title: Efficient virus assembly, but not infectivity, determines the magnitude of hepatitis C virus-induced interferon alpha responses of plasmacytoid dendritic cells.
abstract: Worldwide, approximately 160 million people are chronically infected with hepatitis C virus (HCV), seven distinct genotypes of which are discriminated. The hallmarks of HCV are its genetic variability and the divergent courses of hepatitis C progression in patients. We assessed whether intragenotypic HCV variations would differentially trigger host innate immunity. To this end, we stimulated human primary plasmacytoid dendritic cells (pDC) with crude preparations of different cell culture-derived genotype 2a HCV variants. Parental Japanese fulminant hepatitis C virus (JFH1) did not induce interferon alpha (IFN-α), whereas the intragenotypic chimera Jc1 triggered massive IFN-α responses. Purified Jc1 retained full infectivity but no longer induced IFN-α. Coculture of pDC with HCV-infected hepatoma cells retrieved the capacity to induce IFN-α, whereas Jc1-infected cells triggered stronger responses than JFH1-infected cells. Since the infectivity of virus particles did not seem to affect pDC activation, we next tested Jc1 mutants that were arrested at different stages of particle assembly. These experiments revealed that efficient assembly and core protein envelopment were critically needed to trigger IFN-α. Of note, sequences within domain 2 of the core that vitally affect virus assembly also crucially influenced the IFN-α responses of pDC. These data showed that viral determinants shaped host innate IFN-α responses to HCV.
  
  
  OBJECTIVE
  Although pegylated IFN-α plus ribavirin currently is the standard of care for the treatment of chronic hepatitis C virus infection, not much is known about the relevance of early interferon responses in the pathogenesis of hepatitis C virus infection. Here, we addressed whether intragenotypic variations of hepatitis C virus would account for differential induction of type I interferon responses mounted by primary blood-derived plasmacytoid dendritic cells. Surprisingly, a chimeric genotype 2a virus carrying the nonstructural genes of Japanese fulminant hepatitis C virus (JFH1) induced massive type I interferon responses, whereas the original genotype 2a JFH1 strain did not. Our detailed analyses revealed that, not the virus infectivity, but rather, the efficiency of virus assembly and core protein envelopment critically determined the magnitude of interferon responses. To our knowledge, this is the first example of hepatitis C virus-associated genetic variations that determine the magnitude of innate host responses.
authors.affiliation: Institute for Experimental Infection Research, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Grabski
authors.affiliation: Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Wappler
authors.affiliation: Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Pfaender
authors.affiliation: Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany.
authors.forename: Eike
authors.initials: E
authors.lastname: Steinmann
authors.affiliation: Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany.
authors.forename: Sibylle
authors.initials: S
authors.lastname: Haid
authors.affiliation: Miltenyi Biotec GmbH, Bergisch Gladbach, Germany.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Dzionek
authors.affiliation: Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany ulrich.kalinke@twincore.de thomas.pietschmann@twincore.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pietschmann
authors.affiliation: Institute for Experimental Infection Research, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany ulrich.kalinke@twincore.de thomas.pietschmann@twincore.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kalinke
mesh_terms: D002460:Cell Line; D003713:Dendritic Cells / Q000276:immunology* / Q000821:virology; D005260:Female; D016174:Hepacivirus / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D006526:Hepatitis C / Q000276:immunology* / Q000821:virology; D006801:Humans; D007113:Immunity, Innate; D016898:Interferon-alpha; D008297:Male; D017434:Protein Structure, Tertiary; D014758:Viral Core Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D019065:Virus Assembly
chemical_list: D016898:Interferon-alpha; D014758:Viral Core Proteins