美国国立卫生研究院的科学家揭示了谜团，B型肝炎病毒

StephenW

NIH Scientists Shed Light on Mystery Surrounding Hepatitis B Virus
  Discovery Is Decades in the MakingScientists from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), part of the National Institutes of Health, and the University of Oxford, U.K., have shed light on a long-standing enigma about the structure of a protein related to the Hepatitis B virus. Their findings, reported in Structure, could lead to new therapeutic strategies for chronic liver disease.
World-wide, some 350 million people are chronically infected with Hepatitis B Virus (HBV), of whom 620,000 die each year from HBV-related liver disease. Like any other pathogen, HBV expresses protein antigens that trigger the body’s immune system to defend itself. A relatively small and simple virus, HBV has three major clinical antigens that elicit an immune response: the surface antigen (which is also used safely and effectively to vaccinate individuals against HBV), the core antigen (HBcAg), and the e-antigen (HBeAg).
  Illustration of the hepatitis B virus e-antigen.

The HBV core antigen and the e-antigen are basically two versions of the same protein, but the core antigen is important for virus production, while the e-antigen is not. The e-antigen plays a role in establishing immune tolerance and chronic HBV infection. In addition, the core antigen assembles into the shell (capsid) that houses the genetic material of the virus, while the e-antigen is secreted into the bloodstream in an unassembled form.  The relationship between the e-antigen and the core antigen has been a mystery for the past three decades.
In the new study, Alasdair Steven, Ph.D., Senior Investigator in the NIAMS Laboratory of Structural Biology Research, and Paul Wingfield, Ph.D., Chief of the NIAMS Protein Expression Laboratory developed a unique antibody that binds to and forms a stable complex with e-antigen. This complex was found to form well-diffracting crystals whose analysis allowed the structure of the complex to be determined. They discovered that the e-antigen subunit has essentially the same fold as the core antigen subunit, but that it pairs into dimers (two associated subunits) in an entirely different way, with a relative rotation of 140 degrees between the subunits. The rotation obviates the protein's ability to assemble and transforms its antigenic character. This switch represents a novel mechanism for regulating a protein's structure and function.
Understanding the e-antigen structure provides a framework upon which future studies can build to fully elucidate its role in HBV persistence and possibly a way to prevent the establishment of chronic liver infections.

StephenW

美国国立卫生研究院的科学家揭示了谜团，B型肝炎病毒
发现已经有几十年的制作

的国立关节炎及肌肉骨骼及皮肤疾病（NIAMS），美国国立卫生研究院的一部分，和英国牛津大学，科学家揭示了一个长期存在的谜有关的一种蛋白质的结构B型肝炎病毒。他们的研究结果发表在结构上，可能会导致慢性肝脏疾病的新的治疗策略。

在世界范围内，大约350万人患有慢性B型肝炎病毒（HBV）感染，其中有62万，每年死于HBV相关的肝脏疾病。像任何其他的病原体，HBV表示触发人体的免疫系统的蛋白抗原，为自己辩护。一个相对小的，简单的病毒，乙肝病毒有三个主要的临床引起免疫反应的抗原：表面抗原（它也被用来安全和有效地进行免疫接种的抗HBV的个人），核心抗原（HBcAg）和e抗原（ HBeAg）阳性。
插图的乙肝病毒e抗原。

插图的乙肝病毒e抗原。

HBV核心抗原和e抗原的基本上相同的蛋白质的两个版本的，但核心抗原的病毒生产是重要的，而e抗原不是。 e抗原，建立免疫耐受，慢性HBV感染起到了重要作用。此外，核心抗原组装成的壳体（衣壳）收纳该病毒的遗传物质，而e抗原分泌到血流中的未组装的形式。 e抗原和核心抗原之间的关系在过去三十年一直是个谜。

在这项新的研究中，NIAMS结构生物学研究实验室的资深研究员阿拉斯代尔史蒂芬博士和保罗·温菲尔德，博士，首席NIAMS蛋白表达实验室开发了一种独特的抗体结合，形成了一个稳定的络合物，e抗原。这种复杂的发现，以形成良好的衍射晶体的分析以确定允许的结构的复杂。他们发现，e抗原亚基具有基本上相同的倍作为核心抗原亚基，但，它在一个完全不同的方法，与140度之间的亚基的相对旋转成二聚体（两个相关亚基）对。旋转避免了蛋白质的能力，组装和改变其抗原性。此开关代表了一种新的机制，调节蛋白质的结构和功能。

了解e抗原结构提供了一个框架，未来的研究可以建立完全阐明其作用在HBV的持久性和可能的​​方式，以防止慢性肝病感染的建立。

咬牙硬挺

挺牛的研究，越来越细致入微了

StephenW

回复 咬牙硬挺 的帖子

HBeAg,HBcAg是非常相似的。
乙肝病毒核心抗原是非常的免疫原性(immunogenic)但乙肝病毒核心抗原
不在血液流通.HBeAg在血液流通.

开始，HBeAg是耐受性(tolerogenic)，导致免疫耐受.
但免疫清除后, HBeAg,HBeAb,e抗体, 似乎是重要的 在维持免疫控制.

很复杂.

bigben446

贴2个参考文献

Dimattia, M.A., et al., Antigenic Switching of Hepatitis B Virus by Alternative Dimerization of the Capsid Protein. Structure, 2012.
http://www.ncbi.nlm.nih.gov/pubmed/23219881

Wu, W., et al., Specificity of an anti-capsid antibody associated with Hepatitis B Virus-related  acute liver failure. J Struct Biol, 2013. 181(1): p. 53-60.
http://www.ncbi.nlm.nih.gov/pubmed/23079477

MP4

E抗原的生物学功能及E抗原血清转换的免疫学基础-闻玉梅院士
http://hbvhbv.info/forum/forum-v ... fromuid-320872.html

StephenW

回复 MP4 的帖子

非常感谢，学到了非常多.

"因为免疫需要一定的抗原的刺激，抗病毒治疗后，抗原都下来了，也许就不行了，但也许通过抗病毒治疗后免疫调控的效果会更好" - 非常博学的观察.

StephenW

回复 bigben446 的帖子

谢谢，很有意思.
Antigenic Switching of Hepatitis B Virus by Alternative Dimerization of the Capsid Protein.Dimattia MA, Watts NR, Stahl SJ, Grimes JM, Steven AC, Stuart DI, Wingfield PT.
SourceDivision of Structural Biology, Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Headington OX3 7BN, UK; Laboratory of Structural Biology Research , National Institute of Arthritis and Musculoskeletal and Skin Diseases; National Institutes of Health, Bethesda, MD 20892, USA.

AbstractChronic hepatitis B virus (HBV) infection afflicts millions worldwide with cirrhosis and liver cancer. HBV e-antigen (HBeAg), a clinical marker for disease severity, is a nonparticulate variant of the protein (core antigen, HBcAg) that forms the building-blocks of capsids. HBeAg is not required for virion production, but is implicated in establishing immune tolerance and chronic infection. Here, we report the crystal structure of HBeAg, which clarifies how the short N-terminal propeptide of HBeAg induces a radically altered mode of dimerization relative to HBcAg (∼140° rotation), locked into place through formation of intramolecular disulfide bridges. This structural switch precludes capsid assembly and engenders a distinct antigenic repertoire, explaining why the two antigens are cross-reactive at the T cell level (through sequence identity) but not at the B cell level (through conformation). The structure offers insight into how HBeAg may establish immune tolerance for HBcAg while evading its robust immunogenicity.

慢性乙型肝炎病毒（HBV）感染影响了数百万世界各地的肝硬化和肝癌。乙肝病毒e抗原（HBeAg），疾病的严重程度的临床标志，是一种非颗粒形成建筑块的衣壳蛋白（核心抗原，核心抗原）的变体。 HBeAg的还没有所需的病毒粒子的生产，但在建立免疫耐受和慢性感染被牵连。在这里，我们报告的晶体结构的HBeAg，短的N-端肽诱导的HBeAg阐明如何从根本上改变模式，通过分子内二硫键形成二聚体相对于乙肝病毒核心抗原（〜140°旋转），锁定到位。这种结构上的开关排除了衣壳的装配，并孕育着不同的抗原剧目，解释为什么这两个抗原交叉反应的T细胞水平（通过序列身份），但没有在B细胞水平（通过构象）。该结构提供了深入了解如何大三阳可以建立核心抗原的免疫耐受而逃避其强大的免疫原性。

StephenW

J Struct Biol. 2013 Jan;181(1):53-60. doi: 10.1016/j.jsb.2012.10.004. Epub 2012 Oct 16.
Specificity of an anti-capsid antibody associated with Hepatitis B Virus-related acute liver failure.
Wu W, Chen Z, Cheng N, Watts NR, Stahl SJ, Farci P, Purcell RH, Wingfield PT, Steven AC.
Source

Laboratory of Structural Biology, National Institute for Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, United States.
Abstract

Previously, the livers of patients suffering from acute liver failure (ALF), a potentially fatal syndrome arising from infection by Hepatitis B Virus (HBV), were found to contain massive amounts of an antibody specific for the core antigen (HBcAg) capsid. We have used cryo-electron microscopy and molecular modeling to define its epitope. HBV capsids are icosahedral shells with 25Å-long dimeric spikes, each a 4-helix bundle, protruding from the contiguous "floor". Of the anti-HBcAg antibodies previously characterized, most bind around the spike tip while one binds to the floor. The ALF-associated antibody binds tangentially to a novel site on the side of the spike. This epitope is conformational. The Fab binds with high affinity to its principal determinants but has lower affinities for quasi-equivalent variants. The highest occupancy site is on one side of a spike, with no detectable binding to the corresponding site on the other side. Binding of one Fab per dimer was also observed by analytical ultracentrifugation. The Fab did not bind to the e-antigen dimer, a non-assembling variant of capsid protein. These findings support the propositions that antibodies with particular specificities may correlate with different clinical expressions of HBV infection and that antibodies directed to particular HBcAg epitopes may be involved in ALF pathogenesis.
在此之前，急性肝功能衰竭（ALF），因感染乙型肝炎病毒（HBV），一个潜在的致命性综合征患者的肝脏被发现含有大量的特异性抗体为核心抗原（HBcAg）衣壳。我们使用低温电子显微镜和分子模型，以确定其抗原表位。 HBV衣壳二十面体壳长25A-二聚体尖峰，每一个四螺旋束，突出从连续的“地板”。的抗-HBcAg的抗体先前其特征在于，最绑定的尖钉尖端周围，而1绑定到地板上。 ALF相关抗体结合切向一种新型的网站上侧的尖峰。这是构象表位。的Fab结合高亲和力，其主要的决定因素，但具有较低的亲和力准等同变异体。的最高占用站点是一个尖峰的一侧上，与没有检测到结合到相应的站点的另一侧。也观察到了超高速离心一厂每二聚体的结合。的Fab没有绑定到的e-抗原的二聚体，非组装的核衣壳蛋白的变体。这些研究结果都支持的主张，尤其是特异性的抗体可能与HBV感染不同的临床表现，尤其是乙肝病毒核心抗原表位的抗体可能参与了ALF发病。

LITTLEKING

似乎研究还只停留在原因的不确定性上。