An OMV‐Based Nanovaccine as Antigen Presentation Signal Enhancer for Cancer Immunotherapy

Abstract Antigen‐presenting cells (APCs) process tumor vaccines and present tumor antigens as the first signals to T cells to activate anti‐tumor immunity, which process requires the assistance of co‐stimulatory second signals on APCs. The immune checkpoint programmed death ligand 1 (PD‐L1) not only mediates the immune escape of tumor cells but also acts as a co‐inhibitory second signal on APCs. The serious dysfunction of second signals due to the high expression of PD‐L1 on APCs in the tumor body results in the inefficiency of tumor vaccines. To overcome this challenge, a previously established Plug‐and‐Display tumor vaccine platform based on bacterial outer membrane vesicles (OMVs) is developed into an “Antigen Presentation Signal Enhancer” (APSE) by surface‐modifying PD‐L1 antibodies (αPD‐L1). While delivering tumor antigens, APSE can activate the expression of co‐stimulatory second signals in APCs due to the high immunogenicity of OMVs. More importantly, the surface‐modified αPD‐L1 binds to the co‐inhibitory signals PD‐L1, potentially restoring CD80 function and ensuring efficient co‐stimulatory second signals and activation of anti‐tumor immunity. The results reveal the importance of PD‐L1 blockage in the initiation process of anti‐tumor immunity, and the second signal modulation capability of APSE can expand the application potential of cancer vaccines to less immunogenic malignancies.