Elucidating the role of T-regs in engraftment, GVHD, and DLI immunotherapy

描述（申请人提供）：造血细胞移植（HCT）通过健康细胞替代有缺陷的血细胞，治愈遗传性血液疾病。然而，危及生命的并发症限制了HCT治疗在临床上的应用。受体的并发症是由毒性条件和移植物抗宿主病（GVHD）引起的，GVHD是供体t细胞攻击受体（宿主）组织的一种情况。供体和宿主T细胞的完全、长期耗竭，允许在啮齿类动物中使用低强度条件稳定地植入供体细胞，而不会发生GVHD。然而，人类很难实现完全的T细胞耗竭，感染、造血功能衰竭和GVHD仍然是临床HCT的主要并发症。与人类的结果相似，小型猪在标准的临床清髓条件和HCT后会出现严重的GVHD，感染并发症或血阿片功能衰竭。研究人员最近开发了一种新的、温和的临床前HCT方案，允许供体细胞在没有GVHD的情况下移植。事实上，对小型猪进行低剂量的全身照射、部分t细胞消耗和短疗程的环孢素a治疗，尽管输注了非常高剂量的充满t细胞的单倍同型（例如，亲子间）HCT，但可靠地建立了没有GVHD的供体HC移植。令人惊讶的是，供体白细胞输注（DLI）的额外治疗，一种已知的确保移植啮齿动物HC完全替代的程序，并没有导致完全（供体）造血替代。研究人员推测，供体和受体T细胞在治疗猪体内的持续存在促进了HC的植入，抑制了GVHD，但也阻碍了DLI的转化作用。事实上，初步数据表明，调节细胞在治疗动物体内持续存在，并抑制GVHD和DLI的同种异体反应性。因此，本项目的目标是阐明在没有GVHD的情况下促进移植的免疫学机制，并测试恢复猪DLI转化效应的新策略。研究人员假设，调节细胞参与的免疫调节通过灭活供体、受体和DLI同种异体反应性t细胞来促进移植物移植物，抑制GVHD和DLI效应。这一假设将通过以下具体目标进行验证：1)阐明HCT后体内控制GVH和HVG同种异体反应性T细胞的免疫机制；2)通过特异性免疫调节，恢复DLI在没有GVHD的情况下提高供体移植水平的能力。这个项目的创新之处在于，它研究了利用免疫系统的免疫调节能力而不是免疫消融的HCT方法，以促进更好的植入和更少的并发症。这些研究的长期目标是将有希望的亲子HCT和DLI方案转化为临床。成功的翻译将为许多可筛查的遗传疾病提供治疗，包括血红蛋白病、溶酶体贮积病、遗传性再生障碍性贫血和原发性免疫缺陷疾病。如果这项应用的目的得以实现，这些结果将对临床HCT方法产生重大影响。

DESCRIPTION (provided by applicant): Hematopoietic cell transplantation (HCT) can cure genetic blood disorders through the replacement of defective blood cells by healthy cells. However, life-threatening complications limit the use of HCT therapy in the clinic. Complications in the recipient result from toxic conditioning and from graft-versus-host disease (GVHD), a condition where the donor T-cells attack the recipient (host) tissues. Complete, prolonged depletion of both donor and host T cells permits stable engraftment of donor cells using reduced-intensity conditioning in rodents, without GVHD. However, complete T cell depletion is difficult to achieve in humans and infections, hematopoietic failure, and GVHD remain major complications of clinical HCT. Similar to outcomes in humans, miniature swine develop severe GVHD, infectious complications, or hematopioetic failure following standard clinical myeloablative conditioning and HCT. The investigators recently developed a novel, mild, preclinical protocol for HCT which permits donor cells to engraft without GVHD. Indeed, the treatment of miniature swine with a low-dose of total body irradiation, partial T-cell depletion, and a short course of cyclosporine A has reliably established donor HC engraftment without GVHD despite infusion of a very high dose of T-cell replete haploidentical (e.g., parent-into-child) HCT. Surprisingly, additional treatment with donor leukocyte infusion (DLI), a procedure known to ensure full replacement of HC in engrafted rodents, did not result in full (donor) hematopoietic replacement. The investigators surmise that the persistence of donor and recipient T cells in treated pigs promotes HC engraftment, inhibits GVHD, but also hinders the DLI conversion effect. Indeed, preliminary data suggest that regulatory cells persist in treated animals and inhibit both GVHD and DLI alloreactivity. Thus, the goal of this project is to elucidate the immunological mechanisms responsible for facilitating engraftment without GVHD, and to test new strategies to restore the DLI conversion effect in swine. The investigators hypothesize that immune modulation with regulatory cell involvement promotes engraftment and inhibits GVHD and DLI effects by inactivating donor, recipient, and DLI alloreactive T-cells. This hypothesis will be tested by the following specific aims, to: 1) elucidate the immunological mechanisms controlling GVH and HVG alloreactive T cells in vivo following HCT; and 2) restore the ability of DLI to enhance donor engraftment levels without GVHD through specific immune modulation. This project is innovative in that it investigates approaches for HCT that harness the immunomodulatory capacities of the immune system, rather than immune ablation, to promote better engraftment with fewer complications. The long-term goal of these studies is to translate promising protocols for parent-into-child HCT and DLI to the clinic. Successful translation would provide a cure for many screenable genetic disorders including hemoglobinopathies, lysosomal storage diseases, inherited aplastic anemias, and primary immunodeficiency diseases. If the aims of this application are achieved, these results could have a major impact on clinical HCT approaches. RELEVANCE: Toxicities and complications associated with hematopoietic cell transplantation (HCT) currently limit this curative therapy for genetic blood disorders in the clinic. The goal of this application is to understand the immunological mechanisms responsible for facilitating high-level haploidentical (e.g., parent into child) donor hematopoietic cell engraftment without complications. The long-term goal of these studies is to translate promising nontoxic HCT protocols using parental donors to replace diseased blood cells and cure genetic blood disorders in children.