The IFNαβ response mediates reduced transduction efficiency and plays a role in immune-mediated vector clearance. IFNαβR^−/− and wild-type strain-matched controls (129sv) were treated with 15 μg VSV.LV (n=6/group/time point). (A) Cytokine profile of the liver and spleen (not shown) were measured by RPA. Analysis was carried out as described in Figure 2. (B) Q-PCR analysis of LV DNA content within the liver and spleen of wild-type (▪) and IFNαβR^−/− (⊡) mice at 24 hours after injection. All samples were normalized to murine β-actin. Values are presented as the means ± SEM. Asterisks indicate t-test significance values of wild-type compared with IFNαβR^−/− mice (*P <.05; **P < .005). (C) Confocal immunofluorescence analysis of liver sections at the indicated time. Fixed frozen sections were costained with anti-GFP (green) antibodies to identify transduced cells. TO-PRO-3 (blue) was used to stain nuclei. Images are representative of 6 mice analyzed. Scale bars equal 75 μm. (D) ELISPOT analysis of the frequency of GFP-specific IFN-γ secreting CD8⁺ T cells from the liver (left) and spleen (right) of treated mice. Results are presented as the means ± SEM (n=3/group/time point). ND indicates not detected.