The global demand for complex biopharmaceuticals like recombinant proteins, vaccines, or viral vectors is steadily rising. To further improve process productivity and to reduce production costs, process intensification can contribute significantly. The design and optimization of perfusion processes toward very high cell densities require careful selection of strategies for optimal perfusion rate control. In this chapter, various options are discussed to guarantee high cell-specific virus yields and to achieve virus concentrations up to 1010 virions/mL. This includes reactor volume exchange regimes and perfusion rate control based on process variables such as cell concentration and metabolite or by-product concentration. Strategies to achieve high cell densities by perfusion rate control and their experimental implementation are described in detail for pseudo-perfusion or small-scale perfusion bioreactor systems. Suspension cell lines such as MDCK, BHK-21, EB66®, and AGE1.CR.pIX® are used to exemplify production of influenza, yellow fever, Zika, and modified vaccinia Ankara virus.
Keywords: Alternating tangential flow filtration; Control strategy; High cell density cultivation; On-line sensors; Perfusion bioreactor; Perfusion rate; Pseudo-perfusion; Viral vaccine.