Objective: To obtain the mimotope recognized by anti-keratin antibody (AKA) by screening a phage random peptide library and evaluate its diagnostic value.
Methods: IgG was purified from AKA positive pooled serum of rheumatoid arthritis (RA) patients by 33.3% (NH4)2SO4 (AKA measured with indirect immunofluorescence). Then the antibody was used as the ligand for biopanning of a 12-mer phage random peptide library. The serum of patients with RA, SLE and normal people were detected with the positive clone by indirect ELISA.
Results: After 4 rounds of screening, the peptide of mimotope associated with RA was acquired. The diagnostic specificity, positive predictive value and Youden's index were 95.6%, 90% and 155.6% respectively. Its amino acid sequence was QSESAGPTTSRR. This sequence was similar to 137-148 amino acid sequence of human filaggrin.
Conclusion: The RA-associated peptide is acquired by screening a phage random peptide library using polyclonal AKA of RA patients. It may be a specific diagnostic tool of RA.