Development of a new Immunoassay for the accurate determination of anti-infliximab antibodies in Crohnʼs Disease

Abstract

The formation of antibodies to infliximab (ATIs) is closely associated with the loss of a response to infliximab in patients with Crohn's disease (CD). We evaluated the clinical utility of a novel method to measure serum ATI levels in the presence of infliximab. ATI levels were measured by a novel method of immunoassay with protein A and the conventional method in a cohort of 58 patients with CD under infliximab maintenance therapy. The serum infliximab trough levels were determined by enzyme-linked immunosorbent assay. ATIs were detected in 16 out of 58 patients (27.6%) by the new method, but the conventional method detected only 2 patients (3.4%) who had the 2 highest ATI titers assayed by the new method. The presence of ATIs in those samples positive according to the new method but negative by the conventional method was confirmed by Western blotting analysis. It also indicated that the new method could restore the binding capacities of the ATIs to infliximab, which were occupied by free infliximab. In the current method, the addition of infliximab to the samples dosedependently blocked the detection of ATIs. Patients positive for ATIs had significantly lower serum trough levels of infliximab (p<0.01), and significantly higher clinical activity scores (p<0.001) and higher laboratory markers for inflammation (CRP and ESR) (p<0.01) as compared to patients negative for ATI. The current method makes it possible to measure serum ATI levels in the presence of infliximab. This new method seems to be useful for deciding the optimal management strategies for CD patients with a loss of response to infliximab.