The impact of the hepatitis B virus polymerase rtA181T mutation on replication and drug resistance is potentially affected by overlapping changes in surface gene.
The emergence of drug-resistant hepatitis B virus (HBV) is a major problem for antiviral treatment in chronic hepatitis B infection. In this study, we analyzed the evolution of drug-resistant mutations and characterized the effects of the rtA181T and rtI233V mutations on viral replication and drug resistance. We performed a clonal analysis of the HBV polymerase gene from serum samples during viral breakthrough treated with antiviral agents. A series of mutant clones containing rtA181T and/or rtI233V mutations were constructed and determined the effect of these mutations on the replication ability and drug resistance. An in vitro study revealed that the effect of the rtA181T mutation on viral replication and drug resistance is dependent on the mutations in the overlapping surface gene. Compared to the rtA181T surface missense mutation (rtA181T/sW172S), the introduction of rtA181T surface nonsense mutation (rtA181T/sW172*) resulted in decreased viral replication and increased drug resistance. Complementation assay revealed that the truncated PreS1 is responsible for reduced replication of rtA181T/sW172* mutant. Moreover, the rtA181T/sW172* mutant exhibited a defect in viral particle secretion. The rtI233V mutation that emerged during adefovir therapy reduced viral replication and conferred resistance to adefovir. Our data suggest that the impact of the rtA181T mutation on replication and drug resistance differs based on the mutation status of the corresponding surface gene. The rtI233V mutation also affects replication ability and drug resistance. This observation suggests the need for genotypic analysis of overlapping surface genes to manage antiviral drug resistance if clinical isolates harbor the rtA181T mutation.


OBJECTIVE
The emergence of drug-resistant HBV that are no longer susceptible to nucleos(t)ide analogues is a major problem for antiviral treatment in chronic hepatitis B infection. Among drug-resistant mutations, the single rtA181T mutation is known to confer cross-resistance to antiviral drugs. This mutation causes intermediate or reduced susceptibility to tenofovir. Moreover, the clinical occurrence of the rtA181T mutation during antiviral therapy is also high. Our study revealed that the effect of the rtA181T mutation on viral replication and drug resistance is dependent on the mutations in the overlapping surface gene. This observation suggests the need for genotypic analysis of overlapping surface genes to manage antiviral drug resistance if clinical isolates harbor the rtA181T mutation. We believe that our study will not only extend the understanding of the drug resistance mechanism, but it will also ultimately provide new treatment options for patients with multidrug resistant HBV.
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea.
Sung Hyun
SH
Ahn
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea Institute of Functional Genomics, Konkuk University, Seoul, South Korea.
Yong Kwang
YK
Park
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea Institute of Functional Genomics, Konkuk University, Seoul, South Korea.
Eun-Sook
ES
Park
Department of Internal Medicine, Konkuk University School of Medicine, Seoul, South Korea.
Jeong Han
JH
Kim
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea.
Doo Hyun
DH
Kim
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea.
Keo-Heun
KH
Lim
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea.
Moon Sun
MS
Jang
Department of Internal Medicine, Konkuk University School of Medicine, Seoul, South Korea.
Won Hyeok
WH
Choe
Department of Internal Medicine, Konkuk University School of Medicine, Seoul, South Korea.
Soon Young
SY
Ko
Department of Internal Medicine, Konkuk University School of Medicine, Seoul, South Korea.
In-Kyung
IK
Sung
Department of Internal Medicine, Konkuk University School of Medicine, Seoul, South Korea.
So Young
SY
Kwon
Department of Pharmacology and Center for Cancer Research and Diagnostic Medicine, IBST, School of Medicine, Konkuk University, Seoul, South Korea Institute of Functional Genomics, Konkuk University, Seoul, South Korea Research Institute of Medical Sciences, Konkuk University, Seoul, South Korea khkim10@kku.ac.kr.
Kyun-Hwan
KH
Kim
D000998:Antiviral Agents / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D015967:Gene Expression Regulation, Viral; D006509:Hepatitis B / Q000821:virology*; D006514:Hepatitis B Surface Antigens / Q000235:genetics* / Q000378:metabolism; D006515:Hepatitis B virus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D006801:Humans; D020125:Mutation, Missense; D012194:RNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism; D014779:Virus Replication / Q000187:drug effects
D000998:Antiviral Agents; D006514:Hepatitis B Surface Antigens; D014764:Viral Proteins; D012194:RNA-Directed DNA Polymerase