BASTA, a simple whole blood assay for measuring β-cell antigen specific CD4 ⁺ T-cell responses in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease where T-cells mediate the destruction of the insulin-producing β-cells found within the Islets of Langerhans in the pancreas. Currently, autoantibodies to β-cell antigens are the only tests available to detect β-cell autoimmunity. T-cell responses to β-cell antigens, which are known to cause T1D, can only be measured in research settings due to the complexity of assays and the large blood volumes required. Here we describe the β -cell a ntigen s pecific T -cell a ssay – BASTA. BASTA is a simple whole blood assay that can detect human CD4 ⁺ T-cell responses to β-cell antigens by measuring antigen-stimulated IL-2 production. BASTA is both more sensitive and specific than the CFSE-based Proliferation Assay. We used BASTA to identify the regions of preproinsulin which stimulated T-cell responses specifically in blood from people with T1D. BASTA can be done with as little as 2-3 mL of blood. We found that effector memory CD4 ⁺ T cells are the primary producers of IL-2 in response to preproinsulin peptides. We then evaluated responses to individual and pooled preproinsulin peptides in a cross-sectional study of pediatric subjects: without T1D, without T1D but with a first-degree relative with T1D, or diagnosed with T1D. In contrast to other preproinsulin peptides, full-length C-peptide (PI _33-63 ) showed excellent specificity for T1D (AUC = 0.86). We suggest that BASTA will be a useful tool for monitoring changes in β-cell specific CD4 ⁺ T-cell responses both in research and clinical settings.