Robust allograft tolerance in non-human primates

 描述(由申请人提供)：器官和组织移植的成功受到长期免疫抑制治疗和晚期移植排斥反应的副作用的限制，尽管全球免疫抑制仍会发生。同种异体移植耐受将在防止排斥的同时消除长期免疫抑制治疗的需要。在非人类灵长类动物(NHP)和患者中，通过联合肾和骨髓移植(CKBMT)，已经获得了“混合嵌合体”可以导致器官移植跨越MHC障碍的原理证据。然而，在NHP中，混合嵌合体只是暂时的，对其他器官如胰岛、肝、心或肺的移植物没有耐受性。对小鼠的研究表明，持久的混合嵌合体与强大的系统耐受性有关，这种耐受性允许最具挑战性的同种异体移植物存活。因此，需要可靠的方法来实现持久的混合嵌合体，而不需要GVHD，这是人类造血细胞移植(HCT)的主要并发症，以促进混合嵌合体的使用，实现对所有类型的器官和组织移植的耐受。我们已经获得的初步证据表明，在接受完全没有GVHD的低毒、非清髓性BMT方案的NHP中，在供者骨髓输注中加入扩增的受体调节性T细胞(Tregs)可以产生比单独使用BMT更持久的混合嵌合体和更强大的耐受性。我们现在的目标是：1)开发一种结合非清髓性预适应、输注扩增的受体Tregs和移植后一过性免疫抑制的最佳方案，以诱导食蟹猴持久的混合同种异体嵌合体。我们将改善观察到的延长的、高水平的嵌合体，在使用骨髓移植后28天的雷帕霉素的方案中添加扩大的受体Tregs。我们将尝试通过延迟骨髓输注来减少ATG对干细胞的有害影响，并通过加强最初的免疫抑制来提高供者造血干细胞(HSC)的存活率。然后我们将确定获得持久嵌合体所需的最小Treg剂量。骨髓移植后4个月移植的供体皮肤将作为耐受性的可靠测试；2)评估在AIM 1中制备的耐久混合嵌合体中Tregs的持久性和耐受机制。将评估调节机制和缺失在维持耐受性中的作用。在无GVHD的非清髓性条件作用下，在NHP模型中安全可靠地实现跨越MHC障碍的持久混合嵌合体的能力将是一个重大突破。这些研究的成功将使人类对所有类型的器官和组织移植获得耐受性，并将增加HCT治疗非恶性遗传性血液疾病和自身免疫性疾病的安全性，这些疾病可以通过持久的混合嵌合体状态来纠正。

 DESCRIPTION (provided by applicant): Success of organ and tissue transplantation is limited by side effects of long-term immunosuppressive therapy and late graft rejection, which occurs despite global immunosuppression. Allograft tolerance would obviate the need for long-term immunosuppressive therapy while preventing rejection. Proof of principle that "mixed chimerism" can lead to organ allograft tolerance across MHC barriers in non-human primates (NHPs) and patients has been obtained using combined kidney and bone marrow transplantation (CKBMT). However, mixed chimerism was only transient and tolerance was not been achieved to other organs such as islet, liver, heart or lung allografts with this transient chimerism approach in NHPs. Studies in mice indicate that durable mixed chimerism is associated with robust, systemic tolerance that permits survival of the most challenging allografts. Thus, reliable methods of achieving durable mixed chimerism without GVHD, the major complication of hematopoietic cell transplantation (HCT) in humans, are needed to advance the use of mixed chimerism to achieve tolerance for all types of organ and tissue allografts. We have obtained preliminary evidence that the addition of expanded recipient regulatory T cells (Tregs) to donor bone marrow infusion results in more durable mixed chimerism and more robust tolerance than is induced by BMT alone in NHPs receiving a low-toxicity, non-myeloablative BMT regimen that has been completely free of GVHD. We now aim to: 1) Develop an optimal regimen combining non-myeloablative conditioning, infusion of expanded recipient Tregs and transient post-transplant immunosuppression for the induction of durable mixed allogeneic chimerism in cynomolgus monkeys. We will improve upon the prolonged, high level chimerism observed with the addition of expanded recipient Tregs to a protocol using 28 days of post-BMT rapamycin. We will attempt to enhance donor hematopoietic stem cell (HSC) survival by delaying BM infusions to minimize deleterious effects of ATG on stem cells and by enhancing initial immunosuppression. We will then identify the minimal Treg dose required to achieve durable chimerism. Donor skin grafted 4 months post- BMT will be used as a robust test of tolerance; 2) Assess the persistence of Tregs and mechanisms of tolerance in durable mixed chimeras prepared in AIM 1. The roles of regulatory mechanisms and deletion in maintaining tolerance will be assessed. The ability to safely and reliably achieve durable mixed chimerism across MHC barriers with non-myeloablative conditioning, without GVHD, in a NHP model will be a major breakthrough. Success of these studies will allow the achievement of tolerance to all types of organ and tissue allografts in humans and will increase the safety of HCT for the treatment of non-malignant inherited hematological disorders and autoimmune diseases that are correctable by a state of durable mixed chimerism.