CANINE T-CELLS TRANSDUCED WITH A HERPES-SIMPLEX VIRUS THYMIDINE KINASE GENE - A MODEL TO STUDY EFFECTS ON ENGRAFTMENT AND CONTROL OF GRAFT-VERSUS-HOST DISEASE

Background. Alloreactive donor T cells in marrow grafts mediate graft- versus-host disease (GVHD), but T-cell depletion has resulted in incre ased graft failure. Add-back of gene-modified alloreactive donor T cel ls could prevent graft rejection. After engraftment, in vivo depletion of those modified T cells with ganciclovir may control GVHD. Methods. Canine recipient-specific donor cytotoxic T lymphocytes (CTL) were re trovirally transduced with the herpes simplex virus thymidine kinase g ene. Results. Gibbon ape leukemia virus-pseudotyped vector yielded pri mary CTL transduction efficiency of 22.9+/-9.9%. After selection and e xpansion, 96.7+/-0.8% of CTL expressed retrovirally transferred genes. Recipient-specific cytotoxic activity was maintained with 84.3% speci fic lysis. After ganciclovir treatment, herpes simplex virus thymidine kinase-transduced CTL proliferation was reduced 98.7+/-0.2% compared with controls. Conclusions. We have demonstrated efficient ex vivo tra nsduction, expansion, maintenance of alloreactivity, and ganciclovir-m ediated ablation of canine CTL, which will permit in vivo studies in t he dog, a well-established model for GVHD and engraftment.