A single amino acid variation within an immunodominant AKR/Gross MuLV cytotoxic T-lymphocyte epitope leads to a loss in immunogenicity.
C57BL/6 mice characteristically generate vigorous H-2K(b)-restricted cytotoxic T lymphocytes (CTL) directed against an immunodominant CTL epitope (KSPWFTTL) expressed by endogenous AKR/Gross murine leukemia viruses (MuLV). These AKR/Gross MuLV-specific CTL do not efficiently recognize tumor cells induced by Friend/Moloney/Rauscher (FMR) MuLV, which express the highly homologous peptide RSPWFTTL. In this report, we not only confirm the inefficient recognition of FMR tumors by AKR/Gross MuLV-specific CTL, but also demonstrate that RSPWFTTL is poorly immunogenic in C57BL/6 mice. To gain insight into the mechanism(s) contributing to the inefficient recognition of FMR MuLV-induced tumors, we examined the RSPWFTTL dissociation rate from H-2K(b) as well as the ability for RSPWFTTL to diminish CTL effector functions by T-cell antagonism. In contrast to immunogenic peptides, which form stable MHC class I-peptide complexes having slow dissociation rates, poorly immunogenic peptides characteristically have faster dissociation rates. On the basis of a cell-surface MHC class I peptide stabilization assay, the dissociation rate of RSP-WFTTL from H-2K(b) is characterized by a half-life that is nearly identical to the half-life of KSPWFTTL. In addition, we could find no evidence for antagonistic inhibition of AKR/Gross MuLV-specific CTL over a wide concentration range of RSPWFTTL. Analysis of the role of the transporter associated with antigen processing (TAP), by use of recombinant vaccinia and Sindbis viruses expressing a hydrophobic amino-terminal endoplasmic reticulum (ER) targeting sequence coupled to RSPWFTTL, indicated that RSPWFTTL cell-surface presentation can be dramatically enhanced when directly targeted into the ER.
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Department of Microbiology, Dartmouth Medical School and The Norris Cotton Cancer Center, Lebanon, New Hampshire 03756, USA.
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D000406:AKR murine leukemia virus / Q000235:genetics / Q000276:immunology*; D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000276:immunology; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000276:immunology*; D005260:Female; D014644:Genetic Variation; D006183:H-2 Antigens / Q000276:immunology; D016056:Immunodominant Epitopes / Q000235:genetics / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D018984:Epitopes, T-Lymphocyte; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D016056:Immunodominant Epitopes; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse