Performance of prototype serological immunoassays for foot-and-mouth disease virus using G-H loop peptides and...

Inter-serotype cross-reactivity of foot-and-mouth disease (FMD) antibody enzyme-linked immunosorbent assays (ELISAs) can exceed 50%, leading to incorrect serotyping of outbreaks with implications for vaccine selection. In this study, synthetic peptides that mimic the hypervariable G-H loop of FMD viruses (FMDVs) that currently circulate in East Africa (O, A, SAT1, and SAT2) were evaluated as capture antigens in ELISAs (pELISAs). A panel of monovalent bovine sera was tested using these novel assays in parallel with separate ELISAs that utilized stabilized virus-like particles (VLPs). Virus neutralization tests using the same viruses were used to benchmark the status of the sera, which revealed evidence of cross-reactivity for the serotype O and SAT2 antigens (encompassing 2/19 and 3/19 of the heterologous sera, respectively). Equivalent diagnostic serotype sensitivity was observed for prototype peptide and VLP ELISAs for serotype O and SAT1 antigens (86% and 100%, respectively), while there was higher diagnostic serotype sensitivity for the VLP ELISAs targeting serotypes A and SAT2 compared to the corresponding pELISAs (86% vs 71% and 100% vs 86%, respectively). The serotype specificity of these tests ranged from 71% to 79% and 52% to 89% for the pELISA and VLP ELISA formats, respectively. Peptides offer a simple, biosafe, and cost-effective approach to present FMDV-specific epitopes, and these initial findings suggest that peptide ELISAs could be a promising approach to develop serological ELISA assays to present authentic epitopes in comparison to ELISAs that use full capsid VLPs.

This study marks a significant advancement in the development of safe, affordable, and scalable diagnostic tools for foot-and-mouth disease virus. By employing the G-H loop, a critical epitope on the receptor-binding domain within the viral capsid, we demonstrate that the G-H loop peptide-based ELISAs can effectively mimic and present authentic epitopes as the full virus particles in serological assays. This approach offers several important benefits: enhanced biosafety is achieved by eliminating the need for whole virus particles, thereby reducing biosafety risks. Cost-effectiveness: through simplifying antigen production, enabling broader deployment in low and middle income (LMI) regions. Serotype-specific accuracy: tailored antibody ELISAs improve diagnostic accuracy and post-vaccination monitoring. It also improves the sensitivity and specificity when compared to the commercially available kits, which suffer from cross-reactivities (>50% in some cases). The performance of the developed ELISA is comparable to gold-standard virus neutralization tests as a benchmark, which underscores the reliability of the approach.