Abstract: Objective To design and testify a novel strategy for acquiring mimetic epitope mapping by screening for a phage random peptide library using polyclonal anti keratin autoantibodies (AK auto Ab). Methods AK auto Ab were isolated and purified from pooled human sera by keratin affinity column in which keratin had been linked with CNBr Sepharose 4B,then biotinylated by the biotin ester. A 15 mer phage random peptide library was biopanned for 3 cycles and positive clones were identified by ELISA,competition assay and DNA sequencing. Results By sequence comparison 23 positive clones were selected randomly and three epitopes were confirmed. Among the three epitopes SLSPMPTTNRR was the dominant epitope. The phages carrying positive clones reacted with AK auto Ab specifically and keratin could prevent interaction between AK auto Ab and positive phages. Conclusion The designed strategy is successfully applied in acquiring epitopes of polyclonal autoantibodies to keratin, which could provide a new approach for the discovery of epitope mapping which binds to natural autoantibodies.

Key words: Keratin, Autoantibodies, Bacteriophages, Epitopes, Peptide library