Abstract: This study aimed to establish a reliable indirect ELISA method for detecting PDCoV IgG antibody and to understand the prevalence of PDCoV in Sichuan. The prokaryotic expression system was used to express PDCoV membrane protein (M) as a detection antigen. By optimizing the reaction conditions, an indirect ELISA method named PDCoV-rM-ELISA based on PDCoV M protein was established, and 430 clinical samples were detected by this method. The recombinant expression E.coli strain BL21-pET-32a-M was successfully constructed, and the recombinant M protein was expressed after induction. Western blot assay showed that the recombinant protein had good reactivity. PDCoV-rM-ELISA method could specifically detect PDCoV antibody, and had no cross reaction with five common pathogen positive sera, suggesting good specificity; The sensitivity of this method was high. PDCoV-rM-ELISA was high reproducible with the coefficients of variation were less than 10%; Forty-eight clinic serums were detected using both PDCoV-rM-ELISA and PDCoV antibody detection kits. The results showed that the positive agreement rate was 88.46%, the negative agreement rate was 90.91%, and overall coincidence rate was 89.58%. The results of clinical samples detection showed that the average positive rate of PDCoV antibody was 11.86%, and the statistical analysis showed that the sows were 2.25 times more likely to be infected PDCoV than piglets and fattening pigs. An indirect ELISA was established by using the recombinant M protein of PDCoV express in E. coli BL21. PDCoV-rM-ELISA method had good specificity, reproducibility and stability, and could be used for the detection of PDCoV antibody in clinic.

Key words: PDCoV, recombinant M protein, prokaryotic express, indirect ELISA