CRISPR-mediated genome editing for HBV Cure: the promise and challenge

Current antiviral therapy fails to cure chronic hepatitis B. Persistence of HBV cccDNA under antiviral therapy forms the major barrier to eradication of HBV infection. CRISPR-mediated genome editing has emerged as a promising therapeutic approach to specifically disrupt persistent cccDNA, holding promise for HBV cure. Previous studies including ours have shown that the CRISPR-Cas system could specifically cleave HBV genome. However, CRISPR-mediated cleavage of HBV cccDNA inevitably causes collateral damage of integrated HBV DNA, resulting in host DNA double-strand break (DSB) and genome instability. Newly developed CRISPR-derived base editors (BEs), which fuse a catalytically disabled nuclease with a nucleobase deaminase enzyme, can introduce irreversible point mutations of target DNAs without DSBs. We thus utilized CRISPR-derived BEs to introduce premature stop codons to both HBV integrated DNA and cccDNA, demonstrating its ability in permanent inactivation of HBV genome without damaging host DNA. Although promising, CRISRP-mediated base editing still faces some challenges before its clinical application, including the base-editing efficacy, the off-target effect, and in vivo delivery efficiency. Several strategies have been adopted to optimize the efficiency and specificity of CRISPR-BEs and to improve in vivo delivery efficacy through novel viral and non-viral delivery approaches. Particularly, the non-viral delivery of Cas mRNA and ribonucleoprotein by lipid nanoparticles (LNPs) exhibits attractive potential for liver-targeted delivery in clinical. To summarize, the optimized CRISPR-mediated BEs combined with LNPs may be a promising therapeutic strategy for HBV cure.