Gene Modified Donor T Cell Infusion into Mixed Chimeras

描述(由申请人提供)： 非清髓性异基因造血细胞移植(HCT)是治疗恶性血液病的一项重大进展，与化疗方案相关的毒性显著降低。然而，疾病复发仍然是一个重大问题。非清髓性异基因HCT依赖于T细胞介导的移植物抗宿主(GVH)反应来消除潜在的血液病。为了预防或治疗异基因HCT后的疾病复发，需要加强对GVH反应和移植物抗白血病(GVL)效应的控制而不发生GVH病(GVHD)。利用非清髓方案建立的犬混合造血嵌合体模型，我们提出用基因修饰供者淋巴细胞输注(DLI)来增强GVH效应。2Gy全身照射、DLA相合的小鼠骨髓移植、联合应用霉酚酸酯(MMF)和环孢素A的移植后免疫抑制分别在移植后4周和5周可靠地建立了长期、稳定的混合造血嵌合体。由于完全(100%)供体嵌合是治疗恶性血液病患者所必需的，我们将在这个犬模型中将混合供体嵌合转换为完全供体嵌合，供体T细胞具有相对于宿主具有免疫学优势的供体T细胞。供体T细胞将被慢病毒载体转导，该载体含有突变的肌苷单磷酸脱氢酶II(IMPDH*)基因，使细胞对MMF产生抗药性。我们将询问，将IMPDH*转导的供体T细胞输入稳定的混合嵌合体犬，同时接受MMF治疗，是否会将混合供体嵌合体转化为完全供体嵌合体。我们假设MMF将选择性地抑制宿主，阻止对IMPDH*转基因的免疫反应，同时允许IMPDH*转导的供体T细胞的GVH效应。如果狗患上GVHD，未来的研究将致力于用抗病毒药物更昔洛韦去除转导了IMPDH*和单纯疱疹病毒胸苷激酶基因的供体T细胞。如果成功，这项研究可能转化为改善对GVH反应的控制，并提高异基因HCT后的存活率。

DESCRIPTION (provided by applicant): Nonmyeloablative allogeneic hematopoietic cell transplantation (HCT) is a major advance in the curative treatment of patients with hematologic malignancies, with significantly decreased regimen-related toxicity. However, disease relapse remains a substantial problem. Nonmyeloablative allogeneic HCT relies on the T cell mediated graft-versus-host (GVH) reaction for elimination of the underlying hematologic disease. Strategies to enhance the control of the GVH reaction and the graft-versus-leukemia (GVL) effect without GVH disease (GVHD) are needed to prevent or treat disease relapse following allogeneic HCT. Using the dog model of mixed hematopoietic chimerism established with a nonmyeloablative regimen, we propose to enhance the GVH-effect with gene modified donor lymphocyte infusion (DLI). Long-term, stable mixed hematopoietic chimerism has been reliably established following 2 Gy total body irradiation, transplantation of DLA-identical littermate marrow and postgrafting immuncsuppression with combined mycophenolate mofetil (MMF) and cyclosporine for 4 and 5 weeks after transplant, respectively. Since complete (100%) donor chimerism is necessary to treat patients with hematologic malignancies, we will convert mixed to complete donor chimerism in this dog model with donor T cells that have an immunologic advantage over the host. Donor T-cells will be transduced with a lentiviral vector containing a mutant inosine monophosphate dehydrogenase II (IMPDH*) gene that renders cells resistant to MMF. We will ask if IMPDH* transduced donor T-cells infused into stable mixed chimeric dogs treated concurrently with MMF will convert mixed to complete donor chimerism. We hypothesize that MMF will selectively suppress the host and prevent an immune response to the IMPDH* transgene while permitting the GVH-effect of IMPDH* transduced donor T-cells. If dogs develop GVHD, future studies will aim to ablate donor T-cells transduced with IMPDH* and the herpes simplex thymidine kinase gene with the antiviral drug ganciclovir. If successful, this study could translate into improved control of the GVH reaction and improved survival after allogeneic HCT.