Oncolytic Adenovirus Armoring with <i>CXCL9</i> and <i>IL15</i> Shows Potent Antitumor Activity and Boosts CAR-T Therapy for Prostate Cancer

Chimeric antigen receptor T cell (CAR-T) therapy has achieved great success and progress for treatment of hematological malignancy, but it still cannot overcome the obstacles in solid tumors. The hostile tumor microenvironment (TME), such as dense extracellular matrix, hypoxia, low pH, and tumor-derived metabolites, largely impedes CAR-T function. Oncolytic virus, as a form of immunotherapy, provides a way to antagonize the TME and improve the efficacy of CAR-T cells in solid tumors. In this study, the chemokine <i>CXCL9</i> and interleukin 15 (<i>IL15</i>) genes were genetically integrated into adenoviral vector to construct oncolytic adenovirus (OAV) Ad-CXCL9-IL15, which could infect tumor cells to express and secrete CXCL9 and IL15. Ad-CXCL9-IL15 showed potent antitumor activity in xenografted prostate cancer model and augmented the tumor infiltration of CD45⁺CD3⁺ T and CD8⁺ T cells in immunocompetent mice. Moreover, Ad-CXCL9-IL15 treatment decreased Treg cells in tumor mass and increased CD44⁺CD62L⁺ T cells in spleen. Indicating that Ad-CXCL9-IL15 modified the TME and augmented antitumor immune responses <i>in vivo</i>. Furthermore, administration of Ad-CXCL9-IL15 dramatically promoted infiltration and survival of B7H3-targeting CAR-T cells, improved the therapeutic efficacy, and prolonged the survival time of prostate cancer-bearing mice. Therefore, cytokine-armored OAV Ad-CXCL9-IL15 could be used as a bioenhancer to modify TME and boost immunotherapy for solid tumors.