One amino acid difference is critical for suppression of the development of experimental autoimmune diabetes (EAD) with intravenous injection of insulinB:9-23 peptide

InsulinB:9-23 peptide (insB:9-23) reactive T cells has been reported as crucial for type 1 diabetes. In this study, experimental autoimmune diabetes (EAD) mice, which subcutaneous immunization of ins1 or 2B:9-23 induced autoimmune diabetes in F1(B7.1B6 × BALB/c), was investigated for antigen specific therapy to delete pathogenic T cells. Intravenous injection of ins1 or 2B:9-23 significantly delayed the development of diabetes on the corresponding peptide-induced EAD (ins1EAD or ins2EAD) concomitant with reduced insulitis and insulin autoantibodies expression. Population of Foxp3⁺ CD4⁺ T cell was unchanged whereas the level of anti-insB:9-23 specific IgG_2a but not IgG₁ were specifically decreased, suggesting reduction of pathogenic insB:9-23 reactive T cells. Most interestingly, intravenous administration of ins2B:9-23, whose amino acid sequence had one amino acid difference at position 9 delayed the development of diabetes in both ins1EAD and ins2EAD whereas ins1B:9-23 administration delayed diabetes in the ins1EAD but not ins2EAD, suggesting that one amino acid difference gives critical influence on the effect of intravenous injection of antigenic peptide for type 1 diabetes.