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Product yields of biologicals such as monoclonal antibodies, recombinant proteins and vaccines produced in mammalian cell culture have to be improved constantly to cope with increasing demands and process economics. As an example we investigate an influenza vaccine production process with adherently growing MDCK cells [Genzel et al., 2004]. The process consists of a cell growth phase and a virus replication phase. We want to achieve high-density cell cultures and finally higher virus yields in microcarrier systems. Main focus is on batch-to-batch reproducibility and scale-up. To quantitatively analyze this process various mathematical models are being developed to describe phenomena such as attachment, proliferation and contact inhibition of cells.
In the past, we achieved higher cell numbers in small scale bioreactors using different control strategies for perfusion systems during cell growth [Bock et al., 2005]. A perfusion mode with cell retention by filtration allowed a continuous medium exchange preventing substrate limitations, and metabolite inhibitions.
So far, the virus titers (HA) did not increase in the same magnitude as expected from cell numbers. Similar results were obtained by Genzel et al, 2005 in an influenza vaccine process in a wave® bioreactor system and by Pohlscheidt et al., 2005 in a parapoxvirus vaccine production process. Furthermore, Pohlscheidt et al. demonstrated a successful increase in virus titers by using a 20 kDa dialysis system or an Expanded-Volume-Batch during virus replication. Therefore, a perfusion system might also be successfully applied during influenza virus replication. In addition, the removal of virus particles from the culture broth might increase the virus yield (HA) by avoiding unspecific degradation of virions by enzymes released from lysed cells. Here, we present results concerning the influence of perfusion rates during virus replication on virus yields.
Bock et al., 2005. Closed loop control of perfusion systems in high-density cell culture. Proceedings of the 19th meeting of ESACT in Harrogate, United Kingdom
Genzel et al., 2005. Serum-free influenza production with MDCK cells in wave-bioreactor and 5L-stirred tank bioreactor. Proceedings of the 19th meeting of ESACT in Harrogate, United Kingdom
Pohlscheidt et al., 2005. Strategies for large scale production of Parapoxvirus Ovis by micro-carrier cell culture. Proceedings of the 19th meeting of ESACT in Harrogate, United Kingdom
