Purification and in vitro labeling of interferon from a human fibroblastoid cell line

Interferon was produced from a clonal human fibroblastoid line. This cell line was derived from an established fibroblastoid culture treated with ethylmethane sulfonate and is capable of producing higher amounts human interferon than primary human fibroblast cultures. The interferon produced from this cell line was purified by concanavalin A and phenyl-Sepharose column chromatography followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified interferon was then labeled with [125I]-iodine, with [3H]5-dimethylaminonaphthalene-1-sulfonyl-chloride and with sodium [3H]borohydride after periodate oxidation. An appreciable amount of biological activity was retained after both tritium labelings but not after iodination. When subjected to electrophoresis in the presence of sodium dodecyl sulfate all three radioactive interferon preparations comigrated with the purified interferon preparation as a single protein component with a molecular weight of 19,000. Both purified and radioactive preparations were also shown to migrate with the antiviral activity in polyacrylamide gels in the absence of sodium dodecyl sulfate. The specific activity of purified interferon preparations ranged from 2 X 10(8) to 10 X 10(8) units/mg of protein.