A Single L/D-Substitution at Q4 of the mInsA2-10 Epitope Prevents Type 1 Diabetes in Humanized NOD Mice

Autoreactive CD8(+) T cells play an indispensable key role in the destruction of pancreatic islet beta-cells and the initiation of type 1 diabetes (T1D). Insulin is an essential beta-cell autoantigen in T1D. An HLA-A*0201-restricted epitope of insulin A chain (mInsA(2-10)) is an immunodominant ligand for autoreactive CD8(+) T cells in NOD.beta 2m(null).HHD mice. Altered peptide ligands (APLs) carrying amino acid substitutions at T cell receptor (TCR) contact positions within an epitope are potential to modulate autoimmune responses via triggering altered TCR signaling. Here, we used a molecular simulation strategy to guide the generation of APL candidates by substitution of L-amino acids with D-amino acids at potential TCR contact residues (positions 4 and 6) of mInsA(2-10), named mInsA(2-10)DQ4 and mInsA(2-10)DC6, respectively. We found that administration of mInsA(2-10)DQ4, but not DC6, significantly suppressed the development of T1D in NOD.beta 2m(null).HHD mice. Mechanistically, treatment with mInsA(2-10)DQ4 not only notably eliminated mInsA(2-10) autoreactive CD8(+) T cell responses but also prevented the infiltration of CD4(+) T and CD8(+) T cells, as well as the inflammatory responses in the pancreas of NOD.beta 2m(null).HHD mice. This study provides a new strategy for the development of APL vaccines for T1D prevention.