West Nile virus (WNV) is a flavivirus that is maintained in a bird-mosquito transmission cycle. Humans, horses and other non-avian vertebrates are usually incidental hosts. However, WNV is a neurotropic virus, which requires an efficient humoral response for the control of a neuroinvasive infection. The WNV genome encodes three structural (capsid, premembrane/membrane and envelope) and seven non-structural proteins. Bioinformatic analysis performed on the WNV genomes detected a conserved alternative open reading frame restricted to the lineage I virus. To quickly verify the existence of this putative protein, entitled West Nile Alternative Reading Frame 4 (WARF4), we produced a prokaryotic recombinant source of WARF4 and verified its immunogenicity in vivo by analyzing 43 horse serum samples, of which 15 were positive for antibodies to WNV premembrane and envelope (prM-E) proteins. Specific antibodies to WARF4 were significantly detected in 5 out of the 15 serum samples testing positive for antibodies to prM-E WNV proteins. Our findings provide evidence of a significant antibody response to the WARF4 protein in the serum of the horse testing positive for antibodies to prM-E proteins, thus indicating that this antigen might be a potential tool for further characterization of the immune response of WNV infections in humans as well.
Faggioni, G., Ciammaruconi, A., De Santis, R., Pomponi, A., Scicluna, M., Barbaro, K., et al. (2009). Evidence of a humoral response to a novel protein WARF4 embedded in the West Nile virus NS4B gene encoded by an alternative open reading frame. INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE, 23(4), 509-512 [10.3892/ijmm_00000158].