Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2009
Publication Date: 1/1/2010
Citation: Ciacci-Zanella, J.R., Vincent, A.L., Prickett, J.R., Zimmerman, S.M., Zimmerman, J.J. 2010. Detection of Anti-Influenza A Nucleoprotein Antibodies in Pigs Using a Commercial Influenza Epitope-Blocking Enzyme-Linked Immunosorbent Assay Developed for Avian Species. Journal of Veterinary Diagnostic Investigation. 22(1):3-9. Interpretive Summary: Swine influenza virus causes acute respiratory disease in pigs and is of concern for its potential public health significance. The recent emergence of the 2009 H1N1 human outbreak virus has heightened the need for increased surveillance in swine globally. Current swine influenza antibody diagnostic assays are less than optimal due to their recognition of a limited number of influenza subtypes. An accurate, broad-spectrum and high through-put diagnostic test is needed to detect infections in swine herds and to aid in the implementation of control measures. Here we report performance of a commercial serological assay, previously developed for avian species, for its ability to detect anti-influenza antibodies in swine serum. This commercial avian influenza assay has excellent sensitivity and specificity for swine influenza and can be used for influenza antibody screening in swine. We believe this to be the first report of an influenza test developed and licensed for avian serum samples that can be used to detect influenza nucleoprotein antibodies in serum from pigs infected or vaccinated with North American influenza viruses. A distinct advantage of this assay is that it works with standardized reagents in a format compatible with the diagnostic technology already available in most veterinary diagnostic laboratories around the world. In addition to detecting pigs with a history of exposure to influenza infections, the assay could also be useful for monitoring responses to influenza vaccination. If widely implemented for use with swine, this avian influenza diagnostic assay that already benefits poultry producers, could also benefit swine producers, veterinarians and public health officials by improving both the breadth and uniformity of serologic data for assessing exposure of swine to influenza virus at a global level.
Technical Abstract: Influenza virus causes acute respiratory disease in pigs and is of concern for its potential public health significance. Many subtypes of influenza virus have been isolated from pigs and the virus continues to evolve in swine populations. Current antibody assays have limited antigenic recognition and accurate, broad-spectrum, high through-put screening tests are needed to detect infections in swine herds and to aid in the implementation of control measures. In this study, a commercial blocking enzyme-linked immunosorbent assay (ELISA) developed for the detection of influenza A nucleoprotein antibodies in avian species was evaluated for the detection of anti-influenza serum antibodies in swine. Serum samples used to evaluate the test were archived samples from influenza research conducted at USDA-ARS NADC and included samples from influenza-inoculated pigs (H1N1, H1N2, H2N3, H3N2), contact-infected pigs, vaccinates, and negative controls. Based on samples of known status (n = 453), a receiver operating characteristic (ROC) curve analysis of the ELISA results estimated the optimized diagnostic sensitivity and specificity at 96.6% (95% C.I. 92.3, 98.9) and 99.3% (95% C.I. 97.6, 99.9), respectively. Overall, the assay showed excellent diagnostic performance against the range of influenza subtypes investigated and could serve as a useful screening assay for swine.