Conserved MHC Class I Peptide Binding Motif Between Humans and Rhesus Macaques

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Single amino acid substitution analogs of the known Mamu A*01 binding peptide gag 181-190 and libraries of naturally occurring sequences of viral or bacterial origin were used to rigorously define the peptide binding motif associated with Mamu A*01 molecules. The presence of S or T in position 2, P in position 3, and hydrophobic or aromatic residues at the C terminus is associated with optimal binding capacity. At each of these positions, additional residues are also tolerated but associated with significant decreases in binding capacity. The presence of at least two preferred and one tolerated residues at the three anchor positions is necessary for good Mamu A*01 binding; optimal ligand size is 8–9 residues. This detailed motif has been used to map potential epitopes from SIVmac239 regulatory proteins and to engineer peptides with increased binding capacity. A total of 13 wild type and 17 analog candidate epitopes were identified. Furthermore, our analysis reveals a significantly lower than expected frequency of epitopes in early regulatory proteins, suggesting a possible evolutionary- and/or immunoselection directed against variants of viral products that contain CTL epitopes.

Section: S Imian Immunodeficiency Virus-infected Rhesus Macaquesmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Definition of the Mamu A*01 Peptide Binding Specificity: Application to the Identification of Wild-Type and Optimized Ligands from Simian Immunodeficiency Virus Regulatory Proteins

Sidney¹,

Dzuris²,

Newman³

et al. 2000

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“…Peptide binding to equine MHC class I molecule 7-6 expressed on transduced 721.221 cells was measured as previously described with minor modifications (41,46,47). 721.221 cells (2 ϫ 10 6 /ml) transduced with equine classical MHC class I gene 7-6 or with a retroviral vector that did not express an equine gene were preincubated overnight in RPMI with 15% FBS and 3 g/ml of human ␤ 2 -microglobulin (The Scripps Clinic, La Jolla, CA) at 27°C.…”

Section: Live Cell Peptide Binding Assaymentioning

confidence: 99%

Presentation and Binding Affinity of Equine Infectious Anemia Virus CTL Envelope and Matrix Protein Epitopes by an Expressed Equine Classical MHC Class I Molecule

McGuire

Leib

Mealey

et al. 2003

Control of a naturally occurring lentivirus, equine infectious anemia virus (EIAV), occurs in most infected horses and involves MHC class I-restricted, virus-specific CTL. Two minimal 12-aa epitopes, Env-RW12 and Gag-GW12, were evaluated for presentation by target cells from horses with an equine lymphocyte Ag-A1 (ELA-A1) haplotype. Fifteen of 15 presented Env-RW12 to CTL, whereas 11 of 15 presented Gag-GW12. To determine whether these epitopes were presented by different molecules, MHC class I genes were identified in cDNA clones from Arabian horse A2152, which presented both epitopes. This horse was selected because it is heterozygous for the SCID trait and is used to breed heterozygous females. Offspring with SCID are used as recipients for CTL adoptive transfer, and normal offspring are used for CTL induction. Four classical and three putative nonclassical full-length MHC class I genes were found. Human 721.221 cells transduced with retroviral vectors expressing each gene had equine MHC class I on their surface. Following peptide pulsing, only cells expressing classical MHC class I molecule 7-6 presented Env-RW12 and Gag-GW12 to CTL. Unlabeled peptide inhibition of 125I-labeled Env-RW12 binding to 7-6-transduced cells demonstrated that Env-RW12 affinity was 15-fold higher than Gag-GW12 affinity. Inhibition with truncated Env-RW12 demonstrated that amino acid positions 1 and 12 were necessary for binding, and single substitutions identified positions 2 and 3 as possible primary anchor residues. Since MHC class I 7-6 presented both epitopes, outbred horses with this allele can be immunized with these epitopes to optimize CTL responses and evaluate their effectiveness against lentiviral challenge.

“…Peptides used were synthesized at Epimmune (San Diego, CA) as described elsewhere (44) or were purchased as crude material from Mimotopes (Minneapolis, MN). Peptides synthesized at Epimmune were typically purified to Ͼ95% homogeneity by reverse-phase HPLC.…”

Section: Peptide Synthesis and Radiolabelingmentioning

confidence: 99%

The HLA Molecules DQA10501/B10201 and DQA10301/B10302 Share an Extensive Overlap in Peptide Binding Specificity

Sidney

Guercio

Southwood

et al. 2002

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Assays to measure the binding capacity of peptides for HLA-DQA1*0501/B*0201 (DQ2.3) and DQA1*0301/B*0302 (DQ3.2) were developed using solubilized MHC molecules purified from EBV-transformed cell lines. These quantitative assays, based on the principle of the inhibition of binding of a high-affinity radiolabeled ligand, were validated by examining the binding capacity of known DQ-restricted epitopes or ligands. The availability of these assays allowed an investigation of patterns of cross-reactivity between different DQ molecules and with various common DR molecules. DQ2.3 and DQ3.2 were found to have significantly overlapping peptide binding repertoires. Specifically, of 13 peptides that bound either DQ2.3 or DQ3.2, nine (69.2%) bound both. The molecular basis of this high degree of cross-reactivity was further investigated with panels of single substitution analogs of the thyroid peroxidase 632–645Y epitope. It was found that DQ2.3 and DQ3.2 bind the same ligands by using similar anchor residues but different registers. These data suggest that in analogy to what was previously described for HLA-DR molecules, HLA-DQ supertypes characterized by largely overlapping binding repertoires can be defined. In light of the known linkage of both HLA-DQ2.3 and -DQ3.2 with insulin-dependent diabetes mellitus and celiac disease, these results might have important implications for understanding HLA class II autoimmune disease associations.