In vivo cytotoxicity of insulin-specific CD8⁺ T-cells in HLA-A*0201 transgenic NOD mice

OBJECTIVE - CD8⁺ T-cells specific for islet antigens are essential for the development of type 1 diabetes in the NOD mouse model of the disease. Such T-cells can also be detected in the blood of type 1 diabetic patients, suggesting their importance in the pathogenesis of the human disease as well. The development of peptide-based therapeutic reagents that target islet-reactive CD8⁺ T-cells will require the identification of disease-relevant epitopes. RESEARCH DESIGN AND METHODS - We used islet-infiltrating CD8⁺ T-cells from HLA-A*0201 transgenic NOD mice in an interferon-γ enzyme-linked immunospot assay to identify autoantigenic peptides targeted during the spontaneous development of disease. We concentrated on insulin (Ins), which is a key target of the autoimmune response in NOD mice and patients alike. RESULTS - We found that HLA-A*0201-restricted T-cells isolated from the islets of the transgenic mice were specific for Ins1 L3-11, Ins1 B5-14, and Ins1/2 A2-10. Insulin-reactive T-cells were present in the islets of mice as young as 5 weeks of age, suggesting an important function for these specificities early in the pathogenic process. Although there was individual variation in peptide reactivity, Ins1 B5-14 and Ins1/2 A2-10 were the immunodominant epitopes. Notably, in vivo cytotoxicity to cells bearing these peptides was observed, further confirming them as important targets of the pathogenic process. CONCLUSIONS - The human versions of B5-14 and A2-10, differing from the murine peptides by only a single residue, represent excellent candidates to explore as CD8⁺ T-cell targets in HLA-A*0201-positive type 1 diabetic patients.