DEVELOPMENT OF A SERUM-FREE CULTURE-MEDIUM FOR THE LARGE-SCALE PRODUCTION OF RECOMBINANT PROTEIN FROM A CHINESE-HAMSTER OVARY CELL-LINE

A serum-free medium, WCM5, has been developed for the large scale prop agation of CHO (Chinese hamster ovary) cells which express recombinant protein using dihydrofolate reductase as a selectable marker. WCM5 wa s prepared by supplementing Iscoves medium without lecithin, albumin o r transferrin with a number of components which were shown to benefit growth. WCM5 medium contained 5 mg l(-1) human recombinant insulin (Nu cellin) but was otherwise protein-free. CHO 3D11 cells which had been engineered to express a humanised antibody, CAMPATH-1H, were routine ly grown using serum-containing medium. From a seeding density of 10(5 ) cells ml(-1), cells grown in static culture with serum reached a max imal cell density of 6.5 x 10(5) cells ml(-1) after 6 days in culture and produced a maximal antibody concentration of 69 mg l(-1) after 11 days in culture. CHO 3D11 cells grown with serum were washed in serum -free medium then cultured in WCM5 medium. Following a period of adapt ation the cell growth and product yield was superior to that achieved with serum-containing medium. CHO cells producing CAMPATH-1H grown in an 8000 l stirred bioreactor seeded with 2 x 10(5) cells ml(-1) reache d a maximal viable cell density of 2.16 x 10(6) cells ml(-1) after 108 h in culture and a maximal antibody concentration of 131.1 mg l(-1) a fter 122 h in culture.