Immune recognition of His-WARF4 by WNV-positive human sera. Eight human sera, 4 of which positive for IgGs anti-WNV by IFA were analyzed for the presence of anti-N-NS4B/WARF4 antibodies by western blotting. The assay was performed by testing simultaneously the reactivity to 3 other recombinant WNV proteins: the domain III of the Envelope, a prem/M protein fragment and the NH2-terminal portion of NS5. Panel A shows the 4 recombinant proteins stained with the comassie-blue. Panel B shows the results of the western blotting analysis; 4 human sera testing negative for IgGs-anti WNV (1–4) showed no reactivity with the four antigens. The WNV-positive human sera (5–8) showed a different reactivity with the four recombinant antigens. Two sera (7, 8) reacted with His-WARF4 protein.