Enhanced productivity during controlled proliferation of BHK cells in continuously perfused bioreactors

A perfused cell-culture process was developed to investigate the stability of IRF-1-mediated proliferation control in BHK cells and to evaluate the ef ficacy of a novel promoter in these cells. The cell density of proliferatio n-controlled producer cells was effectively regulated for over 7 weeks in a microcarrier-based continuously perfused bioreactor. An IRF-1-inducible pr omoter was employed to express a heterodimeric IgG antibody as a relevant m odel protein. Basal expression levels were equivalent to that of a highly a ctive viral promoter, while productivity increased up to sixfold during gro wth arrest. However, no stably expressing clone was isolated in this study. Protein expression decreased gradually with time and could not be induced further in subsequent growth-repression cycles. The results demonstrate tha t the regulator/ system is sufficiently stable to allow controlled growth i n a continous scalable reactor system and that productivity increases can b e achieved in a proliferation controlled microcarrier culture. (C) 2000 Joh n Wiley & Sons, Inc.