A quantitative human monoclonal antibody immunoassay using anti-idiotypic antibody as a membrane antigen surrogate with surface-plasmon-resonance detection

摘要

Biologically active membrane proteins are difficult to isolate. Very often the isolated membrane proteins have low binding affinity or no biological integrity at all. Despite some success in isolation, one has to overcome the hurdles of obtaining sufficient quantity of the proteins and maintaining biological activity upon coating them on surfaces for developing an ELISA. Thus an alternative approach may be useful. The present study describes a quantification assay method for a therapeutic hmAb-1 (human monoclonal antibody-1) that recognizes a cell-surface protein employing an anti-ID (anti-idiotypic antibody) to hmAb-1 as a surrogate antigen in an immunoassay format using surface- plasmon-resonance technology. This assay is applicable for quantification of hmAb-1 in process streams, final drug-product quality control, as well as low-concentration drug substances in intravenous-solution bags. The surrogate nature of the anti-ID was confirmed by demonstrating that the anti-ID displaced the interaction between the hmAb-1 and its membrane antigen in a FACS titration test. The assay format involves first capturing hmAb-1 on the flow-cell surface, which then binds quantitatively to anti-ID in a mixture of increasing quantity of hmAb-1 in solution. An inverse dose-response relation between this anti-ID bound signal (or resonance units) and hmAb-1 concentration was established. The dose-response range of the calibration curve for hmAb-1 was between 20 and 300ng/ml. The precision, accuracy and specificity of the assay are reported in the present paper.