Host Factors DDB2 and DNA Polymerase Delta Are Linked to cccDNA Persistence in Hepatitis B Virus and Occult Hepatitis B Virus-Related Hepatocellular Carcinoma.

Covalently closed circular DNA (cccDNA), a stable episomal form of the hepatitis B virus (HBV) genome, functions as the transcriptional template for viral replication and persistence, posing a major barrier to HBV cure. While host DNA repair factors such as DDB2 and DNA polymerase delta (Pol δ) have been involved in cccDNA regulation in vitro, clinical validation remains limited. This study investigated the role of DDB2 and Pol δ in cccDNA maintenance using HBV-infected cell models and liver tissues from patients with HBV-related and occult HBV infection (OBI)-associated hepatocellular carcinoma (HCC). HepG2-NTCP cells infected with HBV were transfected with siRNAs targeting DDB2 or Pol δ, followed by quantification of intracellular cccDNA using droplet digital PCR (ddPCR). In liver tissues from HBV-HCC and OBI-HCC patients, the expression of DDB2 and Pol δ was assessed, while intrahepatic HBV DNA and cccDNA were measured by qPCR and ddPCR. Serum HBcrAg levels were evaluated using the iTACT-HBcrAg assay. Knockdown of DDB2 and Pol δ significantly reduced intracellular cccDNA levels (p = 0.010 and p = 0.006, respectively). In patient tissues, intrahepatic HBV DNA and cccDNA were markedly lower in OBI-HCC compared to HBV-HCC, despite comparable DDB2 and Pol δ expression. HBcrAg was detectable in 91.3% of HBV-HCC versus only 23.8% of OBI-HCC cases (p < 0.001). DDB2 expression correlated with intrahepatic viral markers in both groups and with HBcrAg only in HBV-HCC. These findings suggest that DDB2 is involved in cccDNA persistence and represents potential therapeutic targets for both overt and occult HBV-related HCC.