基于重组乳酸乳球菌真核-原核双表达 OVA 制备的树突状细胞疫苗通过直接呈递和交叉呈递增强抗肿瘤疗效

Probiotic Lactococcus lactis (L. L) can act as an antigen delivery carrier to cross-present (XPT) exogenous antigens in dendritic cells (DCs). To optimize antigen XPT in a DC-based vaccine for improved antitumor efficacy, we produced recombinant L. L strains expressing the model antigen OVA via distinct methods: prokaryotic expression alone, eukaryotic expression alone, or dual prokaryotic-eukaryotic expression (designated pOVA-L.

L, eOVA-L. L, and dOVA-L. L, respectively). These strains were used to deliver antigens into DCs. Although all three recombinant OVA-L. L strains significantly enhanced DCs' ability to promote OT-I cell proliferation (with dOVA-L. L-treated DCs (dOVA-L. L-DCs) showing the strongest effect), only dOVA-L. L-DCs demonstrated significantly more potent antitumor efficacy in the B16-OVA tumor mouse model, consistent with the in vitro data.

Further investigation into the mechanisms underlying the enhanced antigen XPT and anti-tumor efficacy of dOVA-L. L-DCs revealed that pOVA-L. L and dOVA-L. L resided both inside and outside lysosomes, whereas eOVA-L. L was located exclusively outside lysosomes. Consequently, dOVA-L. L-DCs could XPT higher amounts of MHC I-OVA peptide complex on their surface.

Furthermore, these DCs could also directly present lysosome-derived OVA peptide-MHC II complexes to stimulate antigen-specific CD4 + T cell responses in vivo. Collectively, these mechanisms induced more persistent cellular immune responses than either of the other two recombinant L. L-DCs.

In conclusion, we developed an enhanced antigen delivery system using probiotic food-grade bacteria. This system promotes the prolonged expression of exogenous antigens and significantly enhances the XPT capacity of DC vaccines for tumor immunotherapy.