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Setting up a SPF Chicken Model for the Pathotyping of West Nile Virus (WNV) Strains
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Edité par CCSD ; Wiley-Blackwell -
Birds play a central role in WNV epidemiology by spreading and amplifying thevirus. Increasing numbers of WNV isolates are detected in Europe, and the virulenceof these genetically variable isolates is not well characterized for birds.Therefore, we investigated whether SPF chickens could be a valuable avian modelfor the pathotyping of WNV strains. One-day-old SPF chickens were inoculatedsubcutaneously (SC) or intracerebrally (IC) with four lineage 1 WNV strains(Is98, It2008, Fr2000 or Kunjin) and were daily clinically monitored for 2 weeksafter infection. Additionally, one-day-old SPF chickens were SC inoculated,and one-week-old SPF chickens were SC or IC inoculated with twoEuro-Mediterranean isolates, Is98 and Fr2000, to sample blood and feathers atregular time points. These samples were analysed by WN NS2a-specific rRT-PCRand WN NS1 antigen-capture ELISA that were developed for the purpose of thisstudy. Differences in strain virulence were evidenced after IC inoculation of oneday-old SPF chickens, with Is98 eliciting the highest mortality rates and Kunjinthe lowest ones, while lethality of Fr2000 and It2008 was intermediate. Neitherviral load in sera and feathers nor NS1 antigen in the serum correlated with thedifferential pathogenicity of Is98 and Fr2000. However, irrespective of the inoculatedstrain, younger chickens showed higher and longer-lasting viremias thanolder chickens. In all experimental groups, the detection window for viral RNA infeathers lasted up to 14 dpi. Altogether, the data presented in this study show thatWNV strain virulence can be discriminated in a one-day-old SPF chicken modelon the basis of mortality rates, while viremia and viral load in feathers appear tobe age dependent rather than strain dependent.
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