Optimization of microcarrier cell culture process for the inactivated enterovirus type 71 vaccine development.

Enterovirus 71 (EV71) is an enterovirus that could lead to severe neurological disorders and fatalities. The inactivated vaccine is an appropriate EV71 vaccine format for meeting current needs. Large-scale preparation of the inactivated EV71vaccine depends on a scalable cell culture system for industrial mass production. In this paper, Vero cells were found to produce higher titers of EV71 than did MRC-5 and WI-38 cells. High-density microcarrier Vero cell cultures were established using 5g/L Cytodex 1 microcarriers and found to promote the release of EV71s from infected Vero cells. For the large-scale production of the inactivated vaccine antigen, the extracellular virus titers produced in the 2L bioreactor were found to be 10 times lower than the spinner flask culture but improved by 30-folds using glucose/glutamine feedings during infection. A serum-free Vero cell microcarrier culture was also established in the bioreactor, yielding a high-titer of 5.8 x 10(7) TCID50/mL for EV71 production. The immunogenicity of the inactivated virions produced in serum-free culture elicited a slightly higher level of neutralizing antibody response in immunized mice. These results constitute valuable information on the development of a large-scale microcarrier cell culture process for producing inactivated EV71 vaccine.