Neutralizing epitope mapping for deltacoronavirus receptor-binding domain and seroepidemiological survey across different animal species

Porcine deltacoronavirus (PDCoV) is an emerging enteric pathogen that poses a significant threat to the global swine industry and carries a potential public health risk. The development of neutralizing monoclonal antibodies (mAbs) is crucial for preventing and controlling PDCoV. However, research on neutralizing linear epitopes within the PDCoV receptor-binding domain (RBD) and the establishment of serological assays based on such mAbs remains limited. In this study, we generated two neutralizing mAbs, 1C12 and 3A11, targeting the PDCoV RBD. Epitope mapping revealed that 1C12 recognizes a linear epitope (³¹⁶DFGEARLD³²³), whereas 3A11 binds to a conformational epitope. Further residue analysis identified Arg321 as the most critical residue for binding to 1C12. Additionally, the integrity of the entire ³²¹RLD³²³ motif was found to be indispensable for the conformational recognition by mAb 3A11. Using these mAbs, we developed two blocking enzyme-linked immunosorbent assay (bELISA) methods (bELISA-1C12 and bELISA-3A11). Evaluation of 150 clinical samples demonstrated that bELISA-1C12 exhibited 93.3% concordance with a virus neutralization test (VNT), indicating higher diagnostic sensitivity than bELISA-3A11 (92.7%). A large-scale serosurvey of pig populations across ten Chinese provinces in 2025, conducted using bELISA-1C12, revealed a PDCoV seropositivity rate of 13.6%. Notably, when extending the serological screening to 21 additional animal species, we detected PDCoV antibodies in peafowl serum for the first time, suggesting possible exposure to the virus. This study identifies key antigenic epitopes on the PDCoV RBD and provides valuable tools for epidemiological surveillance and assessing the transmission risk of PDCoV.