Negative vaccination with IGRP-pulsed dendritic cells expressing ectopic IL-35Ig prevents the development of NOD autoimmune Diabetes

Dendritic cells (DCs) are specialized antigen presenting cells capable of triggering either stimulatory or regulatory T cell immune responses, according to their cell maturation state and micro-environment stimuli. IL-35, a hetero-dimeric cytokine belonging to the IL-12 family, is produced by regulatory T and B cells and is known to induce a strong immunosuppressive response. In this study, we explored the possible regulatory and protective effect of IL-35 in a tolerogenic vaccination protocol aimed to prevent autoimmune Diabetes in pre-diabetic NOD mice. To this purpose we prepared murine splenic DCs transfected with an IL-35Ig single chain gene construct and loaded with IGRP peptide (one of the most relevant Type 1 Diabetes self-antigens) to be administered in a prophylactic cell therapy. Interestingly, we found that such IL-35Ig-producing and IGRP-presenting DCs capable to suppress antigen specific, T cell-mediated responses in a skin test assay induced in pre-diabetic NOD mice a delayed and less severe form of Diabetes, an effect accompanied by the increase of CD4+CD39+ suppressive T cells in pancreatic lymph nodes. Protective immunosuppression achieved in this model suggests that DCs overexpressing ectopic IL-35Ig might represent a powerful tool in negative vaccination strategies.