Recombinant Oncolytic Viruses: Hexagonal Warriors in the Field of Solid Tumor Immunotherapy

In the past decade, research on recombinant oncolytic viral agents in the treatment of solid tumors has evolved from the initial stage of simple genetic engineering to the current stage of multiple pipelines of parallel clinical application and combination therapy. Compared with T-VEC, the classical therapeutic agent that only expresses GM-CSF, which was approved in 2015, most new oncolytic virus designs include diverse gene constructs to reduce toxic effects, enhance multiple antitumor immunity, avoid immune clearance, or enhance tumor targeting. The single route of administration that activates the inflammatory tumor immune microenvironment by intratumoral injection is no longer sufficient to meet the treatment needs of refractory solid tumors. In this review, we illustrated the construction patterns of typical recombinant oncolytic viral agents and their latest clinical trial progress. Secondly, we summarized the underlying mechanisms of the combined application of antiviral and antitumor immunity in the field of solid tumor immunotherapy. Finally, we explored the feasibility of the intravenous application of oncolytic viruses and their future development directions. We believe that the diversified treatment design of oncolytic viruses will bring more surprises to the immunotherapy of refractory tumors.