Antitumor activity of VSV in a murine AML C1498.GFP model. (A) C57BL/6 mice were given C1498.GFP IV and, on day 20, received 1 dose 10⁸ TCID₅₀ VSV-mIFNβ-NIS IV; the mice were harvested 48 hours later. Representative photographs show abundant GFP-positive C1498 cells in control mice, but fewer C1498.GFP cells in VSV-treated mice. (B) Single-cell suspensions from the liver and bone marrow were analyzed by flow cytometry after staining with an anti-PD-L1 Ab and gating GFP-positive cells. Bar and error bars (top right) represent the mean ± SEM (n = 4 mice) from each group, showing significantly lower levels of PD-L1 on tumor cells from mice that received the Ab treatment. (C) Kaplan-Meier survival curves of mice in the various treatment groups (n = 11 or 12 mice in each group). Mice received VSV-mIFNβ-NIS IV on day 0, followed 3 days later with anti-PD-L1 Ab or isotype control Ab (3 total doses). The P values are shown. (D) Kaplan-Meier survival curves of mice that received VSV and anti-PD-L1 Ab, with and without depletion of specific immune cell populations (n = 15 mice in each group). Untreated mice (isotype) or mice depleted of CD4, CD8, or NK cells received VSV-mIFNβ-NIS IV on day 0, followed 3 days later with IP injections of 200 μg of anti-PD-L1 Ab. The P values indicating significance level between groups are shown. BM, bone marrow.