Fig. 3

Interaction of OVs, macrophages, and tumor cells. After OVs are delivered, some OVs are attacked by activated monocytes/macrophages, causing the viral titer of OVs to decrease. Another portion of OVs can be transported to the tumor site for viral replication, lysing tumor cells and releasing viral progeny, damage-associated molecular patterns (DAMPs), pathogen-associated molecular patterns (PAMPs), and tumor-associated antigens (TAAs). Antigen-presenting cells (APCs) take up and present these antigens, and the resulting activated antigen-specific CD8 + T cells as well as natural killer (NK) cells exert antitumor effects. Secreted IFN-γ and PAMPs repolarize pro-tumorigenic M2-like macrophages into anti-tumorigenic M1-like macrophages, and the anti-tumor/viral effects of the immune system can be further enhanced by secreting IFN-γ and TNF-α