Early dynamic changes of quasispecies in the reverse transcriptase region of hepatitis B virus in telbivudine treatment.

Background: Telbivudine (LdT) - a synthetic thymidine β-L-nucleoside analogue (NA) - is an effective inhibitor for hepatitis B virus (HBV) replication. The quasispecies spectra in the reverse transcriptase (RT) region of the HBV genome and their dynamic changes associated with LdT treatment remains largely unknown.

Methods: We prospectively recruited a total of 21 treatment-naive patients with chronic HBV infection and collected sequential serum samples at five time points (baseline, weeks 1, 3, 12, and 24 after LdT treatment). The HBV RT region was amplified and shotgun-sequenced by the Ion Torrent Personal Genome Machine (PGM)® system. We reconstructed full-length haplotypes of the RT region using an integrated bioinformatics framework, including de novo contig assembly and full-length haplotype reconstruction. In addition, we investigated the quasispecies' dynamic changes and evolution history and characterized potential NAs resistant mutations over the treatment course.

Results: Viral quasispecies differed obviously between patients with complete (n = 8) and incomplete/no response (n = 13) at 12 weeks after LdT treatment. A reduced d/d ratio in quasispecies demonstrated a selective constraint resulting from antiviral therapy. The temporal clustering of sequential quasispecies showed different patterns along with a 24-week observation, although its statistic did not differ significantly. Several patients harboring pre-existing resistant mutations showed different clinical responses, while NAs resistant mutations were rare within a short-term treatment.

Conclusion: A complete profile of quasispecies reconstructed from in-depth shotgun sequencing may has important implications for enhancing clinical decision in adjusting antiviral therapy timely.