Constitutive expression of a murine interferon alpha gene in hamster cells and characterization of its protein product.

The coding part of a murine interferon alpha (MuIFN-alpha) gene was cloned into an expression plasmid containing the simian virus 40 early promoter and the rabbit beta-globin polyadenylation signal. This construct was transfected into Chinese hamster ovary cells, together with a plasmid containing the Ecogpt gene as a selection marker. Resulting colonies were assayed for constitutive interferon production and analysed for integration of MuIFN-alpha genes. There was no obvious correlation between the number of genes integrated and the amount of interferon produced. The highest producer, designated CHO-pSV10EF-3, contained four copies of the mouse gene and constitutively secreted up to 100 000 International Units of interferon per ml per day. The MuIFN-alpha subspecies produced by this clone was characterized by analysis of its antiviral activity on heterologous cells, heparin-Sepharose affinity chromatography and chromatofocusing. The results obtained indicate that it is identical or closely related to a minor component present in conventional MuIFN-alpha preparations.