Brief CommunicationCombination of worm antigen and proinsulin prevents type 1 diabetes in NOD mice after the onset of insulitis

•Combined treatment with filarial antigen and pro-insulin improves protection.•Combination therapy prevents diabetes onset in NOD mice after insulitis occurred.•Combination therapy induces regulatory T cells in the pancreatic lymph nodes.•Combination therapy reduces pancreatic islet inflammation.

Animal studies demonstrated that administration of helminth products can protect from autoimmune diseases. However, the success of such administrations is limited in the case of type 1 diabetes, as protection is only provided if the administration is started before the development of insulitis. In this study we investigated whether inclusion of helminth antigen administrations to an antigen-specific treatment with proinsulin improves the protective effect by triggering non-specific regulatory immune responses. Using a combination therapy of intraperitoneal Litomosoides sigmodontis antigen and intranasal pro-insulin, onset of diabetes was prevented in NOD mice after insulitis started, while either administration alone failed to protect. This protection was associated with an increased frequency of regulatory T cells within the pancreatic lymph nodes and a reduced inflammation of the pancreatic islets. This suggests that inclusion of helminth antigens improve the protective effect provided by antigen-specific therapies and represent a new potential therapeutic approach against autoimmune diseases.