Intrahepatic levels and replicative activity of covalently closed circular hepatitis B virus DNA in chronically infected patients

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Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) is responsible for viral persistence in the natural course of chronic HBV infection and during prolonged antiviral therapy and serves as the template for the production of HBV pregenomic RNA (pgRNA), the primary step in HBV replication. In this study, we have developed and applied sensitive and specific quantitative real-time polymerase chain reaction (PCR) assays for the measurement of intrahepatic concentration, pgRNA production, and replicative activity of cccDNA in liver biopsy samples from 34 non-treated patients with chronic hepatitis B (CHB); 12 hepatitis B e antigen (HBeAg)(+) and 22 HBeAg(−). Median copy number for cccDNA was 1.5 per cell and for pgRNA significantly higher, 6.5 copies per cell, with a good correlation between cccDNA and pgRNA levels in all samples. In HBeAg(−) patients, median values of cccDNA and pgRNA levels were 10-fold and 200-fold lower than in HBeAg(+), respectively, reflecting the differences in viral activity and clinical characteristics of the two groups. Furthermore, the replicative activity of intrahepatic cccDNA was significantly lower in HBeAg(−) patients harboring mutant HBV strains than in HBeAg(+) patients: median 3.5 versus 101 pgRNA copies per cccDNA molecule.In conclusion, the levels of both HBV cccDNA, a marker of HBV persistence, and pgRNA, an indicator of viral replication, in the liver of chronically infected patients correlate with viral activity and the phase of HBV infection. The combined measurement of cccDNA and pgRNA levels provides valuable information on the presence and replicative activity of intrahepatic HBV cccDNA.

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