Optimizing Nonmyeloablative Stem Cell Transportation

描述（由申请人提供）： 作为弗雷德哈钦森癌症研究中心的一名医学肿瘤学研究员，我对常规造血干细胞移植（HSCT）中使用的预处理方案的毒性印象深刻。非消融性预处理的最新发展降低了HSCT相关毒性，允许治疗老年患者和患有合并症的患者，这些患者不符合常规HSCT的条件。大多数非消融性预处理方案都包含照射，这被认为是防止移植排斥反应所需的。然而，低剂量的辐射与晚期恶性肿瘤的风险增加相关，并且对于治疗非恶性疾病（例如镰状细胞病、免疫缺陷）的患者和患有恶性疾病的儿科患者，避免这些晚期毒性将是高度期望的。我们假设，可以开发其他毒性较小的制备策略，以进一步降低辐射剂量，同时确保稳定的供体造血细胞植入。理论上，这可以通过a）增加受体的免疫学“可见性”，导致增加的移植物抗宿主和移植物抗肿瘤活性，和/或B）降低供体的免疫学“可见性”，导致降低的导致排斥的供体定向免疫反应来实现。 在犬白细胞抗原相同的同窝HSCT模型中，与人类患者一样，当与有效的移植后免疫抑制剂联合使用时，200 cGy的辐照剂量可以实现长期稳定的植入。然而，在初步的犬研究中，50 cGy的辐射剂量与环孢素一起使用5周仅导致短暂的混合供体-宿主嵌合体。我们建议使用这些初步研究作为基线，以制定策略，以实现稳定的植入在这个模型。在特定目标1中，在移植前使用FIT-3-配体扩增宿主树突状细胞（DC）以增强宿主定向免疫应答，从而更有效地根除受体中的移植物排斥介导的T细胞。然后DC扩增和功能将与植入相关。在特定目标2中，将通过测试4种策略在该模型中诱导供体特异性耐受。这些策略包括阻断CD 28/B7、CD 40/CD 154和CD 27/CD 70共刺激通路，以及将宿主T细胞依次暴露于供体特异性抗原和抗代谢物甲氨蝶呤，以触发供体反应性T细胞中活化诱导的细胞死亡。有效的战略将在具体目标3中结合起来，以实现协同效应。这些研究的结果将有助于设计无毒的移植方案，不依赖于受体的一般免疫抑制，而是特异性靶向介导移植物排斥和移植物抗宿主病的免疫过程。

DESCRIPTION (provided by applicant): As a Medical Oncology fellow at the Fred Hutchinson Cancer Research Center I have been impressed by the toxicities associated with conditioning regimens used for conventional hematopoietic stem cell transplantation (HSCT). The recent development of nonablative conditioning has lowered HSCT-associated toxicities allowing for treatment of older patients and of patients with comorbidities, who would not have been eligible for conventional HSCT. Most nonablative conditioning regimens contain irradiation, which is thought to be required to prevent graft rejection. However, low doses of irradiation are associated with increased risks of late malignancies, and avoiding these late toxicities would be highly desirable for patients treated for non-malignant diseases (e.g. sickle cell disease, immunodeficiencies) and pediatric patients with malignant diseases. We hypothesize that other less toxic preparative strategies can be developed to further reduce the irradiation dose yet ensure stable donor hematopoietic cell engraftment. In theory, this can be achieved by a) increasing the recipient's immunologic "visibility" resulting in increased graft-versus-host and graft-versus-tumor activities, and/or b) decreasing the donor's immunologic "visibility" resulting in decreased donor-directed immune reactions that cause rejection. In the dog leukocyte antigen identical littermate HSCT model, as in human patients, long-term stable engraftment can be achieved with irradiation doses of 200 cGy when used in conjunction with potent post-grafting immunosuppression. In preliminary canine studies, however, irradiation doses of 50 cGy used with cyclosporine given for 5 weeks resulted in only transient mixed donor-host chimerism. We propose to use these preliminary studies as a baseline to develop strategies to achieve stable engraftment in this model. In Specific Aim 1, host dendritic cells (DC) will be expanded before transplant using FIt-3-ligand to enhance host-directed immune responses for more efficient eradication of graft-rejection-mediating T cells in the recipient. DC-expansion and function will then be correlated with engraftment. In Specific Aim 2, donor-specific tolerance will be induced in this model by testing 4 strategies. These strategies include blockade of the CD28/B7, CD40/CD154, and CD27/CD70 costimulatory pathways, and sequential exposure of host T cells to donor-specific antigen and the antimetabolite methotrexate to trigger activation-induced cell death in donor-reactive T cells. Effective strategies will then be combined in Specific Aim 3 to achieve synergistic effects. The results of these studies will help devise non-toxic transplant regimens that do not rely on general immunosuppression of the recipient, but rather specifically target immune processes that mediate graft-rejection and graft-versus-host disease.