Epitope selection by HLA-DR

描述(申请人提供)：获得性免疫反应始于对主要组织相容性复合体(MHC)第二类分子呈递的多肽抗原的识别。这些分子的两个突出特征是它们的多态和每个等位基因结合大量多肽的能力。这项研究的长期目标是了解人类第二类MHC分子人类白细胞抗原-DR在抗原提呈中的功能以及多态在其中的作用。有了更好的了解，人类白细胞抗原DR发挥重要作用的两个实际领域--疫苗接种和移植--可以取得进展。这个 短期目标是在基础水平上检查多肽结合，目的是了解这一过程，从而能够建立合理的病原体表位鉴定方法。我们的模型是，我们正在解剖一个复杂的系统，其中一个交互作用受到其他交互作用的影响。我们的初步数据表明，这种相互作用之间的协同性确实是结合机制的一个重要方面。在目标1中，我们更详细地研究了协作性现象。我们将确定我们在与溶剂接触的多肽残基中观察到的协作性是否延伸到其他残基。在目标2中，我们分析了多肽结合的其他方面，包括疏水成核位置的可能作用和侧翼残基赋予的额外稳定性。在目标3中，前两个目标中获得的信息将在一个假设的背景下进行分析，该假设认为内在稳定性、协作性和允许不同表观亲和力的多肽稳定结合的构象变化之间存在关系。这就是允许大量多肽结合的原因。多肽结合是在辅助分子--人类白细胞抗原-DM的存在下进行的，它促进了多肽的交换。在目标4中，我们将确定影响DM介导肽交换的结构特征，从而提供对于特定的HLA-DR等位基因什么是可接受的肽的洞察力。这也可能有助于理解人类白细胞抗原-DM的作用机制。我们的这种相互作用的模型是，人类白细胞抗原-DM将人类白细胞抗原-DR置于一种构象中，在这种构象中，总的多肽结合属性发生变化，多肽仅根据它们的亲和力进行相互作用。

DESCRIPTION (provided by applicant): The adaptive immune response starts with recognition of peptide antigens presented by class II molecules of the Major Histocompatibility Complex (MHC). Two outstanding features of these molecules are their polymorphism and the ability of each allele to bind a large panoply of peptides. The long-term goal of the research proposed here is to understand the function of the human class II MHC molecule HLA-DR in antigen presentation and the role of polymorphism therein. With a better understanding, progress can be made in two practical areas where HLA-DR plays a significant role, vaccination and transplantation. The short-term goal is to examine peptide binding at a basic level with the goal of understanding the process to the point that rational approaches to pathogen epitope identification can be established. Our model is that we are dissecting a complex system where one interaction is affected by other interactions. Our preliminary data indicates that this cooperativity between interactions is indeed an important aspect of the binding mechanism. In Aim 1 we investigate the phenomenon of cooperativity in more detail. We will determine whether the cooperativity we have observed in peptide residues that contact solvent extend to other residues. In Aim 2 we analyze further aspects of peptide binding including the possible role of hydrophobic nucleation sites and additional stability conferred through flanking residues. In Aim 3, the information gained in the two previous aims will be analyzed in the context of a hypothesis that there is a relation between intrinsic stability, cooperativity and a conformational change that allows stable binding of peptides of different apparent affinities. This is what allows the binding of a large number of peptides. Peptide binding takes place in the presence of an adjunct molecule, HLA-DM, which promotes the exchange of peptides. In Aim 4 we will determine structural characteristics that influence DM-mediated peptide exchange, thus providing insight as to what is an acceptable peptide for a particular HLA-DR allele. This may also lead to an understanding of the mechanism by which HLA-DM functions. Our model for this interaction is that HLA-DM puts the HLA-DR in a conformation in which the overall peptide-binding properties are changed and peptides interact based solely on their affinity.