Characterization of antibody response to porcine reproductive and respiratory syndrome virus ORF5 product following infection and evaluation of its diagnostic use in pigs

The sensitivity and specificity of recombinant open reading frame 5 product s used in the Western blotting assay for confirmation of porcine reproducti ve and respiratory syndrome virus (PRRSV) serologic status were evaluated. The recombinant antigen-based assays were specifically compared with a comm ercial enzyme-linked immunosorbent assay (ELISA) for PRRSV antibodies using 1) PRRSV antibody-negative reference sera (n = 30), 2) naturally infected pig sera (n = 40), 3) sequential sera obtained from 24 experimentally infec ted pigs, and 4) sera submitted to 3 state diagnostic laboratories (n = 200 ). The recombinant antigen assay yielded an average increased sensitivity o f 10% over the commercial PRRSV ELISA. The negative controls (group 1 sera) showed no difference between the 2 assays. This comparison confirmed that the recombinant antigen-specific assay was more sensitive than the commerci al ELISA and is well suited for routine confirmation of the presence of PRR SV antibodies.