Peptides mimicking antigenic epitopes targeted by antibodies can be powerful tools to be used as antigen surrogates for the specific diagnosis and treatment of autoimmune diseases. Obtaining structural insights about the nature of peptide–antibody interaction in complex mixtures such as sera is a critical goal. In multiple sclerosis (MS), we previously demonstrated that the N‐linked β‐d‐glucopyranosyl moieties (N‐Glc) containing epitopes in nontypeable Haemophilus influenzae adhesin C‐terminal portion HMW1(1205–1526) were essential for high‐affinity antibody binding in a subpopulation of MS patients. With the aim of developing peptide probes and assessing their binding properties to antibodies from sera of representative patients, we performed the systematic analysis of synthetic peptides based on HMW1(1347–1354) fragment bearing one or two N‐Glc respectively on Asn‐1349 and/or Asn‐1352. The N‐glucosylated nonapeptides efficiently bind to IgG antibodies, displaying IC₅₀ in the range 10⁻⁸–10⁻¹⁰ M by competitive indirect enzyme‐linked immunosorbent assay (ELISA) in three representative MS patient sera. We selected the di‐N‐glucosylated adhesin peptide Ac‐KAN (Glc)VTLN (Glc)TT‐NH₂ as the shortest sequence able to inhibit high‐avidity interaction with N‐Glc targeting IgM antibodies. Nuclear magnetic resonance (NMR)‐ and circular dichroism (CD)‐based characterization showed that the binding properties of these antigens could not be ascribed to structural differences induced by the presence of up to two N‐glucosyl moieties. Therefore, the antibody binding is not easily correlated to the position of the sugar or to a determined conformation in water.

中文翻译：

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高糖基化粘附素衍生肽作为多发性硬化症的抗原探针：结构优化和免疫学评估

模仿抗体靶向的抗原表位的肽可以用作强有力的工具，用作抗原替代物，用于自身免疫性疾病的特异性诊断和治疗。获得有关复杂混合物（例如血清）中肽-抗体相互作用性质的结构见解是一个关键目标。在多发性硬化症（MS），我们以前表明，在Ñ -连接的β- d吡喃葡萄糖基部分（Ñ -Glc）在不可分型含有表位的流感嗜血杆菌粘附素C末端部分HMW1（1205-1526）对于MS患者亚群中的高亲和力抗体结合至关重要。为了开发肽探针并评估其与代表性患者血清中抗体的结合特性，我们对基于分别带有一个或两个N - Glc的HMW1（1347-1354）片段的Asn-1349和Asn-1349进行了合成肽的系统分析/或Asn-1352。所述Ñ -glucosylated有效地结合到IgG抗体的九肽，显示IC ₅₀范围为10 ^-8 -10 ^-10在三种代表性MS患者血清M分别间接竞争酶联免疫吸附测定（ELISA）。我们选择了二ñ葡糖基化粘附素肽Ac-KAN（Glc）VTLN（Glc）TT-NH ₂是能够抑制与靶向IgM N - Glc的高亲和力相互作用的最短序列。基于核磁共振（NMR）和圆二色性（CD）的表征表明，这些抗原的结合特性不能归因于最多存在两个N-葡萄糖基部分而引起的结构差异。因此，抗体结合不容易与糖的位置或水中确定的构象相关。