title: Cross-reactivity of Japanese encephalitis virus-vaccinated horse sera in serodiagnosis of West Nile virus.
abstract: Flavivirus-infected sera are known to show cross-reactions in serodiagnoses of heterologous flavivirus infections. Japanese encephalitis virus (JEV) is endemic in Asia and, in Japan, many horses are vaccinated against JEV. However, the cross-reactivity level of JEV-vaccinated horse sera in the serodiagnosis of West Nile virus (WNV) has not been clarified. The antibody cross-reactivity of JEV-vaccinated horse sera in WNV serological tests, such as the plaque reduction neutralization test (PRNT), IgG indirect ELISA (IgG-ELISA) and hemagglutination inhibition (HI) test, was examined. All JEV-vaccinated horse sera were positive for JEV antibodies with JEV PRNT at both 90% and 50% plaque reductions. In WNV PRNT, 16.7% of the horses were positive at 90% plaque reduction, and 50% of the horses were positive at 50% plaque reduction. All the JEV-vaccinated horse sera showed positive-to-negative (P/N) ratios of over 2.0 with JEV IgG-ELISA, and half of them had P/N ratios of over 2.0 with WNV IgG-ELISA. There was little difference between the JEV HI and WNV HI titers in individual horses. These results indicate that in serosurveillance of WNV, JEV-vaccinated horses can produce false-positive results in WNV IgG-ELISA, HI and PRNT.
authors.affiliation: Research Team for Advanced Biologicals, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Hirota
authors.forename: Hideki
authors.initials: H
authors.lastname: Nishi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsuda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsunemitsu
authors.forename: Shinya
authors.initials: S
authors.lastname: Shimiz
mesh_terms: D000818:Animals; D003429:Cross Reactions; D004664:Encephalitis Virus, Japanese / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D006385:Hemagglutination Inhibition Tests; D006734:Horse Diseases / Q000097:blood / Q000276:immunology* / Q000821:virology; D006736:Horses; D007074:Immunoglobulin G / Q000097:blood; D007157:Immunologic Surveillance; D022321:Japanese Encephalitis Vaccines / Q000276:immunology*; D012698:Serologic Tests; D010948:Viral Plaque Assay / Q000662:veterinary; D014901:West Nile Fever / Q000097:blood / Q000276:immunology / Q000662:veterinary*; D014902:West Nile virus / Q000276:immunology*
chemical_list: D007074:Immunoglobulin G; D022321:Japanese Encephalitis Vaccines