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Abstract:
Increasing efforts are made to establish mammalian cell culture as host system for the propagation of influenza viruses instead of embryonated hen’s eggs. Especially, considering the seasonal production of different virus subtypes and in case of a pandemic the flexibility of mammalian cell culture is advantageous. For process optimization comprehensive knowledge of physiological changes during cell growth and virus production is crucial. Therefore, cultivations of different adherent cell lines, in different bioreactors and process variations were investigated and compared. Pivotal parameters are the cell growth physiology, metabolism, viral infection and the release of viral particles.
Cell growth physiology, represented by the cell cycle phase distributions was determined via DNA content measurements using flow cytometry. Influenza infection in the cultivated host cells was detected via fluorocrome-labelled monoclonal antibodies against intracellularly accumulated viral components and quantified cytometrically. Extracellular metabolic educts and products were quantified using a multiparametric enzyme sensor (Bioprofile). The tissue culture infectious dose (TCID50) for infectious virus concentrations was determined via immunotitration whereas the total virus particle concentration was measured with a hemagglutination assay.
Results for the investigation of bioreactors, cell lines and process variations indicate differences in both cell cycle and virus propagation behaviour compared to a standard cultivation process. Based on insights on cell physiology inoculum preparation strategies could be optimized. The results obtained from cell cycle and infection studies were also used for the formulation of mathematical models, which supports process analysis and directed optimization.
