Introduction: West Nile virus (WNV) is a flavivirus with a natural cycle involving mosquitoes and birds. Over the last 11 years, WNV has spread throughout the Americas with the imminent risk of its introduction in Brazil.
Methods: Envelope protein domain III of WNV (rDIII) was bacterially expressed and purified. An enzyme-linked immunosorbent assay with WNV rDIII antigen was standardized against mouse immune fluids (MIAFs) of different flavivirus.
Results: WNV rDIII reacted strongly with St. Louis encephalitis virus (SLEV) MIAF but not with other flaviviruses.
Conclusions: This antigen may be a potentially useful tool for serologic diagnosis and may contribute in future epidemiological surveillance of WNV infections in Brazil.