162-OR: Identification of Autoantibodies to ZnT8 Extracellular Epitope(s) in Patients with T1D

Previous studies demonstrate ZnT8 is displayed on the β-cell surface upon insulin secretion and IgG from ZnT8A-positive T1D patient sera stains the surface of live pancreatic β-cells. To further identify autoantibodies (AAb) to the ZnT8 extracellular epitope(s) (ZnT8ec) and to develop a ZnT8ec AAb assay, we first stabilized its native structure without the N-terminal domain (a.a 66-369; R325 or W325) by forming ZnT8-intracellular domain-Ab (ZnT8ic) complexes prior to release from liposome membranes. Sulfo-tagged ZnT8-Ab complexes were used as antigen in our electrochemiluminescence (ECL) AAb assay to analyze 130 sera (96 T1D patients, 22 T2D patients and 12 normal controls). Autoantibodies to ZnT8ec were identified in T1D patient sera by cross-reactivity of sera previously identified as exclusively ZnT8R or W positive, and ZnT8A negative sera. The prevalence of ZnT8ec AAbs in T1D patients was 21% (22/96: 5/37 of R+ sera, 7/24 of W+ sera and 8/35 of ZnT8A- sera) compared to 1/22 T2D patients and 0/12 normal controls. These are the first biochemically defined AAbs from T1D sera reported to target the β-cell surface. Further analysis of the role of these autoantibodies in β-cell autoimmunity and T1D etiopathology will be interesting and important for future studies.