Identification of novel serological agents for porcine deltacoronavirus infection based on the immunogenic accessory protein NS6

Porcine deltacoronavirus (PDCoV) is a swine enteropathogenic CoV that causes severe vomiting, diarrhea and dehydration in suckling piglets, leading to economic losses in the swine industry. There is a great need for a convenient method to detect circulating antibodies and help in accurate diagnosis and disease control. Previously, we demonstrated that a unique PDCoV accessory protein, NS6, is expressed during PDCoV infection in pigs and is incorporated into PDCoV virions; thus, we deduced that NS6 is likely an immunogenic target that can be used for the diagnosis of PDCoV infection. In this study, we first confirmed that NS6 is immunogenic in PDCoV-infected pigs by performing a serum western blot. Furthermore, we developed a novel NS6-based indirect enzyme-linked immunosorbent assay (iELISA) method and compared it to an established S1-based iELISA for the survey of anti-PDCoV IgG or IgA in pigs of different ages in China. The NS6-iELISA has high specificity for the detection of IgG antibodies and no cross-reactivity with other porcine enteric CoVs (transmissible gastroenteritis coronavirus, porcine epidemic diarrhea virus, or swine acute diarrhea syndrome coronavirus). This NS6 serology-based method has great sensitivity and good repeatability, making it a new and cost-saving option for the rapid diagnosis and immunosurveillance of PDCoV, which may also be important for the prevention and control of deltacoronavirus-related infection in pigs and other animals.