Genetically modified bacterial vesicles with interferon-γ and tumor antigen remodel anti-tumor cellular immunity by modulating dendritic cells.

The tumor vaccine is regarded as a promising immunotherapeutic approach for the treatment of malignant tumors by activating dendritic cell (DC) and eliciting T-cell responses. Toll-like receptor (TLR) ligands are recognized as effective stimulators of DC maturation. Another critical factor in DC maturation is interferon-γ (IFN-γ), which amplifies the TLR signaling pathway and elevates the expression of inflammatory cytokines in DCs. Furthermore, IFN-γ can markedly enhance the synthesis of interleukin-12 (IL-12) and facilitates T cells in recognizing tumor cells. Consequently, IFN-γ and TLR ligands is utilized to generate mature DCs (mDCs) for the development of clinical tumor vaccines aimed at treating solid tumors. However, the technology facilitating the co-delivery of IFN-γ and TLR ligands to DCs is currently limited. Here, we engineered a strategy utilizing modified bacterial biomimetic vesicles (BBVs) as a delivery system, which effectively stimulated the maturation and migration of DCs, facilitating the differentiation of CD4 Th1 cells and CD8 CTLs, thereby surface displaying IFN-γ and TLR ligands on the BBVs. The engineered BBV/IFN-γ which carry human papillomavirus type 16 (HPV 16) E7 protein and a fusion peptide of three 4T1 neoantigens, respectively triggered Th1/CTLs-polarized T cell responses, promoted tumoral effector T cells infiltration and reshaped the tumor microenvironment, and significantly inhibited tumor growth and metastasis in the TC-1 tumor and orthotopic immune cold 4T1 breast tumor model. Furthermore, the tumor vaccine exhibited synergistic effects with anti- PD-L1 monoclonal antibodies in 4T1 tumor-bearing mice. In conclusion, the functionally modified BBVs demonstrate significant potential to overcome immunosuppression and elicit effective anti-tumor immunity.