In vivo persistence of LV'VFas-modified T cells in macaques. (A) LV'VFas+ T cells (5 × 10⁹/m²) were administered by intravenous infusion to macaque no. 1 at 6-week intervals indicated by the arrows. AP1903 (0.1 mg/kg) was given beginning 1 day after the second cell dose and then every other day for 10 doses. DNA was isolated from PBMCs collected from macaque no. 1 before and at the indicated days after the T-cell infusions and assayed for the frequency of vector containing cells by TaqMan PCR. * indicates the frequency of LV'VFas⁺ T cells among PBMCs 30 minutes after infusion. (B) Transgene product-specific cytolytic T-cell responses are elicited after transfer of LV'VFas⁺ T cells. PBMCs were collected from macaque no. 1 on the indicated days before and after T-cell infusion and stimulated with autologous γ-irradiated LV'VFas-modified T cells twice 1 week apart. Specific cytotoxicity was examined in a chromium release assay for recognition of either parental (□) or LV'VFas⁺ (▪) target cells. Data are shown for an effector-to-target (E/T) ratio of 20:1.