West Nile Virus Seroprevalence in Blood Donors from Central Anatolia, Turkey

Introduction: West Nile virus (WNV) is a reemerging flavivirus that has displayed a drastic change in epidemiology in the last decade. Data on WNV activity in Turkey are currently limited. This study investigated WNV exposure in blood donors from Central Anatolia, Turkey. Materials and Methods: A total of 2516 sera, collected from blood donors at four major branches of the Turkish Red Crescent Middle Anatolia Regional Blood Center, were evaluated by a commercial WNV immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA). Positive and borderline samples were investigated further by a WNV IgG indirect immunofluorescence test (IIFT), IgG ELISAs for tick-borne encephalitis virus and dengue virus, an IgG IIFT for yellow fever virus, and a multi-Flavivirus biochip IgG IIFT. WNV antibody specificity and titer values were determined by plaque reduction neutralization assay. IgG avidity and IgM were determined for confirmed samples. IgM-positive samples were also evaluated by a real-time reverse transcription polymerase chain reaction assay. Results: Twenty-five samples (25/2516; 0.99%) were found reactive in the WNV ELISA/IIFT assays, and 14 could be confirmed by the plaque reduction neutralization assay (14/2516; 0.56%). All IgGs were of high avidity, and four samples (4/14; 28.6%), which were negative for viral RNA, were IgM positive. Although samples with neutralizing WNV IgGs had strong fluorescence intensity in IIFTs, no correlation between antibody titer values and IIFT intensity or quantitative ELISA results could be found. Three WNV nonreactive samples were positive in the dengue IgG ELISA test; one of these also displayed positive results for dengue virus in the mosaic biochip IIFT and reactivity in yellow fever virus IIFT. Discussion: WNV exposure is confirmed in 0.56% of the tested healthy blood donors in Central Anatolia, with evidence for dengue/yellow fever and/or other flaviviral infections. This study is the first to document WNV exposure in individuals from Konya, Yozgat, and Sivas provinces in Central Anatolia, and it also establishes viral activity in Ankara, the capital of Turkey.