Osteopontin is an autoantigen of the somatostatin cells in human islets: identification by screening random peptide libraries with sera of patients with insulin-dependent diabetes mellitus

Random peptide libraries (RPLs) screening with IDDM sera has identified 5 d isease-specific 'mimotopes' displayed on phage (phagotopes). We characteris ed one phagotope (CH1p), by raising a rabbit antibody against the peptide i nsert on phage, which was employed in immunohistochemistry, Western blottin g and cDNA libraries screening. The CH1p mimotope was detected in somatosta tin cells of human islets and experimentally raised anti-osteopontin antibo dies or human sera positive for the phagotope, detected a similar subpopula tion of islet cells. The screening of cDNA library identified a clone corre sponding to human osteopontin. In summary, RPLs proved to be successful in the identification of a novel islet-related autoantigen (osteopentin), whos e significance in disease remains to be established. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.