Immunosupression-Resistant Gene Modified Donor T Cells

描述(申请人提供)：异基因造血细胞移植(HCT)是一种癌症免疫疗法，依靠捐献者的T细胞促进植入并诱导有益的移植物抗白血病效应。然而，同种异体反应性供者T细胞也可导致致命性移植物抗宿主病(GVHD)。用“自杀”基因--单纯疱疹病毒胸苷激酶(HSV-tk)对供者T细胞进行基因修饰，有可能通过用更昔洛韦杀死同种异体反应性、GVHD引起的T细胞来显著提高同种异体HCT的安全性。到目前为止，HSV-tk修饰的供者T细胞在异基因HCT后输注的临床研究表明，在体内的作用非常有限。我们提出了一种新的策略，在大的同种异体血细胞移植动物模型中支持转基因T细胞的体内免疫功能。该假说认为，慢病毒转导携带免疫抑制耐药基因的供体T细胞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的T细胞的体内功能。我们将评估表达HSV-tk和显性突变的肌苷一磷酸脱氢酶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，对免疫抑制药物霉酚酸酯(MMF)耐药。采用MHC不相合供者T细胞移植模型，检测MMF耐药供者T细胞的体内功能，以促进T细胞耗竭(TCD)供者骨髓在全身照射后的植入。输注IMPDH*转导的供体T细胞后用MMF治疗受者，可抑制对基因修饰T细胞的免疫反应，并使转导的T细胞具有增殖优势。这种方法允许耐MMF的供者T细胞的移植物抗宿主功能，同时抑制宿主对移植物的反应。目的1研究转导IMPDH*基因的供体T细胞在清髓性脑损伤后促进植入的体内效应。患有GVHD的狗将接受更昔洛韦治疗。目的2将减少移植TCD骨髓所需的TBI剂量，方法是在移植后联合应用环孢素和MMF，并输注MMF和环孢素耐药的T细胞。植入后给予更昔洛韦控制GVHD。本项目的主题是应用一种免疫抑制耐药的基因治疗策略来操纵HCT后的免疫功能，使其有利于供者免疫细胞。这些研究的结果有很大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.