Operation of PER.C6 Cells in Continuous Perfusion

Perfusion presents a number of advantages over other modes of cultivation, such as increased volumetric productivity and rapid removal of easily inactivated products from the culture environment [26]. These homogeneous perfusion systems can be operated under conditions of total cell retention, or with the removal of part of the biomass through culture bleeding [27]. Total cell retention facilitates kinetics studies and, as demonstrated in other studies [28], prevents unnecessary cell division, allowing for cells to produce product at higher rates [29]. 

A perfusion process has been developed for the production of monoclonal antibodies in PER.C6 cells. The process typically results in a more than 30-fold increase in antibody yield compared to the batch process, and a 10-fold increase compared to the fed-batch process. As for the development of the fed-batch process, the perfusion strategy is based on the metabolic and physico-chemical requirements of the PER.C6 cell line. 

The first feature investigated was the impact of cell perfusion rate (CSPR) on cell culture performance using a spinfilter as the cell retention device. Fig. 3.17 shows the viable cell concentration of a PER.C6 cell line expressing antibody A operated under the same conditions with two different CSPR implemented at the 7-L scale. 

It was observed that a doubling of the CSPR resulted in a 65% increase in the upper cell density. The fact that such an increase was achieved suggested that significant improvements in cell density (and related productivity) could be obtained by modification of the CSPR. By day 18, both of these cultures were prematurely ended due to clogging of the spinfilter. Upon inspection of the spinfilter material, a cake of cells was observed to have gathered, which suggested that the high cell densities achieved with this culture are not compatible with a standard spinfilter operation as a cellular retention device. 

A complete metabolic characterization of these cultures was performed (data not 

---