Probiotic neoantigen delivery vectors for precision cancer immunotherapy

Abstract Microbial systems have been synthetically engineered to deploy therapeutic payloads in vivo 1–4 . With emerging evidence that bacteria naturally home to tumors 5–7 and modulate anti-tumor immunity 8,9 , one promising application is the development of bacterial vectors as precision cancer vaccines 10–12 . In this study, we engineered probiotic E. coli Nissle 1917 (EcN) as an anti-tumor vaccination platform optimized for enhanced production and cytosolic delivery of neoepitope-containing peptide arrays, with increased susceptibility to blood clearance and phagocytosis. These features enhance both safety and immunogenicity, achieving a system which drives potent and specific T cell–mediated anti-cancer immunity that effectively controls or eliminates tumor growth and extends survival in advanced murine primary and metastatic solid tumors. We demonstrate that the elicited anti-tumor immune response involves extensive priming and activation of neoantigen-specific CD4 + and CD8 + T cells, broader activation of both T and NK cells, and a reduction of tumor-infiltrating immunosuppressive myeloid and regulatory T and B cell populations. Taken together, this work leverages the advantages of living medicines to deliver arrays of tumor-specific neoantigen–derived epitopes within the optimal context to induce specific, effective, and durable systemic anti-tumor immunity.