A novel reactive epitope-based antigen targeted by serum autoantibodies in oligoarticular and polyarticular juvenile idiopathic arthritis and development of an electrochemical biosensor.

Currently, there are no specific markers for juvenile idiopathic arthritis (JIA) diagnosis, which is based on clinical symptoms and some blood tests for diseases' exclusion. Aiming to select new epitope-based antigens (mimotopes) that could recognize circulating autoantibodies in most JIA forms, we screened a phage displayed random peptide library against IgG antibodies purified from serum of JIA patients. ELISA assay was carried out to confirm immunoreactivity of selected peptides against sera IgG antibodies from JIA patients, healthy children and patients with other autoimmune diseases. The mimotope PRF+1 fused to phage particles was able to efficiently discriminate JIA patients from controls, and for this reason was chosen to be chemically synthesized for validation in a larger sample size. The synthetic peptide was immobilized onto bioelectrodes' surface for antibody detection by electrochemical analyses through differential pulse voltammetry. The PRF+1 synthetic peptide has efficiently discriminated JIA patients from control groups (p<0.0001) with a very good accuracy (AUC>0.84; sensitivity=61%; specificity=91%). The electrochemical platform proved to be fast, low cost and effective in detecting anti-PRF+1 antibodies from JIA patients compared to healthy controls (p=0.0049). Our study describes a novel and promising epitope-based biomarker for JIA diagnosis that can become a useful tool for screening tests, which was successfully incorporated onto an electrochemical biosensor and could be promptly used in field diagnostics.