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PLoS Neglected Tropical Diseases Jan 2018West Nile virus (WNV) and Rift Valley fever virus (RVFV) are two emerging arboviruses transmitted by Culex pipiens species that includes two biotypes: pipiens and...
West Nile virus (WNV) and Rift Valley fever virus (RVFV) are two emerging arboviruses transmitted by Culex pipiens species that includes two biotypes: pipiens and molestus. In Lebanon, human cases caused by WNV and RVFV have never been reported. However, the introduction of these viruses in the country is likely to occur through the migratory birds and animal trades. In this study, we evaluated the ability of Cx. pipiens, a predominant mosquito species in urban and rural regions in Lebanon, to transmit WNV and RVFV. Culex egg rafts were collected in the West Bekaa district, east of Lebanon and adult females of Cx. pipiens were experimentally infected with WNV and RVFV Clone 13 strain at titers of 1.6×108 and 1.33×107 plaque forming units (PFU)/mL, respectively. We estimated viral infection, dissemination and transmission at 3, 7, 14 and 19 days post infection (dpi). Results showed that infection was higher for WNV than for RVFV from 3 dpi to 19 dpi. Viral dissemination and transmission started from 3 dpi for WNV; and only from 19 dpi for RVFV. Moreover, Cx. pipiens were able to excrete in saliva a higher number of viral particles of WNV (1028 ± 405 PFU/saliva at 19 dpi) than RVFV (42 PFU/saliva at 19 dpi). Cx. pipiens from Lebanon are efficient experimental vectors of WNV and to a lower extent, RVFV. These findings should stimulate local authorities to establish an active entomological surveillance in addition to animal surveys for both viruses in the country.
Topics: Animals; Culex; Host Specificity; Lebanon; Mosquito Vectors; Rift Valley fever virus; Saliva; Time Factors; West Nile virus
PubMed: 29324834
DOI: 10.1371/journal.pntd.0005983 -
Methods in Molecular Biology (Clifton,... 2023The plaque-forming assay is a gold standard technique to determine the concentration of infectious viral particles. In this assay, lytic viruses infect and lyse the...
The plaque-forming assay is a gold standard technique to determine the concentration of infectious viral particles. In this assay, lytic viruses infect and lyse the cells but are immobilized due to the presence of an agarose-containing overlay medium. The progeny viruses can only spread locally to and kill the adjacent cells and finally form a clear zone or plaque after staining the live cells. The number of plaques formed can be theoretically considered as the initial number of the infectious viral particles present in the sample and hence can be expressed as plaque-forming units (PFU) in a volume of the sample. Here, we provide a step-by-step method to carry out a plaque-forming assay to determine the titer of West Nile virus in a cell culture medium, which also can be adapted to other lytic viruses of eukaryotic cells.
Topics: West Nile virus; Viral Plaque Assay
PubMed: 36331760
DOI: 10.1007/978-1-0716-2760-0_2 -
Antiviral Chemistry & Chemotherapy Apr 2014West Nile virus (WNV) is a human pathogen which is rapidly expanding worldwide. It is a member of the Flavivirus genus and it is transmitted by mosquitos between its... (Review)
Review
West Nile virus (WNV) is a human pathogen which is rapidly expanding worldwide. It is a member of the Flavivirus genus and it is transmitted by mosquitos between its avian hosts and occasionally in mammalian hosts. In humans the infection is often asymptomatic, however, the most severe cases result in encephalitis or meningitis. Approximately 10% of cases of neuroinvasive disease are fatal. To date there is no effective human vaccine or effective antiviral therapy available to treat WNV infections. For this reason, research in this field is rapidly growing. In this article we will review the latest efforts in the design and development of novel WNV inhibitors from a medicinal chemistry point of view, highlighting challenges and opportunities for the researchers working in this field.
Topics: Chemistry, Pharmaceutical; Humans; Microbial Sensitivity Tests; Molecular Structure; Small Molecule Libraries; Structure-Activity Relationship; Viral Proteins; West Nile virus
PubMed: 23636899
DOI: 10.3851/IMP2581 -
Journal of Medical Entomology Oct 2019West Nile virus (WNV) was first identified in North America almost 20 yr ago. In that time, WNV has crossed the continent and established enzootic transmission cycles,... (Review)
Review
West Nile virus (WNV) was first identified in North America almost 20 yr ago. In that time, WNV has crossed the continent and established enzootic transmission cycles, resulting in intermittent outbreaks of human disease that have largely been linked with climatic variables and waning avian seroprevalence. During the transcontinental dissemination of WNV, the original genotype has been displaced by two principal extant genotypes which contain an envelope mutation that has been associated with enhanced vector competence by Culex pipiens L. (Diptera: Culicidae) and Culex tarsalis Coquillett vectors. Analyses of retrospective avian host competence data generated using the founding NY99 genotype strain have demonstrated a steady reduction in viremias of house sparrows over time. Reciprocally, the current genotype strains WN02 and SW03 have demonstrated an inverse correlation between house sparrow viremia magnitude and the time since isolation. These data collectively indicate that WNV has evolved for increased avian viremia while house sparrows have evolved resistance to the virus such that the relative host competence has remained constant. Intrahost analyses of WNV evolution demonstrate that selection pressures are avian species-specific and purifying selection is greater in individual birds compared with individual mosquitoes, suggesting that the avian adaptive and/or innate immune response may impose a selection pressure on WNV. Phylogenomic, experimental evolutionary systems, and models that link viral evolution with climate, host, and vector competence studies will be needed to identify the relative effect of different selective and stochastic mechanisms on viral phenotypes and the capacity of newly evolved WNV genotypes for transmission in continuously changing landscapes.
Topics: Animals; Bird Diseases; Birds; Culicidae; Environment; Genome, Viral; Host-Pathogen Interactions; North America; West Nile Fever; West Nile virus
PubMed: 31549720
DOI: 10.1093/jme/tjz112 -
PLoS Neglected Tropical Diseases Feb 2017Half of the human population is at risk of infection by an arthropod-borne virus. Many of these arboviruses, such as West Nile, dengue, and Zika viruses, infect humans...
Half of the human population is at risk of infection by an arthropod-borne virus. Many of these arboviruses, such as West Nile, dengue, and Zika viruses, infect humans by way of a bite from an infected mosquito. This infectious inoculum is insect cell-derived giving the virus particles distinct qualities not present in secondary infectious virus particles produced by infected vertebrate host cells. The insect cell-derived particles differ in the glycosylation of virus structural proteins and the lipid content of the envelope, as well as their induction of cytokines. Thus, in order to accurately mimic the inoculum delivered by arthropods, arboviruses should be derived from arthropod cells. Previous studies have packaged replicon genome in mammalian cells to produce replicon particles, which undergo only one round of infection, but no studies exist packaging replicon particles in mosquito cells. Here we optimized the packaging of West Nile virus replicon genome in mosquito cells and produced replicon particles at high concentration, allowing us to mimic mosquito cell-derived viral inoculum. These particles were mature with similar genome equivalents-to-infectious units as full-length West Nile virus. We then compared the mosquito cell-derived particles to mammalian cell-derived particles in mice. Both replicon particles infected skin at the inoculation site and the draining lymph node by 3 hours post-inoculation. The mammalian cell-derived replicon particles spread from the site of inoculation to the spleen and contralateral lymph nodes significantly more than the particles derived from mosquito cells. This in vivo difference in spread of West Nile replicons in the inoculum demonstrates the importance of using arthropod cell-derived particles to model early events in arboviral infection and highlights the value of these novel arthropod cell-derived replicon particles for studying the earliest virus-host interactions for arboviruses.
Topics: Aedes; Animals; Arbovirus Infections; Arboviruses; Female; Humans; Insect Vectors; Mice; Mice, Inbred C57BL; Replicon; Viral Structural Proteins; Virus Assembly; Virus Cultivation; West Nile Fever; West Nile virus
PubMed: 28187142
DOI: 10.1371/journal.pntd.0005394 -
Epidemiology and Infection Jul 2015Arboviral infections are emerging among tourists travelling to (sub)tropical regions. This study aims to describe the importation of chikungunya virus (CHIKV) and West...
Arboviral infections are emerging among tourists travelling to (sub)tropical regions. This study aims to describe the importation of chikungunya virus (CHIKV) and West Nile virus (WNV) into Belgium over a 6-year period from 2007 to 2012. Clinical samples were obtained from travellers presenting at the outpatient clinic of the Institute of Tropical Medicine (ITM), Antwerp, Belgium or submitted to the Central Laboratory for Clinical Biology of the ITM. Testing was performed by serology and/or by real-time reverse transcriptase-polymerase chain reaction. A total of 1288 returning travellers were investigated for CHIKV infection resulting in 34 confirmed and two probable diagnoses (2·80%). Out of 899 patients, four confirmed and one probable imported WNV infections were diagnosed (0·55%). No locally acquired cases have been registered in Belgium until now and the geographical origin of the imported infections reflects the global locations where the viruses are circulating.
Topics: Adolescent; Adult; Aged; Belgium; Chikungunya Fever; Chikungunya virus; Child; Female; Humans; Male; Middle Aged; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Serologic Tests; Travel; West Nile Fever; West Nile virus; Young Adult
PubMed: 24690286
DOI: 10.1017/S0950268814000685 -
Viruses Jan 2014Flaviviruses are a large group of positive strand RNA viruses transmitted by arthropods that include many human pathogens such as West Nile virus (WNV), Japanese... (Review)
Review
Flaviviruses are a large group of positive strand RNA viruses transmitted by arthropods that include many human pathogens such as West Nile virus (WNV), Japanese encephalitis virus (JEV), yellow fever virus, dengue virus, and tick-borne encephalitis virus. All members in this genus tested so far are shown to produce a unique subgenomic flavivirus RNA (sfRNA) derived from the 3' untranslated region (UTR). sfRNA is a product of incomplete degradation of genomic RNA by the cell 5'-3' exoribonuclease XRN1 which stalls at highly ordered secondary RNA structures at the beginning of the 3'UTR. Generation of sfRNA results in inhibition of XRN1 activity leading to an increase in stability of many cellular mRNAs. Mutant WNV deficient in sfRNA generation was highly attenuated displaying a marked decrease in cytopathicity in cells and pathogenicity in mice. sfRNA has also been shown to inhibit the antiviral activity of IFN-α/β by yet unknown mechanism and of the RNAi pathway by likely serving as a decoy substrate for Dicer. Thus, sfRNA is involved in modulating multiple cellular pathways to facilitate viral pathogenicity; however the overlying mechanism linking all these multiple functions of sfRNA remains to be elucidated.
Topics: 5' Untranslated Regions; Animals; Cytopathogenic Effect, Viral; Disease Models, Animal; Host-Pathogen Interactions; Mice; RNA, Untranslated; RNA, Viral; Virulence; West Nile Fever; West Nile virus
PubMed: 24473339
DOI: 10.3390/v6020404 -
Current Opinion in Virology Dec 2016West Nile virus remains the most common cause of arboviral encephalitis in North America. Since it was introduced, it has undergone adaptive genetic change as it spread... (Review)
Review
West Nile virus remains the most common cause of arboviral encephalitis in North America. Since it was introduced, it has undergone adaptive genetic change as it spread throughout the continent. The WNV transmission cycle is relatively tractable in the laboratory. Thus the virus serves as a convenient model system for studying the population biology of mosquito-borne flaviviruses as they undergo transmission to and from mosquitoes and vertebrates. This review summarizes the current knowledge regarding the population dynamics of this virus within mosquito vectors.
Topics: Adaptation, Biological; Animals; Mosquito Vectors; North America; Population Dynamics; West Nile virus
PubMed: 27788400
DOI: 10.1016/j.coviro.2016.09.007 -
The New England Journal of Medicine Jun 2001
Topics: Animals; Birds; Disease Outbreaks; Disease Vectors; Humans; New York City; Polymerase Chain Reaction; Population Surveillance; West Nile Fever; West Nile virus
PubMed: 11407349
DOI: 10.1056/NEJM200106143442409 -
Frontiers in Immunology 2022Dietary fiber supports healthy gut bacteria and their production of short-chain fatty acids (SCFA), which promote anti-inflammatory cell development, in particular,...
Dietary fiber supports healthy gut bacteria and their production of short-chain fatty acids (SCFA), which promote anti-inflammatory cell development, in particular, regulatory T cells. It is thus beneficial in many diseases, including influenza infection. While disruption of the gut microbiota by antibiotic treatment aggravates West Nile Virus (WNV) disease, whether dietary fiber is beneficial is unknown. WNV is a widely-distributed neurotropic flavivirus that recruits inflammatory monocytes into the brain, causing life-threatening encephalitis. To investigate the impact of dietary fiber on WNV encephalitis, mice were fed on diets deficient or enriched with dietary fiber for two weeks prior to inoculation with WNV. To induce encephalitis, mice were inoculated intranasally with WNV and maintained on these diets. Despite increased fecal SCFA acetate and changes in gut microbiota composition, dietary fiber did not affect clinical scores, leukocyte infiltration into the brain, or survival. After the brain, highest virus loads were measured in the colon in neurons of the submucosal and myenteric plexuses. Associated with this, there was disrupted gut homeostasis, with shorter colon length and higher local inflammatory cytokine levels, which were not affected by dietary fiber. Thus, fiber supplementation is not effective in WNV encephalitis.
Topics: Animals; Brain; Cytokines; Dietary Fiber; Mice; West Nile Fever; West Nile virus
PubMed: 35296081
DOI: 10.3389/fimmu.2022.784486