title: Role of Toll-like receptor 2 in the immune response against hepadnaviral infection.
abstract: OBJECTIVE
  The Toll-like receptor 2 (TLR2) has recently been recognized to play an important role in the pathogenesis of chronic hepatitis B virus (HBV) infection. In the present study, we examined the role of TLR2 in hepadnaviral infection in hepatoma cell lines and the woodchuck model.
  
  
  METHODS
  The expression of TLR2 and pro-inflammatory cytokines was quantified by real time RT-PCR. TLR2-associated signaling pathways in hepatocytes were examined by Western blot. HBV replication and gene expression were assessed by Southern blot, Northern blot and specific ELISA, respectively.
  
  
  RESULTS
  TLR2 ligands activated NF-κB, PI3K/Akt, and different arms of MAPK signaling pathways and induced the production of pro-inflammatory cytokines in hepatocytes. TLR2-mediated innate immune responses led to reduction of HBV/woodchuck hepatitis virus (WHV) replication and gene expression in HepG2.2.15 cells and primary woodchuck hepatocytes. Furthermore, the antiviral activity of TLR2 ligands was abolished by pretreatment with U0126 and rapamycin, inhibitors of the MAPK/ERK and PI3K/Akt pathways, respectively. In the woodchuck model, relatively low levels of TLR2 expression were found in peripheral blood mononuclear cells (PBMCs) and in liver tissues from chronic WHV carriers. TLR2 expression in PBMCs was inversely correlated with WHV DNA titers in acute WHV infection and in entecavir-treated chronic WHV carriers.
  
  
  CONCLUSIONS
  These data suggest that hepatocytes play an active role in TLR2-mediated antiviral responses during hepadnaviral infection. The mutual inhibition of HBV replication and TLR2 signaling represents an important aspect of HBV infection and should be considered in the new therapeutic concept against chronic HBV infection.
authors.affiliation: Institute of Virology, University Hospital of Essen, Essen, Germany.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Zhang
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Ma
authors.forename: Hongyan
authors.initials: H
authors.lastname: Liu
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.forename: Zhongji
authors.initials: Z
authors.lastname: Meng
authors.forename: Ruth
authors.initials: R
authors.lastname: Broering
authors.forename: Dongliang
authors.initials: D
authors.lastname: Yang
authors.forename: Joerg F
authors.initials: JF
authors.lastname: Schlaak
authors.forename: Michael
authors.initials: M
authors.lastname: Roggendorf
authors.forename: Mengji
authors.initials: M
authors.lastname: Lu
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use; D002070:Butadienes / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D004279:DNA, Viral / Q000097:blood; D015536:Down-Regulation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D006147:Guanine / Q000031:analogs & derivatives / Q000627:therapeutic use; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D019694:Hepatitis B, Chronic / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D007963:Leukocytes, Mononuclear / Q000378:metabolism / Q000821:virology; D008024:Ligands; D055666:Lipopeptides / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism / Q000821:virology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008392:Marmota; D016328:NF-kappa B / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D000998:Antiviral Agents; D002070:Butadienes; D016207:Cytokines; D004279:DNA, Viral; D008024:Ligands; D055666:Lipopeptides; D016328:NF-kappa B; D009570:Nitriles; C508075:Pam(3)CSK(4) peptide; C560312:Pam2CSK4 lipopeptide; D012333:RNA, Messenger; D051195:Toll-Like Receptor 2; C113580:U 0126; C413685:entecavir; D006147:Guanine; D058539:Phosphatidylinositol 3-Kinase; D020123:Sirolimus