了ROP5‘S假激酶结构域的晶体结构，发现与菌株毒力差异相关的多态在底物结合结构域附近形成了一个表面。这让我假设，ROP5通过在其假激酶域中结合宿主信号分子来颠覆宿主免疫系统，从而导致免疫信号网络的失调。我将在以下互补目标中验证这一假说：1)确定ROP5调控的特定免疫细胞类型和信号网络；2)确定ROP5在受感染的宿主细胞中进行的物理相互作用以及ROP5对毒力产生深刻影响的生化机制。

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.