PVHA increased anti-PD-L1–mediated growth inhibition in 4T1/HAS3 tumors. PVHA increased anti-PD-L1–mediated growth inhibition in 4T1/HAS3 tumors. A, 4T1/HAS3 tumor-bearing mice treated with vehicle + IgG2b isotype control, or anti-PD-L1 5 mg/kg once weekly i.p., or PVHA 1 mg/kg once weekly i.v. + IgG2b isotype control, or anti-PD-L1 5 mg/kg once weekly i.p. Vehicle or PVHA was administered 24 hours prior to IgG2b or anti-PD-L1. B, Randomly selected representative images of IHC staining of CD8 cells (brown; scale bar, 500 μm) on formalin-fixed, paraffin-embedded tumor sections 24 hours after treatment with vehicle, PVHA (1 mg/kg), vehicle + IgG2b, PVHA (1 mg/kg) + IgG2b, vehicle + anti-PD-L1 (5 mg/kg), or PVHA (1 mg/kg) + anti-PD-L1 (5 mg/kg) treatment. C, Kaplan–Meier survival plot for PVHA + anti-PD-L1–treated mice. Treatment regimen was the same as described in A. ****, P < 0.0001. Renee Clift et al. Cancer Res 2019;79:4149-4159 ©2019 by American Association for Cancer Research