Objective: To evaluate the effect of multiple amino acid substitutions of C II 263-272 peptide on collagen-induced arthritis, and explore a therapeutic strategy of rheumatoid arthritis.
Methods: A panel of altered C II 263-272 peptides was synthesized with substitutions of TCR-contact residues of C II 263-272 with alanine. The competitive inhibition of APL to wild type C II 263-272 was analyzed by 3H incorporation assay. CIA model was induced by intradermal injection of bovine CII. Altered CII peptide was injected subcutaneously in different doses (1, 10, 100 microg, respectively, twice per week) after onset of CIA. The arthritis index, radiologic and histologic scores were recorded to evaluate the severity change of arthritis. Serum levels of IFN-gamma were examined by ELISA.
Results: Competitive inhibition to wild type C II 263-272 of the altered C II 263-272 peptides (APL1, APL2, APL3) was found in PBMC from RA patients. Among them, APL3 with substitution of residues 267(Q), 270(K) and 271(G) to A showed the most significant effect and thus was used in the treatment of CIA rats. We observed significantly reduced arthritis scores in CIA rats treated with 100 microg/dose of APL as compared with rats treated with PBS and peptide control. The mean radiographic and histologic scores was also markedly lower in APL-treated CIA rats than in PBS or peptide control-treated rats. On day 35 after immunization, the serum level of IFN-gamma in rats was examined and a significantly low level of serum IFN-gamma was found in APL-treated rats.
Conclusion: C II 263-272 peptide with TCR-contact residues substitutions inhibited joint destruction in CIA rats and down-regulated IFN-gamma production, suggesting that altered CII peptide might be potentially therapeutic in rheumatoid arthritis.