Il22^−/− mice are resistant to lethal WNV infection.

<p><b>a</b>) Plasma IL-22 levels of WT mice were measured by ELISA, and viremia was quantified by q-PCR using WNV envelope gene (<i>WNV-E</i>) primers and probes and normalized with mouse actin. <b>b</b>) IL-22Rα1 transcripts in the WT mouse brain were examined by q-PCR and normalized with actin, and viral loads were quantified by q-PCR for <i>WNV-E</i> and normalized with mouse actin; *<i>p</i><0.05; **<i>p</i><0.01. Each dot represents one mouse. <b>c</b>) Immunofluorescence microscopy of IL-22Rα1 (red signal) in the WT mouse brain (cerebral cortex is shown). DAPI nuclear counter-stain is shown in blue. Arrows indicate blood vessels, shown in higher-magnification insets. <b>d</b>) Survival curve of <i>Il22</i>^−/−<i>vs</i>. WT mice challenged with WNV. Mice were infected with 200 PFU of WNV via s.c. footpad injection and monitored daily for survival for 21 days (n = 30 for WT and n = 24 for <i>Il22</i>^−/− mice). Data are pooled from 3 independent experiments.