研究人员确定了慢性乙型肝炎感染必不可少的因素

StephenW

Researchers identify factors essential for chronic hepatitis B infection

by Princeton University
Human hepatoma cells harboring modified hepatitis B virus cccDNA are labeled by green fluorescent proteins. Blue oval shapes are cell nuclei labeled by fluorescent Hoechst dye, which stains DNA. Nuclei without green fluorescent protein are cells that do not contain hepatitis B virus cccDNA. Credit: Lei Wei and Alexander Ploss, Princeton University

Researchers at Princeton University have identified a set of human proteins that the hepatitis B virus (HBV) uses to establish itself permanently inside liver cells. The study, published in the journal Nature Microbiology, could suggest new directions for therapies to treat chronic HBV infection, a condition that increases the risk of developing liver cancer and is responsible for almost 900,000 deaths worldwide each year.

Over 250 million people are chronically infected with HBV. The condition remains incurable and patients currently require lifelong treatment with antiviral drugs that still leave them at an increased risk of developing not only liver cancer but also other liver diseases, including liver cirrhosis.

When HBV first enters its host's liver cells, its DNA genome contains several gaps and other imperfections that need to be repaired before the virus can establish a permanent infection. To do this, HBV must enlist the help of its host cell's DNA repair machinery, but exactly which components of this machinery the virus needs has remained a mystery for decades.

To identify the components required to repair HBV DNA, Alexander Ploss, an associate professor of molecular biology at Princeton, and postdoctoral fellow Lei Wei recreated the process in a test tube. The researchers tested dozens of DNA repair factors and found that a set of just five factors purified from human cells was sufficient for the repair process. Removing even one of these five factors prevented the repair process from being successfully completed, suggesting that targeting any of these five factors can potentially prevent HBV infection.

One of the essential repair factors, an enzyme known as DNA polymerase delta, is inhibited by a drug called aphidicolin. Wei and Ploss found that aphidicolin treatment can prevent the repair of HBV DNA, not only in the test tube but also in virally infected liver cells.

Ploss hopes that further studies will reveal exactly how the five repair factors work together to fix the HBV genome. "Our study is an excellent starting point to finally answer the decades-old question of how the stable form of the virus's DNA is generated," Ploss said. "Until we understand this process, which is crucial for HBV persistence, targeted clinical therapies that can completely clear the infection will remain out of reach."
More information: Core components of DNA lagging strand synthesis machinery are essential for hepatitis B virus cccDNA formation, Nature Microbiology (2020). DOI: 10.1038/s41564-020-0678-0 , https://nature.com/articles/s41564-020-0678-0

StephenW

研究人员确定了慢性乙型肝炎感染必不可少的因素

普林斯顿大学
携带修饰的乙型肝炎病毒cccDNA的人肝癌细胞被绿色荧光蛋白标记。蓝色椭圆形是被荧光Hoechst染料标记的细胞核，可以染色DNA。没有绿色荧光蛋白的核是不包含乙型肝炎病毒cccDNA的细胞。图片来源：普林斯顿大学雷威和亚历山大·普拉斯（Alexander Ploss）

普林斯顿大学的研究人员已经鉴定出一组人类蛋白质，乙型肝炎病毒（HBV）可用于在肝细胞中永久建立自身的蛋白质。这项发表在《自然微生物学》杂志上的研究可能会为治疗慢性乙肝病毒感染提供新的治疗方向，这种疾病会增加患肝癌的风险，并且每年导致全球近90万人死亡。

超过2.5亿人长期感染HBV。该病仍然无法治愈，患者目前需要使用抗病毒药物进行终生治疗，这不仅使他们面临罹患肝癌和包括肝硬化在内的其他肝脏疾病的风险增加。

当HBV首次进入其宿主的肝细胞时，其DNA基因组包含多个缺口和其他缺陷，在病毒能够建立永久性感染之前需要对其进行修复。为此，HBV必须借助其宿主细胞的DNA修复机制，但数十年来，该病毒确切需要该机制的哪些组件仍是一个谜。

为了确定修复HBV DNA所需的成分，普林斯顿大学分子生物学副教授Alexander Ploss和博士后研究员Lei Wei在试管中重新创建了该过程。研究人员测试了数十种DNA修复因子，发现从人细胞中纯化出的仅五种因子就足以完成修复过程。即使除去这五个因素之一，也无法成功完成修复过程，这表明针对这五个因素中的任何一个都可以潜在地预防HBV感染。

一种基本的修复因子，一种称为DNA聚合酶δ的酶，被一种被称为蚜虫的药物抑制。 Wei和Ploss发现，蚜虫毒素治疗不仅可以在试管中而且可以在病毒感染的肝细胞中阻止HBV DNA的修复。

Ploss希望进一步的研究将准确揭示出五个修复因子如何共同作用以修复HBV基因组。普洛斯说：“我们的研究是一个很好的起点，可以最终回答几十年来有关如何稳定生成病毒DNA的问题。” “直到我们了解这一对HBV持久性至关重要的过程，才能完全清除感染的靶向临床疗法仍遥不可及。”
更多信息：DNA落后链合成机器的核心成分对于乙型肝炎病毒cccDNA的形成至关重要，《自然微生物学》（2020年）。 DOI：10.1038 / s41564-020-0678-0，https://nature.com/articles/s41564-020-0678-0