Quantification of Neutralizing Antibodies to Human Type I Interferons Using Division-Arrested Frozen Cells Carrying an Interferon-Regulated Reporter-Gene

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Abstract
Development of neutralizing antibodies (NAbs) to interferons (IFNs) can reduce the clinical response to IFN therapy. As current cell-based assays for quantifying NAbs have limitations, a highly sensitive and reproducible assay was developed, using division-arrested frozen human U937 cells transfected with the luciferase reportergene controlled by an IFN-responsive chimeric promoter, which allows IFN activity to be determined with precision within hours. Assay-ready PIL5 cells can be stored frozen for >3 years without loss of IFN sensitivity or the need for cell propagation. The assay is highly IFN sensitive (detecting TM (Schering-Plough, Levallois-Perret,France), or PegasysTM (Hoffmann-La Roche, Neuilly-sur-Seine, France, than against 10 LU/mL IFN-α2. Similarly, NAbs from patients treated with IFN-β1a exhibit lower titers against 10 LU/mL of low specific activity IFN-β1b than against IFN-β1a. The combination of the use of division-arrested, IFN-responsive human cells transfected with the luciferase reporter-gene makes the rapid PIL5 assay for NAbs highly advantageous.