Evaluation of the cellular and humoral immune response against AdGRE.mTPO vector with or without dexamethasone (Dex) administration in vivo. After administration of the AdGRE.mTPO vector (5 × 10⁸), dexamethasone was administered intraperitoneally (50 μg/dose) on 3 consecutive days starting at days 1, 22, and 43. (A and B) CTL at day 43 after administration of AdGRE.mTPO with and without dexamethasone. Splenocytes were evaluated for their ability to lyse syngeneic cells infected with AdGRE.mTPO or AdNull. Data are presented as percent lysis of target cells mixed at various ratios with splenocytes relative to the total amount of⁵¹Cr that could be released by lysing 100% of the cells. Shown are data for uninfected target cells (“alone,” ▵), target cells infected with AdNull (○), and target cells infected with AdGRE.mTPO (•). (A) Mice receiving AdGRE.mTPO vector alone (no Dex). (B) Mice receiving AdGRE.mTPO vector plus dexamethasone administration (+Dex). (C) Serum concentration (titer/4.5 μL) of neutralizing antibody directed against Ad vectors before and 22 to 64 days following AdGRE.mTPO administration (5 × 10⁸ pfu) with or without dexamethasone. The dashed line indicates the limit of sensitivity of the assay (titer < 10). Shown are data for serum anti-Ad neutralizing antibodies titer with dexamethasone (•) and without dexamethasone (○). The data are presented as individual time points for each animal.