IL-6 decreases the formation of HBV cccDNA. Confluent cells (day0) were treated with or without 20 ng/ml of IL-6 for 4 days (day4) or 6 days (day6) and subjected to Hirt extraction to prepare HBV cccDNA. The Hirt extract was thermally denatured at 85°C for 5 min, digested with EcoRI and analyzed by Southern blotting using an HBV-specific probe. Bands corresponding to HBV cccDNA and HBV single-stranded DNA (SS) are indicated. The signals were quantified by densitometry analysis and expressed as percentage of the control cells to indicate the IL-6 effect on the accumulation of HBV cccDNA.