LV-mediated induction of innate immunity is dependent on vector infectivity. (A) Balb/c mice were injected via tail vein with PBS, 10 μg VSV.LV, or 15 μg gp64.LV. Spleen and liver samples were analyzed at 4 hours after injection by Q-PCR to measure LV copies per genome (C/G). All samples were normalized to murine β-actin. Values are presented as the means ± SEM for 3 mice per group. □ indicates PBS; ▪, VSV.LV; and ⊡, gp64.LV mice. (B) Confocal immunofluorescence microscopy analysis of liver and spleen sections from mice administered gp64.LV 7 days earlier. Fixed frozen sections were costained with anti-GFP (green) antibodies to identify transduced cells, and anti-CD45 (red) antibodies to identify hematopoietic lineage cells. Arrows indicate selected cells that costain for both GFP and CD45; these cells appear yellow. TO-PRO-3 (blue) was used to stain nuclei. Scale bars equal 200 μm. (C) The cytokine profile, as measured by RPA, of the liver (left) and spleen (right) 4 hours after injection with the indicated LV (n=3 per group). Analysis was carried out as described in Figure 2. HI.LV indicates heat-inactivated LV; bald.LV, envelope-negative LV. Asterisks indicate t-test significance value of treatment group compared with bald.LV (*P < .05; **P < .005; ***P < .001).