Slattery, S.; Huo, W.; Arif, A.; Gordon, J.; Takeuchi, R.

Gene editing technologies have opened the possibility of directly targeting viral DNA in therapeutic applications. In chronically infected hepatocytes with hepatitis B virus (HBV), covalently closed circular DNA (cccDNA) serves as the master template for viral transcripts and gene products. In the present study, we evaluated the outcomes of anti-HBV multiplex gene editing with the CRISPR-Cas9 endonuclease from Staphylococcus aureus (SaCas9) using primary human hepatocytes (PHHs) and HBV mouse models. Nonviral delivery of SaCas9-encoding mRNA and a pair of HBV-targeting guide RNAs (gRNAs) substantially reduced viral biomarkers and intrahepatic HBV DNA copies in vitro and in vivo, suggesting that fragmentation of HBV DNA primarily leads to its degradation. Hybridization capture sequencing analyses indicated that small insertions and deletions (indels) and structural variants including excisions and inversions of the viral sequences were accumulated in the residual HBV DNA. These assays also demonstrated that transient expression of the HBV-targeting SaCas9 significantly suppressed random integration of HBV DNA, while this therapeutic approach was unlikely to affect chromosomal translocations involving viral copies. Taken together, our results suggest that anti-HBV multiplex gene editing eliminates viral DNA from chronically infected hepatocytes, potentially reducing the risk of hepatocarcinogenesis associated with HBV DNA integration.