Recombinant production of immunogenic West Nile Virus (WNV) proteins is described. These proteins, heterodimers comprising the proteins, fusions thereof, polynucleotides encoding the proteins, and combinations thereof, as well as antibodies produced therefrom, can be used in immunogenic compositions for preventing, treating and diagnosing WNV infection. Also described are highly sensitive ELISA and strip immunoassay methods for detecting the presence of WNV in biological samples.