Antigenic structure of wild poliovirus type 1 strains endemic in Pakistan is highly conserved and completely neutralized by Sabin’s Oral Polio Vaccine

Abstract

Abstract Background Elimination of poliovirus in Pakistan and Afghanistan is challenged by notions against the role of oral polio vaccine in eradicating contemporary wild poliovirus strains. Methods 1,055 WPV1 strains isolated between 2013-2018 were categorized into 68 antigenic groups and tested for neutralization by OPV derived antibodies. Molecular docking was conducted to determine neutralization efficiency of antibodies against wild poliovirus. The clinical significance of WPV1 variants was assessed to ascertain their role in patient’s outcome. Results We found that 88% of WPV1 strains isolated from paralytic children belonged to a single antigenic lineage identical to WPV1 strain detected in 1993. WPV1 antigenic variants were effectively neutralized by OPV derived antibodies with geometric mean titers comparable to the neutralization titers found for three strains in OPV (OPV1-3: 7.96-9.149, 95%CI: 6.864-10.171; WPV1 strains: 7.542-8.786, 95%CI: 6.493-9.869). Docking examination underscored a strong antigen-antibody interaction despite variations within the VP1 epitopes. No significant association (p-value = 0.78) of clinical prognosis was inferred among patients infected with antigenically diverse WPV1 strains and patients’ outcome including death. Conclusions Our findings substantiate the robustness of OPV to neutralize the contemporary WPV1 strains endemic in Pakistan and Afghanistan. The vaccination coverage must be augmented to achieve eradication early on.