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Adult domestic chickens were infected with West Nile virus (WNV) or St. Louis encephalitis virus (SLEV) and challenged with homologous or heterologous virus at 21 or 56 days postinfection (dpi). Sera were collected at selected time points after infection and assayed by enzyme immunoassay (EIA), plaque reduction neutralization test (PRNT), and a Western blot (WB) alternative to PRNT. EIA results were sensitive and accurate (few false positives) but not specific, requiring a confirmatory test to determine virus infection history. PRNT results generally were specific until challenge, after which test results were frequently equivocal and inadequate to determine first or second infecting virus. WB results confirmed the serologic cross-reactivity between WNV and SLEV envelope protein. Non-structural protein 1 and pre-membrane protein reactivities were highly specific for WNV during SLEV infection, but less specific for SLEV during WNV infection. WB and PRNT specificities were similar for both viruses from 6 to 14 dpi, and sensitivities to WNV were virtually identical.
Received May 1, 2007. Accepted for publication December 10, 2007.
Acknowledgments: The authors thank Vincent Martinez and Scott Halam, Center for Vectorborne Diseases, UC Davis, for assistance with the care and blood sampling of the chickens, and Dr. Harvey Motulsky, President, GraphPad Software, for assistance with sensitivity analysis.
Financial support: This research was funded, in part, by NIH Grant AI-65359 and R01-AI55607 to WKR and CDC Grant U50/ CCU923677.
* Address correspondence to Peter J. Patiris, California Department of Public Health, Viral and Rickettsial Disease Laboratory, 850 Marina Bay Parkway, Richmond, CA 94804. E-mail: ppatiris{at}dhs.ca.gov
Authors addresses: Peter J. Patiris, Leopoldo F. Oceguera III, Robert E. Chiles, and Carl V. Hanson, California Department of Public Health, Viral and Rickettsial Disease Laboratory, 850 Marina Bay Parkway, Richmond, CA 94804, Telephone: 510-307-8555, Fax: 510-307-8955, E-mail: ppatiris{at}dhs.ca.gov. George W. Peck, Northwest Mosquito and Vector Control District, 1966 Compton Avenue, Corona, CA 92881, Telephone: 951-340-9792. William K. Reisen, Center for Vectorborne Diseases, University of California, Old Davis Rd., Davis, CA 95616, Telephone: 530-752-0124.
Reprint requests: Peter J. Patiris, California Department of Public Health, Viral and Rickettsial Disease Laboratory, 850 Marina Bay Parkway, Richmond, CA 94804, Telephone: 510-307-8556, Fax: 510-307-8955, E-mail: ppatiris{at}dhs.ca.gov.
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