Wits/SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, South Africa.
Wits/SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, South Africa.
Adv Drug Deliv Rev. 2021 Jan;168:134-146. doi: 10.1016/j.addr.2020.05.010. Epub 2020 May 30.
Chronic infection with the hepatitis B virus (HBV) remains a significant worldwide medical problem. While diseases caused by HIV infection, tuberculosis and malaria are on the decline, new cases of chronic hepatitis B are on the rise. Because often fatal complications of cirrhosis and hepatocellular carcinoma are associated with chronic hepatitis B, the need for a cure is as urgent as ever. Currently licensed therapeutics fail to eradicate the virus and this is attributable to persistence of the viral replication intermediate comprising covalently closed circular DNA (cccDNA). Elimination or inactivation of the viral cccDNA is thus a goal of research aimed at hepatitis B cure. The ability to engineer nucleases that are capable of specific cleavage of a DNA sequence now provides the means to disable cccDNA permanently. The scientific literature is replete with many examples of using designer zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and RNA-guided endonucleases (RGENs) to inactivate HBV. However, important concerns about safety, dose control and efficient delivery need to be addressed before the technology is employed in a clinical setting. Use of in vitro transcribed mRNA to express therapeutic gene editors goes some way to overcoming these concerns. The labile nature of RNA limits off-target effects and enables dose control. Compatibility with hepatotropic non-viral vectors is convenient for the large scale preparation that will be required for advancing gene editing as a mode of curing chronic hepatitis B.
慢性乙型肝炎病毒（HBV）感染仍然是一个全球性的医学难题。虽然 HIV 感染、结核病和疟疾等疾病的发病率正在下降，但慢性乙型肝炎的新发病例却在上升。由于肝硬化和肝细胞癌等常常致命的并发症与慢性乙型肝炎有关，因此治愈该病的需求比以往任何时候都更加迫切。目前已获得许可的治疗方法无法彻底清除病毒，这是由于病毒复制中间体共价闭合环状 DNA（cccDNA）的持续存在。因此，消除或失活病毒的 cccDNA 是旨在实现乙型肝炎治愈的研究目标。能够对特定 DNA 序列进行特异性切割的工程核酸酶的出现为实现这一目标提供了手段。科学文献中有许多利用设计的锌指核酸酶（ZFNs）、转录激活因子样效应核酸酶（TALENs）和 RNA 指导的内切酶（RGENs）来灭活 HBV 的例子。然而，在将该技术应用于临床之前，需要解决关于安全性、剂量控制和有效传递等重要问题。使用体外转录的 mRNA 来表达治疗性基因编辑工具在一定程度上解决了这些问题。RNA 的不稳定性限制了脱靶效应，并实现了剂量控制。与嗜肝性非病毒载体的兼容性便于大规模制备，这对于将基因编辑作为治疗慢性乙型肝炎的一种模式非常重要。
