Endocrine Abstracts

Biopharmaceuticals are complex molecules and can show variation between production batches. Physicochemical tests and biological activity measurements contribute complementary data to the characterisation of these products.

As part of a project to correlate physicochemical and bioassay data, under the Department of Trade and Industry’s Measurements for Biotechnology programme, we have developed a simple, robust cellbased bioassay protocol for interferon alfa 2a (IFN alfa 2a). This bioassay measures the antiproliferative action of IFN alfa 2a on cultured Daudi cells (CCL-213, ATCC). It is performed in 96well cell culture plates and the readout is colorimetric, measuring the metabolic activity of the cell population by reduction of the redox dye alamarBlue™ (Serotec). Cells are seeded at a density of 5×10⁴ cells/ml (1×10⁴ cells/well) and dosed on seeding with a 2-fold dilution series of IFN alfa 2a, starting from 193.8 IU/ml (approx. 155 pg/well for the International Standard). After incubation (37°C, 5% CO₂ in air) for 72 hours, 40 microlitre/well of alamarBlue™ is added and the plates are incubated for a further 16 hours, before the difference in absorbance at 570 nm and 600 nm is read.

The assay has been used to compare the activities of the 2nd International Standard for IFN alfa 2a (code 95/650), the EDQM reference standard (ref. I0320300; note this is a standard for specified physicochemical tests with no specification as to its suitability for biological assays) and various preparations of recombinant IFN alfa 2a. Differences in specific activity of these IFN preparations have been measured.