Oncolytic viruses, as a therapeutic vaccine, offer an elegant approach to cancer therapy. They offer a dual mode of action, as they cause direct tumor cell lysis, and can stimulate immune responses combating the tumor. To address the unprecedented demand and the requirement for high dose inputs of infectious virus, batch-based manufacturing strategies need to be intensified. For high-cell concentration cultivations, membrane-based systems utilizing hollow-fiber modules are widely employed. However, these systems are prone to filter fouling and retention of virus particles, which leads to unwanted accumulation of virus inside the bioreactor within the cell environment until full harvest of the bioreactor broth is possible.

In this study, we evaluated the applicability of a tangential flow depth filtration (TFDF) perfusion system as a novel cell retention device for both perfusion cultivation and continuous harvesting with clarification in a single unit operation at the 3 L scale. Using suspension BHK-21 cells and a fusogenic oncolytic hybrid virus of recombinant vesicular stomatitis virus (rVSV) and Newcastle disease virus (NDV), rVSV-NDV, the integrated TFDF technology allowed to achieve high cell concentrations, continuous virus harvesting, and clarification. Compared to an optimized batch process, 11-fold higher infectious virus titers were obtained in the clarified permeate, resulting in a 460% increase in space-time yield.

Overall, the TFDF module showed very good performance as a perfusion system for the tested fusogenic oncolytic virus. Continuous virus harvesting with subsequent clarification through the TFDF module in one step can simplify process operation and potentially help to develop an integrated, scalable (up to 2000 L), and economical process for future vaccine manufacturing.