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)可以通过用健康细胞替换有缺陷的血细胞来治愈遗传性血液疾病。然而，危及生命的并发症限制了HCT治疗在临床上的使用。受体的并发症是由毒性条件反射和移植物抗宿主病(GVHD)引起的，移植物抗宿主病是供者T细胞攻击受体(宿主)组织的一种情况。完全、长期耗尽供体和宿主T细胞允许在啮齿类动物中使用降低强度的条件作用稳定地植入供体细胞，而不会发生移植物抗宿主病。然而，人类T细胞的完全耗尽是很难实现的，感染、造血衰竭和移植物抗宿主病仍然是临床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后会出现严重的移植物抗宿主病、感染性并发症或造血衰竭。研究人员最近开发了一种新的、温和的HCT临床前方案，允许供体细胞在没有GVHD的情况下植入。事实上，通过低剂量全身照射、部分T细胞耗尽和短程环孢素A治疗小型猪，尽管输注了非常高剂量的T细胞半相合(例如，亲子)HCT，但仍可靠地建立了没有GVHD的供体HC移植。令人惊讶的是，供者白细胞输注(DLI)的额外治疗并没有导致完全的(供者)造血替换。DLI是一种已知的程序，可以确保植入啮齿动物的HC完全替代。研究人员推测，供体和受体T细胞在治疗后持续存在，促进了HC的植入，抑制了GVHD，但也阻碍了DLI的转化效应。事实上，初步数据表明，在接受治疗的动物中，调节细胞持续存在，并抑制GVHD和DLI同种异体反应。因此，本项目的目标是阐明促进非移植物抗宿主病植入的免疫学机制，并测试恢复猪DLI转换效果的新策略。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细胞来促进植入并抑制GVHD和DLI效应。这一假说将通过以下特定目的进行验证：1)阐明HCT后体内GVH和HVG同种反应性T细胞的免疫学机制；2)通过特定的免疫调节，恢复DLI在无GVHD的情况下提高供者植入水平的能力。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来促进更好的植入和更少的并发症的HCT方法。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性疾病提供治疗，包括血红蛋白病、溶酶体储存疾病、遗传性再生障碍性贫血和原发免疫缺陷疾病。如果这项应用的目标得以实现，这些结果可能会对临床HCT方法产生重大影响。 相关性：目前，与造血细胞移植(HCT)相关的毒性和并发症限制了遗传性血液疾病的临床治疗。这项应用的目的是了解促进高水平单倍体相合(例如，亲子相合)的供者造血细胞移植而没有并发症的免疫学机制。这些研究的长期目标是翻译有希望的无毒红细胞移植方案，使用父母捐赠者来替换患病的血细胞，并治愈儿童的遗传性血液疾病。

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.