CD274 and neoplasm: Still, the oncolytic viruses’ effect on T-cell exhaustion and immune checkpoint regulation within the tumor microenvironment have not been conclusively elucidated: some suggested that T-cell exhaustion can be prevented or reversed by oncolytic virotherapy, while others demonstrated that the virus infection can upregulate PD-L1 expression on the surface of tumor cells and simultaneously increase PD-1 expression on T cells that are suggestive of exhaustion (40–42).