Production and Purification of Human MG63 Cell Interferon

Abstract

MG63 cells induced by Sendai virus were a convenient source of human interferon, which was of the I' type in antigenicity. When analyzed by SDSpolyacrylamide gel electrophoresis (SDS-PAGE), the interferon migrated as a single component with a molecular weight of 22,000 daltons. It was purified to apparent homogeneity by chromatography on Blue Sepharose, followed by SDS-PAGE, and estimated to have a specific activity of 4 x 10 8 international units/rug of protein.Production of large quantities of human interferon (IFN) is essential for both biological and clinical investigations. This has long been difficult but now is being achieved by using bacteria harboring recombinant IFN genes (7,10,24,32). The f3 type of human IFN produced in cell cultures, however, is a glycoprotein (6, 15,23), whereas the bacteria-derived IFN molecules are nonglycosylated. Therefore, the role of the carbohydrate moiety must be elucidated by using the natural IFN molecules.The most commonly used source of human IFN-f3 is diploid fibroblasts (5, 12), induced by polyinosinate-polycytidylate (poly(I)'poly(C)), and subjected to a "superinduction" procedure using actinomycin D and cycloheximide (30), which is laborious for large-scale culture. Other convenient sources of human IFN-f3 are thus desirable.MG63 cells, derived from human osteogenic sarcoma, were recently shown by Billiau et al (4) to produce high yields of human IFN-f3 when induced by poly(I). poly(C) combined with a superinduction procedure. This cell line was further examined in the present study. It was found that Sendai virus is a suitable inducer, giving high levels of IFN without superinduction. The IFN obtained was antigenically of the f3 type, similar to the poly(I) -polyt Cj-induced IFN. Its purification to apparent homogeneity and some of its properties are described in this report. MATERIALS AND METHODSInterferon production. Human MG63 cells, obtained from the American Type Culture Collection (ATCC), were cultured in Eagle's minimum essential medium (MEM) supplemented with 6% calf serum. For determining the conditions of IFN 433