Combination of virotherapy and T-cell therapy: arming oncolytic virus with T-cell engagers

While cure rates for several cancers have significantly improved, the outcome for patients with advanced solid tumors remains grimly unchanged over the last decades. Thus, there is a need for new therapies that could improve outcome for patients who fail current therapies. Oncolytic vaccinia virus (VV) would be an appealing addition to the current therapies of cancers because of its ability to infect, replicate in, and lyse tumor cells, and spread to other tumor cells in successive rounds of replication. While clinical studies have demonstrated their safety, the antitumor efficacy of oncolytic VVs has been suboptimal. Oncolytic VVs' major mode of action is the destruction of tumor cells, which can subsequently activate a component of the immune system called T cells that can travel to distant sites and target against any tumor they find. At present, virus spread through tumors, as well as the activation of tumor-specific T cells, is limited, explaining the observed suboptimal antitumor activity of current oncolytic VVs. Thus it would be desirable to make the oncolytic VVs more powerful stimulators of immunity through activating resident T cells within the tumors so that they will kill tumor cells and stop new tumors from growing. To activate T cells within tumors, a new molecule called a T-cell engager that couples the T cell and the tumor cell, which increases the effectiveness of the T cells and their activation, has been constructed. This review summarizes the progress of the emerging field of combinations of oncolytic virotherapy and T-cell based therapy.