HLA-B15 peptide ligands are preferentially anchored at their C termini.
Therapies to elicit protective CTL require the selection of pathogen- and tumor-derived peptide ligands for presentation by MHC class I molecules. Edman sequencing of class I peptide pools generates "motifs" that indicate that nonameric ligands bearing conserved position 2 (P2) and P9 anchors provide the optimal search parameters for selecting immunogenic epitopes. To determine how well a motif represents its individual constituents, we used a hollow-fiber peptide production scheme followed by the mapping of endogenously processed class I peptide ligands through reverse-phase HPLC and mass spectrometry. Systematically mapping and characterizing ligands from B*1508, B*1501, B*1503, and B*1510 demonstrate that the peptides bound by these B15 allotypes i) vary in length from 7 to 12 residues, and ii) are more conserved at their C termini than their N-proximal P2 anchors. Comparative peptide mapping of these B15 allotypes further pinpoints endogenously processed ligands that bind to the allotypes B*1508, B*1501, and B*1503, but not B*1510. Overlapping peptide ligands are successful in binding to B*1501, B*1503, and B*1508 because these B15 allotypes share identical C-terminal anchoring pockets whereas B*1510 is divergent in the C-terminal pocket. Therefore, endogenous peptide loading into the B15 allotypes requires that a conserved C terminus be anchored in the appropriate specificity pocket while N-proximal anchors are more flexible in their location and sequence. Queries for overlapping and allele-specific peptide ligands may thus be contingent on a conserved C-terminal anchor.
Prilliman
K R
KR
Department of Microbiology and Immunology, William K. Warren Medical Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
Jackson
K W
KW
Lindsey
M
M
Wang
J
J
Crawford
D
D
Hildebrand
W H
WH
D000483:Alleles; D000595:Amino Acid Sequence; D017951:Antigen Presentation; D002851:Chromatography, High Pressure Liquid; D017124:Conserved Sequence / Q000235:genetics / Q000276:immunology; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D015235:HLA-B Antigens / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D059910:HLA-B15 Antigen; D006801:Humans; D008024:Ligands; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D010449:Peptide Mapping
D015235:HLA-B Antigens; D059910:HLA-B15 Antigen; D008024:Ligands; D010446:Peptide Fragments