title: Fast type I interferon response protects astrocytes from flavivirus infection and virus-induced cytopathic effects.
abstract: Neurotropic flaviviruses such as tick-borne encephalitis virus (TBEV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and Zika virus (ZIKV) are causative agents of severe brain-related diseases including meningitis, encephalitis, and microcephaly. We have previously shown that local type I interferon response within the central nervous system (CNS) is involved in the protection of mice against tick-borne flavivirus infection. However, the cells responsible for mounting this protective response are not defined.
  
  
  
  Primary astrocytes were isolated from wild-type (WT) and interferon alpha receptor knock out (IFNAR-/-) mice and infected with neurotropic flaviviruses. Viral replication and spread, IFN induction and response, and cellular viability were analyzed. Transcriptional levels in primary astrocytes treated with interferon or supernatant from virus-infected cells were analyzed by RNA sequencing and evaluated by different bioinformatics tools.
  
  
  
  Here, we show that astrocytes control viral replication of different TBEV strains, JEV, WNV, and ZIKV. In contrast to fibroblast, astrocytes mount a rapid interferon response and restrict viral spread. Furthermore, basal expression levels of key interferon-stimulated genes are high in astrocytes compared to mouse embryonic fibroblasts. Bioinformatic analysis of RNA-sequencing data reveals that astrocytes have established a basal antiviral state which contributes to the rapid viral recognition and upregulation of interferons. The most highly upregulated pathways in neighboring cells were linked to type I interferon response and innate immunity. The restriction in viral growth was dependent on interferon signaling, since loss of the interferon receptor, or its blockade in wild-type cells, resulted in high viral replication and virus-induced cytopathic effects. Astrocyte supernatant from TBEV-infected cells can restrict TBEV growth in astrocytes already 6 h post infection, the effect on neurons is highly reinforced, and astrocyte supernatant from 3 h post infection is already protective.
  
  
  
  These findings suggest that the combination of an intrinsic constitutive antiviral response and the fast induction of type I IFN production by astrocytes play an important role in self-protection of astrocytes and suppression of flavivirus replication in the CNS.
authors: Department of Clinical Microbiology, Virology, Umeå University, 90185, Umeå, Sweden.|The Laboratory for Molecular Infection Medicine Sweden (MIMS), 90187, Umeå, Sweden.
authors: Richard
authors: R
authors: Lindqvist
authors: The Broad Institute of MIT and Harvard, Proteomics and Biomarkers, 415 Main Street, #5033-A, Cambridge, MA, 02142, USA.
authors: Filip
authors: F
authors: Mundt
authors: Department of Pharmacology and Clinical Neuroscience, Umeå University, 90187, Umeå, Sweden.
authors: Jonathan D
authors: JD
authors: Gilthorpe
authors: Bundeswehr Institute of Microbiology, Neuherbergstraße 11, 80937, Munich, Germany.
authors: Silke
authors: S
authors: Wölfel
authors: Department of Molecular Biology, Umeå University, 90187, Umeå, Sweden.
authors: Nelson O
authors: NO
authors: Gekara
authors: Innate Immunity and Infection, Helmholtz Centre for Infection Research, Inhoffen Str 7, 38124, Braunschweig, Germany.|Institute of Medical Microbiology, Otto-von-Guericke-University Magdeburg, Leipziger Str. 44, 39120, Magdeburg, Germany.
authors: Andrea
authors: A
authors: Kröger
authors: Department of Clinical Microbiology, Virology, Umeå University, 90185, Umeå, Sweden. anna.overby@umu.se.|The Laboratory for Molecular Infection Medicine Sweden (MIMS), 90187, Umeå, Sweden. anna.overby@umu.se.
authors: Anna K
authors: AK
authors: Överby
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000998:Antiviral Agents / Q000494:pharmacology; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology / Q000821:virology; D019295:Computational Biology; D005416:Flavivirus / Q000502:physiology*; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D007074:Immunoglobulin G / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000821:virology; D010078:Oxazines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D053633:Receptor, Interferon alpha-beta / Q000235:genetics / Q000378:metabolism*; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; D007074:Immunoglobulin G; D010078:Oxazines; D012333:RNA, Messenger; D014966:Xanthenes; D053633:Receptor, Interferon alpha-beta; C005843:resazurin
keywords: Astrocytes; Flavivirus; Interferon; TBEV; Viperin