Adalimumab (ADA) is a TNF-α blocker drug antibody fully humanized and thus indistinguishable in structure and function from natural human IgG1, used in the juvenile idiopathic arthritis (JIA) treatment. Immunogenicity against the drug has been frequently detected in treated patients, and the presence of anti-ADA antibodies is correlated to treatment failure or lower clinical remission. Herein, we measured by surface plasmon resonance (SPR) both the binding and the affinity of anti-ADA antibodies to the ADA-immobilized biosensor. The binding of anti-ADA antibodies was evaluated by testing sera from ADA-treated patients (n = 30), untreated patients (n = 9), and healthy donors (n = 20) in the SPR biosensor. The optimal cut-off point was defined using the receiver operating characteristic curve (ROC-curve) analysis with 79 % (60.28 to 92.01 %, 95 % CI) sensitivity, 99 % (88.06 to 100.0 %, 95 % CI) specificity, and a positive likelihood ratio of 23. The area under the curve was 0.9298 (p < 0.0001). The apparent affinity of anti-ADA antibodies from pediatric patients' sera was measured, analyzing the interaction of anti-drug antibodies using whole sera, enriched IgG fractions, and isolated anti-ADA antibodies. The immobilized drug ADA interacted with purified antibodies at low affinities (10(-6) M > K D > 10(-9) M). Graphical Abstract Adalimumab immobilized on the biosensor chip surface detects specific anti-drug antibodies in treated patients' sera.
Keywords: Adalimumab; Affinity; Anti-drug antibodies; Surface plasmon resonance.