Chinese yam polysaccharide-loaded aluminium hydroxide nanoparticles used as vaccine adjuvant to induce potent humoral and cellular immune responses

Due to their safety and efficacy, aluminium salts (Alum) are considered the most important adjuvants in human vaccines. However, Alum adjuvants are unable to elicit a cellular immune response, which is vital for the prevention of various chronic infectious diseases and cancers. Herein, we isolated and purified a water-soluble polysaccharide from Chinese yam, named CYP, which was primarily composed of →4)-α-D-Glcp-(1→, →4,6)-α-D-Glcp-(1→, and α-D-Glcp-(1→. Meanwhile, we prepared aluminium hydroxide nanoparticles (Al NPs) with a nanometer-scale size and thin stick-like shape. Being an immunostimulant, the CYP was then loaded onto the Al NPs to obtain a novel adjuvant delivery system (CYP-Al NPs) that enhances the immunostimulatory activity of CYP. Our findings showed that the CYP-Al NPs facilitated macrophages activation and promoted the antigen uptake by macrophages. The in vivo experiment showed that the CYP-Al NPs, as the adjuvant to ovalbumin, promoted the activation of dendritic cells and germinal center B cells in draining lymph nodes, induced a durable and strong antibody response, especially the Th1-type IgG2a antibody response, and improved the cytotoxic T lymphocytes response. These results demonstrated that the CYP-Al NPs could generate robust humoral and cellular responses, and has the great potential to serve as an adjuvant delivery system.