MIMOTOPES IDENTIFIED BY PHAGE DISPLAY FOR THE MONOCLONAL-ANTIBODY CII-C1 TO TYPE-II COLLAGEN

The characterization of B cell epitopes has been advanced by the use o f random peptide libraries displayed within the coat protein of bacter iophage. This technique was applied to the monoclonal antibody (mAb) C 1 to type II collagen (CII-C1). CII-C1 is known to react with a confor mational epitope on type II collagen that includes residues 359-363. T hree rounds of selection were used to screen two random nonameric phag e libraries and 18 phagotopes were isolated. CII-C1 reacted by ELISA w ith 17 of the 18 phagotopes: one phagotope contained a stop codon. Of the eight most reactive phage, seven inhibited the reactivity by ELISA of CII-C1 with type II collagen. Of the 18 phage isolated, 11 encoded the motif F-G-x-Q with the sequence F-G-S-Q in 6, 2 encoded F-G-Q, an d one the reverse motif Q-x-y-F. Most phagotopes that inhibited the re activity of CII-C1 encoded two particular motifs consisting of two bas ic amino acid residues and a hydrophobic residue in the first part of the insert and the F-G-x-Q or F-G-Q motif in the second part; phagotop es which contained only one basic residue in the first part of the seq uence were less reactive. These motifs are not represented in the line ar sequence of type II collagen and thus represent mimotopes of the ep itope for CII-C1 on type II collagen. There were five phagotopes with peptide inserts containing the sequence RLPFG occurring in the Epstein -Barr virus nuclear antigen, EBNA-1. This is of interest because EBV h as been implicated in the initiation of rheumatoid arthritis (RA) by r eason of increased reactivity to EBNA-1 in RA sera. In conclusion, the phage display technique disclosed mimotopes for a conformational epit ope of type II collagen, and revealed an interesting homology with a s equence of the EBNA-1 antigen from Epstein Barr virus. (C) 1998 Academ ic Press.