Multifunctional manganese-containing vaccine delivery system Ca@MnCO3/LLO for tumor immunotherapy

The ideal vaccine delivery systems can not only deliver antigens in intelligent manners but also act as adjuvants. Recently found that Mn2+ can effectively stimulate anti-tumor immune responses, and Ca2+ can regulate autophagy to promote the cross-presentation of antigens. Thus, we constructed such a manganese-containing multimode vaccine delivery system by using calcium-doped manganese carbonate microspheres (Ca@MnCO3) and perforin-listeria hemolysin (LLO), as termed as Ca@MnCO3/LLO. The two components Ca@MnCO3 and LLO, not only act as vaccine adjuvants by themselves, but also contribute to achieve cellular immunity. Among them, Ca@MnCO3 microspheres as an excellent Mn2+ and Ca2+ reservoir, can continuously release adjuvants Mn2+ and Ca2+ to enhance immune response in dendritic cells, while LLO can contribute to induce lysosomal escape. Particularly, Ca2+ was added firstly to MnCO3 microspheres to improve the stability and load capacity of the microspheres. Along with the degradation of intracellular Ca@MnCO3 microspheres, and the lysosomal membrane-lytic effects of perforin LLO, the Mn2+, Ca2+ and OVA were released to the cytoplasm. These outcomes cooperatively promote antigen cross-presentation, elicit CD8+ T cell proliferation, and finally achieve prominent anti-tumor effects. The results indicate that the manganese-containing vaccine delivery system Ca@MnCO3/LLO provides a promising platform for the construction of tumor vaccines.