Sensitive immunoassays for the autoantibodies reacting against citrullinated carboxy-terminal telopeptides of type I and type II collagens in patients with rheumatoid arthritis

We developed sensitive assay methods for autoantibodies recognizing the citrullinated synthetic peptides derived from type I and type II collagens in patients with rheumatoid arthritis (RA). These peptides were tested with the chemiluminescence method (Nichols Advantage (R) System). In 44 RA patients out of 120, the sera showed increased binding of citrullinated synthetic C-telopeptide derived from the alpha 1 chain of type I collagen (p=0.003 compared to controls). For a corresponding C-telopeptide pair from the alpha 1 chain of type II collagen, 35 patient sera bound the citrullinated peptide more strongly than the arginine peptide, but the difference compared to the controls was not significant (p=0.074). Correlation between the two carboxy-telopeptides was r=0.473 (p < 0.001). The anti-CCP assay (antibodies against citrullinated filaggrin sequence-derived peptides) was positive in 59% of our RA patients. There was no relationship between the anti-CCP results and the antibodies against collagen C-telopeptides, but both are increased in RA patients. We demonstrated autoantibodies in RA patients that bound citrullinated C-telopeptides derived from type I and type II collagen antigens. The peptide sequences detected (-YYXA and -YMXA) were different from that based on the cyclic filaggrin antigen (-STXG-, where X represents citrulline).