Pivotal epitopes for islet antigen-specific CD8+ T cell detection improve classification of suspected type 1 diabetes with the HLA-A*0201 allele.

A proportion of patients with new-onset diabetes share similar symptoms with type 1 diabetes (T1D) patients but they are negative for islet antigen-specific autoantibodies. This study was to develop an islet antigen-specific CD8⁺ T-cell assay to provide autoimmune evidence regarding these "suspected" T1D patients. HLA-A*0201 individuals with autoAbs⁺ T1D, autoAbs^- suspected T1D, and type 2 diabetes, along with HLA-A*0201 healthy controls were recruited. Using interferon-γ enzyme-linked immunospot assays, the percentages of participants in each group with various islet antigen-specific CD8⁺ T cells were determined. Sixteen out of the 28 islet antigen-specific epitopes tested were T1D specific, meaning that there was a significantly (P < 0.05) greater epitope positivity rate in the autoAbs⁺ T1D cohort than in the healthy controls. Using a cutoff value of two positive epitopes, the 16-epitope panel led to a sensitivity of 75.0% and a specificity of 94.4% regarding the autoAbs⁺ T1D patients. Even when using an optimized five-epitope panel, the results were highly accurate. Notably, in the application phase of the study, 77.8% of a new cohort of autoAbs^- suspected T1D patients exhibited positivity when using the five-epitope optimized panel. This highly accurate method, especially for pediatric patients, will improve clinical diagnosis and etiological classification of autoimmune T1D.