T regulatory cells and immunity in tuberculosis

项目摘要 尽管卡介苗的广泛免疫已有近100年的历史，但结核病（TB）仍然是世界上最严重的结核病之一。 最具破坏性的传染病，每年造成超过一百万人死亡。主要原因是， 根除结核病已被证明是困难的是，结核分枝杆菌（Mtb），细菌引起的 结核病已经设计出了逃避免疫系统的策略。感染通过吸入发生，Mtb建立了一个 在肺部的利基中，它可以在宿主的一生中持续存在。目前急需一种有效的疫苗， 首先，我们必须从机制上了解结核分枝杆菌如何逃避免疫根除， 设计一种疫苗接种策略来规避这些策略。我们实验室的工作揭示了其核心作用 Mtb特异性调节性T细胞（T细胞）在结核病期间抑制免疫力。我们发现结核分枝杆菌 表位特异性胸腺来源的T细胞在肺引流淋巴结中扩增，并限制了T细胞的发育。 适应性免疫反应因此，效应T细胞到达肺部的时间延迟，使Mtb能够复制 长时间不减弱，并建立肺生态位。利用我们现有的实验系统 为了研究结核分枝杆菌特异性T细胞，我们将询问病原体-宿主相互作用， 扩展和功能。在目标1中，我们将继续我们最近的发现，即分枝杆菌毒力脂质 苯硫代蜡醇二霉菌蜡酸酯（PDIM）抑制对Mtb感染的炎症反应，并促进 病原体特异性T reg扩增。我们将鉴定树突状细胞（DC）亚群，其驱动结核分枝杆菌特异性T细胞， reg扩增并确定PDIM是否促进这些T reg诱导DC的抗原呈递，或 或者改变它们的功能激活状态。促进结核分枝杆菌特异性 将识别和表征T reg扩增。在目标2中，我们将定义所使用的抑制机制 通过Mtb特异性T细胞，专注于T细胞和T细胞之间同源相互作用的功能后果， DCs在体内感染过程中的作用，以及CTLA-4在调节这种活性中的作用。我们还将在全球范围内调查 Mtb特异性T细胞中的转录景观，高度特化的细胞共表达主调节因子 转录因子Foxp 3和T-bet，并定义所用的免疫抑制途径。在目标3中， 评估由来自北京家族谱系的高毒力临床Mtb分离株诱导的T reg扩增。我们将 检查这些菌株是否触发扩增和/或延长的Mtb特异性T reg应答，如果是， 这种反应是否指导它们的高毒力表型。酚糖脂（PGL）的作用， 携带另外的糖基化酚部分的PDIM在促进这些过程中也将是有效的。 考察本提案中概述的基本实验将为人类研究奠定基础， 阐明了在临床环境中需要解决的相关问题。对病原体-宿主的见解 驱动结核特异性T细胞扩增和功能的相互作用将为结核病的治疗提供新的潜在途径。 通过接种疫苗和宿主靶向治疗预防结核病。

PROJECT ABSTRACT Despite almost 100 years of widespread immunization with BCG, tuberculosis (TB) remains one of the world's most devastating infectious diseases, killing over one million people every year. The principal reason that eradication of TB has proven to be difficult is that Mycobacterium tuberculosis (Mtb), the bacterium that causes TB, has devised strategies to evade the immune system. Infection occurs by inhalation and Mtb establishes a niche in the lung where it can persist for the lifetime of the host. An effective vaccine is urgently needed, but first we must gain a mechanistic understanding of how Mtb evades immune eradication in order to rationally devise a vaccination strategy that circumvents these maneuvers. Work in our lab has revealed a central role for Mtb-specific regulatory T cells (T regs) in dampening immunity during TB. We have discovered that Mtb epitope-specific, thymically-derived T regs expand in the lung draining lymph node and restrict the developing adaptive immune response. As a result, effector T cell arrival in the lung is delayed, allowing Mtb to replicate unabated for a prolonged period and establish a lung niche. Utilizing the experimental systems that we have developed to study Mtb-specific T regs, we will interrogate the pathogen-host interactions that govern their expansion and function. In Aim 1, we will pursue our recent discovery that the mycobacterial virulence lipid phthiocerol dimycocerosate (PDIM) dampens the inflammatory response to Mtb infection and promotes pathogen-specific T reg expansion. We will identify the dendritic cell (DC) subset(s) that drive Mtb-specific T reg expansion and determine whether PDIM promotes antigen presentation by these T reg-inducing DCs, or alternatively, changes their functional activation state. Key host molecular determinants that foster Mtb-specific T reg expansion will be identified and characterized. In Aim 2, we will define suppressive mechanisms utilized by Mtb-specific T regs, focusing on the functional consequences of cognate interactions between T regs and DCs during in vivo infection, and the role of CTLA-4 in modulating this activity. We will also globally survey the transcriptional landscape in Mtb-specific T regs, highly specialized cells that co-express the master regulator transcription factors Foxp3 and T-bet, and define the immunosuppressive pathways utilized. In Aim 3 we will assess T reg expansion induced by hypervirulent clinical Mtb isolates from the Beijing family lineage. We will examine whether these strains trigger an amplified and/or prolonged Mtb-specific T reg response, and if so, whether this response directs their hypervirulent phenotype. The role of phenolic glycolipids (PGL), a modified PDIM that bears an additional glycosylated phenolic moiety, in promoting these processes will also be examined. The basic experiments outlined in this proposal will set the stage for human studies and will illuminate pertinent questions that need to be addressed in the clinical setting. Insights into the pathogen-host interactions that drive the expansion and function of Mtb-specific T regs will provide new potential avenues to prevent TB via vaccination and host-targeted therapy.