Virus-like particle-based liquid phase blocking ELISA for evaluating the efficacy of O-type foot-and-mouth disease vaccines.

Virus-like particles (VLPs), which closely mimic the structural and antigenic properties of native foot-and-mouth disease (FMD) virions while lacking infectious genetic material, provide a more economical solution by replacing inactivated viruses in liquid-phase blocking ELISA (LPBE) testing for FMD serodiagnosis and vaccine evaluation. In this study, a novel LPBE was developed by replacing inactivated antigens with serotype O foot-and-mouth disease virus (FMDV) VLPs expressed in Escherichia coli. Based on evaluation of sensitivity and specificity, its correlation with virus neutralization test (VNT) results in immunized animal sera, as well as the feasibility and broad applicability for clinical serum sample detection, was further analyzed. Validation showed that VLPs-LPBE achieved high specificity (98.75%) and sensitivity (97.02%). Notably, in quantifying VLP-induced antibodies, the correlation with VNT results (R² = 0.6809, P < 0.0001) was significantly stronger than that of commercial-LPBE. Blind evaluation of 853 clinical serum samples from vaccinated subjects demonstrated excellent agreement between VLPs-LPBE and conventional LPBE, with a kappa coefficient (&#x3ba;) of 0.896, an intraclass correlation coefficient (ICC) of 0.904, and the concordance rate of 95.8%. These results confirm the clinical reliability and applicability for serological monitoring. In conclusion, VLPs-LPBE provides a safe, economical, and reliable alternative method for the evaluation of FMD vaccines. It eliminates the biosafety risks associated with the handling of inactivated viruses while maintaining compatibility with existing monitoring workflows. KEY POINTS: • VLPs-based ELISA safely replaces inactivated virus, reducing costs while maintaining diagnostic accuracy. • Stronger correlation with neutralization tests enhances VLPs-vaccine evaluation reliability vs. commercial kits. • High clinical concordance validates workflow compatibility for large-scale serological monitoring.