Targeted E3 Region Engineering Boosts Antitumor Efficacy of Conditionally Replicating Adenoviruses in an Immunocompetent Tumor Model.

Abstract

The adenovirusregion's immune-modulating genes (,,) are frequently modified in oncolytic adenoviruses (OAds) through deletion and transgene insertion like granulocyte-macrophage colony-stimulating factor (). However, the synergistic effects of dual-gene deletions on antitumor efficacy and transgene capacity remain unexplored. To address this, we constructed three E3-modified OAds including OAd5-delgp19K (del), M20 (deland), M22-0 (deland), and their-armed derivatives, systematically evaluating the impact ofanddeletions on viral replication, tumor cell lysis, immune modulation, andantitumor activity. Key findings revealed thatdeletion OAd prolonged intracellular viral replication, creating a "viral bomb" effect that delayed cell lysis, evading anti-adenovirus antibodies, sustained GM-CSF expression, and culminating in superior tumor suppression.deletion OAd accelerated viral dissemination but triggered rapid antibody-mediated clearance in immunocompetent hosts, resulting in transient GM-CSF expression and diminished therapeutic persistence. In immunocompetent Syrian hamster Hap-T1 subcutaneous tumor models,deletion OAd demonstrated potent tumor inhibition, durable immune microenvironment remodeling, robust viral replication, and evading anti-adenovirus antibodies. These results underscore the critical role of coordinateddeletion in optimizing viral replication, transgene expression, and immune evasion, providing a strategic framework for engineering next-generation OAds.