dstet5 cells were left untreated (lanes 1 and 2) or treated with 10 μM lamivudine (LAM) (lanes 5 and 6), 100 U/ml chicken IFN-α (lanes 7 and 8) or combination of 10 μM lamivudine and 100 U/ml chichen IFN-α (lanes 9 and 10) in the absence of tet for 3 days. dstet5 cells cultured in the presence of tet (lanes 3 and 4) served as negative controls. DHBV RNA and core-associated DNA were analyzed by Northern or Southern Blot hybridization assays, respectively. For RNA analysis, ribosomal RNAs (28S and 18S rRNA) served as loading controls. The positions of DHBV pgRNA and subgenomic mRNA encoding viral envelope proteins (envRNA) are indicated. The RNA species accumulated in the cells treated with LAM are indicated as novel RNA. For core-associated DHBV DNA, the forms of relaxed circular (RC), double stranded linear (DSL) and single stranded (SS) DNA are indicated.