Isolation of peptides useful for differential diagnosis of Crohn's disease and ulcerative colitis

Background: Phage displayed random peptide technology has been utilised to identify binding epitopes of antibodies or receptor ligands. Aim: To isolates peptides from a phage library which are specifically recognised by antibodies in serum from patients with Crohn's disease (CID). Methods: A phage displayed random peptide library composed of nine amino acids was established and sequentially screened using serum immunogloblin G obtained from CD patients. Results: Five different CID specific peptides were isolated from the phage library. No homology in amino acid sequences was observed among four (CDP-1, -3 to -5) of the five peptides exhibiting different binding characteristics with each CD patient's serum. In contrast, two peptides (CDP-1 and -2) had similar amino acid sequences and similar binding characteristics. Four multiple antigenic pepticles (MAP, CDP-1, -3 to -5) were synthesised, and an enzyme linked immunosorbent assay (ELISA) using the four pepticles was developed to detect serum antibodies against them. Fifty two of 92 CD patients (56.5%) were detected by ELISA, none of 20 ulcerative colitis (UC) patients, only one of 25 duodenal ulcer patients, and only three of 48 healthy subjects. Conclusions: ELISA using the four pepticles isolated in this study may be useful for the differential diagnosis of CD and UC.