Adaptation of suspension Vero cells to commercially available cell culture media and enhanced production of vaccine-strain mumps virus.

Vero cells (referred to as "Vero" henceforth) are a commonly used host for the production of a wide variety of vaccines, but due in part to the typically anchorage-dependent nature of the cells, Vero cells also pose multiple challenges during process development, scale-up, and commercialization. The adaptation of Vero to proliferate in a serum-free suspension culture while remaining non-tumorigenic can be a challenging endeavor, and where successful, has often utilized undisclosed and/or complex custom-designed medium formulations. Additional and expanded options for commercially available serum-free media that can support the robust expansion of suspension-adapted Vero cells for viral vaccine manufacturing would be a significant advantage for increasing the industrial adoption of suspension Vero, as virus production can also be highly medium-dependent and sensitive. In this work, we have successfully transitioned suspension-adapted Vero cells from a proprietary medium to a commercially-available base medium (ExCell VPRO) with supplementation of additional commercially-available components, and subsequently infected the resulting ExCell VPRO cell bank lineage with an attenuated vaccine strain Mumps virus. Like many suspension cell line media formulations, off-the-shelf commercially available ExCell VPRO medium contains dextran sulfate, which serves to minimize cell clumping, but is also well-known to directly impact the infectivity of some viruses. Unexpectedly, we have observed that the presence of dextran sulfate in the infection medium increased both culture longevity and infectious virus titers for attenuated Mumps, potentially eliminating the need for a medium exchange between cell growth and infection for a more streamlined and easily scalable attenuated Mumps virus production process.