Objective: To investigate the HBV quasispecies groups in the patients with chronic HBV infection.
Methods: Specific primers ware synthesized according to HBV strain found in China, the preC/C gene, reverse transcriptase region, whole S region, X gene and whole genome ware amplified by PCR method from the serum of 18 patients with chronic HBV infection, and then the PCR products were subcloned into pGEM Teasy vectors. Positive clones with target sequences were selected out for sequencing. Sequence comparison of the selected clones ware made to find the difference.
Results: The homology between clones from one patient of preC/C gene, reverse transcriptase of polymerase region, whole S region, X gene and whole genome are 98.0% approximately 99.1%, 98.7% approximately 99.3%, 97.5% approximately 100%, 93.0% approximately 98.2% and 96.6% approximately 97.5%, respectively. There was a high-frequency A83 substitution and core antigen internal deletion (CID) in preC/C region. Substitution, deletion and frame-shift by insertion or deletion of short sequence were found in 4 open reading frames. Deletion in X gene (Core promoter, CP) will not only result in the polymorphism of X protein at the carboxyl end, but also regulate the expression of HBeAg. Coding sequence of truncated middle surface antigen and defective HBV genome could also be detected in this study.
Conclusion: There are HBV quasispecies groups in patients with chronic HBV infection. Hot deletion region in X region (CP) will influence the prognosis of the HBV infection. Individually characterized substitutions in amino acid sequence of viral protein is worthy of further study.