Dynamics of hepatitis B virus resistance to lamivudine

Abstract

Lamivudine was the first approved inhibitor of hepatitis B virus (HBV) reverse transcriptase (RT). Lamivudine resistance develops in 53% to 76% of patients after 3 years of treatment. We extensively characterized the dynamics of HBV quasispecies variant populations in four HBV-infected patients who developed lamivudine resistance. Virological breakthrough was preceded by 2 to 4 months by the emergence of quasispecies variants bearing amino acid substitutions at RT position 204, i.e., within the YMDD catalytic motif (rtM204V/I). Three patients had a gradual switch from a YMDD variant population at baseline to a 100% lamivudine-resistant variant population, whereas the remaining patient had a fluctuating pattern of resistance variant dynamics. Careful analysis of amino acid substitutions located outside domain C of HBV RT, including those known to partially restore replication capacities in vitro, showed that the in vivo replication of HBV variants is driven by multiple forces, including intrinsic replicative advantages conferred by mutations accumulating outside domain C and the changing environment in which these variants replicate. Our findings also suggest that individual treatment optimization will require sensitive methods capable of detecting the emergence of viral resistance before the relevant variants acquire optimal replicative capacities.

FIG. 1.

Dynamics of serum HBV DNA levels, serum aminotransferase activities, and lamivudine-sensitive and -resistant HBV viral populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). For each patient, the dynamics of HBV DNA and aminotransferase levels are shown at the top, while the dynamics of HBV variants are shown at the bottom as respective proportions of lamivudine-sensitive and lamivudine-resistant variant populations within the viral quasispecies at each time point. The lamivudine treatment period is shown in gray. The patients continued to receive lamivudine after this study. Abbreviations: bDNA, branched DNA; ALT, alanine aminotransferase; AST, aspartate aminotransferase; M, month.

FIG. 1.

Dynamics of serum HBV DNA levels, serum aminotransferase activities, and lamivudine-sensitive and -resistant HBV viral populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). For each patient, the dynamics of HBV DNA and aminotransferase levels are shown at the top, while the dynamics of HBV variants are shown at the bottom as respective proportions of lamivudine-sensitive and lamivudine-resistant variant populations within the viral quasispecies at each time point. The lamivudine treatment period is shown in gray. The patients continued to receive lamivudine after this study. Abbreviations: bDNA, branched DNA; ALT, alanine aminotransferase; AST, aspartate aminotransferase; M, month.

FIG. 1.

Dynamics of serum HBV DNA levels, serum aminotransferase activities, and lamivudine-sensitive and -resistant HBV viral populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). For each patient, the dynamics of HBV DNA and aminotransferase levels are shown at the top, while the dynamics of HBV variants are shown at the bottom as respective proportions of lamivudine-sensitive and lamivudine-resistant variant populations within the viral quasispecies at each time point. The lamivudine treatment period is shown in gray. The patients continued to receive lamivudine after this study. Abbreviations: bDNA, branched DNA; ALT, alanine aminotransferase; AST, aspartate aminotransferase; M, month.

FIG. 1.

Dynamics of serum HBV DNA levels, serum aminotransferase activities, and lamivudine-sensitive and -resistant HBV viral populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). For each patient, the dynamics of HBV DNA and aminotransferase levels are shown at the top, while the dynamics of HBV variants are shown at the bottom as respective proportions of lamivudine-sensitive and lamivudine-resistant variant populations within the viral quasispecies at each time point. The lamivudine treatment period is shown in gray. The patients continued to receive lamivudine after this study. Abbreviations: bDNA, branched DNA; ALT, alanine aminotransferase; AST, aspartate aminotransferase; M, month.

FIG. 2.

Dynamics of HBV variant populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). This figure illustrates the respective losses and gains of in vivo fitness by the different HBV populations over time, relative to treatment outset and virological breakthroughs. M, month.

FIG. 2.

Dynamics of HBV variant populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). This figure illustrates the respective losses and gains of in vivo fitness by the different HBV populations over time, relative to treatment outset and virological breakthroughs. M, month.

FIG. 2.

Dynamics of HBV variant populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). This figure illustrates the respective losses and gains of in vivo fitness by the different HBV populations over time, relative to treatment outset and virological breakthroughs. M, month.

FIG. 2.

Dynamics of HBV variant populations before and during lamivudine therapy in patients A to D (panels A, B, C, and D, respectively). This figure illustrates the respective losses and gains of in vivo fitness by the different HBV populations over time, relative to treatment outset and virological breakthroughs. M, month.

FIG. 3.

Distribution of HBV RT quasispecies at different time points, showing successive switches in viral populations between months 16 and 24 in patient D. At each time point, the variant amino acid sequences are shown, in order of decreasing frequency, within each population of catalytic motif variants (sensitive YMDD variants and resistant variants rtM204V and rtM204I), with their relative proportions among the quasispecies (percentages to the left of each sequence). The functional domains of the HBV RT are highlighted, and the catalytic motif YMDD is shaded. The reference sequence is the most frequent variant sequence at baseline. wt, wild type.