Production Process Development of Pseudorabies Virus Vaccine by Using a Novel Scale-Down Model of a Fixed-Bed Bioreactor

In this study, a novel tube-fixed-bed bioreactor which consists of a TubeSpin bioreactor 50 tube and 0.44 g macrocarriers was developed as the scale-down model of a fixed-bed bioreactor. The adherent Vero cell–based pseudorabies virus (PRV) production process was tested in this novel model. The Vero cells grew well in the tube-fixed-bed bioreactor, and the cell density reached 5.8 × 106 cells/mL after 7 days of culture. The PRV production parameters (time of infection, multiplicity of infection, and harvest process) were optimized in the tube-fixed-bed bioreactor. Then the optimized process (time of infection = 3 days, multiplicity of infection = 0.001 and multiple harvest process) was scaled up 25-fold to an Xcell 1-L laboratory-scale fixed-bed bioreactor and 125-fold to an Xcell 5-L fixed-bed bioreactor successfully. The total PRV harvest in the Xcell 1-L bioreactor at 5 days after infection (dpi) was 10.25 log10 TCID50 which corresponds to 177,827 doses of vaccine. The total PRV harvest in the Xcell 5-L bioreactor at 5 dpi was 11.13 log10 TCID50 which corresponded to 1,348,962 doses of vaccine. The comparable growth curve, metabolism, and PRV production profile of the scaled-up bioreactors confirmed the feasibility and scalability of the tube-fixed-bed bioreactor as a scale-down model of the fixed-bed bioreactor for virus production process development.