Date Full Report Received02/02/2015
Date Abstract Report Received02/02/2015
InvestigationInstitution: University of Minnesota
Primary Investigator: Michael P. Murtaugh
Co-Investigators: Cheryl Dvorak
Funded ByNational Pork Board
Porcine deltacoronavirus (PDCoV) was first identified in the United States in February 2014 in pigs with unexplained diarrheal disease in which PDCoV was later observed to be present. Diagnosis of PDCoV is performed using a real-time PCR assay to detect viral infection, but a serological test to identify viral antibodies, suggesting earlier infection and protection against PDCoV, has not been created. Our main objectives for this proposal were to develop and characterize a rapid, specific, and sensitive ELISA for PDCoV and to share the reagents and protocols with the swine diagnostic and research community. We were able to express and purify 4 PDCoV antigens; nucleocapsid (N), matrix (M), and the spike protein subunits (S1 and S2). An ELISA assay was developed for each of these 4 antigens to examine the antibody reactivity to each antigen in serum from infected pigs. Serum from confirmed PDCoV-positive animals was difficult to acquire. Serum samples were obtained from 300 animals of unknown PDCoV status, that came from farms in which PDCoV had been observed. These serum samples were then run on our PDCoV ELISA with all 4 antigens. We observed a few animals from each farm that seemed to be antibody positive based on the ELISA results, mainly with reactivity to PDCoV N protein. In order to determine the specificity and cut-off values for the ELISAs, we examined serum samples from known PDCoV-negative (44 samples) and PRCV-positive animals (175 samples, a common coronavirus infection that may cross-react with PDCoV proteins). The negative samples gave low values, but surprisingly the PRCV positive samples showed higher overall values for the N protein than that of the samples with unknown PDCoV status. Comparison to ELISAs with M, S1 and S2 as antigens indicated that N results were false positives since all three of the other antigens gave consistently low ELISA results. Serum samples over a time course of infection would allow us to examine the dynamics of PDCoV antibody production and determine values for a true antibody positive sample.
Dr. Cheryl Dvorak and Dr. Michael Murtaugh