Fig. 2.

Replication-competent viruses infect tumor cells and replicate. As they lead to tumor cell cytotoxicity and spread an infection to surrounding tumor cells, innate immune cells, such as macrophages, are activated and release cytokines, inflaming the tumor microenvironment. Lysis of tumor cells is thought to improve antigen presentation and infiltration of activated effector T cells against tumor and viral antigens. This leads to durable antitumor responses.