Anti-carbamylated protein antibodies as a clinical response predictor in rheumatoid arthritis patients treated with abatacept

Carbamylation is an irreversible post-translational modification of proteins. The presence of anti-carbamylated protein antibodies (anti-CarP) has been observed in rheumatoid arthritis (RA). This study was focused to verify whether anti-CarP antibodies can be used as a predictive factor of clinical response to abatacept (CTLA4-Ig) in RA patients. Sixty RA patients treated with abatacept were enrolled. A home-made ELISA for anti-CarP and a commercial anti-CCP3.1 kit for anti-citrullinated proteins antibodies (anti-CCP) were applied to determine serum levels every six months of therapy. Rheumatoid factor (RF) was also tested. Anti-CarP positive patients (n=18) were younger (p=0.01) and with a longer disease duration (p=0.05) when compared to anti-CarP negative patients (n=42) at baseline. Considering the entire cohort, a significant reduction of anti-CarP titre after twelve-months of treatment was shown (p