|Parapoxvirus-ovis Bovine Kidney Cell Line Fed-Batch Dialysis Volume-Expanded-Fed Batch Scale-Up Shear-Force Membrane Aeration|
The production of recombinant proteins and vaccines in animal cells for therapeutic applications is of increasing interest. Due to the characteristics of mammalian cells, the cultivation requires complex media composition, specific bioreactor design and a sophisticated operation mode. For the production of a chemically inactivated Parapoxvirus ovis NZ-2 (PPVO NZ-2) an adherent Bovine Kidney cell line is cultivated on Cytodex® -3 microcarriers in suspension culture. The inactivated and purified virus particles have shown antiviral activity in several animal models. PPVO NZ-2 is produced by a biphasic batch process at the 3,5 and 10 L scale. Aeration is realised by shear less membrane oxygenation via a tube stator with a central 2-blade anchor impeller. In order to achieve higher efficiency, process robustness and safety, the established process was optimised. The cell line was adapted to a protein free medium except recombinant insulin in order to increase biosafety. In parallel, the biphasic batch process was optimised with special emphasis on the description of the cell line, different operating conditions and process management (fed-batch, dialysis, etc.). A mathematical model was developed to support the development. The quality of the purified virus particles was assessed by quantitative electron microscopy, residual host cell protein and DNA-content. A physical characterisation of the reactors with respect to oxygenation, shear force and homogenisation was performed up to the 200 L scale to realise substantiated scale-up to a possible production scale. This integrated approach led to a new safe, robust and high productive large scale production process, called “Volume-Expanded-Fed” Batch. By subsequent dilution of infected cells into next process scale an increase of productivity by factor 40 related to established biphasic batch process was achieved. A possible large scale production process up to 800 L was designed during this work.