Quantitative measure of anti-infliximab antibodies.

Promonitor®-anti-IFX is an enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of anti-infliximab antibodies in human serum samples. The amount of anti-infliximab antibodies, when considered in conjunction with the infliximab (IFX, Remicade®) level (Promonitor®-IFX Ref. 5060230000) and clinical findings, like disease activity, contributes valuable information to the physician to assess the efficacy of therapies with IFX, predict infusion-related reactions and loss of clinical response by the patient. Due to its chimeric structure, IFX often raises an unwanted immune response in the treated patient, causing Anti-Drug Antibodies (ADA) to form. All Anti-IFX antibodies are neutralizing anti-idiotypic antibodies which can render the therapy completely useless. It is also known that the presence of high titers of anti-IFX antibodies may be related to severe complications like infusion-related reactions. The correlation between reduced serum IFX concentrations, ADA formation and increased disease activity has been demonstrated in several observational clinical studies in a series of pathologies.

Promonitor®-anti-IFX is a bridging ELISA where microwell strips are provided pre-coated with IFX. The bridging ELISA takes advantage of the two arms of IgG subclasses 1, 2 and 3, to crosslink the IFX coated on the plate. Calibrators, controls and diluted patient samples are added to separate wells, allowing anti-IFX antibodies present to bind to pre-immobilized IFX. Unbound sample is washed away, and HRP-labeled IFX is added to each well. A second incubation allows the HRP-labeled IFX to bind to the antibodies that have become attached to the microwells. After washing away unbound HRP conjugate, the remaining enzyme activity is measured by adding a chromogenic substrate and measuring the intensity of the color that develops in a spectrophotometer. The signal obtained is proportional to the amount of anti-IFX binding antibodies in the patient sample.

Optical densities (OD) of the calibrators are plotted to construct the anti-IFX antibodies calibration curve. A four parameter logistic (4PL) model is used to fit the curve. Positive and Negative Controls are used to monitor assay performance. Anti-IFX antibodies titer is calculated by interpolating sample OD in the calibration curve. Interpretation of results in a clinical setting is provided. Warnings for each sample are optionally included; this setting can be configured here.

See also

Related assays: Promonitor®-IFX Ref. 506XX30000