Genetic variation of VP1 region in poliovirus and circulation of vaccine-derived poliovirus

Polioviruses are classified into three serotypes.VP1 is one of the capsid proteins and has four epitopes which can stimulate neutralizing antibody to polioviruses.This capsid protein also determines the specificity of serotypes.Because the viral RNA polymerases generally lack self-proofreading mechanisms,polioviruses become one of the most rapidly evolving viruses and have several rapid variation sites in VP1 gene.With the routine immunization with oral poliovirus vaccine(OPV), the incidence of poliomyelitis has decreased dramatically.However, genetic variation may occur when the OPV viruses replicate in host's intestinal mucosa,resulting in reversion to neurovirulence of the polioviruses and leading to vaccine-associated paralytic poliomyelitis and vaccine-derived poliovirus (VDPV).There have been several events of the circulating VDPV worldwide, which makes new challenge to polio eradication.Therefore, experts suggest an immunization programme of inactivated poliovirus vaccine (IPV) in stead of OPV, or adoption of sequential immunization with IPV and OPV. Key words: Poliovirus vaccine, oral;  Vaccine-derived poliovirus;  Viral structural proteins;  Mutation