An Oncolytic Vaccinia Virus Expressing EpCAM Bispecific T-Cell Engager Enhances Immune Response in Solid Tumors

Background: BiTE (bispecific T-cell engager) molecules establish physical synapses between T cells and tumor cells, and selectively direct T cytotoxicity to tumor cells. Encouraging clinical progress has been made with anti-CD19/CD3 bispecific antibodies. However, due to insufficient intratumoral T cell infiltration, BiTE has repeatedly suffered setbacks in the treatment of solid tumors. Therefore, it is necessary to explore BiTE-armed oncolytic virus to enhance anti-tumor immunity.<br><br>Methods: VV-EpCAM BiTE, a novel recombinant oncolytic vaccinia virus, selectively infected tumor cells and secreted a EpCAM -targeted bispecific T-cell engager (BiTE). The antitumor effect of VV-EpCAM BiTE was validated in a variety of subcutaneous xenograft models.<br><br>Findings: VV-EpCAM BiTE could effectively infect, replicate and lyse tumor cells. EpCAM BiTE bound EpCAM-positive tumor cells to CD3ε on T cells and triggered naive T cells activation and the release of pro-inflammatory factors such as IFN-γ, IL2, IL6 and IL10. Intratumoral injection of VV-EpCAM BiTE significantly enhanced antitumor activity in EpCAM-positive tumor cell models compared with VV-CON. In addition, immune cells infiltration in the tumor microenvironment were significantly increased in the VV-EpCAM BiTE-treated group, and T cell-mediated immune activation was also markedly enhanced.<br><br>Interpretation: The study reveals that VV-EpCAM BiTE is an effective immunotherapy strategy for treating solid tumors. This approach combines the antitumor advantages of bispecific antibodies and oncolytic viruses, providing preclinical evidence for the therapeutic potential of VV-EpCAM BiTE.<br><br>Funding Statement: This work was supported by National Natural Science Foundation of China (81773255 and 81700037).<br><br>Declaration of Interests: The authors declare no competing interests.<br><br>Ethics Approval Statement: All animal experiments were performed in accordance with the guidelines approved by the Animal Care and Use Committee of the Medical School of Nanjing University.