Our previous studies in ovarian, colorectal, and melanoma mouse models demonstrated that IT CPMV significantly increased PD-1 levels in Foxp3−CD4+ effector T cells and CD44+CD8+ effector T cells [21], implying that the strong immunostimulatory properties of CPMV could synergize with anti-PD-1 therapy. This evidence concerns the gene PDCD1 and melanoma.