title: Hepatitis C virus mutation affects proteasomal epitope processing.
abstract: The high incidence of hepatitis C virus (HCV) persistence raises the question of how HCV interferes with host immune responses. Studying a single-source HCV outbreak, we identified an HCV mutation that impaired correct carboxyterminal cleavage of an immunodominant HLA-A2-restricted CD8 cell epitope that is frequently recognized by recovered patients. The mutation, a conservative HCV nonstructural protein 3 (NS3) tyrosine to phenylalanine substitution, was absent in 54 clones of the infectious source, but present in 15/21 (71%) HLA-A2-positive and in 11/24 (46%) HLA-A2-negative patients with chronic hepatitis C. In order to analyze whether the mutation affected the processing of the HLA-A2-restricted CD8 cell epitope, mutant and wild-type NS3 polypeptides were digested in vitro with 20S constitutive proteasomes and with immunoproteasomes. The presence of the mutation resulted in impaired carboxyterminal cleavage of the epitope. In order to analyze whether impaired epitope processing affected T cell priming in vivo, HLA-A2-transgenic mice were infected with vaccinia viruses encoding either wild-type or mutant HCV NS3. The mutant induced fewer epitope-specific, IFN-gamma;-producing and fewer tetramer(+) cells than the wild type. These data demonstrate how a conservative mutation in the flanking region of an HCV epitope impairs the induction of epitope-specific CD8(+) T cells and reveal a mechanism that may contribute to viral sequence evolution in infected patients.
authors.affiliation: Institute of Biochemistry, Charité, Humboldt University, Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Seifert
authors.forename: Heike
authors.initials: H
authors.lastname: Liermann
authors.forename: Vito
authors.initials: V
authors.lastname: Racanelli
authors.forename: Anne
authors.initials: A
authors.lastname: Halenius
authors.forename: Manfred
authors.initials: M
authors.lastname: Wiese
authors.forename: Heiner
authors.initials: H
authors.lastname: Wedemeyer
authors.forename: Thomas
authors.initials: T
authors.lastname: Ruppert
authors.forename: Kay
authors.initials: K
authors.lastname: Rispeter
authors.forename: Peter
authors.initials: P
authors.lastname: Henklein
authors.forename: Alice
authors.initials: A
authors.lastname: Sijts
authors.forename: Hartmut
authors.initials: H
authors.lastname: Hengel
authors.forename: Peter-M
authors.initials: PM
authors.lastname: Kloetzel
authors.forename: Barbara
authors.initials: B
authors.lastname: Rehermann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D000939:Epitopes; D015789:HLA-A2 Antigen / Q000235:genetics / Q000276:immunology; D016174:Hepacivirus / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D006526:Hepatitis C / Q000378:metabolism; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D009154:Mutation; D046988:Proteasome Endopeptidase Complex; D016415:Sequence Alignment; D014616:Vaccinia virus / Q000235:genetics / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D003546:Cysteine Endopeptidases; D000939:Epitopes; D015789:HLA-A2 Antigen; D009097:Multienzyme Complexes; D046988:Proteasome Endopeptidase Complex; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases