Novel personalized cancer vaccine platform based on Bacillus Calmette-Guèrin

Abstract

Intratumoural bacillus Calmette-Guérin (BCG) therapy, one of the earliest immunotherapies, can lead to infiltration of immune cells into a treated tumour. Here, we have developed a novel cancer vaccine platform based on BCG that can direct BCG-induced immune responses against tumour antigens. By physically attaching tumour-specific peptides onto the mycobacterial outer membrane, we were able to induce strong systemic and intratumoural T cell-specific immune responses towards the attached tumour antigens. These therapeutic peptides can be attached to the mycobacterial outer membrane using a cell-penetrating peptide sequence derived from human immunodeficiency virus Tat, N-terminally fused to the tumour-specific peptides. Alternatively, therapeutic peptides can be conjugated with a poly-lysine sequence N-terminally fused to the tumour-specific peptides. Using two mouse models of melanoma and a mouse model of colorectal cancer, we observed that the anti-tumour responses of BCG can be significantly improved by coating the BCG with tumour-specific peptides. In addition, by combining this novel cancer vaccine platform with anti-PD-1 immune checkpoint inhibitor therapy, the number of responders to anti-PD-1 immunotherapy can be significantly increased.