Exploring the binding sites of anti-infliximab antibodies in pediatric patients with rheumatic diseases treated with infliximab.

Over the past decade, the treatment of a variety of immune-mediated diseases has improved greatly due to the introduction of biologics for therapies in cases that are nonresponsive to traditional treatments. However, a side effect not encountered in traditional treatments is the immunogenicity of the biologics themselves. Our aim was to investigate the anti-infliximab-antibody response in pediatric patients receiving infliximab for juvenile idiopathic arthritis and other pediatric rheumatic diseases, with a focus on an analysis of the binding sites of these antibodies. We show that anti-infliximab antibodies developed in 43% of patients receiving infliximab therapy. Neutralization studies showed that in all these patients, the antibodies were directed toward the variable domains of infliximab, as they inhibited binding of infliximab to TNF. A more precise determination of the antibody epitopes using synthetic peptides was not achieved, indicating that all the antibody binding sites were composed of discontinuous segments of infliximab.