We showed that a ppinsΔA12-21 antigen (lacking the critical Kb/A12-21 epitope) primed regulatory T cells with a TGF-β+ Foxp3+ CD25+ CD4+ signature and efficiently suppressed CD8+ T cell-mediated diabetes development by a subsequent injection of the diabetogenic pCI/ppins vector. Here, FOXP3 is linked to diabetes mellitus.