Population balance modelling captures host cell protein dynamics in CHO cell cultures

Abstract

Monoclonal antibodies (mAbs) have been extensively studied for their wide therapeutic and research applications. Increases in mAb titre has been achieved mainly by cell culture media/feed improvement and cell line engineering to increase cell density and specific mAb productivity. However, this improvement has shifted the bottleneck to downstream purification steps. The higher accumulation of the main cell-derived impurities, host cell proteins (HCPs), in the supernatant can negatively affect product integrity and immunogenicity in addition to increasing the cost of capture and polishing steps. Mathematical modelling of bioprocess dynamics is a valuable tool to improve industrial production at fast rate and low cost. Herein, a single stage volume-based population balance model (PBM) has been built to capture Chinese hamster ovary (CHO) cell behaviour in fed-batch bioreactors. Using cell volume as the internal variable, the model captures the dynamics of mAb and HCP accumulation extracellularly under physiological and mild hypothermic culture conditions. Model-based analysis and orthogonal measurements of lactate dehydrogenase activity and double-stranded DNA concentration in the supernatant show that a significant proportion of HCPs found in the extracellular matrix is secreted by viable cells. The PBM then served as a platform for generating operating strategies that optimise antibody titre and increase cost-efficiency while minimising impurity levels.

Recombinant therapeutic proteins degradation and overcoming strategies in CHO cells

“…Some of the proteases secreted by CHO cells, unlike sialidase(s) and glycosidase (s), which are passively released into the medium upon cell death, are secreted during cell culture in bioreactors. Thus, their activities cannot be minimized by maintaining high cell viability and cause product fragmentation (and subsequent aggregation), while others can lead to immunogenic responses in patients (Alhuthali and Kontoravdi 2022 ). Serine proteases, elastase, collagenase, and plasminogen activators are not only passively released in cell culture upon cell death, but also many proteases are actively secreted into the culture medium, and membrane-bound proteases are in direct contact with RTPs physiologically, so their presence is independent of cell viability or the duration of culture and their degradation of RTPs was particularly significant (Hu et al 2022 ; Mols et al 2005 ).…”