Tissue culture in hollow-fibre systems: implications for downstream processing and stability analysis.

Murine hybridoma cells, not adapted to low-protein or serum-free culture media, were grown in a hollow-fibre bioreactor or a stirred-tank perfusion system. In both situations, the serum content of the medium was gradually decreased during the process. The harvest obtained from the hollow-fibre reactor contained a much higher concentration of monoclonal antibody (MAb) as compared to the supernatant harvested from the stirred-tank perfusion system. Moreover, the production rate of the cells grown in the hollow-fibre reactor system was not affected by decreasing the concentration of serum in the medium to as low as 0.5% while the same cell line required 2% of serum in the stirred-tank reaction system. Consequently, the ratio of the concentration of MAb over serum proteins in the tissue culture supernatant derived from the hollow-fibre system was much higher than the one present in the harvest derived from the stirred-tank perfusion system. To study the stability of the cell mass immobilized in the hollow-fibre perfusion system, culture supernatants were tested for the presence of immunoglobulin heavy chain isotype switch variants at various intervals after initiation of culture from the cell bank. The implications of the features of hollow-fibre bioreactor systems for the production of MAb for clinical applications are discussed.