從細胞中識別出以前未知的乙型肝炎病毒途徑

StephenW

從細胞中識別出以前未知的乙型肝炎病毒途徑

作者：Susanne Stöcker，Paul-Ehrlich-Institut
從 HepAD38 細胞釋放的外泌體的透射電子顯微鏡檢查。 A，來自固定外泌體的 Epon 嵌入（左）或冷凍切片（右）的超薄切片的 TEM 圖像，顯示被膜結構包圍的病毒粒子（用箭頭標記）。星號表示密集的病毒包膜從包圍的核衣殼中突出。 B-C，固定外泌體的超薄解凍冷凍切片的免疫金標記。冷凍切片要么用抗 CD63 抗體（通過 10-nm 金顆粒顯現）或抗 LHBs 抗血清（抗 preS1/preS2 結構域兔血清 [K112-4]）標記（由 5-nm 金顆粒顯現）。箭頭表示特定的膠體金標記。星號表示抗 LHBs (5 nm) 位於可識別的封閉病毒樣顆粒上。冷凍切片外泌體的表面也被抗 LHBs 標記（橙色箭頭）。學分：細胞和分子胃腸病學和肝病學（2022 年）。 DOI: 10.1016/j.jcmgh.2022.09.012

全世界每年約有 150 萬人感染乙型肝炎病毒 (HBV)。由 Paul-Ehrlich-Institut 領導的一個研究小組已經確定了一種以前未知的從細胞中排出乙型肝炎病毒顆粒的途徑：研究人員首次能夠在細胞外囊泡（外泌體）中觀察到完整的病毒顆粒。

外泌體是細胞中釋放到周圍環境中的小囊泡，可用作運輸工具，也可能用作保護性覆蓋物。 Cellular and Molecular Gastroenterology and Hepatology 於 2022 年 9 月 29 日在其在線版中報告了結果。

乙型肝炎是歷史上最常見的傳染病之一。它是由可引起急性和慢性肝炎的乙型肝炎病毒 (HBV) 引起的。全世界估計有 3 億人患有慢性乙型肝炎感染，這與發展為肝硬化或肝細胞癌的風險增加有關。

每年，全世界約有 900,000 人死於 HBV 感染。血清學證據甚至表明，估計有 20 億人以前曾感染或目前感染 HBV。 HBV主要通過血液傳播，但也通過唾液、淚液、精子甚至陰道分泌物等其他體液傳播。

儘管安全有效的疫苗已獲得批准，但 HBV 仍然是一個主要的健康問題。許多處於高流行病負擔的國家沒有有效的疫苗接種策略或缺乏疫苗供應。徹底治愈慢性感染也是一項醫學挑戰。

確定了新的乙型肝炎病毒出口途徑

現在人們對 HBV 的生命週期了解很多。儘管如此，仍有部分尚未完全闡明，例如哪些機制使病毒能夠離開細胞。像所有病毒一樣，HBV 需要從細胞中釋放出來才能繁殖並感染其他細胞。各種研究表明，一些病毒可以在外泌體中找到。這些小囊泡被細胞釋放到周圍環境中。它們用於細胞通訊和分子運輸。

由病毒學部門負責人 Eberhard Hildt 教授領導的 Paul-Ehrlich-Institut 研究小組調查了乙型肝炎病毒是否也使用外泌體作為細胞的運輸工具。目前尚不清楚這是否是 HBV 使用的一種機制。

在他們的工作中，研究小組從產生HBV的人類肝細胞的細胞培養上清液中分離出外泌體，並發現了典型的外泌體標誌物和乙型肝炎病毒的標誌物。這些外泌體部分與含有游離病毒粒子的部分分離，以確定乙型肝炎病毒是否真的存在於外泌體中。病毒粒子是位於細胞外的病毒顆粒。

研究小組有可能在去污劑的幫助下從外泌體逐步釋放完整的 HBV 病毒粒子，從而溶解外泌體的膜。

科學家們能夠觀察到，在實驗室中抑制外泌體形態發生會損害外泌體包裹的 HBV 的釋放。此外，電子顯微鏡證實了檢查的外泌體中存在完整的病毒粒子。研究小組還檢測到外泌體表面存在HBV表面蛋白LHB（大型乙型肝炎病毒表面抗原）。

這種蛋白質的存在使得包裹在外泌體中的乙型肝炎病毒可以感染易感細胞。在通常對 HBV 感染不太敏感的細胞中也觀察到外泌體乙型肝炎病毒的攝取，儘管效率低。
目前的研究數據表明，一些完整的 HBV 病毒粒子可以作為外泌體釋放。 這是以前未發現的乙型肝炎病毒的釋放途徑。 雖然乙型、丙型和戊型肝炎病毒完全不同，但它們都是利用這種途徑離開細胞的。

該研究發表在 Cellular and Molecular Gastroenterology and Hepatology 上。
更多信息：Qingyan Wu 等人，外泌體中存在完整的乙型肝炎病毒粒子，細胞和分子胃腸病學和肝病學 (2022)。 DOI: 10.1016/j.jcmgh.2022.09.012

StephenW

Previously unknown hepatitis B virus pathway from the cell identified

by Susanne Stöcker, Paul-Ehrlich-Institut
Transmission electron microscopy of exosomes released from HepAD38 cells. A, TEM images from ultra-thin sections of Epon-embedded (left) or cryo-sections (right) of fixed exosomes showing virions enclosed by a membrane structure (labeled by arrows). An asterisk indicates that a dense viral envelope stands out from the surrounded nucleocapsid. B–C, Immunogold labeling of ultra-thin thawed cryo-sections of fixed exosomes. The cryo-sections were either labeled with an anti-CD63 antibody (visualized by 10-nm gold particles) or an anti LHBs antiserum (anti-preS1/preS2 domain rabbit serum [K112-4]) (visualized by 5-nm gold particles). Arrows indicate specific colloidal gold labeling. Asterisks represent that anti-LHBs (5 nm) is located at identifiable enclosed virus like particles. The surface of cryo-sectioned exosomes was also labeled by anti-LHBs (orange arrows). Credit: Cellular and Molecular Gastroenterology and Hepatology (2022). DOI: 10.1016/j.jcmgh.2022.09.012

Around 1.5 million people worldwide become infected with the hepatitis B virus (HBV) every year. A research team led by the Paul-Ehrlich-Institut has identified a previously unknown pathway for the egress of hepatitis B virus particles from cells: researchers were able to visualize intact virus particles in extracellular vesicles (exosomes) for the first time.

Exosomes, small vesicles in cells that are released into the surroundings, serve as a means of transport and possibly as a protective covering. Cellular and Molecular Gastroenterology and Hepatology reports on the results in its online edition from September 29, 2022.

Hepatitis B is one of the most common infectious diseases in history. It is caused by the hepatitis B virus (HBV), which can cause acute and chronic hepatitis. An estimated 300 million people worldwide suffer from chronic hepatitis B infection, which is associated with an increased risk of developing cirrhosis of the liver or liver cell carcinoma.

Every year, around 900,000 people worldwide die as a result of an HBV infection. Serological evidence even shows that an estimated two billion people have previously been infected or are currently infected with HBV. HBV is transmitted mainly via blood, but also via other body fluids such as saliva, lacrimal fluid, sperm or even vaginal secretions.

Although safe and effective vaccines have been authorized, HBV continues to pose a major health problem. Many countries under a high epidemic burden do not have effective vaccination strategies or lack vaccine supplies. It is also a medical challenge to completely cure a chronic infection.

New hepatitis B virus egress pathway identified

Much is now known about the life cycle of HBV. Nevertheless, there are still parts that have not been fully elucidated, such as which mechanisms enable the virus to leave the cell. Like all viruses, HBV needs to be released from the cell to reproduce and to infect other cells. Various studies have shown that some viruses can be found in exosomes. These small vesicles are released into the surroundings by the cell. They are used for cellular communication and the transport of molecules.

A research team from the Paul-Ehrlich-Institut, headed by Professor Eberhard Hildt, head of the Virology Division, investigated whether hepatitis B viruses also use exosomes as a means of transport from the cells. It was not yet known whether this was a mechanism used by HBV.

In their work, the research group isolated exosomes from the cell culture supernatant of HBV-producing human liver cells and found both typical exosomal markers and markers of hepatitis B viruses. These exosomal fractions were separated from fractions containing free virions to determine whether hepatitis B viruses were actually present in the exosomes. Virions are virus particles that are located outside of cells.

It was possible for the research team to release intact HBV virions stepwise from the exosomes with the help of detergents, which dissolve the membrane of the exosomes.

The scientists were able to observe that inhibiting exosome morphogenesis in the laboratory impaired the release of exosome-wrapped HBV. In addition, electron microscopy confirmed the presence of intact virions in the examined exosomes. The research team also detected the presence of the HBV surface protein LHB (large hepatitis B virus surface antigen) on the surface of exosomes.

The presence of this protein makes it possible for the hepatitis B viruses encapsulated in exosomes to infect susceptible cells. An uptake of exosomal hepatitis B viruses was also observed in cells which are usually not very susceptible to HBV infection, albeit with low efficiency.

The current research data indicates that some of the intact HBV virions can be released as exosomes. This is a release pathway for hepatitis B viruses which had not been previously identified. Although hepatitis B, C and E viruses are completely different, they all use this pathway to leave cells.

The research was published in Cellular and Molecular Gastroenterology and Hepatology.
More information: Qingyan Wu et al, Presence of Intact Hepatitis B Virions in Exosomes, Cellular and Molecular Gastroenterology and Hepatology (2022). DOI: 10.1016/j.jcmgh.2022.09.012

StephenW

https://medicalxpress.com/news/2 ... -virus-pathway.html