Critical role of an eight-amino acid sequence of VP1 in neutralization of poliovirus type 3

The three serotypes of poliovirus are members of the picornaviradae, a group of viruses which cause a variety of diseases of considerable importance in man and animals. We have previously used antigenic mutants resistant to neutralizing monoclonal antibodies to identify a single antigenic site for the neutralization of poliovirus type 3 (ref. 1). Evidence based on oligonucleotide mapping suggested that this site corresponded largely to one physicochemical region of the capsid protein viral polypeptide 1 (VP1). We now present conclusive evidence that most of the mutations conferring resistance to neutralization are confined to an eight-amino acid region of VP1, specified by a sequence of viral RNA 277-300 bases from the start of the region coding for VP1. These data strongly suggest that this small region constitutes a major antigenic site involved in virus neutralization and they provide the most detailed information currently available on the antigenic site of a human virus.     

Structural and serological evidence for a novel mechanism of antigenic variation in foot-and-mouth disease virus.

Changes resulting in altered antigenic properties of viruses nearly always occur on their surface and have been attributed to the substitution of residues directly involved in binding antibody. To investigate the mechanism of antigenic variation in foot-and-mouth disease virus (FMDV), variants that escape neutralization by a monoclonal antibody have been compared crystallographically and serologically with parental virus. FMDVs form one of the four genera of the Picornaviridae. The unenveloped icosahedral shell comprises 60 copies each of four structural proteins VP1-4. Representatives from each of the genera have similar overall structure, but differences in the external features. For example, human rhinovirus has a pronounced 'canyon' that is proposed to contain the cell attachment site, whereas elements of the attachment site for FMDV, which involves the G-H loop (residues 134-160) and C-terminus (200-213) of VP1, are exposed on the surface. Moreover, this G-H loop, which is a major antigenic site of FMDV, forms a prominent, highly accessible protrusion, a feature not seen in other picornaviruses. It is this loop that is perturbed in the variant viruses that we have studied. The amino acid mutations characterizing the variants are not at positions directly involved in antibody binding, but result in far-reaching perturbations of the surface structure of the virus. Thus, this virus seems to use a novel escape mechanism whereby an induced conformational change in a major antigenic loop destroys the integrity of the epitope.     

传染性法氏囊病病毒结构的分子生物学研究进展

传染性法氏囊病是一种严重危害雏鸡的免疫抑制性、高度接触性传染病.传染性法氏囊病病毒为双RNA病毒,有A、B两个片断.A片断编码4种蛋白VP2,VP3,VP4和VP5,B片断编码VP1蛋白.其中的VP2和VP3是主要的宿主保护性抗原,在病毒的结构、变异、毒力和免疫原性方面有着重要的作用.     

Localization of VP4 neutralization sites in rotavirus by three-dimensional cryo-electron microscopy

Three-dimensional structures of several spherical viruses have been determined by electron microscopy and X-ray crystallography. We report here the first three-dimensional structure of the complex between an intact virus and Fab fragments of a neutralizing monoclonal antibody. The antibody is against VP4, one of the two outer capsid proteins of rotaviruses. These large icosahedral viruses cause gastroenteritis in children and young animals and account for over a million human deaths annually. VP4 in these viruses has been implicated in several important functions such as cell penetration, haemagglutination, neutralization and virulence. Here we demonstrate that the surface spikes on rotavirus particles are made up of VP4. Antigenic sites are located near the distal ends of the spikes and two Fab fragments bind to each of the sixty spikes. The mass of the spike indicates that it is a dimer of VP4. The bilobed structure at the distal end of the spike may be involved in both the attachment to the cell and in viral penetration. A novel feature in the virus-Fab complex is the structural difference between the two chemically equivalent Fab fragments on each spike, which could be indicative of variations in the Fab elbow angles.     

亚洲一型口蹄疫病毒YNAs1.1株结构蛋白VP1基因的核苷酸序列分析

提取BHK21细胞增殖的亚洲一型口蹄疫病毒（foot-and-mouth disease virus Serotype Asial)强毒株YNAs1.1的RNA,用一对引物P7,P13经反转录（RT）－PCR法扩增了约674bp的DNA片段。克隆目的基因后,采用双脱氧DNA链末端终止法测得了YNAs1.1的VP1基因36－633核苷酸序列。分析表明,病毒VP1基因的核苷酸序列与以色列以及印度已报道的Asia1型FMDV的同源性分别为82.11%与88.07%,对应的氨基酸序列同源性为87.94％与93.47％。该序列在GeneBank登陆号为AF241566。     

Myristic acid is coupled to a structural protein of polyoma virus and SV40

In the lytic cycle of papova viruses, both uncoating of the viral genome after infection and assembly of functional virions take place in the cell nucleus. The mechanisms by which newly internalized virions are targeted to the nucleus and viral DNA encapsidated into particles are poorly understood. Although the major capsid protein VP1 is involved in endocytosis, and largely defines virion structure, the functions of the minor proteins VP2 and VP3 have remained obscure. Here we show that VP2 from both polyoma virus and simian virus 40 (SV40) is covalently linked to myristic acid; this is the first report of a myristylated protein in the nucleus and of a fatty acid being important in the structure of a nonenveloped virus. We consider the implications of this unusual modification on encapsidation and suggest that VP2 may be a scaffolding protein for virion assembly.     

Chemical basis of antigenic variation in foot-and-mouth disease virus

One of the difficulties in controlling foot and mouth disease by vaccination is the occurrence of the virus as seven distinct serotypes because immunity conferred by vaccination against one serotype leaves the animals susceptible to infection by the other six. Moreover, the antigenic variation, even within a serotype, can be so great that immunity against the homologous strain of virus need not necessarily ensure protection against infection by other viruses within that serotype. Here we report the separation of three natural antigenic variants, distinguishable in cross-neutralization tests from an isolate of foot-and-mouth disease virus (FMDV). The serological differences could also be demonstrated by antisera elicited by synthetic peptides corresponding to residues 141-160 of the capsid polypeptide VP1, showing that this region contains a major immunogenic site of the virus. The results have practical implications for the choice of viruses for vaccine production.     

Antigen chimaeras of poliovirus as potential new vaccines

Polioviruses occur as three distinct serotypes, 1, 2 and 3, and are composed of a single-stranded positive-sense RNA genome of approximately 7,450 nucleotides enclosed in an icosahedral particle of diameter 27 nm. The three-dimensional crystallographic structure of poliovirus type 1 has been determined at 2.9 A resolution, providing a detailed knowledge of the folding and arrangement of the individual virus proteins, VP1-VP4. From this and the characterization of monoclonal antibody-resistant mutants, the amino acids contributing to antigenic sites have been identified and located on the surface of the virus particle. Here we describe the construction and characterization of a poliovirus chimaera having a defined region of type 3 inserted into type 1. This virus has composite antigenicity and the substitute site is immunogenic in small animals and primates. The ability to construct such viruses has implications for the design of improved poliovirus vaccine strains or vaccines against other picornaviruses, such as hepatitis A.     

HIV-1 evades antibody-mediated neutralization through conformational masking of receptor-binding sites

The ability of human immunodeficiency virus (HIV-1) to persist and cause AIDS is dependent on its avoidance of antibody-mediated neutralization. The virus elicits abundant, envelope-directed antibodies that have little neutralization capacity. This lack of neutralization is paradoxical, given the functional conservation and exposure of receptor-binding sites on the gp120 envelope glycoprotein, which are larger than the typical antibody footprint and should therefore be accessible for antibody binding. Because gp120-receptor interactions involve conformational reorganization, we measured the entropies of binding for 20 gp120-reactive antibodies. Here we show that recognition by receptor-binding-site antibodies induces conformational change. Correlation with neutralization potency and analysis of receptor-antibody thermodynamic cycles suggested a receptor-binding-site 'conformational masking' mechanism of neutralization escape. To understand how such an escape mechanism would be compatible with virus-receptor interactions, we tested a soluble dodecameric receptor molecule and found that it neutralized primary HIV-1 isolates with great potency, showing that simultaneous binding of viral envelope glycoproteins by multiple receptors creates sufficient avidity to compensate for such masking. Because this solution is available for cell-surface receptors but not for most antibodies, conformational masking enables HIV-1 to maintain receptor binding and simultaneously to resist neutralization.     

猿猴空泡病毒40病毒样颗粒的制备及纯化

本研究将猿猴空泡病毒40(Simian virus 40,SV40)的主要衣壳蛋白VP1通过Bac-toBac杆状病毒表达系统在昆虫细胞中大量表达,并自我装配成形态结构及免疫原性均与天然病毒粒子相同或相似的SV40病毒样颗粒(SV40virus-like particles,SV40VLPs),经表达条件优化及分子筛纯化,成功制备出高纯度的VLPs.聚丙烯酰胺凝胶电泳结果可见大小约为46kDa的VP1特异性条带.间接免疫荧光试验(IFA)证实VP1蛋白能够与异硫氰酸荧光素标记的羊抗鼠抗体发生反应,出现明显的特异性绿色荧光,具有良好的抗原性.纯化产物在透射电镜下可见直径约45nm的病毒样颗粒,显示出成功组装了SV40VLPs,免疫印迹试验证明VLPs能够与人抗SV40阳性血清发生反应,具有良好的抗原性.     

Generation of VP5 deficient mutant of infectious bursal disease virus strain HZ2

Infectious bursal disease virus (IBDV) is one of the most significant viral pathogens in chickens[1]. It causes high mortality in young chickens and establishes an immunosuppression state by destroying the precursorsInfectious bursal disease virus (IBDV) …     

Structural rearrangements in the membrane penetration protein of a non-enveloped virus

Non-enveloped virus particles (those that lack a lipid-bilayer membrane) must breach the membrane of a target host cell to gain access to its cytoplasm. So far, the molecular mechanism of this membrane penetration step has resisted structural analysis. The spike protein VP4 is a principal component in the entry apparatus of rotavirus, a non-enveloped virus that causes gastroenteritis and kills 440,000 children each year. Trypsin cleavage of VP4 primes the virus for entry by triggering a rearrangement that rigidifies the VP4 spikes. We have determined the crystal structure, at 3.2 A resolution, of the main part of VP4 that projects from the virion. The crystal structure reveals a coiled-coil stabilized trimer. Comparison of this structure with the two-fold clustered VP4 spikes in a approximately 12 A resolution image reconstruction from electron cryomicroscopy of trypsin-primed virions shows that VP4 also undergoes a second rearrangement, in which the oligomer reorganizes and each subunit folds back on itself, translocating a potential membrane-interaction peptide from one end of the spike to the other. This rearrangement resembles the conformational transitions of membrane fusion proteins of enveloped viruses.     

中蜂囊状幼虫病病毒部分结构蛋白基因的克隆及序列分析

根据小ＲＮＡ 病毒科（ Ｐｉｃｏｒｎａｖｉｒｉｄａｅ） 中病毒ＲＮＡ 所具有的结构特征, 采用ｍＲＮＡｃａｐｔｕｒｅ ｋｉｔ 提取纯化中蜂囊状幼虫病病毒（Ｃｈｉｎｅｓｅｓｃａｂｒｏｏｄ ｖｉｒｕｓ ＣＳＢＶ） 的ＲＮＡ, 并以之为ｃＤＮＡ合成的模板． 依据小ＲＮＡ病毒科中的脊髓灰质炎病毒结构蛋白基因序列设计了一对引物ＶＰ５和ＶＰ３ , 通过ＰＣＲ 扩增获得预期大小约为１ １００ ｂｐ的ＤＮＡ 片段, 将此片段克隆到ｐＧＥＭＴｅａｓｙ载体上并直接测序． 序列分析表明, 该片段为中蜂囊状幼虫病病毒部分结构蛋白基因, 与意蜂幼虫囊状病病毒结构蛋白基因序列的同源性为８６－８ ％ , 与之对应氨基酸序列的同源性高达９３－４ ％ ． 该病毒株为一种新型的蜜蜂囊状幼虫病病毒株     

Identification of in vivo interaction between rabbit hemorrhagic disease virus capsid protein and minor structural protein

We investigated the ability of the rabbit hemorrhagic disease virus(RHDV) capsid protein(VP60) to interact specifically with the minor structural protein VP10,using an in vivo cell-based CheckMate Mammalian Two-Hybrid System.RHDV VP60 protein interacted specifically with VP10.Immunofluorescence analysis and co-immunoprecipitation with specific antibodies revealed the existence of biologically important VP60/VP10 complexes.However,when VP60 was divided into two fragments,the interaction between VP60 and VP10 was impaired dramatically.These results will be helpful for further investigating the mechanism of RHDV particle assembly.     

应用聚合酶链式反应检测犬细小病毒

将具有犬细小病毒病典型症状的病犬肠溶物经ＳＤＳ－酚裂解法提取总ＤＮＡ,并以此ＤＮＡ为模板,通过人工合成的两条２０ｍｅｒ引物进行ＰＣＲ扩增,该对引物扩增的片段为犬细小病毒结构蛋白ＶＰ２基因中间１／３区段,ＰＣＲ产物经琼脂糖凝胶电泳,试验结果表明：用ＰＣＲ扩增检测犬细小病毒具有良好的特异性,应用该方法检测的２７份病犬肠溶物样品块获得了预计长度的ＤＮＡ片段（５３１ｂｐ）,而健康犬的肠溶物样品ＰＣＲ结果为     

全息图的转印及效率研究

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