Optimizing Mixed-Chimerism for Heart Transplantation in Non-Human Primates

这个为期两年的项目的目的是通过阐明通过混合嵌合体方法诱导供体特异性耐受的机制来改善心脏移植后的结局。在我们的实验室中，已经使用非清髓性预处理和供体骨髓移植（DBMT）的组合实现了非人灵长类动物（NHP）肾同种异体移植的耐受性，这导致了短暂的混合造血嵌合体。基于这些开创性的观察，类似的方案已经在活体亲属肾移植的人类受体中进行了测试，并已被证明是成功的。然而，尽管这一成就是戏剧性的，但它利用了一种治疗方案，其目前的成功仅限于活体供体移植（预处理从第-6天开始）。显然，需要在活体供体肾脏已经取得的令人印象深刻的成功的基础上，优化混合嵌合体策略，使其能够更广泛地应用于尸体供体器官，如心脏。最近，我们在我们的NHP肾移植模型中开发了一种新的方案，即“延迟耐受”方案，该方案可以扩展混合嵌合体方法的临床适用性。在该方案中，受者首先接受常规免疫抑制移植，然后接受非清髓性预处理和DBMT。本项目的目标是开发延迟耐受方案，使用新的药物和新的策略来诱导心脏移植物的耐受。我们将检验这一假设，即通过促进THP或实现更持久的多系供体嵌合体来增强外周耐受机制将导致NHP心脏同种异体移植物的长期耐受。在为期两年的研究中，我们将特别： (1)开发一种适用于人类心脏移植受者的延迟耐受诱导混合嵌合体方案;（2）评价TCFs在促进心脏长期耐受中的作用，尽管延迟耐受方案诱导的混合嵌合体是短暂的。事实上，这种方法可以被证明比我们的标准（非延迟）方案更有效，因为耐受性调节方案将在不存在促炎细胞因子的情况下建立，这些促炎细胞因子在移植前后始终存在。将进行的详细机制研究和计划的分析应该为设计后续研究提供相关信息，这些研究将合理地扩展这一最新临床创新的适用性，以增加移植受者的数量。

The objective of this two-year project is to improve the outcome following heart transplantation by clarifying the mechanisms involved with the induction of donor-specific tolerance via the mixed chimerism approach. Tolerance of kidney allografts in non-human primates (NHPs) has already been achieved in our laboratories using a combination of non-myeloablative conditioning and donor bone marrow transplantation (DBMT) that results in transient mixed hematopoietic chimerism. Based upon these seminal observations, a similar protocol has been tested in human recipients of living related renal allografts and has proven successful. Dramatic as this achievement is, however, it utilizes a therapeutic protocol whose current success is limited to living donor transplantation (conditioning begins on day -6). There is an obvious need to build upon the impressive successes already achieved with living donor kidneys and optimize the mixed chimerism strategy so that it can be applied more widely to cadaveric donor organs like hearts. Recently, we have developed, in our NHP renal allograft model, a novel regimen, the "Delayed Tolerance" protocol which can extend the clinical applicability of the mixed chimerism approach. In this protocol, recipients initially undergo transplantation with conventional immunosuppression and then receive non-myeloablative conditioning and DBMT sometime later. The goal of this project is to develop the Delayed Tolerance regimen using new agents and novel strategies to induce tolerance of cardiac allografts. We will test the hypothesis that either enhancing peripheral mechanisms of tolerance by promoting Tregs or achieving more durable multilineage donor chimerism will result in long-term tolerance of cardiac allografts in NHPs. During the 2-year study we will specifically: (1) Develop a mixed chimerism protocol of Delayed Tolerance induction applicable to human heart transplant recipients, and, (2) Evaluate the role of Tregs in contributing to long-term tolerance of hearts despite the transience of the mixed chimerism induced by the Delayed Tolerance protocol. In fact, this approach could prove to be even more effective than our standard (non-delayed) protocol, since the tolerance conditioning regimen would be instituted in the absence of the proinflammatory cytokines that are invariably present during the peri-transplant period. The detailed mechanistic studies that will be performed and the analyses planned should provide relevant information for designing subsequent studies that will rationally extend the applicability of this recent clinical innovation to increasing numbers of transplant recipients.