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，我对用于常规造血干细胞移植(HSCT)的调理方案的毒性印象深刻。非消融性条件作用的最新发展降低了与HSCT相关的毒性，允许治疗老年患者和合并HSCT的患者，这些患者本来不符合常规HSCT的条件。大多数非消融性调节方案都包含辐射，这被认为是防止移植物排斥反应所必需的。然而，低剂量的辐射会增加晚期恶性肿瘤的风险，对于接受非恶性疾病(如镰状细胞病、免疫缺陷)治疗的患者和患有恶性疾病的儿科患者来说，避免这些晚期毒性是非常可取的。我们推测，可以开发其他毒性较低的制备策略，以进一步减少照射剂量，同时确保稳定的供者造血细胞植入。从理论上讲，这可以通过a)提高受者的免疫“能见度”，从而提高移植物抗宿主和移植物抗肿瘤的活性，和/或b)降低供者的免疫“能见度”，从而减少导致排斥反应的供者导向的免疫反应来实现。 在狗白细胞抗原相合的小鼠HSCT模型中，与人类患者一样，当辐射剂量为200cGy时，如果联合使用有效的移植后免疫抑制，可以实现长期稳定的植入。然而，在初步的犬类研究中，50 cGY的照射剂量与环孢素联合使用5周，仅导致短暂的供体-宿主混合嵌合体。我们建议以这些初步研究为基线来制定策略，以在该模型中实现稳定的植骨。在具体目标1中，宿主树突状细胞(DC)将在移植前使用FIT-3配体进行扩增，以增强宿主定向的免疫反应，从而更有效地根除受体体内的移植排斥介导性T细胞。DC扩张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者特异性耐受。这些策略包括阻断CD28/B7、CD40/CD154和CD27/CD70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药物甲氨蝶呤，以触发供体反应性T细胞的激活诱导细胞死亡。然后，将在具体目标3中结合有效的战略，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，这些方案不依赖于受者的一般免疫抑制，而是专门针对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.