Developing a Model for Virus Contamination in Perfusion Bioreactors to Establish Rational Control Strategies for...

A viral contamination model for steady-state perfusion cell culture was developed to assess how sampling frequency and volume impacted the expected downstream viral clearance factor in integrated continuous biomanufacturing processes. The model used population balance rate equations for cells and free virions, incorporating the virus infection cycle. It simulated the states of cell cultures for both endogenous viruses, which are potentially present within the cells and can be released from them, and adventitious viruses after contamination. The model also reproduced differences in virus concentration between bioreactors and harvests caused by sieving through the cell retention device. For virus risk assessments in integrated continuous biomanufacturing, the model evaluated the probability of detecting contamination based on the volume fraction of the sample tested and the downstream viral transmission by number of days after contamination. Considering the infection scenario with mouse minute virus (MVM) in 100 × 10⁶ cells/mL cell culture for adventitious virus contamination, a notable decline in viable cell density was observed starting from Day 4. To ensure 99.999% safety of final products, the total downstream clearance achieving a log reduction value (LRV) > 15 LRV is required to remove the increased virus. If daily sampling is conducted and a downstream clearance is planned to satisfy the removal of potentially undetected MVM, a total clearance of 9 LRV is sufficient. This model enables us to simulate different scenarios for viral contamination and has the advantage of allowing assessments of virus safety strategies.