Oncolytic cancer therapy with a vaccinia virus strain

Oncolytic vaccinia virus is currently undergoing evaluation as a biological anticancer agent in clinical trials. This treatment exploits the lytic nature of a viral infection to eradicate the tumor mass in a cancer cell‑specific manner. So far, various vaccinia strains have been used as backbones in the design of oncolytic agents. However, the efficacy as oncolytic virotherapy of Chinese vaccinia strain Tian Tan (VTT) has not been reported. Vaccinia strain Guang9 (VG9), derived from VTT by consecutive plaque‑cloning selection, was attenuated to a greater extent than its parental strain. In this study, the oncolytic efficacy of VG9 was evaluated. We examined in vitro replication and cytotoxicity, in vivo biodistribution, and antitumor effects in a B16 tumor model. The results revealed that VG9 replicated rapidly, but the cytotoxicity varied in different cell lines. Significant antitumor effects of VG9 were observed in a murine melanoma tumor model, and an antitumor cytotoxic T‑lymphocyte response induced by VG9 was also observed. The results indicated that the Chinese vaccinia strain VG9 holds promise in the construction of a recombinant vaccinia virus vector and as a potential therapeutic strategy in cancer treatment.