Targeted delivery of antigen to intestinal dendritic cells induces oral tolerance and prevents autoimmune diabetes in NOD mice

The intestinal immune system is an ideal target to induce immune tolerance physiologically. However, the efficiency of oral protein antigen delivery is limited by degradation of the antigen in the gastrointestinal tract and poor uptake by antigen-presenting cells. Gut dendritic cells (DCs) are professional antigen-presenting cells that are prone to inducing antigen-specific immune tolerance. In this study, we delivered the antigen heat shock protein 65-6×P277 (H6P) directly to the gut DCs of NOD mice through oral vaccination with H6P-loaded targeting nanoparticles (NPs), and investigated the ability of this antigen to induce immune tolerance to prevent autoimmune diabetes in NOD mice. A targeting NP delivery system was developed to encapsulate H6P, and the ability of this system to protect and facilitate H6P delivery to gut DCs was assessed. NOD mice were immunised with H6P-loaded targeting NPs orally once a week for 7 weeks and the onset of diabetes was assessed by monitoring blood glucose levels. H6P-loaded targeting NPs protected the encapsulated H6P from degradation in the gastrointestinal tract environment and significantly increased the uptake of H6P by DCs in the gut Peyer’s patches (4.1 times higher uptake compared with the control H6P solution group). Oral vaccination with H6P-loaded targeting NPs induced antigen-specific T cell tolerance and prevented diabetes in 100% of NOD mice. Immune deviation (T helper [Th]1 to Th2) and CD4+CD25+FOXP3+ regulatory T cells were found to participate in the induction of immune tolerance. In this study, we successfully induced antigen-specific T cell tolerance and prevented the onset of diabetes in NOD mice. To our knowledge, this is the first attempt at delivering antigen to gut DCs using targeting NPs to induce T cell tolerance.