Characterisation of monoclonal antibodies against porcine epidemic diarrhea virus S1/S2 junction protein.

Pig producers have suffered serious economic losses from porcine epidemic diarrhea virus (PEDV) infection. Development of PEDV antibodies for detection or treatment has become an important research direction.The S1/S2 junction (S1S2J) cleavage site of S protein of PEDV is one of the major determinants of coronavirus infection success. In this study, we specifically selected the S1S2J protein of PEDV-AJ1102 (a representative strain of the G2 type) as target protein to immunise mice and generated monoclonal antibodies (mAbs) using hybridoma technology. Three mAbs showed high-binding activity to the S1S2J protein were further analysed. To reveal the characterisation of mAbs, variable region genes of antibodies were studied by using DNA sequencing, which revealed differences in their CDR3 amino acid sequences. We then developed a new method to identify the isotypes of these three mAbs. Results showed that these three antibodies were of the IgM type. As for the functions of these three mAbs, indirect immunofluorescence assay confirmed their good binding ability to Vero E6 cells infected with PEDV-SP-C strain (G1 type). Epitope analysis showed linear epitopes for all three mAbs. These antibodies were also used to detect infected cells via flow cytometry analysis. In summary, we have prepared and examined three mAbs against PEDV-S1S2J. The focal antibodies can be employed as detection antibodies for diagnostic reagents and further developed for other applications. We also designed a novel technique for easy and cost-saving identification of isotypes of mouse mAbs. Our results lay a good foundation for the development of research for PEDV.