Department of Microbiology, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan; Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan; Department of Internal Medicine, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan.
Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan; Department of Internal Medicine, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan; Hepatitis Research Center, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan; Department of Medical Research, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan.
Virus Res. 2018 Jan 15;244:304-310. doi: 10.1016/j.virusres.2017.06.010. Epub 2017 Jun 13.
Current antiviral therapy fails to cure chronic hepatitis B virus (HBV) infection, primarily because of the persistence of covalently closed circular DNA (cccDNA). Although nucleos(t)ide analogues (NAs) can inhibit the reverse transcriptase of HBV and suppress its replication to levels below the detection limit, viremia often rebounds after cessation of therapy. Nuclear cccDNA serves as the HBV replicative template and exhibits extraordinary stability, and is not affected by NAs. Therefore, curing chronic hepatitis B (CHB) requires novel therapy for purging cccDNA from patients. The CRISPR/Cas9 system is a newly developed programmable genome-editing tool and allows for sequence-specific cleavage of DNA. Compared to other genome-editing tools, the CRIPSR/Cas9 system is advantageous for its simplicity and flexibility of design. Theoretically, Cas9 can be redirected to specifically cleave any desired genome sequences simply by designing guide RNAs with about 20 nucleotides that match the particular sequences of genomes with downstream protospacer adjacent motifs. Recently, it has been demonstrated that the CRIPSR/Cas9 system can specifically destruct HBV genomes in vitro and in vivo. Although promising, the CRISPR/Cas9 system faces several challenges that need to be overcome for the clinical application, namely, off-target cleavage and the in vivo delivery efficiency. Cutting integrated HBV genomes by CRISPR/Cas9 also raises serious concern because this has the risk of genome instability. In summary, the CRISPR/Cas9 system bears the potential for curing CHB as long as several challenging issues can be successfully solved.
目前的抗病毒疗法无法治愈慢性乙型肝炎病毒 (HBV) 感染，主要是因为共价闭合环状 DNA (cccDNA) 的持续存在。尽管核苷酸类似物 (NAs) 可以抑制 HBV 的逆转录酶并将其复制抑制到检测限以下，但在停止治疗后病毒血症往往会反弹。核 cccDNA 是 HBV 的复制模板，具有非凡的稳定性，不受 NAs 的影响。因此，治愈慢性乙型肝炎 (CHB) 需要新的疗法来清除患者体内的 cccDNA。CRISPR/Cas9 系统是一种新开发的可编程基因组编辑工具，可以对 DNA 进行序列特异性切割。与其他基因组编辑工具相比，CRISPR/Cas9 系统具有设计简单、灵活的优势。理论上，通过设计与基因组特定序列匹配的约 20 个核苷酸的向导 RNA，Cas9 可以被重新定向到特定的切割任何所需的基因组序列。最近，已经证明 CRISPR/Cas9 系统可以在体外和体内特异性破坏 HBV 基因组。尽管前景广阔，但 CRISPR/Cas9 系统在临床应用中还面临着几个需要克服的挑战，即脱靶切割和体内递送效率。CRISPR/Cas9 通过切割整合的 HBV 基因组也引起了严重的关注，因为这有基因组不稳定的风险。总之，只要能够成功解决几个具有挑战性的问题，CRISPR/Cas9 系统就有可能治愈 CHB。
