Role of TIGIT Signaling in Transplantation

摘要移植是终末期器官衰竭的治愈性治疗，但 并且由于免疫抑制诱导的毒性引起的移植物损失仍然高得不可接受。贝拉西普，一种CTLA-4 Ig 融合蛋白和20多年来第一种用于移植免疫抑制的新疗法，提供了一种 对肾移植受者的显着益处在于，它在7天后的死亡或移植物丢失风险降低了43%。 与基于钙调磷酸酶的方案相比，然而，贝拉西普赋予显著的 与钙调磷酸酶抑制剂相比，急性排斥反应的风险增加。两种主要的细胞亚群 涉及贝拉西普抗性排斥的是1）Foxp 3 + Treg和2）CD 8+记忆T细胞。第一、 许多研究表明由于贝拉西普/CTLA-4 Ig结合CTLA-4的CD 80/86配体， 在这些条件下，CTLA-4介导的Treg抑制功能受损。二是 一个独立的研究表明，不同的CD 8+记忆T细胞群表现出降低的需求， CD 28共刺激。在小鼠、NHP和人类中的研究已经鉴定了CD 8+同种异体反应性记忆T细胞 在移植过程中形成移植物接受的障碍。因此，确定替代途径，1） 在CTLA-4阻断的情况下增强Treg抑制功能和2）控制记忆性CD 8 + T细胞 排斥或耐受期间的群体是移植中的临床相关问题。我们的初步 数据显示，虽然单独的TIGIT的激动对移植物存活没有影响，但TIGIT的激动减轻了移植物存活。 在用CTLA-4 Ig治疗的情况下观察到的共刺激阻断抵抗性排斥，导致 延长同种异体移植物的存活时间。然而，这些现象背后的机制尚不清楚。 在CTLA-4 Ig的背景下，TIGIT激动对TCLT的影响是什么？什么是细胞和分子 TIGIT激动TIGIT的下游途径？TIGIT激动作用对记忆是否有细胞内在作用 CD 8 + T细胞在CTLA-4 Ig？Foxp 3 + Treg的TIGIT激动如何影响记忆CD 8 + T细胞 细胞？贝拉西普治疗从移植受者中分离的人T细胞对这些 路径？在该提议中，我们将分析TIGIT激动对Foxp 3 + Treg的作用（其可以是TIGIT激动对Foxp 3 + Treg的作用）。 其次影响移植物反应性CD 8 + T细胞应答）和对CD 8+记忆T细胞的细胞内在效应 在Foxp 3 + Treg或记忆CD 8 + T细胞上使用TIGIT的条件性敲除。这项提案将回答 这些基本问题，从而填补了我们目前对TIGIT共抑制作用的理解中的空白 在移植过程中T细胞同种异体免疫。最后，我们建议直接测试这些的临床相关性。 通过询问TIGIT激动对Foxp 3 + Treg和CD 8 + T细胞的影响， 从贝拉西普治疗的人肾移植受者分离的效应/记忆T细胞。了解 TIGIT信号转导克服贝拉西普抗性排斥的机制将提供重要的 本发明提供了优化贝拉西普在临床移植中的使用的信息。

Summary. Transplantation is a curative treatment for end-stage organ failure, but rates of significant morbidity and graft loss due to immunosuppression-induced toxicities remain unacceptably high. Belatacept, a CTLA-4Ig fusion protein and the first new therapy for immunosuppression in transplantation in over 20 years, offers a significant benefit to renal transplant recipients in that it carries a 43% reduced risk of death or graft loss after 7 years as compared to calcineurin inhibitor-based regimens. However, belatacept confers a significantly increased risk of acute rejection as compared to calcineurin inhibitors. The two main cellular subsets that have been implicated in belatacept-resistant rejection are 1) Foxp3+ Treg and 2) CD8+ memory T cells. First, numerous studies have shown that because belatacept/CTLA-4Ig binds to the CD80/86 ligands for CTLA-4, the CTLA-4-mediated suppressive function of Treg is compromised under these conditions. Second, a separate body of work has shown that distinct CD8+ memory T cell populations exhibit reduced requirements for CD28 costimulation. Studies in mouse, NHP, and humans have identified CD8+ alloreactive memory T cells as forming a barrier to graft acceptance during transplantation. As such, identifying alternate pathways that 1) augment Treg suppressive function in the context of CTLA-4 blockade and 2) control memory CD8+ T cell populations during rejection or tolerance are clinically relevant questions in transplantation. Our preliminary data show that that while agonism of TIGIT alone had no effect on graft survival, agonism of TIGIT mitigated the costimulation blockade-resistant rejection observed in the setting of treatment with CTLA-4Ig, resulting in prolonged allograft survival. However, the mechanisms underlying these observations are not understood. What is the impact of TIGIT agonism on Tregs in the context of CTLA-4Ig? What are the cellular and molecular pathways downstream of TIGIT agonism on Tregs? Is there a cell-intrinsic role for TIGIT agonism on memory CD8+ T cells in the context of CTLA-4Ig? How does TIGIT agonism of Foxp3+ Treg impact memory CD8+ T cells? What is the impact of belatacept treatment of human T cells isolated from transplant recipients on these pathways? In this proposal, we will parse apart the effect of TIGIT agonism on Foxp3+ Treg (which could secondarily impact graft-reactive CD8+ T cell responses) and a cell-intrinsic effect on CD8+ memory T cells using conditional knockouts of TIGIT on either Foxp3+ Treg or memory CD8+ T cells. This proposal will answer these fundamental questions, thereby filling a gap in our current understanding of the role of TIGIT coinhibition in T cell alloimmunity during transplantation. Finally, we propose to directly test the clinical relevance of these findings and hypotheses by interrogating the impact of TIGIT agonism on both Foxp3+ Treg and CD8+ effector/memory T cells isolated from belatacept-treated human renal transplant recipients. Understanding the mechanisms by which TIGIT signaling overcomes belatacept-resistant rejection will provide important information to optimize the use of belatacept for use in clinical transplantation.