Detection of antibodies to West Nile virus in equine sera using microsphere immunoassay

Udeni B.R. Balasuriya, Pei Yong Shi, Susan J. Wong, Valerie L. Demarest, Ian A. Gardner, Pamela J. Hullinger, Gregory L. Ferraro, Joshua D. Boone, Casey L. De Cino, Amy L. Glaser, Randall W. Renshaw, Michel Ledizet, Raymond A. Koski, N. James MacLachlan

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


One hundred and ninety-one sera from horses that recently were exposed to West Nile virus (WNV) by either vaccination or natural infection or that were not vaccinated and remained free of infection were used to evaluate fluorescent microsphere immunoassays (MIAs) incorporating recombinant WNV envelope protein (rE) and recombinant nonstructural proteins (rNS1, rNS3, and rNS5) for detection of equine antibodies to WNV. The rE MIA had a diagnostic sensitivity and specificity, respectively, of 99.3% and 97.4% for detection of WNV antibodies in the serum of horses that were recently vaccinated or naturally infected with WNV, as compared to the plaque reduction neutralization test (PRNT). The positive rE MIA results were assumed to be WNV-specific because of the close agreement between this assay and the PRNT and the fact that unvaccinated control horses included in this study were confirmed to be free of exposure to the related St Louis encephalitis virus. The NS protein-based MIA were all less sensitive than either the rE MIA or PRNT (sensitivity 0-48.0), although the rNS1 MIA distinguished horses vaccinated with the recombinant WNV vaccine from those that were immunized with the inactivated WNV vaccine (P < 0.0001) or naturally infected with WNV (P < 0.0001). The rE MIA would appear to provide a rapid, convenient, inexpensive, and accurate test for the screening of equine sera for the presence of antibodies to WNV.

Original languageEnglish (US)
Pages (from-to)392-395
Number of pages4
JournalJournal of Veterinary Diagnostic Investigation
Issue number4
StatePublished - Jul 2006
Externally publishedYes


  • Horse
  • Microsphere immunoassay
  • Serology
  • West Nile virus

ASJC Scopus subject areas

  • General Veterinary


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