T regulatory cells and immunity in tuberculosis

项目摘要 尽管用卡介苗进行了近100年的广泛免疫，但结核病(TB)仍然是世界上最严重的 最具破坏性的传染病，每年导致100多万人死亡。主要原因是 已经证明很难根除结核病的是结核分枝杆菌(Mtb)，这种细菌会导致 已经制定了逃避免疫系统的策略。感染通过吸入发生，结核分枝杆菌建立了一种 在肺中的利基，在那里它可以持续宿主的一生。迫切需要一种有效的疫苗，但 首先，我们必须从机制上了解结核分枝杆菌是如何逃避免疫根除的，以便理性地 制定一种疫苗接种策略，绕过这些策略。我们实验室的工作揭示了一个核心角色 结核分枝杆菌特异性调节性T细胞(T Regs)在抑制结核病免疫中的作用。我们发现结核分枝杆菌 表位特异的胸腺来源的T细胞在肺引流淋巴结内扩张并限制发育 适应性免疫反应。其结果是，效应T细胞到达肺部的时间延迟，从而允许结核分枝杆菌复制 长期有增无减，建立肺脏生态位。利用我们已有的实验系统 为了研究结核分枝杆菌特异的T调节器，我们将询问控制它们的病原体和宿主的相互作用 扩展和功能。在目标1中，我们将继续我们最近的发现，分枝杆菌毒力脂质 磷酸甘油二酯(PDIM)抑制结核分枝杆菌感染引起的炎症反应，促进 病原体特异性T基因的扩增。我们将确定驱动MTB特异性T细胞的树突状细胞(DC)亚群(S) REG扩增，并确定PDIM是否促进这些T-REG诱导的DC的抗原提呈，或者 或者，改变它们的功能激活状态。促进结核分枝杆菌特异性的关键宿主分子决定因素 将识别和表征T_REG扩展。在目标2中，我们将定义所使用的抑制机制 作者：Mtb特定的T regs，重点是T regs和Tregs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在调节这一活性中的作用。我们还将在全球范围内调查 结核分枝杆菌特异性T细胞中的转录图谱，高度特化的细胞共同表达主调节因子 转录因子Foxp3和T-bet，并定义所使用的免疫抑制途径。在《目标3》中，我们将 评估来自北京家系的超强毒力临床Mtb分离株诱导的T-reg扩增。我们会 检查这些菌株是否触发放大的和/或延长的结核分枝杆菌特异性T-reg反应，如果是， 这一反应是否指导了它们的超强毒力表型。酚醛糖脂(PGL)的作用 PDIM带有额外的糖基化酚基，在促进这些过程中也将 检查过了。该提案中概述的基本实验将为人体研究奠定基础，并将 阐明需要在临床环境中解决的相关问题。对病原体-宿主的洞察 推动结核分枝杆菌特异性T调节基因的扩展和功能的相互作用将提供新的潜在途径 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.