Expression and serological reactivity of Nsp7 protein of PRRS genotype I virus

Abstract

The aim of this work was to express recombinant nonstructural Nsp7 protein of European genotype of porcine reproductive and respiratory syndrome virus and to evaluate its diagnostic sensitivity and specificity in serological diagnostics of the disease. The gene coding for Nsp7 protein was expressed in Escherichia coli cells and purified by IMAC. Serological reactivity of purified protein was assessed on a panel of swine sera in indirect ELISA test. Serum samples originated from PRRS positive farms, herds free of PRRS infection and PRRS free herds vaccinated with an inactivated vaccine. Nsp7 antigen proved to be suitable for serological detection of PRRS specific antibodies, showing diagnostic sensitivity of 82.2% and specificity of 97.6% when compared with IDEXX ELISA test. The nonstructural protein proved to be suitable for use as an antigen for the differentiation of post-infection and post-vaccination antibodies in pigs vaccinated with the inactivated vaccine. But the low overall antibody response to N protein after this type of vaccination makes this concept rather theoretical.