Standardization of ELISA with Senecavirus A recombinant VP2 protein and its use in swine herds in Brazil
Senecavirus A (SVA) is a nonenveloped, single-stranded RNA virusThe icosahedral viral particle is composed of four structural proteins: VP1, VP2, VP3 and VP4, among which VP2 is strongly involved in the antibody immune response. The virus causes vesicles on the snout and feet in pigs, which are clinically indistinguishable from other vesicular diseases such as foot-and-mouth disease. Outbreaks of SVA have been reported worldwide since 2014; however, its prevalence in Brazil remains unknown. In this study, the VP2 structural protein was produced and purified from E. coli, and recombinant VP2 (rVP2), based on the most recent Brazilian strain, was used to develop an indirect ELISA to identify antibodies against SVA in Brazilian swine herds. Sensitivity and specificity values of the rVP2 ELISA were determined using receiver operating characteristic analysis performed on 43 SVA positive and 219 negative serum samples. In addition, serum samples from pigs immunized with eight distinct Brazilian SVA inactivated strains were tested with the rVP2 ELISA. For the specificity of the assay, 17 serum samples from vesicular stomatitis virus (VSV) from naturally infected pigs were tested. The rVP2 ELISA was found to have 100% specificity and 74.4% sensitivity. The performance of the assay using samples collected during the SVA outbreak, had a sensitivity of 100%, and with those collected nine months after the outbreak it had a sensitivity of 73.4%. The rVP2 ELISA developed here was able to detect specific SVA antibodies in acute disease and recovered pigs, and no cross-reactivity with VSV was observed. This assay has potential as a useful tool for monitoring SVA infection and could help to improve disease diagnosis.