Modulation of Host Responses by Mycobacterium Tuberculosis

描述(申请人提供)：结核病(TB)仍然是全球公共卫生的主要威胁，结核分枝杆菌(Mtb)感染估计每年导致200多万人死亡。目前的结核病治疗既漫长又艰难，并导致出现多药耐药(MDR)和广泛耐药(XDR)结核病。为了开发新的结核病疫苗和药物，我们需要了解结核分枝杆菌是如何逃避天然免疫并在恶劣的免疫环境中生存的。结核分枝杆菌发病机制的一个主要特征是它能够在巨噬细胞内生长，调节其活动并干扰杀菌功能。我们已经确定了一种编码丝氨酸水解酶的细胞膜定位的脂蛋白Rv2224c，它对结核分枝杆菌在体内的毒力、在巨噬细胞中的存活和对细胞膜定向应激的抵抗至关重要。我们将这个蛋白命名为Hip1(水解酶对发病机制1很重要)。我们证明，Hip1抑制先天免疫反应；Hip1突变在巨噬细胞Toll样受体(TLR)信号下游诱导增强的促炎反应。我们假设Hip1通过修饰细胞膜或分泌底物来调节先天免疫和宿主防御。这一应用的重点是了解Hip1如何抑制宿主的先天免疫途径，并确定Hip1功能的分子和生化机制。其具体目的是(1)研究Hip1在抑制宿主反应中的作用。我们将定义Hip1调节的TLR依赖的通路，并评估Hip1介导的免疫抑制是否促进巨噬细胞Mtb的生长。我们还将通过研究T细胞反应的启动和功能来确定hi1突变引起的增强的先天免疫反应是否影响适应性免疫。(2)确定Hip1功能的分子基础。首先，我们将描述Hip1与候选生理底物GroEL2相互作用的分子和生化基础。我们将研究依赖于Hip1的GroEL2裂解的功能意义及其在免疫抑制和抵抗抗菌素防御中的作用。其次，我们将使用一组合成底物来评估Hip1水解酶活性的范围和特异性。最后，我们将使用遗传和生化方法确定其他Hip1相互作用伙伴和生理底物。 与公共卫生相关：全球结核病流行是由艾滋病毒合并感染和耐药性传播助长的，对公共卫生构成严重威胁。这里概述的研究将增加我们对一个重要的毒力因子的理解，该因子介导免疫抑制和对宿主抗菌素防御的抵抗。这些蛋白质是有吸引力的新的抑制药物靶点，因为它们可以潜在地与抗生素协同作用，同时增强免疫介导的对结核分枝杆菌的杀伤。

DESCRIPTION (provided by applicant): Tuberculosis (TB) remains a major threat to global public health and infection with Mycobacterium tuberculosis (Mtb) is estimated to result in over 2 million deaths annually. Current TB treatments are long and arduous and contribute to the emergence of multi-drug resistant (MDR)- and extensively drug-resistant (XDR)-TB. In order to develop new vaccines and drugs for TB, we need to understand how Mtb evades innate immunity and survives in hostile immune environments. A central feature of Mtb pathogenesis is its ability to grow within macrophages, modulate their activities and interfere with microbicidal functions. We have identified a cell envelope-localized lipoprotein encoding a serine hydrolase, Rv2224c, which is critical for Mtb virulence in vivo, survival in macrophages and resistance to cell envelope-directed stresses. We have named this protein Hip1 (Hydrolase important for pathogenesis 1). We demonstrate that Hip1 suppresses innate immune responses; hip1 mutants induce enhanced proinflammatory responses downstream of Toll-like receptor (TLR)-signaling in macrophages. We hypothesize that Hip1 modifies cell envelope or secreted substrates to modulate innate immunity and host defense. The focus of this application is to understand how Hip1 suppresses host innate immune pathways and determine the molecular and biochemical mechanisms for Hip1 function. The specific aims are (1) To study the role of Hip1 in suppressing host responses. We will define the TLR-dependent pathways modulated by Hip1 and evaluate whether Hip1-mediated immune suppression promotes Mtb growth in macrophages. We will also determine whether enhanced innate immune responses elicited by the hip1 mutant impact adaptive immunity by studying the priming and functionality of T cell responses. (2) To determine the molecular basis for Hip1 function. First we will characterize the molecular and biochemical basis for Hip1 interaction with a candidate physiological substrate, GroEL2. We will investigate the functional significance of Hip1-dependent cleavage of GroEL2 and its contribution to immune suppression and resisting antimicrobial defense. Second, we will use a panel of synthetic substrates to evaluate the range and specificity of Hip1 hydrolase activity. Finally we will identify additional Hip1 interaction partners and physiological substrates using genetic and biochemical approaches. PUBLIC HEALTH RELEVANCE: The global TB epidemic is fueled by HIV co-infection and the spread of drug resistance, posing a grave threat to public health. The studies outlined here will increase our understanding of an important virulence factor that mediates immune suppression and resistance to host antimicrobial defense. Such proteins are attractive new drug targets for inhibition as they can potentially synergize with antibiotics and simultaneously enhance immune-mediated killing of Mtb.