A colourimetric dye assay to detect anti-viral activity of interferons: sensitivity for measuring cellular responsiveness to interferons.

Colourimetric assays which rely on the conversion of metabolic dyes are becoming increasingly used for measuring cell proliferation and cytotoxicity. We developed a method for measuring cellular responsiveness to interferons based on the property of interferons to induce cell defenses to virus-mediated killing. The assay has several advantages over previous assays for measuring anti-viral activity and efficiently detected cytoprotective responses to human interferon of five human melanoma cell lines infected with Semliki Forest virus. The melanoma cell lines showed a varying cytoprotective response to interferons alpha 2, alpha 4, beta and gamma, in agreement with the results of previous assays for measuring melanoma cell responsiveness to interferons based upon the inhibition of cell growth (1).