Boosting CAR T cell functionality with oncolytic viruses for the treatment of pediatric diffuse midline gliomas

Despite the success of CAR (chimeric antigen receptor) T cells in hematological malignancies, their effectiveness against solid or brain tumors, such as pediatric diffuse midline gliomas (DMGs), is limited. CAR T cell success is hampered by factors including immunosuppression from DMGs and their surrounding tumor microenvironment (TME). Oncolytic viruses (OVs) can reverse this immunosuppression, suggesting a potential combination with CAR T cells. Here, we show that infection with Goravir adenovirus and R124 reovirus induced DMG cell lysis (n = 6 cultures), with minimal effect on the viability of B7H3- or GD2-targeted CAR T cells, even at high virus concentrations. In addition, RNA sequencing of infected tumor cells revealed altered gene expression in cell cycle and antiviral response pathways. Furthermore, co-cultures of CAR T cells with OV-infected DMGs enhanced CAR T-specific anti-tumor killing in 14 out of 24 cases. The successful combinations exhibited enhanced cytokine and chemokine release, coupled with an increased cytotoxic phenotype. These findings highlight the benefit of DMG pre-infection with OVs to boost CAR T cell activity and suggest that immune stimulation is a key driver of enhanced combination responses.