Mechanisms of Innate Immune Evasion by Mycobacterium Tuberculosis

摘要 这个项目的目标是了解结核分枝杆菌(Mtb)的两个毒力因子CPSA是如何 和邻苯二甲酸甘油酯(PDIM)，通过破坏经典和非经典的方式来损害免疫力 自噬。结核分枝杆菌是结核病(TB)的病原体，是全球范围内由细菌引起的主要死亡原因 感染。结核分枝杆菌的主要细胞生态位是巨噬细胞和中性粒细胞，也就是免疫细胞。 来清除感染。结核分枝杆菌是如何在先天免疫反应中存活下来，从而建立感染的，目前还不清楚。在……里面 在上一个项目期间，我们发现一种出口蛋白CPSA对结核分枝杆菌的毒力至关重要。 我们发现CPSA能抑制NADPH氧化酶的吞噬体募集。NADPH氧化酶使 活性氧(ROS)，先天免疫反应的重要介体。除了它的直接 抗菌活性，ROS是溶酶体转运途径所必需的，称为LC3相关的吞噬作用 (LAP)，一种非经典的自噬形式。因此，通过抑制ROS，CPSA也抑制了LAP。我们两个都展示在 巨噬细胞和小鼠，CPSA保护线粒体免受NADPH氧化酶和LAP的伤害。有趣的是，CPSA在身体上 与NDP52和TAX1BP1相互作用，这是一种以经典自噬(异种吞噬)的形式发挥作用的自噬适配器， 这表明CPSA也可能会损害异种吞噬作用。此外，我们还发现结核分枝杆菌毒力脂，PDIM，也 抑制NADPH氧化酶。以前的研究提出了PDIM的一系列角色，并表明它可以保护 结核分枝杆菌来自一种不明确的先天杀死机制。我们的数据表明，一种未经评估的致命性 PDIM的作用是阻断NADPH氧化酶和LAP。因此，我们假设CPSA抑制异体吞噬和 与PDIM协同工作，抑制NADPH氧化酶和LAP。此外，我们还提出，感染剂量 结核分枝杆菌的感染依赖于它逃避这些被招募到肺部的髓系细胞的先天防御的能力。 在最初的感染期间。在这里，我们将定义CPSA是如何抑制NADPH氧化酶的，并研究它是否也 通过阻断NDP52和TAX1BP1功能而损害异种吞噬功能。我们将确定PDIM是否也会损害 NADPH氧化酶在分枝杆菌噬菌体中的募集及PDIM的作用 在体内颠覆NADPH氧化酶和LAP。以确定CPSA是否促进 建立感染模型后，我们将采用超低剂量感染小鼠。使用条件淘汰法 (CKO)小鼠，我们将确定在急性发作期间，CPSA在哪些细胞中发挥抑制NADPH氧化酶和LAP的作用 和慢性感染。我们的发现将为结核分枝杆菌的两个关键毒力因素提供机械洞察 合谋破坏豁免权。我们的研究将揭示细菌特定细胞类型的毒力策略， 描述在体内参与LAP的细胞类型，并定义管理LAP的宿主-病原体相互作用 建立感染机制。我们的研究将为免疫逃避提供详细的机制洞察 世界上最可怕的病原体之一的策略。通过阐明两个关键分子的作用机制 在结核分枝杆菌的毒力因素方面，我们将推进防治结核病的创新方法。

SUMMARY The goal of this project is to understand how two virulence factors from Mycobacterium tuberculosis (Mtb), CpsA and phthiocerol dimycocerosate (PDIM), impair immunity by undermining both classical and non-classical autophagy. Mtb is the causative agent of tuberculosis (TB), the leading cause of death worldwide from a bacterial infection. The main cellular niche for Mtb is macrophages and neutrophils, the very immune cells that are meant to clear infection. How Mtb survives the innate immune response to establish infection is not well understood. In the previous project period, we discovered that an exported protein, CpsA, is critically important for Mtb virulence. We showed that CpsA inhibits phagosomal recruitment of the NADPH oxidase. The NADPH oxidase makes reactive oxygen species (ROS), an important mediator of the innate immune response. In addition to its direct antimicrobial activity, ROS is required for a lysosomal trafficking pathway called LC3-associated phagocytosis (LAP), a non-classical form of autophagy. Thus, by inhibiting ROS, CpsA also inhibits LAP. We showed both in macrophages and mice that CpsA protects Mtb from the NADPH oxidase and LAP. Interestingly, CpsA physically interacts NDP52 and TAX1BP1, autophagy adaptors that function in a form of classical autophagy (xenophagy), suggesting that CpsA may also impair xenophagy. Moreover, we found that the Mtb virulence lipid, PDIM, also inhibits the NADPH oxidase. Previous studies proposed an array of roles for PDIM and showed that it protects Mtb from a poorly defined innate killing mechanism. Our data suggest that an unappreciated virulence property of PDIM is blocking the NADPH oxidase and LAP. Thus, we hypothesize that CpsA inhibits xenophagy and works in concert with PDIM to inhibit the NADPH oxidase and LAP. Further, we propose that the infectious dose of Mtb depends upon its ability to evade these innate defenses in myeloid cells that are recruited to the lungs during initial infection. Here, we will define how CpsA inhibits the NADPH oxidase and investigate whether it also impairs xenophagy by blocking NDP52 and TAX1BP1 function. We will determine whether PDIM also impairs recruitment of the NADPH oxidase to mycobacterial phagosomes and evaluate the contribution that PDIM plays towards subverting the NADPH oxidase and LAP in vivo. To determine whether CpsA promotes the establishment of infection, we will use an ultra-low dose infection model in mice. Using conditional knockout (cKO) mice, we will determine in which cells CpsA functions to inhibit the NADPH oxidase and LAP during acute and chronic infection. Our findings will provide mechanistic insight into how two key virulence factors in Mtb collaborate to undermine immunity. Our studies will reveal a cell type-specific virulence strategy of the bacilli, delineate the cell types that participate in LAP in vivo, and define host-pathogen interactions that govern the establishment of infection. Our studies will provide detailed mechanistic insight into the immune evasion strategies of one of the world's most formidable pathogens. By elucidating the mechanism of action of two crucial virulence factors in Mtb, we will advance innovative approaches to prevent and treat TB.