Jurcevic S, Praud C, Coppin H L, Bertrand A, Ricard S, Thomsen M, Lakhdar-Ghazal F, De Preval C
INSERM Unité 395, Université Paul Sabatier, Toulouse, France.
Immunology. 1996 Mar;87(3):414-20. doi: 10.1046/j.1365-2567.1996.458547.x.
A study was made of the binding properties of 96 human immunodeficiency virus peptides to human leucocyte antigen (HLA)-DR1 and HLA-DR103 molecules, which differ by three amino acids at positions 67, 70 and 71 in the beta chains. The affinity of the peptides was characterized by their inhibitory concentrations in competitive binding assays which displace half of the labelled influenza haemagglutinin peptide HA306-318 (IC50). Among the high-affinity peptides (IC50 < or = 1 microM), seven bound to DR1, three to DR103 and five equally well to both alleles (promiscuous peptides). Thirty-two other peptides showed medium or low affinity for DR molecules. The role of polymorphic residues was analysed using six mutated DR molecules, intermediates between DR1 and DR103 and differing by one or two substitutions at positions 67, 70 or 71. We reached the same conclusions when using DR1-specific or DR103-specific peptides: modification of residue 70 had no effect on peptide affinity, but single substitution at positions 67 or 71 decreased the allele specificity of the peptides while double substitution at 67 and 71 completely reversed the peptide specificity. In functional assays, DR-binding peptides are able to outcompete specific T-cell proliferation. Furthermore, modification at position 67 or 70 significantly affects the T-cell response and mutation at position 71 abolishes completely the T-cell proliferation. Thus, the polymorphic positions 67 and 71 contributed to the peptide binding with direct effects on T-cell receptor (TCR) recognition while position 70 seems to be mostly engaged in TCR interactions. Furthermore, our results suggest that polymorphic residues may select allele-specific peptides and also influence the conformation of promiscuous peptides.
对96种人类免疫缺陷病毒肽与人类白细胞抗原（HLA）-DR1和HLA-DR103分子的结合特性进行了研究，这两种分子的β链在第67、70和71位氨基酸处有三个氨基酸的差异。通过竞争性结合试验中肽的抑制浓度来表征肽的亲和力，该试验中标记的流感血凝素肽HA306-318被取代一半时的抑制浓度（IC50）。在高亲和力肽（IC50≤1μM）中，七种与DR1结合，三种与DR103结合，五种与两个等位基因结合的亲和力相同（混杂肽）。另外32种肽对DR分子表现出中等或低亲和力。使用六个突变的DR分子分析了多态性残基的作用，这些分子是DR1和DR103之间的中间体，在第67、70或71位有一个或两个取代。当使用DR1特异性或DR103特异性肽时，我们得出了相同的结论：第70位残基的修饰对肽亲和力没有影响，但第67或71位的单取代降低了肽的等位基因特异性，而第67和71位的双取代完全逆转了肽的特异性。在功能试验中，与DR结合的肽能够竞争特异性T细胞增殖。此外，第67或70位的修饰显著影响T细胞反应，第71位的突变完全消除了T细胞增殖。因此，多态性位点67和71有助于肽的结合，对T细胞受体（TCR）识别有直接影响，而第70位似乎主要参与TCR相互作用。此外，我们的结果表明多态性残基可能选择等位基因特异性肽，也影响混杂肽的构象。
