OBJECTIVETo study the quasispecies and mutation features of hepatitis B virus polymerase (HBV P) gene in chronic hepatitis B patients before and after lamivudine treatment.

METHODSThe HBV P gene was amplificated with PCR and cloned, then single strand conformation polymorphism / heteroduplex analysis (SSCP/HDA) was applied to analyze the quasispecies complexity and mutation characters of HBV P gene.

RESULTSThe quasispecies number of HBV P gene before treatment was larger than that after treatment (7 to 14 vs. 4 to 8, t = 3.98, P < 0.05). Six patients had one or two predominant quasispecies before therapy, but the percentages of predominant quasispecies were lower than those after therapy (33.3% to 81.8% vs. 78.8% to 90.9%, t = 3.42, P < 0.05). By sequencing the predominant clones, there were 2 patients with M550V/L528M mutation, 3 patients with M550I mutation and 1 patient with wild type after lamivudine therapy. Additionally, there were individualization mutations which had no obvious tender.

CONCLUSIONQuasispecies of hepatitis B virus are changed under the selection of lamivudine, meanwhile, the mutation at YMDD motif emerges.