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Keywords:

  • hepatitis B virus;
  • liver failure;
  • molecular evolution;
  • mutation;
  • quasispecies

Abstract

Background and Aim

The cause of hepatitis B virus associated acute-on-chronic liver failure (ACLF) remains unclear. Quasispecies can contribute to virus persistence and pathogenesis. We used a bioinformatics-based molecular evolution approach to compare quasispecies characteristics and positive selection sites within HBV precore/core gene between ACLF and chronic hepatitis B (CHB) patients.

Methods

HBV precore/core gene were amplified from 11 ACLF and 10 CHB patients harboring HBV genotype B; following DNA cloning and sequencing quasispecies complexity, diversity, and positive selection sites within the precore/core gene were determined by bioinformatics analysis, and compared between the patient groups.

Results

Both quasispecies complexity (P = 0.022 at nucleotide level and 0.008 at amino acid level) and diversity (P < 0.05) were found to be significantly greater in ACLF than in CHB. The frequency of G1896/A mutation in ACLF (175/298 clones, 58.7%) was also significantly higher than in CHB (100/230 clones, 43.5%) (P = 0.0005). Moreover, analysis of positive selection revealed that significantly more patients with such sites were present in ACLF than in CHB (8/11 VS 2/10, P = 0.03); the majority of these positive selection sites lay within HLA-restricted epitopes.

Conclusions

The ACLF patients showed distinct quasispecies characteristics with higher complexity and diversity within the HBV precore/core gene. The increased HBV quasispecies complexity and diversity, together with a distinct set of positive selection sites, is likely associated with the development of ACLF.