Diagram of experimental design. Bone marrow (BM) was harvested from CLAD dogs and enriched for CD34⁺ cells. CD34⁺ cells were used immediately, or cryopreserved and thawed 2 to 3 weeks later. After transduction, cells were harvested, washed, and reinfused into CLAD pups that had received conditioning with either 200 cGy TBI on day 0 or –1 (n = 9), or 10 mg/kg busulfan intravenously on day –2(n = 2). Four dogs (A1-A4) received posttransplantation immunosuppression with CSP starting on day –1 and continuing until day +65 (35 days at 30 mg/kg, 30 days at 15 mg/kg), along with MMF from day 0 to day +28 (at 20 mg/kg). Seven dogs received no posttransplantation immunosuppression. LTR, retroviral long terminal repeat; Ψ+, extended packaging signal; gln tRNA PBS, glutamine tRNA primer binding site; PCMV, PCC4-cell passaged myeloproliferative sarcoma virus.