Purification of Japanese encephalitis virus vaccine by zonal centrifugation.

A large-scale procedure for purification and concentration of Japanese encephalitis virus vaccine by a continuous-flow isopycnic banding technique in a sucrose density gradient solution, using a K-III zonal centrifuge rotor, is presented. The quality of zonal-purified vaccine was compared with commercial and Japanese National Institutes of Health reference vaccines for antigenicity, immunodiffusion, and allergic encephalitogenicity tests to show its high purity.