Monitoring lentiviral vector production kinetics using online permittivity measurements

Lentiviral vectors (LVs) are effective delivery vehicles that have been successfully used in gene and cell therapy. LVs are most commonly produced via the transient transfection of several plasmid constructs in adherent cell cultures. Recently, we described an efficient and scalable LV production in serum-free suspension cultures. To further facilitate the translation of LV-based interventions to the clinic, the robustness of the production process needs to be ensured to ultimately achieve a specified quality and quantity of LV production lots. However, routine processes are largely empirical, and strategies to monitor LV production kinetics in real-time have not yet been described. In this work, in situ real-time permittivity measurements were assessed to document the production of LVs. Characteristic process phases that were closely associated with LV production kinetics were identified. The permittivity signal evolution was interpreted by exploiting various independent online and offline monitoring measurements. Cellular membrane properties and, to a lesser extent, cell size were the main factors contributing to the permittivity variations. It is concluded that the permittivity-related parameters can be used for the detection of viral release, allowing real-time assessment of process performance. The technology should thus greatly facilitate process development and optimization.