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Detection of Influenza A Virus Nucleoprotein Antibodies in Oral Fluid Specimens From Pigs Infected Under Experimental Conditions Using a Blocking ELISA

Authors

  • Y. Panyasing,

    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
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  • C. K. Goodell,

    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
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  • C. Wang,

    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
    2. Department of Statistics, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA
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  • A. Kittawornrat,

    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
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  • J. R. Prickett,

    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
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  • K. J. Schwartz,

    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
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  • A. Ballagi,

    1. IDEXX Laboratories, Inc., Westbrook, ME, USA
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  • S. Lizano,

    1. IDEXX Laboratories, Inc., Westbrook, ME, USA
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  • J. J. Zimmerman

    Corresponding author
    1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
    • Correspondence:

      J. Zimmerman. Veterinary Medical Research Institute (Building 1), 1802 University Blvd. College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1240, USA. Tel.: 515 2941073; E-mail: jjzimm@iastate.edu

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Summary

In commercial swine populations, influenza is an important component of the porcine respiratory disease complex (PRDC) and a pathogen with major economic impact. Previously, a commercial blocking ELISA (FlockChek Avian Influenza Virus MultiS-Screen® Antibody Test Kit, IDEXX Laboratories, Inc., Westbrook, ME, USA) designed to detect influenza A nucleoprotein (NP) antibodies in avian serum was shown to accurately detect NP antibodies in swine serum. The purpose of this study was to determine whether this assay could detect NP antibodies in swine oral fluid samples. Initially, the procedure for performing the NP-blocking ELISA on oral fluid was modified from the serum testing protocol by changing sample dilution, sample volume, incubation time and incubation temperature. The detection of NP antibody was then evaluated using pen-based oral fluid samples (n = 182) from pigs inoculated with either influenza A virus subtype H1N1 or H3N2 under experimental conditions and followed for 42 days post inoculation (DPI). NP antibodies in oral fluid were detected from DPI 7 to 42 in all inoculated groups, that is, the mean sample-to-negative (S/N) ratio of influenza-inoculated pigs was significantly different (P < 0.0001) from uninoculated controls (unvaccinated or vaccinated-uninoculated groups) through this period. Oral fluid versus serum S/N ratios from the same pen showed a correlation of 0.796 (Pearson's correlation coefficient, P < 0.0001). The results showed that oral fluid samples from influenza virus-infected pigs contained detectable levels of NP antibodies for ≥42 DPI. Future research will be required to determine whether this approach could be used to monitor the circulation of influenza virus in commercial pig populations.

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