737. Efficient In Vivo Selection and Chemoprotection Following Drug Resistance Gene Therapy in a Nonmyeloablative Allogeneic Transplantation Setting in the Dog
Year: 2006
Type: article
Abstract: We have previously demonstrated successful in vivo selection and chemoprotection in dogs that received myeloablative allogeneic stem cell transplantation with gene-modified cells. Here we wished to investigate whether I vivo selection, chemoprotection, and modulation of donor chimerism could also be achieved after nonmyeloablative transplantation which should be less toxic and thus more appropriate for older patients and patients with genetic diseases. We have used a lentivirus vector encoding the P140K mutant of methylguanine-DNA methyltransferase (MGMT-P140K) to transduce DLA matched littermate CD34+ cells. The use of a lentivirus vector allowed us to keep the ex vivo/transduction time short, less than 24 hours which improves engraftment in the allogeneic setting. Three dogs received a nonmyeloablative dose of total body irradiation (TBI) ranging from 200 cGy to 400 cGy before infusion of the gene-modified CD34+ cells and early post-transplant chemotherapy to facilitate engraftment. All three dogs had stable gene marking and donor chimerism, before receiving a course of treatment with O6BG/BCNU. One to three treatments led to a sustained increase in gene marking in all dogs with maximum levels achieved of >75%. Furthermore, the transduced cells conferred chemoprotection relative to control animals and prevented severe neutropenia even with ascending doses of BCNU. Our initial analysis of retrovirus integration with LAM-PCR suggest that before and after in vivo selection of chemoprotected cells multiple clones contribute to hematopoiesis and no side effects or malignancies have been observed. Our results suggest that drug resistance gene therapy and subsequent in vivo selection is feasible and safe in the nonmyeloablative transplantation setting. We are continuing to modify the pre-transplant immunosuppression and post-transplant in vivo selection to facilitate engraftment of gene-modified cells. In nonmyeloablative allogeneic transplantation for leukemia where post-transplant relapse remains a substantial complication, the application of this model could reduce the toxicity of chemotherapy treatment and allow for more intensive treatment regimens. In addition this strategy could be used to increase the percentage of gene-marked donor cells in patients with genetic diseases and low donor chimerism. These studies and future studies in the nonmyeloablative setting are required to assess the long-term safety of chemo-protective gene therapy.
Source: Molecular Therapy
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W2011119965