title: Characterization of an epitope of the human cytomegalovirus protein IE1 recognized by a CD4+ T cell clone.
abstract: CD4+ T cells specific for human cytomegalovirus (HCMV) IE1 protein are potential effectors of the control of HCMV infection through cytokine production. Better knowledge of major histocompatibility complex (MHC)-peptide-T cell receptor (TcR) interactions in the CD4+ T cell response should result in a better design of immunizing peptides and is a prerequisite for the development of vaccines or anti-cytomegalovirus therapy. In this study, the recombinant protein comprising residues 86-491 encoded by exon 4 of IE1 (GST-e4) was cleaved by enzymatic digestion and analyzed by high pressure liquid chromatography-mass spectroscopy (HPLC-MS). We identified the 14-residue epitope 162-DKREMWMACIKELH-175 recognized by an HLA-DR8-restricted clone, BeA3. Synthetic elongated, truncated and di-Ala-substituted peptides of the 18-mer IE1 158-IVPEDKREMWMACIKELH-175 sequence were used to analyze the amino acid motifs involved in binding to HLA-DR8 and recognition by the BeA3 clone. Substitutions which abolished (MW --> AA), or decreased (RE --> AA and MA --> AA) T cell clone proliferation, cytokine production and cytotoxicity were identified. Loss of T cell function induced by the MW --> AA substitution was associated with poor HLA-DR8 binding. Decreased T cell function (RE --> AA and MA --> AA) was associated with good HLA-DR8 binding, which suggested that these motifs were involved in TcR binding. Other substitutions induced potentiation of the T cell clone response: the IV --> AA substitution induced stronger proliferation, but equivalent cytokine production, when compared with the reference peptide IE1 (158-175). CI --> AA substitution induced strong potentiation of HLA-DR8 binding, proliferation and interferon-gamma and interleukin-4 production, possibly due to the removal of negative effects of Cys, Ile, or both side chains. Cytotoxicity was not improved by any substitution. Our results show modulation of the CD4+ T cell response according to the peptide residues involved in the HLA-DR8-peptide-TcR interaction.
authors.affiliation: INSERM U395, Toulouse, France.
authors.forename: N
authors.initials: N
authors.lastname: Gautier
authors.forename: E
authors.initials: E
authors.lastname: Chavant
authors.forename: E
authors.initials: E
authors.lastname: Prieur
authors.forename: B
authors.initials: B
authors.lastname: Monsarrat
authors.forename: H
authors.initials: H
authors.lastname: Mazarguil
authors.forename: C
authors.initials: C
authors.lastname: Davrinche
authors.forename: J E
authors.initials: JE
authors.lastname: Gairin
authors.forename: J L
authors.initials: JL
authors.lastname: Davignon
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002999:Clone Cells / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis; D003587:Cytomegalovirus / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D010450:Endopeptidases; D000939:Epitopes / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D006684:HLA-DR Antigens / Q000737:chemistry; D059810:HLA-DR Serological Subtypes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D017874:Immediate-Early Proteins / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D009980:Influenza A virus / Q000276:immunology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D011485:Protein Binding / Q000276:immunology; D014764:Viral Proteins
chemical_list: D016207:Cytokines; D000939:Epitopes; D006684:HLA-DR Antigens; D059810:HLA-DR Serological Subtypes; C041559:HLA-DR8 antigen; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral; C088645:IE1 protein, cytomegalovirus; D017874:Immediate-Early Proteins; D010446:Peptide Fragments; D014764:Viral Proteins; D010450:Endopeptidases; D000409:Alanine