Effects of Hepatitis B Virus quasispecies and reverse Transcriptase variants on treatment responsiveness to entecavir

Abstract

Background and Aims: Entecavir therapy reduces hepatitis B virus (HBV) DNA to an undetectable level in around 60–80% of patients after 1 year of treatment, but HBV DNA may remain detectable in the remaining patients. We aimed to determine whether baseline HBV reverse transcriptase (rt) sequence polymorphisms and quasispecies complexity and diversity are associated with the differences in treatment response.

Methods: Pre-treatment HBV rt sequence from 305 entecavir-treated patients were determined by DNA sequencing. Sequencing data were associated with their virological outcome, as defined by optimal response (undetectable HBV DNA at year 1) or partial response (HBV DNA >60 copies/mL). Quasispecies complexity and diversity were determined using MEGA 5.0 software.

Results: Seventeen rt variants were more frequently detected in the partial responders (n = 64; 21%) than in the optimal responders (all P <0.05). Multivariate analysis revealed that high baseline HBV DNA, hepatitis B e antigen (HBeAg)-positivity and rt124N were associated with partial entecavir response. Compared with the partial responders, the optimal responders had a higher quasispecies complexity at nucleotide and amino acid levels (P = 0.036 and 0.087, respectively) and higher quasispecies diversity, as reflected by a greater genetic distance at both nucleotide and amino acid levels (P = 0.019 and 0.032, respectively) and a greater number of synonymous substitutions per synonymous site (dS; P = 0.015) and number of non-synonymous substitutions per non-synonymous site (dN; P = 0.039).

Conclusions: High baseline HBV DNA, HBeAg-positivity and rt124N were associated with partial entecavir response at year 1. Baseline HBV quasispecies complexity and diversity were higher in the optimal responders than in the partial responders.