梅毒螺旋体4种主要膜蛋白分子的研究现状

梅毒螺旋体是梅毒的病原体。因其体外培养至今尚未成功,该螺旋体获取困难,从而制约了其基础研究。但随着基因工程技术的发展,梅毒螺旋体全基因序列已经成功揭示,其主要结构蛋白研究也取得了重大进展,这些都为进一步深入开展研究提供了基础和前提。本文从梅毒螺旋体几种主要外膜蛋白的结构在梅毒致病机制中的作用和功能,以及有关实际应用等几方面进行综述。     

梅毒螺旋体外膜蛋白Tp92及其同源蛋白的研究进展

梅毒是由梅毒螺旋体(Tp)引起的一种严重危害人类健康的慢性感染性疾病,由于Tp目前尚不能体外人工培养,从而限制了对Tp致病机制的深入研究。Tp对宿主靶细胞的早期黏附定植是其后续病程发展的关键,而最早与宿主细胞直接接触的Tp外膜及外膜蛋白就成了关注的焦点。随着Tp全基因组序列的解析和分子生物学技术的发展,Tp外膜蛋白的筛选、鉴定及功能研究取得了一定进展。Tp92是首个在感染了梅毒的兔调理素抗毒血清中通过差示免疫筛选方法筛选出来的Tp外膜蛋白,序列高度保守,具有较强的抗原性,与其他螺旋体属及许多革兰阴性菌的外膜蛋白均具有较高的同源性,其在Tp的致病过程及机体的免疫应答中可能发挥着重要作用。就目前Tp外膜蛋白Tp92及其同源蛋白的研究进展进行了综述。     

早期先天梅毒几种实验室诊断方法的评价

目的评价梅毒螺旋体蛋白印迹试验(TPPA-IgM-WB)和梅毒螺旋体19(s)-IgM酶联免疫吸附法[TP-19(s)-IgM-ELISA]在先天梅毒早期诊断中的作用。方法对45例梅毒孕妇所产46例(1例双胞胎)新生儿运用血清IgM-WB试验、梅毒螺旋体19(s)-IgM酶联免疫吸附法[TP-19(s)-IgM-ELISA]和常规血清学方法(TPPA、RPR、FTA-ABS-IgM)检测,评价上述试验诊断方法在先天梅毒早期诊断中的作用。结果45例梅毒孕妇所生的新生儿中,按常规综合诊断方法21例确诊为先天梅毒,新生儿血清IgM蛋白印迹试验23例阳性,梅毒螺旋体19(s)-IgM酶联免疫吸附法24例阳性(21例常规方法诊断为先天梅毒)。30例作为对照的非梅毒孕妇及新生儿各项检查均为阴性。结论血清IgM蛋白印迹试验和梅毒螺旋体19(s)-IgM酶联免疫吸附法[TP-19(s)-IgM-ELISA]诊断先天梅毒具有较高的特异性和敏感性,结果显示可能高于现行的常规综合诊断方法的诊断价值。     

梅毒螺旋体膜蛋白研究进展

梅毒螺旋体苍白亚种（ Tp）引起的梅毒是一种严重危害人类健康的慢性性传播性疾病,其发病具有多阶段、进行性的特点。由于Tp尚不能体外培养,抗原获取困难,其致病机制研究尚不清楚。随着Tp全基因序列的解析,重组Tp膜蛋白的成功表达及蛋白功能结构日益明确,为Tp发病机制的研究及疫苗的研制奠定了良好的基础。对于Tp主要外膜蛋白的结构、功能研究进展进行了综述。     

梅毒螺旋体感染实验室诊断方法研究进展

梅毒是一种性传播疾病,病程长、危害大、临床表现复杂,容易造成漏诊和误诊.梅毒的早期诊断对控制梅毒传播具有重要意义.本文对当前梅毒螺旋体的病原学、血清学及分子生物学等检测方法及研究进展作一综述.     

免疫-PCR法检测梅毒螺旋体特异性抗体

以梅毒螺旋体重组蛋白为抗原,应用免疫-PCR方法检测梅毒螺旋体抗体,并同常规ELISA法进行比较,探讨免疫-PCR方法检测梅毒螺旋体特异性抗体的可行性。结果免疫-PCR法敏感性是常规ELISA法的104倍,阳性检出率高于ELISA法;对照血清标本梅毒螺旋体抗体检测为阴性。表明免疫-PCR方法具有较高敏感性和特异性,有一定的临床推广价值,对梅毒患者的早期诊断及时治疗等具有重要意义。     

莱姆病螺旋体外膜蛋白分子生物学及免疫学研究进展

莱姆病（Ｌｙｍｅ ｄｉｓｅａｓｅ）螺旋体是引起人蓄姆病的病原体,本文从莱姆螺旋体外膜蛋白的组成,生化结构特征、编码基因及基遗传学特征,致病性和免疫性以及外膜蛋白克隆与表达研究等方面归纳总结了近年来的研究成果,并简要介绍了这些研究成果在莱姆病原体分类鉴定,莱姆病诊断以及莱姆病疫苗研制中的应用。     

苍白螺旋体基因亚型研究及其意义

苍白螺旋体(Treponema pallidum,Tp)是引起梅毒的病原体,几乎可侵犯全身各个组织和器官,导致组织器官损伤,甚至引起感染者死亡.梅毒在许多发展中国家高度流行,在发达国家社会经济地位较低人群中仍为一重要的公共卫生问题.有关研究肯定梅毒是增加人类免疫缺陷病毒(humanimmunodeficiency virus,HIV)传播的危险因素,因而对Tp的研究愈加受到重视.     

梅毒螺旋体蛋氨酸亚枫还原酶基因克隆及生物信息学分析

[目的]克隆梅毒螺旋体(Treponema pallidum)蛋氨酸亚枫还原酶(methionine sulfoxide reductase,Msr)基因并对其进行生物分信息学分析。[方法]根据梅毒螺旋体Msr基因序列,设计特异性引物,PCR法扩增目的基因,将其连接到p MD19-T载体,进行DNA测序及生物信息学分析。[结果]从梅毒螺旋体中扩增得到的大小为873 bp的Msr基因,编码291个氨基酸。Msr蛋白含有Msr A和Msr B的保守区,为亲水性蛋白,无信号肽,定位在细菌细胞质。三维结构与牛Msr蛋白(PDB:1fvg.1)类似。Msr蛋白含有几个B表位。[结论]克隆获得了Tp Msr基因,并分析了其生物学特性。     

梅毒螺旋体膜抗原基因在毕赤酵母中的表达和蛋白纯化

以梅毒螺旋体(Treponema pallidumsubsp.pallidum)Nichols菌株基因组DNA为模板,通过PCR扩增梅毒螺旋体47kDa、17kDa和15kDa 3个膜抗原基因,克隆进毕赤酵母表达载体pPICZ B,构建重组表达载体pTP47、pTP17、pTP15,转化酵母菌株GS115,甲醇诱导表达。表达菌体裂解后通过镍离子亲和层析获得3个抗原与6xHis tag的融合蛋白,重组蛋白的获得量分别为His-TP15:4.8mg/L;His-TP 17:6.6mg/L;His-TP47:25mg/L,经SDS-PAGE鉴定纯度都在96%以上,ELISA鉴定均具有很好的抗原性。从而首次在毕赤酵母中表达出梅毒螺旋体膜抗原,为梅毒血清学检测方法开辟了新的抗原制备途径。     

Treponema pallidum and the quest for outer membrane proteins

Treponema pallidum, the syphilis spirochaete, has a remarkable ability to evade the humoral and cellular responses it elicits in infected hosts. Although formerly attributed to the presence of an outer coat comprised of serum proteins and/or mucopolysaccharides, current evidence indicates that the immuno-evasiveness of this bacterium is largely the result of its unusual molecular architecture. Based upon a combination of molecular, biochemical, and ultrastructural data, it is now believed that the T. pallidum outer membrane (OM) contains a paucity of poorly immunogenic transmembrane proteins (‘rare outer membrane proteins’) and that its highly immunogentc proteins are lipoproteins anchored predominantly to the periplasmic leaflet of the cytoplasmic membrane. The presence in the T. pallidum OM of a limited number of transmembrane proteins has profound implications for understanding syphilis pathogenesis as well as treponemal physiology. Two major strategies for molecular characterization of rare outer membrane proteins have evolved. The first involves the identification of candidate OM proteins as fusions with Escherichia coli alkaline phosphatase. The second involves the characterization of candidate OM proteins identified in outer membranes isolated from virulent T. pallidum. Criteria to define candidate OM proteins and for definitive identification of rare OM proteins are proposed as a guide for future studies.     

Treponema pallidum in gel microdroplets: a novel strategy for investigation of treponemal molecular architecture

Controversy exists regarding the constituents and antigenic properties of the Treponema pallidum outer membrane; a major point of contention concerns the cellular location(s) of the spirochaete's lipoprotein immunogens. To address these issues and circumvent problems associated with prior efforts to localize treponemal surface antigens, we developed a novel strategy for investigating T. pallidum molecular architecture. Virulent treponemes were encapsulated in porous agarose beads (gel microdroplets) and then probed in the presence or absence of Triton X-100. Intact., encapsulated treponemes were not labelled by monospecific antisera directed against four major T. pallidum lipoproteins or a candidate T. pailidum outer membrane protein (TpN50) with C-terminal sequence homology to Escherichia coli OmpA or by human or rabbit syphilitic serum. Each of these immunologic reagents, however, labelled encapsulated treponemes co-incubated with detergent. In contrast, antibodies generated against isolated T, pal-lidum outer membranes labelled intact organisms and the pattern of fluorescence was consistent with the distribution of rare outer membrane proteins visualized by freeze-fracture electron microscopy. In addition to providing strong evidence that the protein portions of treponemal lipoproteins are located within the periplasmic space, these studies have extended our understanding of the topographical relationships among T. pallidum cell envelope constituents. They also demonstrate the feasibility of generating antibodies against rare outer membrane proteins and detecting them on the surfaces of virulent treponemes.     

Bipartite Topology of Treponema pallidum Repeat Proteins C/D and I: OUTER MEMBRANE INSERTION,TRIMERIZATION, AND PORIN FUNCTION REQUIRE A C-TERMINAL β-BARREL DOMAIN*

We previously identified Treponema pallidum repeat proteins TprC/D, TprF, and TprI as candidate outer membrane proteins (OMPs) and subsequently demonstrated that TprC is not only a rare OMP but also forms trimers and has porin activity. We also reported that TprC contains N- and C-terminal domains (TprC^N and TprC^C) orthologous to regions in the major outer sheath protein (MOSP^N and MOSP^C) of Treponema denticola and that TprC^C is solely responsible for β-barrel formation, trimerization, and porin function by the full-length protein. Herein, we show that TprI also possesses bipartite architecture, trimeric structure, and porin function and that the MOSP^C-like domains of native TprC and TprI are surface-exposed in T. pallidum, whereas their MOSP^N-like domains are tethered within the periplasm. TprF, which does not contain a MOSP^C-like domain, lacks amphiphilicity and porin activity, adopts an extended inflexible structure, and, in T. pallidum, is tightly bound to the protoplasmic cylinder. By thermal denaturation, the MOSP^N and MOSP^C-like domains of TprC and TprI are highly thermostable, endowing the full-length proteins with impressive conformational stability. When expressed in Escherichia coli with PelB signal sequences, TprC and TprI localize to the outer membrane, adopting bipartite topologies, whereas TprF is periplasmic. We propose that the MOSP^N-like domains enhance the structural integrity of the cell envelope by anchoring the β-barrels within the periplasm. In addition to being bona fide T. pallidum rare outer membrane proteins, TprC/D and TprI represent a new class of dual function, bipartite bacterial OMP.     

Identification of lactoferrin-binding proteins from Treponema pallidum subspecies pallidum and Treponema denticola

Lactoferrin-binding or -associated proteins were identified in Treponema pallidum subspecies pallidum and Treponema denticola by affinity column chromatography using human lactoferrin and detergent-solubilized, radiolabelled spirochaetes. Two discrete polypeptides of T. pallidum with masses of 45 and 40kDa and a broad band from 29-34 kDa exhibited association with human apo- and partially ferrated lactoferrin. T. denticola produced two proteins that associated with a lactoferrin affinity matrix (50 and 35 kDa). T. pallidum and T. denticola did not associate with soluble, human transferrin in parallel experiments. Soluble human lactoferrin competed with all lactoferrin-associated proteins from T. pallidum and T. denticola in competitive-binding assays. However, the T. denticola proteins dissociated from a lacto-ferrin-affinity matrix in the presence of differing concentrations of unlabelled, soluble lactoferrin competitor. Treatment with phospholipase D altered migration of the diffuse 29-34 kDa band of T. pallidum suggesting that the polypeptide was lipid-modified. Each of the lactoferrin-binding proteins from T. pallidum and T. denticola reacted with pooled rabbit syphilitic antisera. The lactoferrin-binding proteins of T. pallidum reacted with human sera from patients at all stages of syphilis. In addition, a monoclonal antibody generated against the 45 kDa polypeptide of T. pallidum crossreacted with the 29–34 kDa protein.     

Crystal structure of lipoprotein GNA1946 from Neisseria meningitidis

GNA1946, a conserved outer membrane lipoprotein from Neisseria meningitidis, has been identified as a candidate antigen for an urgently needed broad-spectrum meningococcal vaccine. It has been predicted to be a periplasmic receptor in the d-methionine uptake ABC transporter system. The crystal structure of GNA1946 was solved by the single-wavelength anomalous dispersion (SAD) method to a resolution of 2.25 Å, and it reveals a Venus flytrap-like structure. GNA1946 consists of two globular lobes connected by a hinge region. Surprisingly, the structure showed an l-methionine bound within the cleft between the lobes. A comparison of GNA1946 with two other outer membrane lipoproteins, the l-methionine-binding Tp32 from Treponema pallidum and the dipeptide GlyMet-binding protein Pg110 from Staphylococcus aureus, revealed that although these three proteins share low sequence similarities, there is a high degree of structural conservation and similar substrate-binding frameworks. Our results reveal that GNA1946 is an l-methionine binding lipoprotein in the outer membrane, and should function as an initial receptor for ABC transporters with high affinity and specificity. The GNA1946 structure reported here should provide a valuable starting point for the development of a broad-spectrum meningococcal vaccine.     

Production of proinflammatory cytokines in the human THP-1 monocyte cell line following induction by Tp0751, a recombinant protein of <Emphasis Type="Italic">Treponema pallidum</Emphasis>

The tissue destruction characteristic of syphilis infection may be caused by inflammation due to Treponema pallidum and the ensuing immune responses to the pathogen. T. pallidum membrane proteins are thought to be potent inducers of inflammation during the early stages of infection. However, the actual membrane proteins that induce inflammatory cytokine production are not known, nor are the molecular mechanisms responsible for triggering and sustaining the inflammatory cascades. In the present study, Tp0751 recombinant protein from T. pallidum was found to induce the production of proinflammatory cytokines, including TNF-α, IL-1βand IL-6, in a THP-1 human monocyte cell line. The signal transduction pathways involved in the production of these cytokines were then further investigated. No inhibition of TNF-a, IL-1β, or IL-6 production was observed following treatment with the SAPK/JNK specific inhibitor SP600125 or with an ERK inhibitor PD98059. By contrast, anti-TLR2 mAb, anti-CD14 mAb, and the p38 inhibitor SB203580 significantly inhibited the production of all three cytokines. In addition, pyrrolidine dithiocarbamate (PDTC), a specific inhibitor of NF-κB, profoundly inhibited the production of these cytokines. Tp0751 treatment strongly activated NF-κB, as revealed by Western blotting. However, NF-κB translocation was significantly inhibited by treatment with PDTC. These results indicated that TLR2, CD14, MAPKs/p38, and NF-κB might be implicated in the inflammatory reaction caused by T. pallidum infection.     

Functional clues from the crystal structure of an orphan periplasmic ligand‐binding protein from Treponema pallidum

The spirochete Treponema pallidum is the causative agent of syphilis, a sexually transmitted infection of major global importance. Other closely related subspecies of Treponema also are the etiological agents of the endemic treponematoses, such as yaws, pinta, and bejel. The inability of T. pallidum and its close relatives to be cultured in vitro has prompted efforts to characterize T. pallidum's proteins structurally and biophysically, particularly those potentially relevant to treponemal membrane biology, with the goal of possibly revealing the functions of those proteins. This report describes the structure of the treponemal protein Tp0737; this polypeptide has a fold characteristic of a class of periplasmic ligand‐binding proteins associated with ABC‐type transporters. Although no ligand for the protein was observed in electron‐density maps, and thus the nature of the native ligand remains obscure, the structural data described herein provide a foundation for further efforts to elucidate the ligand and thus the function of this protein in T. pallidum.     

Expression and purification of two major outer membrane proteins from <Emphasis Type="Italic">Vibrio alginolyticus</Emphasis>

Vibrio alginolyticus, a Gram-negative bacterium, is one of Vibrio pathogens common to human and marine animals. Outer membrane proteins of bacteria play an important role during infection and induction of host immune response. In present research, two outer membrane protein genes (OmpK and OmpW) of V. alginolyticus were cloned and expressed. The open reading frames of OmpK and OmpW contain 846 bp and 645 bp, respectively, the mature proteins consist of 261 and 193 amino acid residues. At the signal peptides positions −3 to −1, the amino acids were V-M-A in OmpK and V-F-A in OmpW, which consistented with the observed sequence V-X-A of the signal peptides of transmembrane OMP. The alignment analysis indicated that both proteins were highly conserved, which could serve as surface antigens for vaccine candidates. SDS-PAGE indicated two genes over-expressed in E. coli BL21 (DE3). By affinity chromatography on Ni²⁺-nitriloaceate resin, the recombinant proteins were purified from inclusion bodies. Western blot analysis revealed that both proteins had immunoreactivity, which provided a base for further study on the evaluation of diagnostication and vaccine candidates.     

Expression of the Neisseria gonorrhoeae major outer membrane protein PI in Escherichia coli

Summary To actively express an outer membrane protein, protein I (PI), from different strains of Neisseria gonorrhoeae in E.␣coli, PI gene fragments from two reference strains and four clinical isolates of Neisseria gonorrhoeae were obtained with PCR amplification. They were cloned into the PCR cloning vector pBS-T to form pBS-T-PI and sequenced. Subsequently, they were cloned into an expression vector pET-30b (+) to generate pET-PI recombinants. After inducing with isopropyl-β-d-thiogalactopyranoside (IPTG), the expressed PI proteins were analysed by SDS-PAGE, Western blotting and ELISA. The results implied that we had successfully constructed the PI gene recombinants from both reference strains and clinical isolates and obtained the recombinant proteins expressed in E. coli at relatively high levels, and the expressed proteins had the immunological activity with the corresponding antibodies. This research will be very helpful for the further study of these proteins in generating preventive vaccines on Neisseria gonorrhoeae infection and clinical diagnosis.     

A chimeric gene (orf256) is expressed as protein only in cytoplasmic male-sterile lines of wheat

Mitochondria derived from Triticum timopheevi have a chimeric gene, orf256, immediately upstream from coxI. Antibodies to a peptide corresponding to a part of the encoded amino acid sequence of orf256 detect a 7 kDa protein on western blots of mitochondrial proteins from cytoplasmic male-sterile (cms) wheat (T. aestivum nucleus, T. timopheevi mitochondria) but not in mitochondrial proteins from T. aestivum, T. timopheevi, or cms plants restored to fertility by introduction of nuclear genes for fertility restoration. The 7 kDa protein appears to serve as a marker for cms wheat. Its occurrence as an integral protein of the inner membrane may indicate a cms effect through an influence on mitochondrial membrane function.