title: Viral pathogen-associated molecular patterns regulate blood-brain barrier integrity via competing innate cytokine signals.
abstract: Pattern recognition receptor (PRR) detection of pathogen-associated molecular patterns (PAMPs), such as viral RNA, drives innate immune responses against West Nile virus (WNV), an emerging neurotropic pathogen. Here we demonstrate that WNV PAMPs orchestrate endothelial responses to WNV via competing innate immune cytokine signals at the blood-brain barrier (BBB), a multicellular interface with highly specialized brain endothelial cells that normally prevents pathogen entry. While Th1 cytokines increase the permeability of endothelial barriers, type I interferon (IFN) promoted and stabilized BBB function. Induction of innate cytokines by pattern recognition pathways directly regulated BBB permeability and tight junction formation via balanced activation of the small GTPases Rac1 and RhoA, which in turn regulated the transendothelial trafficking of WNV. In vivo, mice with attenuated type I IFN signaling or IFN induction (Ifnar(-/-) Irf7(-/-)) exhibited enhanced BBB permeability and tight junction dysregulation after WNV infection. Together, these data provide new insight into host-pathogen interactions at the BBB during neurotropic viral infection.
  
  
  OBJECTIVE
  West Nile virus (WNV) is an emerging pathogen capable of infecting the central nervous system (CNS), causing fatal encephalitis. However, the mechanisms that control the ability of WNV to cross the blood-brain barrier (BBB) and access the CNS are unclear. In this study, we show that detection of WNV by host tissues induces innate immune cytokine expression at the BBB, regulating BBB structure and function and impacting transendothelial trafficking of WNV. This regulatory effect is shown to happen rapidly following exposure to virus, to occur independently of viral replication within BBB cells, and to require the signaling of cytoskeletal regulatory Rho GTPases. These results provide new understanding of host-pathogen interactions at the BBB during viral encephalitis.
authors.affiliation: Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Daniels
authors.affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Holman
authors.affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Lillian
authors.initials: L
authors.lastname: Cruz-Orengo
authors.affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Harsha
authors.initials: H
authors.lastname: Jujjavarapu
authors.affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Durrant
authors.affiliation: rklein@dom.wustl.edu.
authors.forename: Robyn S
authors.initials: RS
authors.lastname: Klein
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000821:virology*; D001921:Brain / Q000166:cytology / Q000821:virology; D002490:Central Nervous System / Q000276:immunology / Q000821:virology; D016207:Cytokines / Q000276:immunology*; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000276:immunology / Q000821:virology; D054884:Host-Pathogen Interactions / Q000276:immunology; D007113:Immunity, Innate; D007370:Interferon Type I / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D051192:Receptors, Pattern Recognition / Q000235:genetics / Q000378:metabolism; D019108:Tight Junctions / Q000276:immunology / Q000821:virology; D014779:Virus Replication; D014901:West Nile Fever / Q000276:immunology*; D014902:West Nile virus / Q000276:immunology / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein
chemical_list: D016207:Cytokines; D007370:Interferon Type I; D009479:Neuropeptides; C484602:Rac1 protein, mouse; D051192:Receptors, Pattern Recognition; C526380:RhoA protein, mouse; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein