Characterization of polyclonal antibodies against nonstructural protein 9 from the porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS) is considered to be one of the most important infectious diseases impacting the swine industry and is characterized by reproductive failure in late term gestation in sows and respiratory disease in pigs of all ages. The nonstructural protein 9 gene, Nsp9, encoding the RNA-dependent RNA polymerase, is generally regarded as fairly conserved when compared to other viral proteins. Antibodies against Nsp9 will be of great importance for the diagnosis and treatment of the causal agent, PRRS virus. A study was undertaken to generate polyclonal antibodies against the immunodominant Nsp9. For this purpose, the Nsp9 was expressed in Escherichia coli and subsequently used as an antigen to immunize New Zealand rabbits. Antiserum was identified via an indirect ELISA, and then verified based on the ability to react with both naturally and artificially expressed Nsp9. Results of virus neutralization test showed that this antiserum could not neutralize the PRRSV. Nevertheless, this antiserum as a diagnostic core reagent should prove invaluable for further investigations into the mechanism of PRRS pathogenesis.