212 Co‐delivery of Vitamin D3 and Antigens by Nanoparticles Enhances Immune Tolerance through Induction of Tolerogenic Dendritic Cells in vivo

Abstract Tolerogenic dendritic cells (tDCs) induces regulatory T cell (Treg) differentiation and promotes immune tolerance. However, the effective generation of tDCs in vivo to treat autoimmune diseases remains a significant challenge. In this study, the potential of 1α, 25‐Dihydroxyvitamin D3 (VD3) is explored, which has been shown to promote tDCs differentiation in vitro, to induce tDCs in a mouse model of experimental autoimmune encephalomyelitis (EAE). To overcome the poor solubility of VD3 and induce autoantigen‐specific Tregs, a PLGA‐PEG‐based nano‐drug delivery system is prepared to co‐deliver VD3 and myelin‐oligodendrocyte glycoprotein (MOG) peptides. It is found that intradermal (i.d.) injection of NP/VD3/MOG significantly enhanced the level of antigen‐specific Tregs in vivo. Furthermore, NP/VD3/MOG remarkedly delayed the onset, reduced the severity, and promoted the recovery of EAE mice. This study provides an effective strategy for the treatment of autoimmune diseases.