Decreasing noncognate MHC-I levels together with PD1 blockade allows TriVax to eliminate advanced tumors in WT mice. (A) Expression levels of H-2Kb, H-2Db, and PD-L1 in B16-Kb^Lo cells treated or not with IFNγ (100 U/mL, 24 hours). Results with IFNγ-treated parental B16 cells are included for comparison. (B) Responses (ELISPOT) of freshly isolated CD8 T cells from Trp1₄₅₅TriVax- and Trp2₁₈₀TriVax-immunized WT mice against IFNγ treated and nontreated B16-Kb^Lo cells. Results represent the average number of spots from triplicate wells with SD (error bars) of the means. (C) Therapeutic effects induced by Trp1₄₅₅TriVax against 7-day-established B16-Kb^Lo tumors in WT mice. Mice (8/group) were inoculated with B16-Kb^Lo cells and immunized with Trp1₄₅₅TriVax or Ova₅₅TriVax as indicated. Anti-PD-L1 mAb was administered intraperitoneally on days 2, 4, 6, and 8 after TriVax administration. Nonvaccinated mice (No Vax) were also included as controls. Arrows, days when the vaccines were administered; gray bars, period of anti–PD-L1 mAb treatment. (D-E). Tumor-growth curves are shown for individual mice from the Trp1₄₅₅TriVax and Trp1₄₅₅TriVax plus anti–PD-L1 groups. Tumor sizes were determined in individual mice by measurements of 2 opposing diameters and are presented as tumor areas in square millimeters. Points, mean for each group of mice; bars, SD. P < .0001, between the Trp1₄₅₅TriVax and the Trp1₄₅₅TriVax + anti–PD-L1 mAb group (obtained using a 2-way ANOVA analysis). *Seven of 8 mice in Trp1₄₅₅TriVax + anti–PD-L1 mAb rejected their tumors; **1 mouse from Trp1₄₅₅TriVax rejected its tumor. These experiments were repeated twice with similar results.