Development and validation of an IL-6 immuno-receptor assay based on surface plasmon resonance

Interleukin-B (IL-G) is a pleiotropic cytokine which interacts with the specific IL-6 receptor at the surface of the T lymphocytes. A combined immuno- and receptor-assay has been developed and validated to characterize the biological activity of recombinant IL-6 (rIL-1). This assay is based on Surface Plasmon Resonance (SPR) technology. From each experiment two successive interactions were monitored: anti-IL-6 antibody/rIL-6 and rIL-6/IL-6 soluble Receptor (sIL-6R), Based on the first interaction an immune-assay for rIL-6 was optimized and validated. Based on the second interaction a receptor-assay for (rIL-6) biological activity was optimized and validated. The assays were validated by performing three different assays on three different days. The intra- and inter-day precisions (%CV) for the immuno-assay were respectively 0.9% and 1.7%. The overall recovery of the immuno-assay was 98.9% +/- 1.6. Intra- and inter-day precisions for the receptor-assay were respectively 1.1% and 1.4%. The overall recovery of the receptor-assay was 99.4% +/- 1.1. This immune-receptor assay has allowed to compare the rIL-6 stability after storage at different temperatures. The results did not show significant difference between the three lower storage temperatures (- 70, - 20 and 5 degrees C). However, results obtained for the aliquot stored at 25 degrees C have shown a drastic denaturation of the rIL-6. These results illustrate the advantage of this method combining the evaluation of the immunological and biological integrity of the drug and high reproducibility and precision of the biosensor based technology. (C) 2000 Elsevier Science B.V. All rights reserved.