Evaluation of an epitope-blocking enzyme-linked immunosorbent assay for the detection of antibodies to influenza A virus in domestic and wild avian and mammalian species.

An epitope-blocking enzyme-linked immunosorbent assay (bELISA) was developed for the detection of antibodies to influenza A virus in taxonomically diverse domestic and wild vertebrate species. In contrast to the bELISAs published previously that require reagent production, manipulation by the end-user, or have not been evaluated for use with both mammalian and avian species, this assay is performed using commercially available recombinant nucleoprotein antigen and corresponding nucleoprotein-specific monoclonal antibody and has been shown to work with multiple avian and mammalian species. The efficacy of the bELISA as a serum screening assay was compared to the agar gel immunodiffusion (AGID) assay using 251 serum samples obtained from experimentally infected mallards (Anas platyrhynchos) and raccoons (Procyon lotor). The concordance between the AGID assay and bELISA was 94.1% (95% CI=89.9, 98.3) for raccoons, and 71.2% (95% CI=63.5, 78.9) for mallards and 82.8% (95% CI=78.2, 87.3) overall. The bELISA was more sensitive than the AGID assay as demonstrated by the detection of antibodies to influenza A virus at earlier time points in experimental infection studies and at higher serial dilutions. The efficacy of the bELISA to monitor natural influenza A virus exposure was also compared to the AGID assay using an additional 745 serum samples from six avian species and six mammalian species. This bELISA provides a rapid, reliable, and inexpensive technique for large-scale surveillance of influenza A virus exposure in taxonomically diverse vertebrate species.