ENGRAFTING SENSITIZED HOSTS WITH NONABLATIVE REGIMENS

移植已经建立在非致敏的主要组织相容性复合体（MHC）匹配的受体与非清髓调节方案。先前输注过血液制品的受者对供体次要组织相容性抗原变得敏感，增加了移植物排斥反应的风险。患有遗传性红细胞疾病的患者需要输血，并且移植物排斥反应的可能性更高。在本提案中，将为致敏受体开发非清髓调节方案，其1)缺乏清髓方案的毒性特征，2)可以在门诊环境中安全使用。致敏患者的非清髓方案的发展将基于两个假设：1)致敏受体的宿主抗移植物（HVG）反应可以通过免疫抑制剂而不是大剂量放化疗来抑制；2)移植物T细胞可抑制宿主免疫系统，包括致敏免疫效应细胞。这些假设将被检验，非清髓性方案将在临床前犬输血致敏模型中开发。在移植前对受者输血致敏可导致常规高剂量条件下的均匀移植排斥反应。在Aim 1中，在TBI的剂量递减研究中，将确定除CSP外，移植前免疫抑制的进一步逐步增强是否会成功促进植入。移植后免疫抑制（MMF/CSP）将单独评估，以确定其是否能预防TBI 920cgy致敏受体的移植排斥反应。如果有效，移植后免疫抑制将在最大TBI剂量下加强，在Aim 1A完成时发生移植物排斥反应。在Aim 2中，将确定促进GVH是否通过抑制致敏宿主T细胞和在骨髓中“创造空间”来实现植入。如果这些研究取得成功，那么供体T细胞将在体外扩增并用“自杀（HSVtk）基因”进行转导，以预防严重的GVHD。在Aim 3中，最佳的免疫抑制方案将与GVH增强方案相结合。这项建议的最终目标是从调理方案中消除细胞毒素。通过降低与常规条件相关的发病率和死亡率，这些研究可以显著改变选定的遗传性红细胞疾病的管理。

Engraftment has been established in nonsensitized major histocompatibility complex (MHC)-matched recipients with nonmyeloablative conditioning regimens. Recipients previously transfused with blood products become sensitized to donor minor histocompatibility antigens, increasing the risk of graft rejection. Patients with inherited red blood cell diseases require blood transfusions and have a higher probability of graft rejection. In this proposal, nonmyeloablative conditioning regimens will be developed for sensitized recipients which 1) lack the toxicities characteristic of myeloablative regimens, and 2) could be safely administered in an outpatient setting. The development of the nonmyeloablative regimen for sensitized patients will be based on two hypotheses: 1) host-versus-graft (HVG) reactions of sensitized recipients can be suppressed with immunosuppressive agents other than high-dose chemoradiotherapy; 2) T cells from the graft can suppress the host immune system including sensitized immune effector cells. These hypotheses will be tested and nonmyeloablative regimens will be developed in a preclinical canine model of transfusion-induced sensitization. Sensitizing recipients with blood transfusions prior to transplant results in uniform graft rejection with conventional high-dose conditioning. In Aim 1, it will be determined if further stepwise intensification of pretransplant immunosuppression in addition to CSP will successfully promote engraftment in a dose de-escalation study of TBI. Posttransplant immunosuppression (MMF/CSP) will be assessed separately to determine if it prevents graft rejection in sensitized recipients at TBI 920 cGy. If effective, intensification of posttransplant immunosuppression will be done at the maximal TBI dose at which graft rejection occurs at the completion of Aim 1A. In Aim 2, it will be determined if promoting GVH will achieve engraftment by suppressing sensitized host T cells and "creating space" in the marrow. If these studies are successful, then donor T cells will be ex vivo expanded and transduced with a "suicide (HSVtk) gene" for prevention of severe GVHD. In Aim 3, the optimal immunosuppressive regimen will be combined with a GVH enhancing regimen. The ultimate goal of this proposal is the elimination of cytotoxic agents from the conditioning regimen. By lessening the morbidity and mortality associated with conventional conditioning, these studies could significantly change the management of selected inherited red blood cell diseases.