title: Supra-agonist peptides enhance the reactivation of memory CTL responses.
abstract: Single amino acid substitutions at TCR contacts may transform a natural peptide Ag in CTL ligands with partial agonist, antagonist, or null activity. We obtained peptide variants by changing nonanchor amino acid residues involved in MHC class I binding. These peptides were derived from a subdominant HLA-A2-presented, latent membrane protein 2-derived epitope expressed in EBV-infected cells and in EBV-associated tumors. We found that small structural changes produced ligands with vastly different activities. In particular, the variants that associated more stably to HLA-A2/molecules did not activate any CTL function, behaving as null ligands. Interestingly, T cell stimulations performed with the combination of null ligands and the natural epitope produced significantly higher specific CTL reactivation than reactivation of CTLs induced by the wild-type epitope alone. In addition, these particular variants activated memory CTL responses in the presence of concentrations of natural epitope that per se did not induce T cell responses. We show here that null ligands increased ZAP-70 tyrosine kinase activation induced by the natural epitope. Our results demonstrate for the first time that particular peptide variants, apparently behaving as null ligands, interact with the TCR, showing a supra-agonist activity. These variant peptides did not affect the effector T cell functions activated by the natural epitope. Supra-agonist peptides represent the counterpart of antagonists and may have important applications in the development of therapeutic peptides.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pharmaceutical Sciences, and Morphology and Embryology, University of Ferrara, Ferrara, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Micheletti
authors.forename: A
authors.initials: A
authors.lastname: Canella
authors.forename: S
authors.initials: S
authors.lastname: Vertuani
authors.forename: M
authors.initials: M
authors.lastname: Marastoni
authors.forename: L
authors.initials: L
authors.lastname: Tosi
authors.forename: S
authors.initials: S
authors.lastname: Volinia
authors.forename: S
authors.initials: S
authors.lastname: Traniello
authors.forename: R
authors.initials: R
authors.lastname: Gavioli
mesh_terms: D000276:Adjuvants, Immunologic / Q000819:agonists* / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D018984:Epitopes, T-Lymphocyte / Q000502:physiology; D015789:HLA-A2 Antigen / Q000378:metabolism; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D009842:Oligopeptides / Q000819:agonists* / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000276:immunology; D014763:Viral Matrix Proteins / Q000819:agonists / Q000276:immunology / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase
chemical_list: D000276:Adjuvants, Immunologic; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D009842:Oligopeptides; D014763:Viral Matrix Proteins; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human