title: The NS5 protein of the virulent West Nile virus NY99 strain is a potent antagonist of type I interferon-mediated JAK-STAT signaling.
abstract: Flaviviruses transmitted by arthropods represent a tremendous disease burden for humans, causing millions of infections annually. All vector-borne flaviviruses studied to date suppress host innate responses to infection by inhibiting alpha/beta interferon (IFN-alpha/beta)-mediated JAK-STAT signal transduction. The viral nonstructural protein NS5 of some flaviviruses functions as the major IFN antagonist, associated with inhibition of IFN-dependent STAT1 phosphorylation (pY-STAT1) or with STAT2 degradation. West Nile virus (WNV) infection prevents pY-STAT1 although a role for WNV NS5 in IFN antagonism has not been fully explored. Here, we report that NS5 from the virulent NY99 strain of WNV prevented pY-STAT1 accumulation, suppressed IFN-dependent gene expression, and rescued the growth of a highly IFN-sensitive virus (Newcastle disease virus) in the presence of IFN, suggesting that this protein can function as an efficient IFN antagonist. In contrast, NS5 from Kunjin virus (KUN), a naturally attenuated subtype of WNV, was a poor suppressor of pY-STAT1. Mutation of a single residue in KUN NS5 to the analogous residue in WNV-NY99 NS5 (S653F) rendered KUN NS5 an efficient inhibitor of pY-STAT1. Incorporation of this mutation into recombinant KUN resulted in 30-fold greater inhibition of JAK-STAT signaling than with the wild-type virus and enhanced KUN replication in the presence of IFN. Thus, a naturally occurring mutation is associated with the function of NS5 in IFN antagonism and may influence virulence of WNV field isolates.
authors.affiliation: Laboratory of Virology, Rocky Mountain Laboratories, 903 S. Fourth St., Hamilton, MT 59840, USA.
authors.forename: Maudry
authors.initials: M
authors.lastname: Laurent-Rolle
authors.forename: Elena F
authors.initials: EF
authors.lastname: Boer
authors.forename: Kirk J
authors.initials: KJ
authors.lastname: Lubick
authors.forename: James B
authors.initials: JB
authors.lastname: Wolfinbarger
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Carmody
authors.forename: Barry
authors.initials: B
authors.lastname: Rockx
authors.forename: Wenjun
authors.initials: W
authors.lastname: Liu
authors.forename: Joseph
authors.initials: J
authors.lastname: Ashour
authors.forename: W Lesley
authors.initials: WL
authors.lastname: Shupert
authors.forename: Michael R
authors.initials: MR
authors.lastname: Holbrook
authors.forename: Alan D
authors.initials: AD
authors.lastname: Barrett
authors.forename: Peter W
authors.initials: PW
authors.lastname: Mason
authors.forename: Marshall E
authors.initials: ME
authors.lastname: Bloom
authors.forename: Adolfo
authors.initials: A
authors.lastname: García-Sastre
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Khromykh
authors.forename: Sonja M
authors.initials: SM
authors.lastname: Best
mesh_terms: D000818:Animals; D002522:Chlorocebus aethiops; D006801:Humans; D007370:Interferon Type I / Q000037:antagonists & inhibitors*; D053612:Janus Kinases / Q000037:antagonists & inhibitors*; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors*; D015398:Signal Transduction / Q000502:physiology*; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000502:physiology*; D014902:West Nile virus / Q000502:physiology
chemical_list: D007370:Interferon Type I; C080107:NS4B protein, flavivirus; C096041:NS5 protein, flavivirus; D050794:STAT1 Transcription Factor; D017361:Viral Nonstructural Proteins; D053612:Janus Kinases