A novel reporter gene assay for interferons based on CHO-K1 cells.

Interferons (IFNs) are cytokines playing an important role in the immune response and defence against viruses. They are widely used as biopharmaceuticals. Currently, the anti-viral assay (AVA) is the most commonly used bioassay for determining interferon potency. In the search for rapid and robust but reliable methods, reporter gene assays (RGA) appear to be the most promising approach, therefore we have designed a new reporter cell line, CHO-ISRE-SEAP, suitable for determination of type I interferon potency. Chinese hamster ovary (CHO-K1) cells were stably transfected with secretory alkaline phosphatase (SEAP) gene under the control of interferon stimulated response element (ISRE) promoter. The amount of SEAP in the cell culture medium can be easily measured colorimetrically and has been found to correlate with the amount of IFN added. The new assay is widely applicable for determination of type I IFNs, such as IFN-alpha, IFN-beta and IFN-omega, in research, development of IFN biopharmaceuticals, in batch release, etc. Interestingly, in this assay, IFN-beta shows approximately 6 times higher response than IFN-alpha, which makes it especially appropriate for measuring low levels of IFN-beta. Compared to other known RGAs, the novel CHO-ISRE-SEAP cell line-based RGA appears to have certain advantages with respect to cost and performance.