Analysis of the accumulation of mutants in Sabin attenuated polio vaccine viruses passaged in Vero cells

To confirm the safety of oral poliomyelitis vaccine (OPV) cultured in Vero cells. the genetic stability of cultured polio vaccine viruses was analysed by MAPREC (mutant analysis by PCR and restriction enzyme cleavage). The ra tes of mutant accumulation of the viruses passaged in Vero cells under a lo w multiplicity of infection (MOI) condition (approximately 10 (-) (3.5) CCI D50/cell; the same as under usual OPV production conditions) were higher th an those passaged in secondary cultured monkey kidney cells. However, the r ates of mutant accumulation were restrained when the viruses were cultured under a high MOI condition (approximately 10 (-1.5) CCID50/cell) in Vero ce lls. Furthermore, neurovirulence of the passaged viruses in pollovirus susc eptible transgenic mice PVR-Tg21 was shown to correlate highly with the res ults of MAPREC. It is expected that our results will contribute to the larg e scale preparation of safe and effective OPV using Vero cells. (C) 2001 El sevier Science Ltd. All rights reserved.