Probiotic neoantigen delivery vectors for precision cancer immunotherapy

Microbial systems have been synthetically engineered to deploy therapeutic payloads in vivo [1][1]–[4][2]. With emerging evidence that bacteria naturally home to tumors[5][3]–[7][4] and modulate anti-tumor immunity[8][5],[9][6], one promising application is the development of bacterial vectors as precision cancer vaccines[10][7]–[12][8]. 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. ### Competing Interest Statement A.R., J.I., T.D., and N.A. have filed a provisional patent application with the US Patent and Trademark Office related to this work. [1]: #ref-1 [2]: #ref-4 [3]: #ref-5 [4]: #ref-7 [5]: #ref-8 [6]: #ref-9 [7]: #ref-10 [8]: #ref-12