Development and application of an indirect enzyme-linked immunosorbent assay using recombinant S1 for sero-test of porcine epidemic diarrhea virus.

Porcine epidemic diarrhea virus (PEDV) that causes severe infectious diseases in all ages of swine, leads to serious economic losses. Serologic tests are widely accepted and used to detect anti-PEDV antibodies which could reflect PEDV infection or vaccination. In this study, recombinant PEDV S1 (rS1) was expressed by Bac-to-Bac system and purified by nickel-affinity chromatography column. An indirect enzyme-linked immunosorbent assay based on rS1 (rS1-ELISA) was then developed and optimized by checkerboard assays with serial dilutions of antigen and serum. Serum samples from 453 domestic pigs and 42 vaccinated pigs were analyzed by IFA and rS1-ELISA. Taking IFA as a gold standard, rS1-ELISA produced a high sensitivity (90.7%) and specificity (94.6%) by a ROC curve. In addition, receiver operating characteristic analysis also revealed that rS1-ELISA was consistent with IFA (area under the curve [AUC]0.9583±0.0082). This rS1-ELISA was then applied to antibody detection in inactivated PEDV vaccinated pigs. The antibody could be detected at 2 to 4 weeks after the first inoculation. These results indicated that the rS1-ELISA established in this study provides a promising and reliable tool for serologic detection of anti-PEDV IgG antibodies in infected or vaccinated pigs.