title: miR-146a suppresses cellular immune response during Japanese encephalitis virus JaOArS982 strain infection in human microglial cells.
abstract: BACKGROUND
  Japanese encephalitis virus (JEV) is the causative agent of Japanese encephalitis which is more prevalent in South and Southeast Asia. JEV is a neurotropic virus which infiltrates into the brain through vascular endothelial cells. JEV infects neurons and microglial cells which causes neuronal damage and inflammation. However, JEV also evades the cellular immune response to survive in host cells. Viruses are known to modulate the expression of microRNAs, which in turn modulate cellular immune response by targeting expression of antiviral genes. The aim of this study is to understand the anti-inflammatory role of miR-146a during JEV infection, which facilitates immune evasion.
  
  
  METHODS
  Human brain microglial cells (CHME3) were infected by JEV: JaOArS982 and P20778 strain, and expression of miR-146a were analyzed. Overexpression and knockdown studies of miR-146a were done to see the effect on NF-κB pathway and antiviral Jak-STAT pathway. Regulatory role of miR-146a on expression of interferon-stimulated genes was determined by real-time PCR and luciferase assays.
  
  
  RESULTS
  JEV infection elevated the expression of miR-146a in JaOArS982 strain which caused downregulation of TRAF6, IRAK1, IRAK2, and STAT1 genes. Exogenous overexpression of miR-146a led to suppression of NF-κB activation and abrogation of Jak-STAT pathway upon JEV infection which led to downregulation of interferon-stimulated genes (IFIT-1 and IFIT-2) and facilitated viral replication. JEV infection initially upregulated cytokine production and activated STAT1 activity but STAT1 levels reduced at later time point, which led to the downregulation of interferon-stimulated genes.
  
  
  CONCLUSIONS
  Upregulation of miR-146a by JEV JaOArS982 strain leads to suppression of NF-κB activity and disruption of antiviral Jak-STAT signaling which helps the virus to evade the cellular immune response. This effect of JEV infection on miR-146a expression was found to be strain specific.
authors.affiliation: Laboratory of Neurovirology and Inflammation Biology, CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, 500007, Hyderabad, AP, India. nikhil@ccmb.res.in.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Sharma
authors.affiliation: Laboratory of Neurovirology and Inflammation Biology, CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, 500007, Hyderabad, AP, India. ruhiverma78@gmail.com.
authors.forename: Ruhi
authors.initials: R
authors.lastname: Verma
authors.affiliation: National Brain Research Centre, Haryana-122050, Manesar, Haryana, India. kanhaiya81@gmail.com.
authors.forename: Kanhaiya Lal
authors.initials: KL
authors.lastname: Kumawat
authors.affiliation: National Brain Research Centre, Haryana-122050, Manesar, Haryana, India. anirban@nbrc.ac.in.
authors.forename: Anirban
authors.initials: A
authors.lastname: Basu
authors.affiliation: Laboratory of Neurovirology and Inflammation Biology, CSIR-Centre for Cellular and Molecular Biology (CCMB), Uppal Road, 500007, Hyderabad, AP, India. sunitsingh2000@gmail.com.|Current Affiliation: Laboratory of Human Molecular Virology and Immunology, Molecular Biology Unit, Faculty of Medicine, Institute of Medical Sciences (IMS), Banaras Hindu University (BHU), 221005, Varanasi, India. sunitsingh2000@gmail.com.
authors.forename: Sunit K
authors.initials: SK
authors.lastname: Singh
mesh_terms: D002461:Cell Line, Transformed; D016207:Cytokines / Q000378:metabolism; D004664:Encephalitis Virus, Japanese / Q000276:immunology*; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D006801:Humans; D007111:Immunity, Cellular; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D017628:Microglia / Q000276:immunology* / Q000821:virology*; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D016207:Cytokines; C542542:MIRN146 microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; D048029:TNF Receptor-Associated Factor 6; C507768:IRAK1 protein, human; C507771:IRAK3 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases