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）是恶性血液病患者治愈性治疗的一项重大进展，其方案相关毒性显著降低。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。需要增强GVH反应和移植物抗白血病（GVL）效应的控制而没有GVH疾病（GVHD）的策略来预防或治疗同种异体HCT后的疾病复发。利用非清髓性方案建立的混合造血嵌合体犬模型，我们建议用基因修饰的供体淋巴细胞输注（DLI）增强GVH效应。经2戈伊全身照射、DLA相合同窝骨髓移植和移植后分别用霉酚酸酯（MMF）和环孢素联合免疫抑制4周和5周后，已可靠地建立了长期稳定的混合造血嵌合体。由于完全（100%）供体嵌合体是治疗血液系统恶性肿瘤患者所必需的，因此我们将在该犬模型中使用比宿主具有免疫优势的供体T细胞将混合供体嵌合体转化为完全供体嵌合体。供体T细胞将用慢病毒载体转导，所述慢病毒载体含有突变的肌苷一磷酸脱氢酶II（IMPDH*）基因，所述突变的肌苷一磷酸脱氢酶II（IMPDH*）基因使细胞对MMF具有抗性。我们将询问是否将IMPDH* 转导的供体T细胞输注到同时接受MMF治疗的稳定混合嵌合体犬中，将使混合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并阻止对IMPDH* 转基因的免疫应答，同时允许IMPDH* 转导的供体T细胞的GVH效应。如果狗发生GVHD，未来的研究将致力于用抗病毒药物更昔洛韦消除用IMPDH* 和单纯疱疹胸苷激酶基因转导的供体T细胞。如果成功，这项研究可以转化为改善GVH反应的控制和改善同种异体HCT后的生存率。

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.