A novel peptide isolated from phage display peptides library recognized by an antibody against connective tissue growth factor (CTGF).

The aim of this study was to isolate a peptide binding to an antibody against CTGF C-terminal domain from the peptide library and to evaluate its immunological and biological activities. A phage display 12-mer peptide library was screened using anti-CTGF/C antibody as the target. Ten of the positive clones were sequenced after three rounds bio-panning. The DNA encoding peptide ZD521 was cloned and expressed as the fusion protein(TrxA-ZD521). The specificity of ZD521 to anti-CTGF/C antibody was determined by competitive inhibition assay. Mice were immunized with purified fusion protein(TrxA-ZD521) and the anti-peptide or anti-CTGF response of antiserum was also tested by enzyme-linked immunoabsorbent assay (ELISA) and Western blot. The inhibition effect of anti-serum on proliferation of kidney mesangial cells was evaluated by MTT. A peptide ZD521(GEPQTKLFSFPL) that could specifically recognize anti-CTGF/C antibody was isolated. No sequence homology was found between ZD521 and CTGF/C. The purified TrxA-ZD521 could specifically bind to anti-CTGF/C antibody and block the binding of anti-CTGF/C antibody to CTGF/C and native CTGF(mesangial cell lysate). Moreover, the antiserum from mice immunized with TrxA-ZD521 could also bind to CTGF/C recombinant protein and native CTGF, as well as significantly inhibit the proliferation of kidney mesangial cells induced by CTGF/C. Therefore, ZD521 might be a conformational epitope of CTGF which is potentially useful to be developed as a vaccine for prevention and treatment of fibrosis disorders.