Production of Modified Vaccinia Ankara Virus by Intensified Cell Cultures: A Comparison of Platform Technologies for Viral Vector Production

Abstract

Modified Vaccinia Ankara (MVA) virus is a promising vector for vaccination against various challenging pathogens or the treatment of some types of cancers. Because this vector is unable to replicate in human recipients, a high amount of virions per dose is required for vaccination and gene therapy. Upstream process intensification combining perfusion technologies, the avian suspension cell line AGE1.CR.pIX and the virus strain MVA‐CR19 is an option to obtain very high MVA yields. Here we compared different options for cell retention in perfusion mode using conventional stirred‐tank bioreactors including an alternating tangential flow filtration system, an acoustic settler and an inclined settler. The last two options allowed continuous MVA virus harvesting. Furthermore, we studied hollow‐fiber based bioreactors and an orbital‐shaken bioreactor in perfusion mode, both available for single‐use. Productivity for the virus strain MVA‐CR19 was compared to results from batch and continuous production reported in literature. Our results demonstrate that MVA virus is highly stable at 37°C in cell culture so that cell retention devices are only required to maximize cell concentration but not for continuous harvesting. Using a stirred‐tank bioreactor, a perfusion strategy during the whole run with working volume expansion after virus infection resulted in the highest yields. Overall, infectious MVA virus titers of 2.1–16.5 × 109 virions/mL were achieved in these intensified processes. Taken together, the study shows a novel perspective on high‐yield MVA virus production in conventional bioreactor systems linked to various cell retention devices and addresses options for process intensification including fully single‐use perfusion platforms.

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