Distribution of Hepatitis B Virus Nuclear DNA.

Area of Science:

• Hepatology
• Virology
• Molecular Biology

Background:

• Chronic hepatitis B virus (HBV) infection impacts over 300 million individuals globally, posing a significant risk for hepatocellular carcinoma.
• Persistence of HBV is attributed to covalently closed circular DNA (cccDNA) within infected hepatocytes, even with antiviral treatments.
• Limited understanding exists regarding cccDNA formation, stability, and fate during host cell division.

Purpose of the Study:

• To develop and validate a fluorescence imaging in situ hybridization (FISH)-based assay for detecting duck hepatitis B virus (DHBV) and HBV cccDNA in cell lines.
• To investigate the distribution and stability of nuclear HBV DNA under conditions simulating chronic infection and antiviral therapy.
• To elucidate the fate of cccDNA during cell division, a critical aspect for understanding viral persistence.

Main Methods:

• Development of a novel FISH assay for visualizing DHBV and HBV cccDNA within cell nuclei.
• Application of the FISH assay to infected cell lines under simulated chronic infection and antiviral treatment conditions.
• Quantification of viral nuclear DNA copy numbers and assessment of its distribution during cell division.

Main Results:

• The FISH assay successfully detected and quantified DHBV and HBV cccDNA in cell lines.
• Significant variability (up to 1.8 orders of magnitude) in nuclear viral DNA copy numbers was observed among individual cells.
• Antiviral therapy resulted in a reduction of nuclear viral DNA, consistent with symmetrical segregation into daughter cells.

Conclusions:

• The developed FISH assay provides novel insights into the intracellular dynamics of HBV cccDNA.
• Understanding cccDNA fate during cell division and antiviral treatment is crucial for designing curative therapies for chronic hepatitis B.
• This study offers the first direct visualization of cccDNA behavior under therapeutic conditions, paving the way for future research.