Immunosupression-Resistant Gene Modified Donor T Cells

描述（由申请人提供）：同种异体造血细胞移植（HCT）是一种癌症免疫治疗形式，依靠供体T细胞促进移植并诱导有益的移植物抗白血病效应。然而，同种异体反应性供体T细胞也可引起致命的移植物抗宿主病（GVHD）。对带有“自杀”基因——单纯疱疹病毒胸苷激酶（HSV-tk）的供体T细胞进行基因修饰，有可能通过用更昔洛韦杀死引起gvhd的同种异体HCT的同种异体反应性T细胞，从而显著提高同种异体HCT的安全性。迄今为止，在同种异体HCT后输注HSV-tk修饰的供体T细胞的临床研究显示其体内功能非常有限。我们提出了一种新的策略来支持转基因T细胞在异体HCT动物模型中的体内免疫功能。假设是慢病毒转导带有免疫抑制耐药基因的供体T细胞，使其比宿主免疫细胞具有选择性增殖优势，可以显著改善基因修饰T细胞的体内功能。我们将评估一种表达HSV-tk和显性突变肌苷单磷酸脱氢酶II （IMPDH*）基因的双链慢病毒载体，该载体使转导的T细胞对更昔洛韦敏感，对免疫抑制药物霉酚酸酯（MMF）耐药。利用mhc错配的狗HCT模型，我们将测试mmf耐药供体T细胞在全身照射（TBI）后促进T细胞耗尽（TCD）供体骨髓移植的体内功能。在输注IMPDH*转导的供体T细胞后用MMF治疗受体，会抑制对基因修饰T细胞的免疫反应，并使转导的T细胞具有增殖优势。这种方法允许mmf抵抗供体T细胞的移植物抗宿主功能，同时抑制宿主抗移植物反应。目的1将研究IMPDH*转导的供体T细胞在清髓性TBI后促进移植的体内有效性。患有GVHD的狗将接受更昔洛韦治疗。Aim 2将通过移植后环孢素和MMF联合治疗以及MMF和环孢素耐药T细胞的输注来减少移植TCD骨髓所需的TBI剂量。植入后给予更昔洛韦控制GVHD。本项目的主题是应用免疫抑制耐药的基因治疗策略来操纵HCT后的免疫功能，以有利于供体免疫细胞。这些研究的结果具有直接转化为未来基因治疗临床试验的强大潜力。

DESCRIPTION (provided by applicant): Allogeneic hematopoietic cell transplantation (HCT) is a form of cancer immunotherapy that relies on donor T cells to facilitate engraftment and induce the beneficial the graft-versus-leukemia effect. However, alloreactive donor T cells can also cause fatal graft-versus-host disease (GVHD). Genetic modification of donor T cells with a "suicide" gene, herpes simplex virus thymidine kinase (HSV-tk), has the potential to significantly improve the safety of allogeneic HCT by killing the alloreactive, GVHD-causing T cells with ganciclovir. To date, clinical studies of HSV-tk modified donor T cells infused after allogeneic HCT have shown very limited in vivo function. We propose a novel strategy to favor the in vivo immune function of genetically modified T cells in a large animal model of allogeneic HCT. The hypothesis is that lentiviral transduction of donor T cells with an immunosuppression drug-resistance gene conferring a selective proliferative advantage over host immune cells can significantly improve the in vivo function of the gene-modified T cells. We will evaluate a bicistronic lentiviral vector expressing HSV-tk and a dominant mutant inosine monophosphate dehydrogenase II (IMPDH*) gene, which renders transduced T cells sensitive to ganciclovir and resistant to the immunosuppressive drug mycophenolate mofetil (MMF). Using the dog model of MHC-mismatched HCT, we will test the in vivo function of MMF-resistant donor T cells to facilitate engraftment of T-cell-depleted (TCD) donor marrow after total body irradiation (TBI). Treatment of recipients with MMF after infusion of IMPDH* transduced donor T-cells would inhibit immune responses to the gene modified T cells and give a proliferative advantage to the transduced T cells. This approach allows the graft-versus-host function of the MMF-resistant donor T cells while suppressing the host-versus-graft response. Aim 1 will study the in vivo effectiveness of the IMPDH* transduced donor T cells to facilitate engraftment after myeloablative TBI. Dogs with GVHD will be treated with ganciclovir. Aim 2 will decrease the TBI dose needed to engraft TCD marrow by treating with a combination postgrafting cyclosporine and MMF and infusion of MMF- and cyclosporine-resistant T cells. After engraftment, ganciclovir will be given to control GVHD. The theme of this project is to apply a gene therapy strategy of immunosuppressive drug resistance to manipulate the immune function in favor of donor immune cells after HCT. Results from these studies have the strong potential to be directly translated to future gene therapy clinical trials.