title: CD81/CD9 tetraspanins aid plasmacytoid dendritic cells in recognition of hepatitis C virus-infected cells and induction of interferon-alpha.
abstract: Recognition of hepatitis C virus (HCV)-infected hepatocyes and interferon (IFN) induction are critical in antiviral immune response. We hypothesized that cell-cell contact between plasmacytoid dendritic cells (pDCs) and HCV-infected cells was required for IFN-α induction through the involvement of cell-surface molecules. Coculture of human peripheral blood mononuclear cells (PBMCs) with genotype 1a full-length (FL) HCV genomic replicon cells or genotype 2a Japanese fulminant hepatitis type 1 (JFH-1) virus-infected hepatoma cells (JFH-1), and not with uninfected hepatoma cells (Huh7.5), induced IFN-α production. Depletion of pDCs from PBMCs attenuated IFN-α release, and purified pDCs produced high levels of IFN-α after coculture with FL replicons or JFH-1-infected cells. IFN-α induction by HCV-containing hepatoma cells required viral replication, direct cell-cell contact with pDCs, and receptor-mediated endocytosis. We determined that the tetraspanin proteins, CD81 and CD9, and not other HCV entry receptors, were required for IFN-α induction in pDCs by HCV-infected hepatoma cells. Disruption of cholesterol-rich membrane microdomains, the localization site of CD81, or inhibition of the CD81 downstream molecule, Rac GTPase, inhibited IFN-α production. IFN-α induction involved HCV RNA and Toll-like receptor (TLR) 7. IFN-α production by HCV-infected hepatoma cells was decreased in pDCs from HCV-infected patients, compared to healthy controls. We found that preexposure of healthy PBMCs to HCV viral particles attenuated IFN-α induction by HCV-infected hepatoma cells or TLR ligands, and this inhibitory effect could be prevented by an anti-HCV envelope glycoprotein 2-blocking antibody.
  
  
  CONCLUSIONS
  Our novel data show that recognition of HCV-infected hepatoma cells by pDCs involves CD81- and CD9-associated membrane microdomains and induces potent IFN-α production.
authors.affiliation: University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Shuye
authors.initials: S
authors.lastname: Zhang
authors.forename: Karen
authors.initials: K
authors.lastname: Kodys
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Babcock
authors.forename: Gyongyi
authors.initials: G
authors.lastname: Szabo
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology / Q000821:virology; D016022:Case-Control Studies; D002450:Cell Communication / Q000502:physiology; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000473:pathology* / Q000502:physiology; D004705:Endocytosis / Q000502:physiology; D016174:Hepacivirus / Q000302:isolation & purification*; D006526:Hepatitis C / Q000378:metabolism / Q000473:pathology / Q000821:virology; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology* / Q000821:virology; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000378:metabolism / Q000473:pathology / Q000821:virology; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology / Q000821:virology; D021962:Membrane Microdomains / Q000502:physiology; D060225:Tetraspanin 28 / Q000502:physiology*; D060245:Tetraspanin 29 / Q000502:physiology*; D059470:Tetraspanins / Q000502:physiology*; D014779:Virus Replication / Q000502:physiology
chemical_list: D016898:Interferon-alpha; D060225:Tetraspanin 28; D060245:Tetraspanin 29; D059470:Tetraspanins