Inflammation and T Cell Memory: Inter-related Barriers to Allograft Tolerance

描述(由申请人提供)：尽管移植后早期存活率在过去20年中有所改善，但在以前成功的肾移植受者中，每年3-5%的无情流失率继续限制着长期结果。胰岛移植的长期结果是不可接受的，只有10%的受者在五年内保持无胰岛素状态。在胰岛中，由于胰岛细胞质量不足导致的代谢衰竭可能是长期移植功能的重要障碍。由于慢性排斥、感染、药物毒性和恶性肿瘤导致的晚期同种异体移植失败，强调了长期应用免疫抑制在肾和胰岛移植中的局限性。因此，移植的最终目的是在不维持免疫抑制的情况下实现长期植入。试点临床耐受性方案目前正在人类身上进行测试，但在人类身上实现真正的耐受性仍然存在重大障碍。这一多项目赠款的主要目标是通过确定诱导对同种异体肾和胰岛移植持久耐受的基本条件，以及确定炎症和记忆T细胞在耐受的主要障碍中的作用，来改善肾和胰岛移植后的结果。我们的中心假设是，早期的促炎反应在很大程度上是由于供体组织的缺血再灌注和缺氧损伤引起的，激发了不利形式的抗供体免疫，从而引发了急性临床或亚临床排斥反应，并夸大了先前存在的供体反应性记忆的后续扩展，以及移植后新获得的供体反应性记忆T细胞的发展。因此，我们假设，亲至抗炎细胞因子和抗供体记忆反应的不利平衡是诱导和维持耐受性的主要障碍。考虑到胰岛和肾移植中与炎症和记忆相关的耐受障碍，我们提出了新的和相互关联的策略来改变同种免疫反应的平衡，以利于调节和长期耐受。将这两个相互关联的体内项目的具体目标与机制研究联系起来的基本原理是，我们现在有了工具来测试炎症反应与攻击性反应和记忆反应的平衡、T细胞调节和耐受诱导的相关性和相互关系。因此，应该有可能定义并系统地应用导致灵长类同种异体移植受者耐受的先天和获得性免疫反应的扰动。此外，该计划将导致从项目1和项目2发展出的最佳耐受性诱导方案的各方面的交叉受精和共享。 项目1：肾移植受者的新耐受策略(科西米，A.本尼迪克特) 项目1说明(申请人提供)：尽管通过使用新的免疫抑制剂改善了短期结果，但在过去十年中，移植肾的长期存活率并没有显著改善，这主要是由于慢性排斥反应，但也是由于感染和移植后的恶性肿瘤，所有这些都可归因于慢性免疫抑制。因此，诱导特异性移植耐受仍然是一个主要目标，这可能会消除常规免疫抑制治疗的大部分局限性。基于混合嵌合体方法，这是一种首次被证明是诱导小鼠同种异体移植耐受的有效方法，我们首次开发了一种临床相关的非清髓性制备方案，该方案允许在MHC完全不相合的食蟹猴骨髓移植(DBMT)后诱导混合嵌合体和肾移植耐受。最近，这项技术被临床应用于人类白细胞抗原相合和单倍型相合肾脏的受者。目前准备方案的一个缺点是要求在器官移植前6天开始进行条件调节，这使得它只适用于活体供体同种异体移植的受者，并且仅适用于预期的器官移植。该项目的主要目标是开发一种新的方案，即“延迟耐受”方案，以扩大混合嵌合体方法的临床适用性。在该方案中，受者最初将接受常规免疫抑制的肾移植(KTX)，然后在一段时间后接受非清髓性调节和DBMT。如果DBM在最初从已故捐赠者那里获得器官时被冷冻保存，该协议可能会将适用范围扩大到所有先前移植的同种异体移植的接受者，包括来自已故捐赠者的器官的接受者。这种方法可能被证明比我们目前的方法更有效，因为耐受性调节方案是在缺乏促炎细胞因子的情况下建立的，这些细胞因子可能会削弱移植围术期的耐受性诱导。另一方面，如果耐受诱导延迟，可以预测移植肾的存在可能导致对供者抗原的增敏，同时记忆T细胞激活增加。因此，为了建立“延迟耐受”方案，我们将明确：1)确定诱导耐受的最佳时机，使炎症反应最小，但记忆T细胞激活的可能性最小；2)评估克服记忆T细胞反应的方法；3)评估混合嵌合体方案中添加抗炎药的情况。将进行详细的机制研究，计划中的分析应为合理开发新的耐受策略提供临床相关信息，不仅适用于肾脏，也适用于所有同种异体移植受者。

DESCRIPTION (provided by applicant): Despite improvements in early post-transplant survival rates over the last two decades, a relentless annual attrition rate of 3-5 % in recipients of previously successful renal allografts continues to limit longer term outcomes. Long term outcomes with islet transplantation are simply unacceptable with only 10% of recipients remaining insulin free at five years. In islets metabolic exhaustion due to an inadequate islet cell mass may be an important impediment to long term graft function. Late allograft failure, resulting from chronic rejection, infection, drug toxicity, and malignancies emphasizes the limitations of chronically administered immunosuppression in kidney and islet transplantations. Therefore the ultimate goal of transplantation is to achieve long-term engraftment without maintenance immunosuppression. Pilot clinical tolerance protocols are currently being tested in humans, but there remain substantial barriers to achieving true tolerance in humans. The major objective of this Multi-Project grant is to improve the outcome following kidney and islet transplantation by defining the essential conditions for induction of durable tolerance to kidney and islet allografts, and defining the roles of inflammation and memory T cells in being major barriers to tolerance. Our central hypothesis is that the early pro-inflammatory responses due in large measure to ischemia-reperfusion and anoxic injury to the donor tissues incites adverse forms of anti-donor immunity, thereby provoking acute clinical or subclinical rejection and exaggerating the subsequent expansion of pre-existing donor reactive memory, and post transplant development of newly acquired donor reactive memory T cells. Thus, we hypothesize that an adverse balance of pro- to anti-inflammatory cytokines and anti-donor memory responses represent major obstacles to the induction and maintenance of tolerance. We propose novel and inter-related strategies to alter the balance of the alloimmune response to favor regulation and long-term tolerance taking into consideration the inflammatory- and memory-related barriers to tolerance in the context of islet and kidney transplantation. The rationale linking the specific aims of the two interrelated in vivo projects and the mechanistic studies is that we now have the tools to test the relevance and inter-relationship of inflammatory responses to the balance of aggressive and memory responses, T cell regulatory and tolerance induction. It, therefore, should be possible to define and systematically apply the perturbations of the innate and adaptive immune response that lead to tolerance in primate allograft recipients. Moreover, the Program will lead to cross-fertilization and sharing of facets of the best tolerance inducing regimens developing from Project 1 with those of Project 2. PROJECT 1: Novel Tolerance Strategy in Renal Allograft Recipients (Cosimi, A. Benedict) PROJECT 1 DESCRIPTION (provided by applicant): Despite improvement in short-term results through the use of new immunosuppressive agents, long-term allograft survival has not improved significantly over the past decade, due predominantly to chronic rejection but also to infection and post-transplant malignancies, all attributable to chronic immunosuppression. Therefore, induction of specific transplantation tolerance, which might eliminate most limitations of conventional immunosuppressive therapy remains a major goal. Based upon the mixed chimerism approach, which was first demonstrated to be an effective means of inducing allograft tolerance in mice, we first developed a clinically relevant non-myeloablative preparative regimen that permitted the induction of mixed chimerism and renal allograft tolerance following donor bone marrow transplantation (DBMT) in MHC fully mismatched cynomolgus monkeys. More recently, this was applied clinically to recipients of HLA-identical and haplo-type identical kidneys. A disadvantage of the current preparative regimen is the requirement for conditioning beginning 6 days prior to organ transplantation, making it applicable only for recipients of living donor allografts and only prospectively with respect to the organ transplant. The major goal of this project is to develop a novel regimen, the "Delayed Tolerance" protocol to extend the clinical applicability of the mixed chimerism approach. In this protocol, recipients would initially undergo kidney transplantation (KTx) with conventional immunosuppression and then receive non-myeloablative conditioning and DBMT sometime later. This protocol could potentially extend the applicability to all recipients of previously transplanted allografts, including recipients of organs from deceased donors, if DBM is cryopreserved at the time of initial organ procurement from the deceased donor. This approach could prove to be even more effective than our current approach, since the tolerance conditioning regimen is instituted in the absence of pro-inflammatory cytokines that may impair tolerance induction in the peritransplant period. On the other hand, if tolerance induction is delayed, it might be predicted that the presence of the renal allograft could result in sensitization to donor antigen with memory T cell activation increasing. Therefore, to establish the "Delayed Tolerance" protocol, we will specifically: 1) identify the optimal timing for tolerance induction with minimal inflammatory responses, yet least likelihood of memory T cell activation, 2) evaluate methods to overcome memory T cell responses and 3) evaluate the addition of anti-inflammatory agents to the mixed chimerism protocol. Detailed mechanistic studies will be performed and the analyses planned should provide clinically relevant information for rationally developing new tolerance strategies for not only kidney but also all allograft recipients.