Conserved Antigenic Structure of Contemporary Wild Poliovirus Type 1 Strains Endemic in Pakistan.

BACKGROUND

Elimination of poliovirus in Pakistan and Afghanistan is challenged by notions against the role of oral poliovirus vaccine (OPV) in eradicating contemporary wild poliovirus (WPV) strains.

METHODS

A total of 1055 WPV type 1 (WPV1) strains isolated between 2013 and 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 WPV. The clinical significance of WPV1 variants was assessed to ascertain their role in patient outcomes.

RESULTS

We found that 88% of WPV1 strains isolated from paralytic children belonged to a single antigenic lineage identical to the 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 3 strains in OPV (OPV1-3, 7.96-9.149 [95% confidence interval, 6.864-10.171]; WPV1 strains, 7.542-8.786 [6.493-9.869]). Docking examination underscored a strong antigen-antibody interaction despite variations within the viral protein 1 epitopes. There was no significant association (P = .78) with clinical prognosis among patients infected with antigenically diverse WPV1 strains and patient outcomes, including death.

CONCLUSIONS

Our findings substantiate the robustness of OPV for neutralizing the contemporary WPV1 strains endemic in Pakistan and Afghanistan. Vaccination coverage must be augmented to achieve early eradication.