Engineered Outer\nMembrane Vesicles as Nanosized Immune\nCell Engagers for Enhanced Solid Tumor Immunotherapy

Although tumor immunotherapy has achieved significant\nsuccess in\nrecent years, tackling solid tumors remains a formidable challenge.\nHere, we present an approach that utilizes outer membrane vesicles\n(OMVs) from bacterial cells as scaffolds to engage immune cells in\nsolid tumor immunotherapy. Two types of nanobodies targeting CD47/SIRPα\nand PD-1/PD-L1 pathways were simultaneously conjugated onto the surfaces\nof the OMVs in divalent and trivalent forms using orthogonal SpyCatcher-SpyTag\nand SnoopCatcher-SnoopTag chemistry. This resulted in the generation\nof an OMV-based nanosized immune cell engager (OMV-NICE) with dual-targeting\nabilities. <i>In vitro</i> assays confirmed the retention\nof the function of the two nanobodies on the OMV-NICE, as evidenced\nby the synergistically enhanced macrophage phagocytosis and T cell\ncytotoxicity against tumor cells. <i>In vivo</i> studies\nusing a B16-F10 melanoma mouse model also revealed the superior antitumor\nactivity of OMV-NICE compared to those of unconjugated nanobodies\nand OMVs alone. Subsequent mechanistic investigations further supported\nthe enhanced recruitment of macrophages and T cells to the tumor region\nby OMV-NICE. Overall, this work expands the current repertoire of\nimmune cell engagers, and the developed OMV-NICE platform holds great\npromise for broad applications, particularly in solid tumor immunotherapy.