Evaluation of antigenic differences between wild and Sabin vaccine strains of poliovirus using the pseudovirus neutralization test

In the endgame of global polio eradication, serosurveillance is essential to monitor each country’s vulnerability to poliomyelitis outbreaks. Previously, we developed pseudovirus poliovirus (PV) neutralization test (pPNT) with type 1, 2, and 3 PV pseudovirus (PV(pv)), which possess a luciferase-encoding PV replicon in the capsids of wild-type strains (PV(pv)[WT]), showing that pPNT with type 2 and 3 PV(pv)(WT) but not type 1 shows high correlation with the conventional PV neutralization test (cPNT) performed with vaccine strains. Here, we analyse the antigenicity of PV(pv)(WT) and PV(pv) with capsid proteins of Sabin vaccine strains (PV(pv)[Sabin]) in human serum. Type 2 and 3 PV(pv)(WT) and PV(pv)(Sabin) show similar antigenicity in the analysed set of human sera in contrast to type 1 PV(pv). The levels of PV(pv)(Sabin) infection (%), including about 70% of PV(pv) infection (%) measured in the presence of human serum diluted to the cPNT titre, serve as the optimal threshold values for pPNT (5% for type 1 and 2, 10% for type 3) to show high correlation with cPNT results. Our results suggest that pPNT with PV(pv)(Sabin) could serve as an alternative to cPNT and provide a rationale for pPNT threshold values.