HLA-B27分子及其与强直性脊柱炎关联的研究进展简

HLA-B27是MHCI类分子,因而具有MHCI类分子的相关生物学特性。在正常免疫状态下,HLA-B27分子执行对内源性抗原如肿瘤及病毒的免疫监视及杀伤功能;但在机体免疫状态出现异常的情况下,它又可能成为引发自身免疫性疾病的主要相关因素,其中最为著名的是其与强制性脊柱炎（As）的关联研究。我们首先概述了HLA—B27分子正常免疫学功能的研究进展,然后对其在AS相关性研究中的进展进行了总结和分析。通过对上述两方面的综述与分析,全方位展示HLA-B27在执行免疫学功能和引发免疫病理性改变方面的作用,为全面认识和深入研究HLA-B27分子的生理与病理学作用提供坚实的基础。     

HLA-B*2736等位基因的序列分析

使用FLOW-SSO、PCR-SSP以及测序等分型技术, 发现一个与HLA-B*270401基因相关的未知基因。设计基因特异性引物单独扩增B*27基因的外显子2-5, 包括内含子2-4, 并进行双向测序, 分析与B*270401基因序列的差异。该基因的扩增产物为1 815 bp。与B*270401相比在外显子3和4共有10个碱基的改变, 从而使相应氨基酸发生错义或同义突变。碱基634 A→C (密码子130丝氨酸→精氨酸); 670 A→T (密码子142苏氨酸→丝氨酸); 683 G→T (密码子146色氨酸→亮氨酸); 698 A→T (密码子151谷氨酸→缬氨酸); 774 G→C (密码子176谷氨酸→天冬氨酸); 776 C→A (密码子177苏氨酸→赖氨酸); 781 C→G (密码子179谷氨酰胺→谷氨酸); 789 G→T (密码子181丙氨酸同义突变); 1 438 C→T (密码子206甘氨酸同义突变); 1 449 G→C (密码子210甘氨酸→丙氨酸)。在IMGT/HLA数据库中B*27组只有3个基因（B*270502 / 2706 / 2732）提交了内含子序列。该未知基因的内含子2序列与B*2706相同, 显示了与B*27组基因的同源性, 但其同源性在内含子3、4均未得到支持, 与B*27组基因相比, 内含子3的第106个碱基C→G, 碱基168缺失, 碱基179 G→A, 碱基536 G→A; 内含子4中碱基82 T→C。但其内含子3、4序列却与B*070201完全相同。该基因序列已提交GenBank, 编号为被DQ915176, 被WHO确认为HLA-B*2736等位基因。     

Identification of an Unconventional Subpeptidome Bound to the Behçet's Disease-associated HLA-B*51:01 that is Regulated by Endoplasmic Reticulum Aminopeptidase 1 (ERAP1)

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Highlights

• •A novel HLA-ABC-triple knockout cell model to study the HLA-B*51 peptidome.
• •Enrichment of the unconventional non-Pro/Ala2 HLA-B*51 peptides following ERAP1 silencing.
• •Knockdown of ERAP1 increases the length of non-Pro/Ala2 and Ala2 peptides, not that of Pro2.
• •ERAP1 regulation of HLA-B*51 cell surface expression is cell type dependent.

     

The Pharmacogenomic HLA Biomarker Associated to Adverse Abacavir Reactions: Comparative Analysis of Different Genotyping Methods

Many pharmacogenomic biomarkers (PGBM) were identified and translated into clinical practice, affecting the usage of drugs via label updates. In this context, abacavir is one of the most brilliant examples of pharmacogenetic studies translated into clinical practice. Pharmacogenetic studies have revealed that abacavir HSRs are highly associated with the major histocompatibility complex class I. Large studies established the effectiveness of prospective HLA-B*57:01 screening to prevent HSRs to abacavir. Accordingly to these results the abacavir label has been modified: the European Medicines Agency (EMA) and the FDA recommend/suggested that the administration of abacavir must be preceded by a specific genotyping test. The HLA locus is extremely polymorphic, exhibiting many closely related alleles, making it difficult to discriminate HLA-B*57:01 from other related alleles, and a number of different molecular techniques have been developed recently to detect the presence of HLA-B*57:01. In this review, we provide a summary of the available techniques used by laboratories to genotype HLA-B*57:01, outlining the scientific and pharmacoeconomics pros and cons.     

Mutational analysis reveals a complex interplay of peptide binding and multiple biological features of HLA-B27

Molecular polymorphism influences the strong association of HLA-B27 with ankylosing spondylitis through an unknown mechanism. Natural subtypes and site-directed mutants were used to analyze the effect of altering the peptide-binding site of this molecule on its stability, interaction with tapasin, folding, and export. The disease-associated subtypes B*2705, B*2702, and B*2704 showed higher thermostability at 50 °C than all other subtypes and mutants, except some mimicking B*2702 polymorphism. The lowest values were found among pocket B mutants, most of which interacted strongly with tapasin, but otherwise there was no correlation between thermostability and tapasin interaction. Mutants resulting in increased hydrophobicity frequently acquired their maximal thermostability faster than those with increased polarity, suggesting that this process is largely driven by the thermodynamics of peptide binding. Folding, export, and tendency to misfold were influenced by polymorphism all along the peptide-binding site and were not specifically dependent on any particular region or structural feature. Frequent uncoupling of thermostability, folding/misfolding, and export can be explained by the distinct effect of mutations on the acquisition of a folded conformation, the optimization rate of B27-peptide complexes, and their quality control in the endoplasmic reticulum, all of which largely depend on the ways in which mutations alter peptide binding, without excluding additional effects on interactions with tapasin or other proteins involved in folding and export. The similarity of the generally disease-associated B*2707 to nondisease-associated subtypes in all the features analyzed suggests that molecular properties other than antigen presentation may not currently explain the relationship between HLA-B27 polymorphism and ankylosing spondylitis.     

汉滩病毒感染血管内皮细胞后上调HLAI类分子的表达

目的:观察汉滩病毒感染血管内皮细胞(EVC304)前后,HLA-I类分子中HLA-A、HLA-B、HLA-Cw3、HLA-Cw5表达上的差异。方法:以汉滩病毒76-118株感染EVC304细胞作为实验组,以无任何刺激的EVC304细胞作为阴性对照组。6h后用RT-PCR的方法对HLA-A、HLA-B、HLA-Cw3、HLA-Cw5的mRNA进行反转录和基因片段的扩增,在mRNA水平上检测其表达差异。结果:在HTNV感染以后,EVC304细胞中HLA-A、HLA-B、HLA-Cw3、HLA-Cw5mRNA表达均呈升高现象,其中HLA-A、HLA-B和HLA-Cw5的mRNA表达与未感染细胞相比明显升高。结论:HTNV感染血管内皮细胞后,可以诱导HLA-A、HLA-B、HLA-Cw3、HLA-Cw5的表达升高,从而诱发机体特异性免疫应答,导致免疫损伤的发生。这或许是肾综合症出血热的发病机制之一。     

中国新疆维族人群HLA-B等位基因与HIV-1感染易感性或抗性

通过对中国维吾尔族人群HLA-B等位基因的分布频率的研究,探讨HLA-B等位基因与HIV感染的易感/或抵抗性的相关性.本研究用PCR-SSP的方法对新疆维吾尔族110例无相关的健康对照者(HIV阴性)和128例HIV阳性感染者进行HLA-B等位基因分型.用POPGEN软件对健康对照者人群进行Hardy-Weinberg平衡检测,用卡方检验分析HLA-B等位基因在健康对照者和HIV阳性感染者频率分布的差异.在HIV-1阳性感染者中,B*4901等位基因频率显著性增加(B*4901P=0.02,OR=3.06,95%CI=1.16～8.10).而在健康对照者中,B*40等位基因频率增加具有统计意义(B*40P=0.02,OR=0.39,95%CI=0.07～0.92).由此可见,B*4901等位基因可能与HIV-1感染的易感性有关,而B*40等位基因可能与与HIV-1感染的抵抗性有关.     

A post-translational modification of nuclear proteins, N(G),N(G)-dimethyl-Arg, found in a natural HLA class I peptide ligand

Presentation of peptides derived from endogenous proteins by class I major histocompatibility complex molecules is essential both for immunological self-tolerance and induction of cytotoxic T-cell responses against intracellular parasites. Despite frequent and diverse post-translational modification of eukaryotic cell proteins, very few class I-bound peptides with post-translationally modified residues are known. Here we describe a natural dodecamer ligand of HLA-B39 (B*3910) derived from an RNA-binding nucleoprotein that carried N(G),N(G)-dimethyl-Arg. Although common among RNA-binding proteins, this modification was not previously known among natural class I ligands. The sequence of this peptide was determined by Edman degradation and electrospray ion trap mass spectrometry. The fragmentation pattern of the dimethyl-Arg side chain observed with this latter technique allowed us to unambiguously assign the isomeric form of the modified residue. The post-translationally modified ligand was a prominent component (1-2%) of the B*3910-bound peptide repertoire. The dimethyl-Arg residue was located in a central position of the peptide, amenable to interacting with T-cell receptors, and most other residues in the middle region of the peptide were Gly. These structural features strongly suggest that the post-translationally modified residue may have a major influence on the antigenic properties of this natural ligand.