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Updated: Sep 25, 2025

Detection of Low Copy Number Integrated Viral DNA Formed by In Vitro Hepatitis B Infection
Published on: November 7, 2018
Novel hepatitis B virus reverse transcriptase mutations in patients with sustained viremia despite long-term
Anni Winckelmann1, Ulrik Fahnøe1, Priyanka Shukla Bajpai1
1Department of Infectious Diseases, Copenhagen University Hospital - Hvidovre, Copenhagen, Denmark; Copenhagen Hepatitis C Program (CO-HEP), Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Background:
Chronic hepatitis B virus (HBV) treatment consists of nucleos(t)ide analogues to suppress viral replication. The HBV inhibitor tenofovir has a high barrier to resistance, however, evidence of virus-escape is emerging. This study investigates HBV evolution in patients undergoing tenofovir treatment with the primary aim to assess the emergence of putative resistance mutations.
Methods:
HBV DNA was extracted from blood samples of two patients with HBeAg-positive chronic HBV infection and persistent viremia despite tenofovir treatment, and subsequently amplified by PCR before full-length HBV genomes were assembled by deep sequencing. The mutation linkage within the viral population was evaluated by clonal analysis of amplicons.
Results:
Sequence analysis of HBV, derived from 11 samples collected 2010-2020 from one patient, identified 12 non-synonymous single-nucleotide polymorphisms (SNPs) emerging during a tenofovir treatment interruption from 2014 to 2017. Two of the SNPs were in the reverse transcriptase (RT; H35Q and D263E). The two RT mutations were linked and persisted despite restarting tenofovir treatment in 2017. For the second patient, we analyzed HBV derived from six samples collected 2014-2020 following 10 years of tenofovir treatment, and identified five non-synonymous SNPs, that confer resistance towards entecavir and/or lamivudine. Two RT mutations (H35N and P237T) emerged during subsequent 5-year entecavir treatment. H35N was maintained during final tenofovir treatment.
Conclusions:
Our findings indicate that changes at the conserved residue 35 (H35N/Q) in the HBV RT may be associated with tenofovir resistance. These variants have not previously been described, and further studies are warranted to assess resistance in vitro and in vivo.
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