Objectives: To investigate the mutation of the basic core promoter (BCP) of hepatitis B virus (HBV) and clarify the significance of HBV quasispecies groups in patients with chronic HBV infection.
Methods: A set of specific primers was synthesized according to the HBV DNA sequence of a Chinese strain. The BCP was amplified by PCR method from the serum of 40 patients with chronic HBV infection, and the PCR products of 2 patients were subcloned into pGEM Teasy vectors. Polyacrylamide gel electrophoresis (PAGE) was employed to display the deletion mutations, and clones with differential length were selected to be sequenced. Sequence comparison was made to find the difference.
Results: Two or three bands were displayed by PAGE in 60% patients. The results of sequence analysis showed that there are some kinds of mutations in the BCP region. The substitution always occurs in TATA-like boxes, especially from T to C on 140 site. The deletion mutations were detected in TA1, TA2 and TA3. The 8bp, 20bp deletion mutations frequently happened.
Conclusions: There is a hot deletion region in the BCP. The deletion and the substitution in the TATA-like box may influence the expression of preC/C protein. The sequencing results indicate that there are HBV quasispecies groups in patients with chronic HBV infection.