Quasispecies groups in the core promoter region of hepatitis B virus

Objectives: To investigate the mutation of the basiccore promoter (BCP) of hepatitis B virus (HBV)and clarify the significance of HBV quasispeciesgroups in patients with chronic HBV infection.Methods: A set of specific primers was synthesizedaccording to the HBV DNA sequence of a Chinesestrain. The BCP was amplified by PCR method fromthe serum of 40 patients with chronic HBV infection,and the PCR products of 2 patients were subclonedinto pGEM Teasy vectors. Polyacrylamide gel elec-trophoresis (PAGE) was employed to display the de-letion mutations, and clones with differential lengthwere selected to be sequenced. Sequence comparisonwas made to find the difference.Results: Two or three bands were displayed byPAGE in 60% patients. The results of sequence anal-ysis showed that there are some kinds of mutations inthe BCP region. The substitution always occurs inTATA-like boxes, especially from T to C on 140 site.The deletion mutations were detected in TA1, TA2and TA3. The 8bp, 20bp deletion mutations fre-quently happened.Conclusions: There is a hot deletion region in theBCP. The deletion and the substitution in the TATA-like box may influence the expression of preC/C pro-tein. The sequencing results indicate that there areHBV quasispecies groups in patients with chronicHBV infection.