Serological Proteome Analysis (SERPA) as a tool for the identification of new candidate autoantigens in type 1 diabetes.

Type 1 diabetes (T1D) is an autoimmune disease characterized by the presence of circulating autoantibodies directed against proteins of islet beta-cell. Autoantibodies (autoAb) testing is utilized for diagnostic purposes; however, up to 2-5% of patients with the clinical diagnosis of T1D are negative for known autoAb, witnessing the fact that T1D autoantigen panel is incomplete. To the aim of searching new T1D autoantigen(s), we used sera from subjects with a clinical diagnosis of T1D, but who tested negative for the four T1D autoantibodies currently used in clinical practice and to the screening of genes involved in sporadic cases of diabetes. Sera from these patients were challenged by Western blot against the proteome from human pancreatic beta-cell resolved by 2DE (“immunoproteomics”): eleven proteins were then identified by MS. Radiobinding assays (RBA) were developed for two proteins targeted by MS: Rab GDP dissociation inhibitor beta (GDI and Peptidylprolyl cis-trans isomerase A. At RBA, more than 50% of a group of 50 patients with T1D were positive to either full-length or COOH-terminus GDIIn addition, 19% of patients with celiac disease also tested positive to the COOH-terminus GDI-RBA. These results indicate that immunoproteomics is a feasible strategy for the identification of new T1D autoantigens.