We previously demonstrated that intraperitoneal delivery of adeno-associated virus serotype 8 (AAV8) stably transduces the pancreas, including the β cells in the pancreatic islets. We further demonstrated the ability to deliver and express target genes specifically in β cells for at least 6 months using a murine insulin promoter in a double-stranded, self-complementary AAV vector. Recombinant interleukin (IL)-2 has been shown to induce CD4(+)CD25(+) regulatory T cells (Tregs) in several mouse models of autoimmune disease. Here we evaluated the effects of double-stranded adeno-associated virus serotype 8-mouse insulin promoter (dsAAV8-mIP)-mediated delivery of 2 to pancreatic β cells in non-obese diabetic (NOD) mice. AAV8-mIP-mediated gene expression of IL-2 to pancreatic β cells of 10-week-old NOD mice prevented the onset of hyperglycemia in NOD mice more in a dose-dependent manner with the lower dose of virus being more effective than a higher dose of AAV-mIP-IL-2 and IL-4. Moreover, the local β-cell expression of IL-2 increased the number of CD4(+)CD25(+)FoxP3(+) cells in the pancreatic lymph node (PLN) and SPL in both NOD and C57BL/6 mice. Taken together, these results demonstrate that local, low expression of mIL-2 in islets prevents progress of diabetes through the regulation of Tregs.