Result of Southern blot. Figure showed various intermediates of HBV DNA such as ssDNA (single strand DNA) and rcDNA (relaxed circular DNA) in liver biopsies from two of the chronically HBV-infected tree shrews collected at different time points after inoculation. The amount of HBV replication intermediates in tree shrew no. 98-2 showed a growing trend with time, though the form of HBV cccDNA (covalently closed circular DNA) was not confirmed well. M: Linear markers. 1: Liver samples of animal no. 90-1 collected at the 18th-week after inoculation. 2-4: Liver samples of animal no. 98-2 collected at the 12th-, 24th- and 36th-week after inoculation, respectively. 5: ssDNA, obtained by denaturing HBV rcDNA at 95°C for 5 min. 6: rcDNA, extracted from HBV-patient’s serum. 7: cccDNA size marker, a circular plasmid with 3.2 kb.