Development of an Indirect-Elisa to Detect Antibodies against Porcine Reproductive and Respiratory Syndrome Virus Nucleocapsid Protein in Gansu China

Porcine reproductive and respiratory syndrome virus (PRRSV), causes reproductive failure in sows and boars, and is an important pig pathogen that is responsible for respiratory symptoms in swine of all ages. PRRS has been a serious problem in swine industry after it was first described in the United States in 1987. PRRSV nucleocapsid protein ( N protein ) is highly conserved among different strains, and it is widely used as a diagnostic antigen for the development of serologic diagnostic tools. In our study, we then developed an indirect enzyme-linked immunosorbent assay (in-ELISA) using the pET-30a (+) expression vector and a Ni-NTA purification kit to purify the viral nucleocapsid protein antigen in order to detect antibodies against the North American porcine reproductive and respiratory syndrome virus (naPRRSV). The in- ELISA was compared with two commercial ELISA kits using 60 infected serum samples , 53 negative serum samples, and 314 serum samples from clinically vaccinated donor pigs, to calculate the specificity and sensitivity. Additional serum samples (979 samples) from different regions of Gansu provinc were used for evaluating the PRRSV antibodies from the different regions. The in-ELISA was more economical, quicker, and easier than the previously described similar methods, and could be suitable for the diagnosis of antibodies and also for epidemiological studies of naPRRSV