基因人性化的老鼠可以加强对抗攻击性肝炎的斗争

StephenW

Genetically humanized mice could boost fight against aggressive hepatitis
June 27, 2018, Princeton University

Hepatitis delta virus (HDV) causes the most aggressive form of viral hepatitis in humans, putting at least 20 million people worldwide at risk of developing liver fibrosis, cirrhosis, and liver cancer. Efforts to develop effective treatments against HDV have been hampered by the fact that laboratory mice are not susceptible to the virus. But, in a study published June 27, 2018, in the journal Science Translational Medicine, Alexander Ploss and colleagues describe a genetically humanized mouse that can be persistently infected with HDV.

HDV is a small, RNA-based "satellite" virus that produces just a single protein of its own and therefore requires additional proteins provided by another liver virus, hepatitis B virus (HBV). HDV can infect patients already carrying HBV, or both viruses can infect patients simultaneously. Though infections can be prevented with an anti-HBV vaccine, there are no antiviral therapies available to cure existing HDV infections.

HDV and HBV infect the liver by binding to a protein called NTCP that is present on the surface of liver cells. But the viruses only recognize the version of NTCP present in humans and a few other primates, and therefore can't infect mice or other small mammals that produce their own versions of NTCP. This has made it difficult to study HBV and HDV infections in the laboratory. Researchers have tried transplanting human liver cells into immunocompromised mice before infecting them with virus, but this approach has produced inconsistent results and is both expensive and time-consuming.

Ploss and colleagues, led by graduate student Benjamin Winer, took a different approach. They generated mice that express the human NTCP protein in their liver cells, allowing these cells to be infected by HBV and HDV.

In these mice, HBV failed to replicate after entering mouse liver cells but HDV was able to establish persistent infection when provided with the HBV proteins it needs to propagate. For example, mice genetically engineered to produce both human NTCP and the entire HBV genome could be infected with HDV for up to 14 days. "To our knowledge, this is the first time the entire HDV life cycle has been recapitulated in a mouse model with inheritable susceptibility to HDV," Ploss said.

The mice were able to rid themselves of HDV before they developed any liver damage, apparently by mounting an immune response involving antiviral interferon proteins and various white blood cell types, including Natural Killer (NK) cells and T cells. Accordingly, mice expressing human NTCP and the HBV genome, but lacking functional B, T, and NK cells could be infected with HDV for two months or more.

These immunocompromised animals allowed Ploss and colleagues to test the effectiveness of two drugs that are currently being developed as treatments for HDV infection. Both drugs—either alone or in combination—suppressed the levels of HDV in immunocompromised mice after viral infection. But the drugs were not able to completely clear the mice of HDV; viral levels rose again within weeks of stopping treatment.

"This is largely in line with recently reported data from clinical trials, showing the utility of our model for preclinical antiviral drug testing," Winer said.

"Our model is amenable to genetic manipulations, robust, and can be adopted as a method to rapidly screen for potential treatments," Ploss added.

Timothy M. Block, president of the Hepatitis B Foundation and its Baruch S. Blumberg Institute, who was not involved in the study, said "These systems should be able to provide practical, and presumably economical tools. Their work is urgently needed, and a desperate community welcomes it. I emphasize that it is often the new methods in science that revolutionize a field such as drug discovery, almost as much as the new drugs themselves."


More information: B.Y. Winer el al., "Preclinical assessment of antiviral combination therapy in a genetically humanized mouse model for hepatitis delta virus infection," Science Translational Medicine (2018). stm.sciencemag.org/lookup/doi/ … scitranslmed.aap9328

Journal reference: Science Translational Medicine search and more info website

Provided by: Princeton University search and more info website

StephenW

基因人性化的老鼠可以加强对抗攻击性肝炎的斗争
2018年6月27日，普林斯顿大学

肝炎三角洲病毒（HDV）引起人类最具侵袭性的病毒性肝炎，使全球至少有2000万人患上肝纤维化，肝硬化和肝癌。努力开发针对病毒影响的有效治疗方法。但是，在一篇发表于2018年6月27日的科学转化医学期刊中，Alexander Ploss及其同事描述了一种可持续感染HDV的遗传人源化小鼠。

HDV是一种小型的基于RNA的“卫星”病毒，可以产生单一病毒乙型肝炎病毒（HBV）。 HDV可以感染已经携带HBV的患者，或者两种病毒都可以同时感染患者。虽然用抗HBV疫苗可以预防感染，但没有抗病毒治疗可用于治愈现有的HDV感染。

HDV和HBV，其通过存在于肝细胞表面上的称为NTCP的蛋白质感染肝脏。但是病毒只能识别人类和其他一些灵长类动物中存在的NTCP版本，因此不能感染任何其他生产自己版本的NTCP的小型哺乳动物。这使得难以在实验室中研究HBV和HDV感染。研究人员已经尝试将人肝细胞移植到免疫受损小鼠中，然后用病毒感染它们，但这种方法产生了不一致的结果，既昂贵又耗时。

普罗斯和同事本杰明·温纳采取了另一种方法。它们产生在其肝细胞中表达人NTCP蛋白的小鼠，使这些细胞被HBV和HDV感染。

在这些小鼠中，HBV感染HDV蛋白后未能复制。例如，基因工程改造产生NTCP和整个HBV基因组的小鼠可能感染HDV长达14天。 “HDV生命周期已经在具有HDV固有易感性的小鼠模型中重演，”Ploss说。

用抗病毒干扰素蛋白和各种类型的血细胞（包括天然杀伤细胞（NK）细胞和T细胞）免疫免疫系统。因此，表达人NTCP和HBV基因组但缺乏功能性B，T和NK细胞的小鼠可能被HDV感染两个月或更长时间。

目前正在对这些免疫抑制动物进行HDV感染测试。病毒感染后，两种药物单独或组合抑制免疫受损小鼠中HDV的水平。但药物不能完全清除HDV的小鼠;停止治疗后数周内病毒水平再次上升。

“这主要是抗病毒药物测试，”维纳说。

“我们的模型适用于遗传操作，鲁棒性强，可作为潜在治疗的快速变化方法，”Ploss补充道。

没有参与这项研究的乙型肝炎基金会和其Baruch S. Blumberg研究所所长Timothy M. Block说：“这些系统应该能够提供切实可行的经济工具。我想说的是，科学领域的新方法，以及新的药物本身，往往是革命性的。“


更多信息：B.Y. Winer等人，“用于肝炎三角洲病毒感染的遗传人源化小鼠模型中的抗病毒组合疗法的临床前评估”，Science Translational Medicine（2018）。 stm.sciencemag.org/lookup/doi/ ... scitranslmed.aap9328

期刊参考：科学转化医学搜索和更多信息网站

由普林斯顿大学提供搜索和更多信息网站