Functional comparison of two full-length genomes of hepatitis B virus strains isolated from two chronic hepatitis B patients.
For studying the characterisitcs of gemomic structures, replication and antigen expression of hepatitis B virus (HBV) strains, the full-length HBV genomes from sera of two chronic hepatitis B patients with high level of serum HBV DNA (10 14 and 10 13 copies/ml respectively) were separately cloned. The full-length genomes of the two HBV strains were sequenced and used to transfect HepG2 cells separately. The HBsAg expressed in the supernatant of transfected HepG2 cells was similar between the two strains, but the level of HBeAg of strain #56 was three times higher than that of strain #2-18 Replication efficiency of HBV strain #56 was significantly higher than that of strain #2-18 detected by Southern blot and hybridization anlaysis of intracelluar viral particles and extracellular replicative intermediates. Both genomes were 3215 nucleotides in length, belonged to genotype B (adw subtype), and were of 98.7% homology. The 42 diverse nucleotides distributed in the C, Pre-S1, Pre-S2, P and X genes and in Sp I, SpII, Xp and ENH I regulatory regions. Since HBV strain #56 had a point mutation at Pre-S2 initial codon (from ATG to GTG), the major protein translated from Pre-S1 contained partial amino acids of Pre-S2, therefore serum sample #56 and the supernatant of transfected HepG2 cells reacted positively with the Pre-S2 antibodies.