COMPARISON OF ORAL INFECTIOUS DOSE OF WEST NILE VIRUS ISOLATES REPRESENTING THREE DISTINCT GENOTYPES IN CULEX QUINQUEFASCIATUS

Dana L. Vanlandingham, PhD¹, C.E. McGee, BS¹, S.E. Galbraith, PhD¹, A.D.T. Barrett, PhD) ¹, and S. Higgs, PhD¹

Department of Pathology and Center for Biodefense and Emerging Infectious Diseases, UTMB

Background: Phylogenetic analysis of West Nile virus in North America has identified replacement of the originally introduced clade, Eastern United States (NY99), by the North American clade. In addition, the transient emergence of other clades and genetic variants has also been observed. In this study, we investigated the potential role of the mosquito in the selection of these clades and genetic variants. Methods: We determined the relative susceptibility of Culex quinquefasciatus to infection with isolates from the Eastern US clade, the North American clade, and the Southeast coastal Texas clade. Conclusions: Although significant differences were observed in the oral infectious dose 50% values between the Eastern US and two attenuated North American genetic variants compared to the North American and Southeast coastal Texas clade viruses, these did not correlate with persistence of the genotype in nature. These results indicate that selection of these viral genotypes was independent of viral oral infectivity in the mosquito. Supported by NIH T32 A107536 Postdoctoral Training Grant under Norbert Roberts and NIH RO1 AI 67847 awarded to A.D.T. Barrett.