Engineered oncolytic viruses have been designed to carry various effector molecules, such as secreting hyaluronidase to dissolve the extracellular matrix and promote CAR-T cell infiltration, carrying specific antigens to increase target antigen abundance after infecting tumor cells, or delivering IL-15 to modulate the tumor immune microenvironment and help CAR-T cells overcome the immunosuppressive microenvironment [148,149,150]. Here, IL15 is linked to neoplasm.