Disrupting Viral Persistence: CRISPR/Cas9-Based Strategies for Hepatitis B and C Treatment, and Challenges.

Hepatitis B and C viruses (HBV and HCV) remain among the leading causes of liver disease worldwide. Current antiviral drugs, such as nucleotide analogues (NAs), can reduce the replication of new HBV and HCV infections but cannot completely eliminate chronic infections. This is primarily because a stable form of viral DNA, known as covalently closed circular DNA (cccDNA), persists in liver cells and continues to sustain the infection. In recent years, the CRISPR/Cas9 gene-editing system has emerged as a powerful tool for precisely cutting and inactivating specific DNA sequences. Due to its efficiency and ease of use, researchers have applied CRISPR/Cas9 in numerous studies to directly target and disrupt the HBV genome, demonstrating promising antiviral effects in both cell cultures and animal models. Targeting multiple sites within the HBV genome has been shown to further enhance its effectiveness, paving the way for potential combination therapies aimed at disabling both cccDNA and HBV and HCV DNA integrated into the host genome. Despite its potential, CRISPR/Cas9 still faces significant challenges before clinical application, most notably the risk of off-target effects-unintended cleavage of non-target DNA sequences-and the difficulty of delivering the system efficiently into liver cells in vivo. Future progress will depend on improving the tool's precision, efficiency, flexibility and delivery methods. In this review, we explore recent advances in designing guide RNAs (gRNAs) for targeting HBV and HCV, as well as the delivery systems used to transport CRISPR/Cas9 into cells. We also discuss the remaining challenges and potential strategies for advancing CRISPR/Cas9 from the laboratory toward a viable clinical cure for HBV and HCV.