Enhanced solid tumor cell targeting by a neoepitope-encoding oncolytic measles virus combined with CAR therapy.

Despite the success of cell therapy in treating hematological malignancies, the treatment of solid tumors remains challenging due to the tumor microenvironment (TME) and a lack of suitable antigens. To address this, we investigated a putative octapeptide neoepitope generated by proteolytic cleavage of the stress-induced protein MHC class I polypeptide-related sequence B (MICB). Antibodies developed via the hybridoma technique exhibited high affinity and specificity toward the octapeptide. Detection of the octapeptide was enhanced by inserting an α-helical linker before the transmembrane domain, improving accessibility on stably transduced cells. Two chimeric antigen receptor (CAR) constructs with differing single-chain variable fragment (scFv) chain orientations were expressed in primary T and natural killer (NK) cells, showing antigen-specific cytotoxicity, particularly when incorporating the rigid linker. Variations in sensitivity between CARs influenced killing efficacy and activation profiles. Oncolytic measles virus (MV) was used as a vector encoding the membrane-anchored octapeptide, selectively infecting tumor cells and enhancing CAR-T cell-mediated cytotoxicity. Combined use of CAR-T and (CAR-)NK cells demonstrated increased persistence of immune cells as well as potent and sustained antitumor effects following MV infection. This study underscores the potential of neoepitope-based CAR therapy for targeting solid tumor cells and highlights the potential synergistic effects of combining cell therapy with virotherapy for improved therapeutic outcomes.