Rapid and Reliable Protein-Free HBV DNA Extraction and Sensitive Branched DNA Southern Blot Assay.

HBV covalently closed circular DNA (cccDNA) plays an important role in the persistence of hepatitis B virus (HBV) infection by serving as the template for transcription of viral RNAs. To cure HBV infection, it is expected that cccDNA needs either to be eliminated or silenced. Hence, precise cccDNA quantification is essential. Sample preparation is crucial to specifically detect cccDNA. Southern blot is regarded as the "gold standard" for specific cccDNA detection but lacks sensitivity. Here, we describe a rapid and reliable modified kit-based, HBV protein-free DNA extraction method as well as a novel enhanced sensitivity Southern blot that uses branched DNA technology to detect HBV DNA in cell culture and liver tissue samples. It is useful for both HBV molecular biology and antiviral research.