Expression of HSV-TK suicide gene in primary T lymphocytes: The dog as a preclinical model

Expression of suicide genes (e.g. herpes simplex virus thymidine kinase,HSV -TK) in T cells is an appealing approach to regulate graft-versus-host dise ase in adoptive immunotherapy. Here we report the optimization of retrovira l infection of canine T cells. Canine T cells were stimulated either with p hytohemagglutinin (PHA, 2 mu g/ml) for 24-72 hours or with 100 U/ml interle ukin-2 for seven days. Stimulated cells were co-cultivated with irradiated virus-producing cells. Transduction efficiencies ranged from 4% to 45% usin g PG13, a gibbon ape leukemia virus envelope (env) pseudotyped packaging ce ll line. Infection of cells with GPenvAM12, expressing the amphotropic Molo ney murine leukemia virus env, did not yield a satisfactory percentage of t ransduced cells. Enrichment of transduced cells was performed using immunos election, and gave a purity of up to 98%. Transfusion of 1 x 10(6) transduc ed cells per kilogram body weight showed that transduced cells could conver t mixed chimerism to 100% and transfer immunity to a specific antigen. Tran sduced cells were repeatedly detected in peripheral blood and bone marrow b y polymerase chain reaction with primers specific for the HSV-TK gene. We h ave demonstrated the feasibility of using the canine model to study gene th erapy as a preclinical model.