title: Preventing the spontaneous modification of an HLA-A2-restricted peptide at an N-terminal glutamine or an internal cysteine residue enhances peptide antigenicity.
abstract: The p68-derived peptide, QIVDVCHDV, was identified by a reverse immunology approach as capable of reconstituting an epitope recognized by the melanoma-reactive cytotoxic T lymphocyte (CTL) line VMM5. The peptide has not been demonstrated definitively on the cell surface by mass spectrometry; thus, it is not yet considered appropriate for use in human melanoma vaccines. Interestingly, however, the antigenicity of this peptide was affected by spontaneous modifications at two distinct residues. Spontaneous modification of the QIVDVCHDV peptide can occur at the cysteine residue at position 6 or at the N-terminal glutamine residue, and both modifications dramatically affect CTL recognition. Avoidance of an acidic environment prevents the conversion of the N-terminal glutamine residue to pyroglutamic acid, a conversion that inhibits binding of the peptide to HLA-A2 and diminishes recognition by CTLs. Substitution of asparagine for the N-terminal glutamine and substitution of serine for the cysteine were shown to enhance the binding of the peptide to HLA-A2 and to enhance the recognition of the peptide by CTLs. These findings suggest general strategies for enhancing the antigenicity of other peptides containing similar amino acids in their sequence.
authors.affiliation: Department of Surgery, University of Virginia, Charlottesville 22908, USA.
authors.forename: Lee W
authors.initials: LW
authors.lastname: Thompson
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Hogan
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Caldwell
authors.forename: Richard A
authors.initials: RA
authors.lastname: Pierce
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Hendrickson
authors.forename: Donna H
authors.initials: DH
authors.lastname: Deacon
authors.forename: Robert E
authors.initials: RE
authors.lastname: Settlage
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Brinckerhoff
authors.forename: Victor H
authors.initials: VH
authors.lastname: Engelhard
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Shabanowitz
authors.forename: Donald F
authors.initials: DF
authors.lastname: Hunt
authors.forename: Craig L
authors.initials: CL
authors.lastname: Slingluff
mesh_terms: D000951:Antigens, Neoplasm / Q000737:chemistry; D019496:Cancer Vaccines; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry*; D053487:DEAD-box RNA Helicases; D019992:Databases as Topic; D000939:Epitopes / Q000737:chemistry; D005973:Glutamine / Q000737:chemistry*; D015789:HLA-A2 Antigen / Q000737:chemistry*; D015395:Histocompatibility Antigens Class I / Q000737:chemistry; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D013058:Mass Spectrometry; D008545:Melanoma / Q000276:immunology / Q000378:metabolism; D008956:Models, Chemical; D010455:Peptides / Q000737:chemistry*; D011494:Protein Kinases / Q000737:chemistry; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry; D013602:T-Lymphocytes, Cytotoxic / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D019496:Cancer Vaccines; D000939:Epitopes; D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D010455:Peptides; D005973:Glutamine; D011494:Protein Kinases; C506749:Ddx5 protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases; D003545:Cysteine