A PLANT-BASED CHOLERA-TOXIN-B SUBUNIT - INSULIN FUSION PROTEIN PROTECTS AGAINST THE DEVELOPMENT OF AUTOIMMUNE DIABETES

Oral administration of disease-specific autoantigens can prevent or de lay the onset of autoimmune disease symptoms. We have generated transg enic potato plants that synthesize human insulin, a major insulin-depe ndent diabetes mellitus autoantigen, at levels up to 0.05% of total so luble protein. To direct delivery of plant-synthesized insulin to the gut-associated lymphoid tissues, insulin was linked to the C-terminus of the cholera toxin B subunit (CTB). Transgenic potato tubers produce d 0.1% of total soluble protein as the pentameric CTB-insulin fusion, which retained GM(1)-ganglioside binding affinity and native antigenic ity of both CTB and insulin. Nonobese diabetic mice fed transformed po tato tuber tissues containing microgram amounts of the CTB-insulin fus ion protein showed a substantial reduction in pancreatic islet inflamm ation (insulitis), and a delay in the progression of clinical diabetes . Feeding transgenic potato tissues producing insulin or CTB protein a lone did not provide a significant reduction in insulitis or diabetic symptoms. The experimental results indicate that food plants are feasi ble production and delivery systems for immunotolerization against thi s T cell-mediated autoimmune disease.