CD80 and neoplasm: Another method to enhance the antitumor immune response is to activate immune cells through the expression of co-stimulatory ligands by OVs (e.g., CD40L, 4-1BB, CD80, ICOS ligand) or, conversely, inhibitors or antagonists of co-inhibitory molecules (e.g., antibodies against “don’t eat me” signals (CD24 and CD47) used by the tumor for immune evasion) (57).