Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


Bridging ELISA As a Screening Assay to Monitor Immunogenicity in Routine Clinical Practice.

Garces1,  Sandra, Demengeot2,  Jocelyne, da Silva3,  J. Canas, Aarden4,  L.

Instituto Gulbenkian Ciência; Hospital Garcia de Orta, Oeiras, Portugal
Instituto Gulbenkian Ciência, Oeiras, Portugal
Hospital Garcia de Orta, Almada, Portugal
Sanquin Research and Landsteiner Laboratory, Amsterdam, Netherlands

Background/Purpose:

Drug immunogenicity can be a significant problem in the treatment of patients with therapeutic antibodies, such as TNF alpha inhibitors. The clinical and scientific relevance of monitoring immunogenicity in clinical practice have been recognized and recommended by the European Agency of Medicine (EMEA). However, its assessment is technically challenging and no consensus exists about the way immunogenicity can be monitored. Newly developed fluid-phase radio-immuno assays (RIA) have been presented as a kind of "gold standard" method to assess immunogenicity. However, RIA requires high doses of radioactivity and special conditions, preventing its use as a routine assay. By contrast, enzyme-linked immunoassay (ELISA) it's a simple and cheap method, ideal candidate to be used as a high-throughput screening assay. Bridging ELISA has increased specificity over the conventional ELISAs methods. Several optimizations of this method were made so that it can become a good screening assay to monitor drug immunogenicity. We aim to test, in a same cohort of patients receiving infliximab, this bridging ELISA in comparison with a fluid-phase antigen-binding RIA to quantify anti-infliximab antibodies.

Methods:

A total of 82 consecutive patients were evaluated (38 rheumatoid arthritis patients, 27 ankylosing spondylitis, 9 psoriatic arthritis and 18 patients with inflammatory bowel disease), 61 females, with a mean age of 41 (4.2) years, that were receiving Infliximab (3–5mg/Kg every 6 or 8 weeks) for a mean period of 3.5 (2.0) years. Blood samples were collected immediately before the next infliximab infusion. Anti-infliximab antibodies were quantified by 1) Bridging ELISA where the antibodies bind to the infliximab coated in a solid phase and revealed by the addition of biotinylated infliximab and by 2) fluid-phase RIA-ABA that uses a sepharose-immobilized protein A, IgG total and IgG4-specific, to bind IgGs in the patient's serum. Anti-infliximab specific IgGs are revealed by the addition of 125I-labeled infliximab F(ab')2. A simple ELISA method was used to quantify serum infliximab levels., Therapeutic response was assessed according to validated criteria established for each disease.

Results:

A total of 22 (27%) were tested positive for the presence of anti-infliximab abs using RIA, coinciding with the samples that were also positives in Bridging ELISA. Bridging ELISA cannot detect monovalent IgG4. No samples testing exclusively IgG4 specific anti-infliximab were detected. All patients (100%) with detectable anti-infliximab antibodies had undetectable serum trough drug levels and were not able to sustain the therapeutic response.

Conclusion:

Bridging ELISA was able to detect the same positive samples as RIA. The presence of IgG4-specific antibodies did not alter the assay's ability in detecting positive samples, since exclusively IgG4-specific antibodies are unlikely to occur. By its simplicity Bridging ELISA is a suitable test to be implemented in routine clinical practice as a screening assay to monitor drug immunogenicity.

To cite this abstract, please use the following information:
Garces, Sandra, Demengeot, Jocelyne, da Silva, J. Canas, Aarden, L.; Bridging ELISA As a Screening Assay to Monitor Immunogenicity in Routine Clinical Practice. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1841
DOI:

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