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）是一种癌症免疫疗法，依赖于供体T细胞促进植入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）。用“自杀”基因，单纯疱疹病毒胸苷激酶（HSV-tk），对供体T细胞进行遗传修饰，有可能通过用更昔洛韦杀死同种异体反应性的、引起GVHD的T细胞，显著提高同种异体HCT的安全性。迄今为止，HSV-tk修饰的供体T细胞在同种异体HCT后输注的临床研究已经显示出非常有限的体内功能。我们提出了一种新的策略，有利于在体内免疫功能的基因修饰的T细胞在一个大型动物模型的同种异体HCT。该假说是，用免疫抑制药物抗性基因对供体T细胞进行慢病毒转导，赋予其相对于宿主免疫细胞的选择性增殖优势，可以显著改善基因修饰的T细胞的体内功能。我们将评估表达HSV-tk和显性突变肌苷酸脱氢酶II（IMPDH*）基因的双顺反子慢病毒载体，该基因使转导的T细胞对更昔洛韦敏感并对免疫抑制药物吗替麦考酚酯（MMF）耐药。使用狗模型的MHC-不匹配的HCT，我们将测试在体内的功能，MMF耐药的供体T细胞，以促进植入T细胞耗尽（TCD）供体骨髓后全身照射（TBI）。输注IMPDH* 转导的供体T细胞后用MMF治疗受体将抑制对基因修饰的T细胞的免疫反应，并为转导的T细胞提供增殖优势。这种方法允许MMF抗性供体T细胞的移植物抗宿主功能，同时抑制宿主抗移植物应答。目的1将研究IMPDH* 转导的供体T细胞在清髓性TBI后促进植入的体内有效性。患有GVHD的犬将用更昔洛韦治疗。目的2通过移植后联合应用环孢素和霉酚酸酯以及输注霉酚酸酯和环孢素抗性T细胞来降低植入TCD骨髓所需的TBI剂量。移植后，将给予更昔洛韦以控制GVHD。本课题的目的是应用免疫抑制耐药的基因治疗策略，操纵HCT后的免疫功能，使其有利于供体免疫细胞。这些研究的结果有很强的潜力直接转化为未来的基因治疗临床试验。

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.