Eleanor R Deardorff

Publications (12) View all

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  Available from: Eleanor R Deardorff

  Article: Candidate vectors and rodent hosts of Venezuelan equine encephalitis virus, Chiapas, 2006-2007.

  Eleanor R Deardorff, Jose G Estrada-Franco, Jerome E Freier, Roberto Navarro-Lopez, Amelia Travassos Da Rosa, Robert B Tesh, Scott C Weaver
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  ABSTRACT: Enzootic Venezuelan equine encephalitis virus (VEEV) has been known to occur in Mexico since the 1960s. The first natural equine epizootic was recognized in Chiapas in 1993 and since then, numerous studies have characterized the etiologic strains, including reverse genetic studies that incriminated a specific mutation that enhanced infection of epizootic mosquito vectors. The aim of this study was to determine the mosquito and rodent species involved in enzootic maintenance of subtype IE VEEV in coastal Chiapas. A longitudinal study was conducted over a year to discern which species and habitats could be associated with VEEV circulation. Antibody was rarely detected in mammals and virus was not isolated from mosquitoes. Additionally, Culex (Melanoconion) taeniopus populations were found to be spatially related to high levels of human and bovine seroprevalence. These mosquito populations were concentrated in areas that appear to represent foci of stable, enzootic VEEV circulation.
  The American journal of tropical medicine and hygiene 12/2011; 85(6):1146-53. · 2.59 Impact Factor
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  Available from: Eleanor R Deardorff

  Article: West Nile virus experimental evolution in vivo and the trade-off hypothesis.

  Eleanor R Deardorff, Kelly A Fitzpatrick, Greta V S Jerzak, Pei-Yong Shi, Laura D Kramer, Gregory D Ebel
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  ABSTRACT: In nature, arthropod-borne viruses (arboviruses) perpetuate through alternating replication in vertebrate and invertebrate hosts. The trade-off hypothesis proposes that these viruses maintain adequate replicative fitness in two disparate hosts in exchange for superior fitness in one host. Releasing the virus from the constraints of a two-host cycle should thus facilitate adaptation to a single host. This theory has been addressed in a variety of systems, but remains poorly understood. We sought to determine the fitness implications of alternating host replication for West Nile virus (WNV) using an in vivo model system. Previously, WNV was serially or alternately passed 20 times in vivo in chicks or mosquitoes and resulting viruses were characterized genetically. In this study, these test viruses were competed in vivo in fitness assays against an unpassed marked reference virus. Fitness was assayed in chicks and in two important WNV vectors, Culex pipiens and Culex quinquefasciatus. Chick-specialized virus displayed clear fitness gains in chicks and in Cx. pipiens but not in Cx. quinquefasciatus. Cx. pipiens-specialized virus experienced reduced fitness in chicks and little change in either mosquito species. These data suggest that when fitness is measured in birds the trade-off hypothesis is supported; but in mosquitoes it is not. Overall, these results suggest that WNV evolution is driven by alternate cycles of genetic expansion in mosquitoes, where purifying selection is weak and genetic diversity generated, and restriction in birds, where purifying selection is strong.
  PLoS Pathogens 11/2011; 7(11):e1002335. · 9.13 Impact Factor
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  Available from: Eleanor R Deardorff

  Article: Nonconsensus West Nile virus genomes arising during mosquito infection suppress pathogenesis and modulate virus fitness in vivo.

  Gregory D Ebel, Kelly A Fitzpatrick, Pei-Yin Lim, Corey J Bennett, Eleanor R Deardorff, Greta V S Jerzak, Laura D Kramer, Yangsheng Zhou, Pei-Yong Shi, Kristen A Bernard
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  ABSTRACT: West Nile virus (WNV) is similar to other RNA viruses in that it forms genetically complex populations within hosts. The virus is maintained in nature in mosquitoes and birds, with each host type exerting distinct influences on virus populations. We previously observed that prolonged replication in mosquitoes led to increases in WNV genetic diversity and diminished pathogenesis in mice without remarkable changes to the consensus genome sequence. We therefore sought to evaluate the relationships between individual and group phenotypes in WNV and to discover novel viral determinants of pathogenesis in mice and fitness in mosquitoes and birds. Individual plaque size variants were isolated from a genetically complex population, and mutations conferring a small-plaque and mouse-attenuated phenotype were localized to the RNA helicase domain of the NS3 protein by reverse genetics. The mutation, an Asp deletion, did not alter type I interferon production in the host but rendered mutant viruses more susceptible to interferon compared to wild type (WT) WNV. Finally, we used an in vivo fitness assay in Culex quinquefasciatus mosquitoes and chickens to determine whether the mutation in NS3 influenced fitness. The fitness of the NS3 mutant was dramatically lower in chickens and moderately lower in mosquitoes, indicating that RNA helicase is a major fitness determinant of WNV and that the effect on fitness is host specific. Overall, this work highlights the complex relationships that exist between individual and group phenotypes in RNA viruses and identifies RNA helicase as an attenuation and fitness determinant in WNV.
  Journal of Virology 09/2011; 85(23):12605-13. · 5.40 Impact Factor
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  Available from: Eleanor R Deardorff

  Article: West Nile virus genetic diversity is maintained during transmission by Culex pipiens quinquefasciatus mosquitoes.

  Doug E Brackney, Kendra N Pesko, Ivy K Brown, Eleanor R Deardorff, Jon Kawatachi, Gregory D Ebel
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  ABSTRACT: Due to error-prone replication, RNA viruses exist within hosts as a heterogeneous population of non-identical, but related viral variants. These populations may undergo bottlenecks during transmission that stochastically reduce variability leading to fitness declines. Such bottlenecks have been documented for several single-host RNA viruses, but their role in the population biology of obligate two-host viruses such as arthropod-borne viruses (arboviruses) in vivo is unclear, but of central importance in understanding arbovirus persistence and emergence. Therefore, we tracked the composition of West Nile virus (WNV; Flaviviridae, Flavivirus) populations during infection of the vector mosquito, Culex pipiens quinquefasciatus to determine whether WNV populations undergo bottlenecks during transmission by this host. Quantitative, qualitative and phylogenetic analyses of WNV sequences in mosquito midguts, hemolymph and saliva failed to document reductions in genetic diversity during mosquito infection. Further, migration analysis of individual viral variants revealed that while there was some evidence of compartmentalization, anatomical barriers do not impose genetic bottlenecks on WNV populations. Together, these data suggest that the complexity of WNV populations are not significantly diminished during the extrinsic incubation period of mosquitoes.
  PLoS ONE 01/2011; 6(9):e24466. · 4.09 Impact Factor
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  Available from: Eleanor R Deardorff

  Article: Vector competence of Culex (Melanoconion) taeniopus for equine-virulent subtype IE strains of Venezuelan equine encephalitis virus.

  Eleanor R Deardorff, Scott C Weaver
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  ABSTRACT: The mosquito Culex (Melanoconion) taeniopus is a proven vector of enzootic Venezuelan equine encephalitis virus (VEEV) subtype IE in Central America. It has been shown to be highly susceptible to infection by this subtype, and conversely to be highly refractory to infection by other VEEV subtypes. During the 1990s in southern coastal Mexico, two VEE epizootics in horses were attributed to subtype IE VEEV. These outbreaks were associated with VEEV strains with an altered infection phenotype for the epizootic mosquito vector, Aedes (Ochlerotatus) taeniorhynchus. To determine the infectivity for the enzootic vector, Culex taeniopus, mosquitoes from a recently established colony were orally exposed to VEEV strains from the outbreak. The equine-virulent strains exhibited high infectivity and transmission potential comparable to a traditional enzootic subtype IE VEEV strain. Thus, subtype IE VEEV strains in Chiapas are able to efficiently infect enzootic and epizootic vectors and cause morbidity and mortality in horses.
  The American journal of tropical medicine and hygiene 06/2010; 82(6):1047-52. · 2.59 Impact Factor