CD4 and cancer: It has been reported that the frequency of activated CD8+PD‐1− TILs increased in the TME following virotherapy with C‐REV.[139] Therefore, combination therapy using oncolytic viruses and immune checkpoint inhibitors dramatically enhances antitumor responses, and the weaknesses of each method alone are covered by the other.[118, 140] In murine rhabdomyosarcoma models, anti‐PD‐1 and HSV‐1716 were used, and findings demonstrated that this combination could be effective in cancer treatment through increasing CD4+ and CD8+ T cell‐mediated antitumor responses but not Tregs.