Generation of Monoclonal Antibodies and a Single-Chain Variable Fragment Against the C-Terminal Domain of Porcine Deltacoronavirus Spike S1 Subunit

Porcine deltacoronavirus (PDCoV) is an emerging enteric coronavirus that causes severe mortality in neonatal piglets that results in significant economic burden to the global swine industry. The spike protein, particularly the C-terminal domain of S1 subunit (S1-CTD), contains immunodominant epitopes and represents an attractive target for antibody development. In this study, we expressed and purified recombinant PDCoV S1-CTD proteins in Escherichia coli and used it to immunize BALB/c mice for generating S1-CTD-specific antibodies. Following hybridoma production, we successfully established four monoclonal antibodies (2B7-G10, 2C7-F6, 7G3-G8, and 4H4 mAbs) that specifically recognized recombinant S1-CTD as well as native PDCoV spike protein. We further engineered a single-chain variable fragment derived from clone 4H4 (4H4-scFv) that retained antigen-binding ability to against S1-CTD and native PDCoV spike. Collectively, these findings demonstrate a practical framework for generating targeted mAbs and scFvs while expanding the repertoire of available reagents for future PDCoV S-targeted studies.