Rapid intratypic differentiation of polioviruses from acute flaccid paralysis cases and screening vaccine-derived strains by Real-time PCR

Abstract

In the last 20 years, thanks to oral polio vaccine (OPV), the Global Polio Eradication Initiative has proven successful in greatly diminishing the number of acute flaccid paralysis (AFP) cases and granting non/free-polio status worldwide. However, this progress has encountered obstacles when these attenuated live viruses in OPV vaccine back mutate and reacquire neurovirulence and transmissibility, or possibly form a wild-like resultant virus. These so-called vaccine-related strains cause paralytic poliomyelitis in susceptible vaccines, which is in the long run, posing a threat to the polio eradication achievement in many countries generally and in Vietnam particularly. Due to technical support from WHO via collaborating Laboratory in CDC, we have successfully applied Real-time RT-PCR in Enterovirus Laboratory, NIHE to rapidly intratypic differentiate poliovirus from AFP cases and to screen VDPVs. Results of Real-time PCR for standard strains, retrospective testing of positive isolates from 2007 until now were of good concordance with the ones done by Regional Reference Laboratory in Japan. Additionally, the positive isolates of 2013 AFP case were also detected to be PV2 - sabinlike – discordant by the two ITD and VDPV assays of this specifically-designed-for-polio Real-timeRT-PCR. Therefore, our poliovirus surveillance capacity is gradually strengthened and we are better equipped to rapidly detect VDPVs and make important contribution towards our retention of polio eradication.