Bioreactor production of rVSV-based vectors in Vero cell suspension cultures

The Vero cell line is the most used continuous cell line in viral vaccine manufacturing. This adherent cell culture platform requires the use of surfaces to support cell growth, typically roller bottles, or microcarriers. We have recently compared the production of rVSV-ZEBOV on Vero cells between microcarrier and fixed-bed bioreactors. However, suspension cultures are considered superior with regard to process scalability. Therefore, we further explore the Vero suspension system for recombinant vesicular stomatitis virus (rVSV)-vectored vaccine production. Previously, this suspension cell line was only able to be cultivated in a proprietary medium. Here, we expand the adaptation and bioreactor cultivation to a serum-free commercial medium. Following small-scale optimization and screening studies, we demonstrate bioreactor productions of highly relevant vaccines and vaccine candidates against Ebola virus disease, HIV, and coronavirus disease 2019 in the Vero suspension system. rVSV-ZEBOV, rVSV-HIV, and rVSV_Ind -msp-S_F -Gtc can replicate to high titers in the bioreactor, reaching 3.87 × 10⁷ TCID₅₀ /ml, 2.12 × 10⁷ TCID₅₀ /ml, and 3.59 × 10⁹ TCID₅₀ /ml, respectively. Furthermore, we compare cell-specific productivities, and the quality of the produced viruses by determining the ratio of total viral particles to infectious viral particles.