Defining the regulation and regulatory mechanisms of TCF-1 in CD8+ T cell differentiation

项目总结 CD8T细胞对细胞内病原体和癌症的免疫监测至关重要。慢性和急性 抗原暴露会导致CD8T细胞明显的分化轨迹。在急性感染中，幼稚的CD8 T细胞 识别抗原的细胞经过克隆扩增并分化为细胞毒效应或静止的 调节对后续感染的快速反应的中央记忆细胞(TCM)。在慢性疾病的背景下 抗原暴露，如癌症，CD8T细胞反而分化为终末耗尽(TeX)细胞。特克斯 已减弱的增殖，细胞因子分泌和细胞溶解功能与效应细胞相关 急性感染。尽管他们仍然对病毒施加了显著的控制，但德克萨斯无法持久 并需要从耗尽的静止、茎状T祖细胞池中持续补充 (TPEX)。重要的是，免疫检查点阻断治疗作用于TPex以动员T细胞对肿瘤的反应 抗原。尽管疫苗接种和TPEX反应引发中医治疗势在必行 癌症，这些T细胞亚群发展的分子机制还不完全清楚。它是 已知转录因子(Tf)TCF-1对中医和TPEX人群都是必需的，并且是 在效应型和耗竭型CD8T细胞分化过程中表达下调。虽然是促炎的 已知IL-2和IL-12等细胞因子可诱导TCF-1(由Tcf7编码)的下调，这是 不清楚这些细胞外信号是如何整合在一起调节TCF-1表达的 效应器和纹理分化。对TCF-1如何促进建立也不完全了解 尽管两个细胞亚群都依赖于这种转铁蛋白，但TPex和Tcm的独特转录图谱。这个 拟议的研究试图通过检验以下中心假设(1)来解决知识中的这些差距： 通过上调IL-2Rα链(IL2ra)放大IL-2受体信号促进 通过IL-2诱导的转录因子AP4和Blimp1直接抑制TCF7下调TCF1，以及(2) Tcf-1对TLE家族共抑制子的不同参与和固有的HDAC活性在TPex和中医药结果中的作用 在TCF-1的亚组特异性转录调控中。这项研究项目将询问IL-1的必要性- 2R自身扩增通过去除IL-2R信号反应顺式调节元件在末端分化中的作用 小鼠慢性和急性感染模型中的Il2ra和Tcf7基因座TLE共抑制剂的要求 通过补充Tcf7缺陷的CD8 T细胞来检测TPex和Tcm中的募集和HDAC活性 与缺乏HDAC或TLE共抑制物结合活性的Tcf7突变体一起感染小鼠 或急性LCMV。拟议的研究项目预计将推进确定 决定Tcm和TPex命运的分子基础，最终目标是工程 持久的CD8T细胞对感染和癌症的反应。

PROJECT SUMMARY CD8 T cells are critical for immune surveillance of both intracellular pathogens and cancer. Chronic and acute antigen exposure entails distinct differentiation trajectories of CD8 T cells. In acute infection, naïve CD8 T cells that recognize antigen undergo clonal expansion and differentiate into either cytotoxic effectors or quiescent central memory cells (Tcm) that mediate rapid responses to subsequent infections. In settings of chronic antigen exposure, such as cancer, CD8 T cells instead differentiate into to terminally exhausted (TEX) cells. TEX have attenuated proliferative, cytokine-secretory, and cytolytic functions relative to the effector cells elicited by acute infection. Although they still exert a significant level of viral control, TEX are unable to sustain durable responses and require constant replenishment from a pool of quiescent, stem-like T progenitor exhausted (TPEX). Importantly, immune checkpoint blockade therapy acts on TPEX to mobilize T cell responses to tumor antigens. Despite the therapeutic imperative to elicit Tcm in response to vaccination and TPEX in responses to cancer, the molecular mechanisms by which these T cell subsets develop are incompletely understood. It is known that the transcription factor (TF) TCF-1 is required for both Tcm and TPEX populations and is downregulated during the differentiation of effector and exhausted CD8 T cells. Although pro-inflammatory cytokines such as IL-2 and IL-12 are known to induce the downregulation of TCF-1 (encoded by Tcf7), it is unclear how these extracellular cues are integrated to regulate TCF-1 expression during the fate decisions of effector and TEX differentiation. It is also incompletely understood how TCF-1 contributes to the establishment of unique transcriptional profiles of TPEX and Tcm despite the dependency of both cell subsets on this TF. The proposed study seeks to address these gaps in knowledge by testing the central hypotheses (1) that self- amplification of IL-2 receptor signaling through upregulation of the IL-2R alpha chain (Il2ra) promotes downregulation of TCF-1 by direct repression of Tcf7 by the IL-2-inducible TFs AP4 and Blimp1 and (2) that differential engagement of TLE family co-repressors and intrinsic HDAC activity by TCF-1 in TPEX and Tcm result in subset-specific transcriptional regulation by TCF-1. The research project will interrogate the necessity of IL- 2R self-amplification in terminal differentiation by ablating IL-2R signaling-responsive cis-regulatory elements in the Il2ra and Tcf7 loci in mouse models of chronic and acute infections. The requirements of TLE co-repressor recruitment and HDAC activity in TPEX and Tcm will be interrogated by complementing Tcf7-deficient CD8 T cells with Tcf7 mutants deficient in either HDAC or TLE co-repressor binding activity and infecting mice with chronic or acute LCMV. The proposed research project is expected to advance the long-term objective of determining the molecular basis by which Tcm and TPEX fate decisions are made, with the ultimate goal of engineering durable CD8 T cell responses to infection and cancer.