Objective: To investigate the mutation of the preS2 gene sequence of HBV and clarify the significance of HBV quasispecies groups in the patients with chronic HBV infection.
Methods: A set of specific primers were synthesized according to HBV DNA sequence of a Chinese strain. The preS2 gene region was amplified by PCR method from the sera of 51 patients with chronic HBV infection, and the PCR products from 5 patients were subcloned into pGEM Teasy vectors. Polyacrylamide gel electrophoresis (PAGE) was employed to display the deletion mutations, clones with differential length were selected and sequenced. Sequence comparison was made to find the difference.
Results: When analyzed by PAGE, 2 approximately 3 bands were displayed in the PCR products from 52.9% (27/51) patients. This phenomena of multiple bands in PAGE was detected in both HBeAg (36.1%) and anti-HBe (93.3%) positive patients, the difference between the 2 groups being statistically significant (P < 0.01). Analysis on deduced amino acid sequence showed the deletion mutations were in the N-terminal half of the preS2-encoded protein.
Conclusion: There is a hot deletion region in preS2 gene sequence. These deletion mutations were more frequently found in patients with both anti-HBe and HBV DNA positivity. The deletion may influence the recognition by neutralizing antibodies. Our results suggest that there are HBV quasispecies in patients with chronic HBV infection.