To determine the epitope recognized by mAb A9E8, biopanning of a phage displayed 12-mer random peptide library was performed using the affinity purified mAb A9E8. After three rounds of biopanning, an enrichment of phages bound to the mAb A9E8 was obtained. The output to input ratios of the three rounds of biopanning were 0.00008%,0.038% and 0.79%.