PD-1 signaling in T cells during chronic viral infection

慢性感染迫使T细胞分化成一种疲惫的状态，在这种状态下，它们仍然可以识别 抗原，但不能释放抗病毒剂和杀死感染的细胞。高表达的共抑制 分子PD-1是T细胞耗竭的标志。重要的是，PD-1阻断导致T 细胞效应子对耗尽的T细胞起作用。目前，有几个悬而未决的问题， PD-1连接改变T细胞：参与后招募到PD-1胞质尾区的因子是什么？ PD-1在效应细胞和耗竭的T细胞中传递相同的信号吗？PD-1参与如何影响 T细胞产生多功能反应的能力PD-1信号转导的中断是否可以改变 T细胞耗竭的进展和易感性？这些问题将在本报告中得到解决。 应用和答案将揭示如何T细胞耗竭是强制性的，以及如何克服它。 我们的中心假设是PD-1连接在T细胞分化的不同阶段诱导不同的信号， 分化[（幼稚->效应器->记忆）与（幼稚->效应器->耗尽）]。我们的总体方法是 同时研究PD-1信号在小鼠和人类系统中的作用，使我们能够 利用每种系统的优势来探测PD-1功能，并破译是否存在任何关键差异。 目的1将检查在体外被募集到PD-1胞质尾区的因子，并将询问PD-1是如何在体外被激活的。 通过使用新试剂与PD-1结合， 由核心B提供的信号通路，并使用核心C提供的最新成像分析。目的 2建议检查PD-1信号传导在体内的作用，以便更好地理解PD-1如何在体内发挥作用。 接合导致并有助于T细胞耗竭。使用定义良好的LCMV模型系统，我们 将测试我们的假设，即不同的信号复合物在耗尽的T细胞中被招募到PD-1， 与效应T细胞和记忆T细胞相比。此外，核心B将产生小鼠，使我们能够 确定PD-1信号的改变如何影响对病毒感染的反应。在适当的情况下，我们会 与其他项目合作，研究PD-1连接改变的全球信号通路 （项目4）以及衰竭在控制艾滋病方面的作用（项目1）。通过这些 结合研究，我们希望了解PD-1连接如何阻断T细胞活化，导致T细胞耗竭， 表型，并发现目标，将恢复T细胞功能的慢性疾病，如HIV-1。

Chronic infection forces T cells to differentiate into a state of exhaustion in which they can still recognize antigen but are unable to unleash antiviral agents and kill infected cells. High expression of the co-inhibitory molecule PD-1 is the hallmark of T cell exhaustion. Importantly, .PD-1 blockade results in the restoration of T cell effector functions to exhausted T cells. Presently, there are several outstanding questions regarding how PD-1 ligation alters a T cell: What are the factors recruited to the PD-1 cytoplasmic tail after engagement? Does PD-1 transmit the same signals in effector and exhausted T cells? How does PD-1 engagement affect the T cell's ability to generate polyfunctional responses? Can disruption of PD-1 signaling alter the progression to and susceptibility to T cell exhaustion? These are the questions that will be addressed in this application and the answers will shed light on how T cell exhaustion is enforced and how it can be overcome. Our central hypothesis is that PD-1 ligation induces distinct signals during various stages of T cell differentiation [(naive -> effector ->memory) versus (naive ->effector -> exhausted)]. Our overall approach is to study the effects of PD-1 signaling in both murine and human systems simultaneously, allowing us to exploit the advantages of each system to probe PD-1 function and decipher if there are any key differences. Aim 1 will examine the factors that are recruited to the PD-1 cytoplasmic tail in vitro and will ask how PD-1 engagement alters the generation of effector responses by employing novel reagents to engage PD-1 signaling pathways supplied by Core B and using state of the art imaging analysis provided by Core C. Aim 2 proposes to examine the effects of PD-1 signaling in vivo in order to better understand how PD-1 engagement leads to and contributes to T cell exhaustion. Using the well defined LCMV model system, we will test our hypothesis that distinct signaling complexes are recruited to PD-1 in exhausted T cells as compared to effector and memory T cells. Additionally, Core B will generate mice that will allow us to determine how alterations in PD-1 signaling affect the response to viral infection. Where appropriate, we will collaborate with the other projects in investigating the global signaling pathways altered by PD-1 ligation (Project 4) as well as the role exhaustion plays in controlling HIV disease (Project 1). Through these combined studies we expect to learn how PD-1 ligation blocks T cell activation, leads to the exhaustion phenotype, and uncover targets that will restore T cell function to chronic diseases such as HIV-1.