title: High frequency of functional anti-YMDD and -mutant cytotoxic T lymphocytes after in vitro expansion correlates with successful response to lamivudine therapy for chronic hepatitis B.
abstract: BACKGROUND
  Many determinants for a sustained response to lamivudine therapy have been reported but the role of T cell responsiveness remains unclear. The finding that tyrosine-methionine-aspartate-aspartate (YMDD) motif of the reverse transcriptase domain of hepatitis B virus (HBV) DNA polymerase carries a HLA-A2 restricted cytotoxic T lymphocyte (CTL) epitope makes quantitative measurement of the numbers of peptide specific CTLs feasible using MHC tetramer-peptide complex staining.
  
  
  OBJECTIVE
  To investigate the correlation between anti-YMDD motif CTL activity and the efficacy of lamivudine therapy in HLA-A2 positive patients with chronic hepatitis B (CH-B).
  
  
  METHODS
  The function and phenotype of peptide and interleukin 2 expanded peripheral blood mononuclear cells were quantified by cell lytic assay and immunocytochemical analysis by staining with HLA-A2-peptide tetramer complexes.
  
  
  RESULTS
  After in vitro expansion, sustained responders had more potent CTL responses against YMDD, YVDD, and YIDD, as well as other epitopes on HBV antigens than non-responders. The frequency of YMDD/YVDD/YIDD motif specific CTLs increased significantly with an effective cell lytic function during and after therapy in sustained responders but not in non-responders. YMDD specific CTLs cross reacted with YIDD and YVDD mutant epitopes, and shared T cell receptor gene usages with YIDD and YVDD specific CTLs.
  
  
  CONCLUSIONS
  Sustained responders, at least HLA-A2 patients, elicited a more potent CTL immunity against YMDD and its mutants. YMDD specific CTLs are cross reactive with YVDD and YIDD mutant epitopes, which may further contribute to immune clearance of the mutant viruses and a successful response to lamivudine therapy in CH-B patients.
authors.affiliation: Department of Surgery, Hong Kong University Medical Center, Queen Mary Hospital, Hong Kong.
authors.forename: C-L
authors.initials: CL
authors.lastname: Lin
authors.forename: S-L
authors.initials: SL
authors.lastname: Tsai
authors.forename: T-H
authors.initials: TH
authors.lastname: Lee
authors.forename: R-N
authors.initials: RN
authors.lastname: Chien
authors.forename: S-K
authors.initials: SK
authors.lastname: Liao
authors.forename: Y-F
authors.initials: YF
authors.lastname: Liaw
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D004279:DNA, Viral / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D024882:Drug Resistance, Viral / Q000235:genetics; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000276:immunology; D005260:Female; D015789:HLA-A2 Antigen / Q000032:analysis; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D019694:Hepatitis B, Chronic / Q000188:drug therapy* / Q000276:immunology / Q000821:virology; D006801:Humans; D007111:Immunity, Cellular; D019259:Lamivudine / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D012194:RNA-Directed DNA Polymerase; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000276:immunology; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D004279:DNA, Viral; D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D016693:Receptors, Antigen, T-Cell, alpha-beta; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D012194:RNA-Directed DNA Polymerase; D004259:DNA-Directed DNA Polymerase