Prevalence, viral replication efficiency and antiviral drug susceptibility of rtQ215 polymerase mutations within the hepatitis B virus genome

A high prevalence of the rtI187V polymerase substitution of hepatitis B virus (HBV) was detected in nucleoside/nucleotide-analogue-naive and -treated chronic hepatitis B (CHB) patients. We aimed at assessing the replicative capacity and susceptibility to lamivudine (LAM) and adefovir (ADV) in vitro of HBV harbouring rtI187V alone or in conjunction with LAM- or ADV-resistant mutations. The reverse transcriptase region of HBV isolates was directly sequenced from a cohort of 300 CHB patients from China. Replication-competent HBV constructs containing rtI187V and combined with LAM-resistant (rtM204I, rtL180M/rtM204V) mutations were generated, and compared with WT, LAM-resistant single (rtM204I) or double (rtL180M/rtM204V) and ADV-resistant (rtN236T) clones. In a Chinese cohort of 300 CHB patients, 8.7 % (26/300) showed substitution of rtI187 with V. Of note, the rtI187V prevalence in HBV genotype B was significantly higher than that in HBV genotype C (95.2 vs 4.8 %). In vitro phenotypic assays showed that the viruses bearing the rtI187V substitution had impaired replication efficacy when compared with the WT and the virus carrying rtI187V combined with LAM-resistant single or double mutations showed even more significantly impaired replicative capacities. Furthermore, rtI187V HBV remained susceptible towards treatment with LAM or ADV in vitro whereas the combination of the rtI187V substitution with LAM-resistant mutations rendered HBV resistant to LAM but still sensitive to ADV. Our study revealed that the rtI187V substitution in the HBV polymerase frequently occurred in CHB patients, particularly those with HBV genotype B. However, the emergence of the rtI187V substitution significantly impaired viral replication but without affecting drug sensitivity in vitro.

Download Full-text

Quasispecies of Hepatitis B Virus

Infection International ◽

10.1515/ii-2017-0025 ◽

2012 ◽

Vol 1 (4) ◽

pp. 177-182

Author(s):

Jun Cheng ◽

Min Quan ◽

Min Li ◽

Shun-ai Liu ◽

Qi Wang

Keyword(s):

Drug Resistance ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Viral Replication ◽

Antiviral Drug ◽

Host Immune System ◽

Genetic Barrier ◽

Reading Frame ◽

Hbv Replication ◽

B Virus

Abstract Hepatitis B virus (HBV) circulates in blood and replicates in the presence of quasispecies. During HBV replication, HBV DNA polymerase lacks fidelity and proofreading function partly because its exonuclease activity is either absent or deficient. Therefore, HBV genome is mutated with unusually high frequency. And these mutations can affect more than one open reading frame due to overlapping genes. Otherwise, natural substitutions, deletions or insertions involving the Cp/EN∥ locus in the X gene can significantly alter the extent of viral replication activity. Particular selection pressures such as host immune system and antiviral therapy readily select out escape mutants from this pre-existing quasispecies pool. Antiviral drug resistance in chronic hepatitis B (CHB) can be caused by the viral mutation frequency, the intrinsic mutability of the antiviral target site, the selective pressure exerted by the drug, the magnitude and rate of virus replication, the overall replication fitness of the mutant, the genetic barrier of the compound and the availability of replication space. Potent inhibition of HBV replication could be able to prevent the development of drug resistance because mutagenesis is replication dependent. Viral load may decline to a point where the continued production of quasispecies with the potential to resist new drug treatments no longer occurs, if viral replication can be suppressed for a sufficient length of time.

Download Full-text

Telbivudine (Sebivo) in patients with hepatitis B virus (HBV) chronic infection

Farmeconomia Health economics and therapeutic pathways ◽

10.7175/fe.v9i4.238 ◽

2008 ◽

Vol 9 (4) ◽

pp. 215-218

Author(s):

Viola Sacchi

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Viral Replication ◽

Liver Damage ◽

Chronic Infection ◽

Hbeag Seroconversion ◽

Specific Antigen ◽

Antiviral Drug ◽

B Virus

Hepatitis B is the most common serious liver infection in the world, with about 350 million people who are infected with the hepatitis B virus (HBV) and about 1 million deaths annually.Hepatitis B is characterized by an acute and a chronic phase, if the subject fails to produce adequate immune response.About 5-10% of adults infected with HBV go on to develop chronic infection and become chronic carriers (CHB); moreover, the liver damage, if not stopped, continues until cirrhosis or hepatocellular carcinoma. In the natural history of HBV infection, the most important event is HBeAg seroconversion, characterized by loss of HBeAg (a specific antigen of the virus) and development of anti-HBe antibodies (HBeAg-positive patients). If the seroconversion has occurred early (when liver damage is not already significant) and is maintained, long-term prognosis is excellent. The disease can follow a more aggressive course if active viral replication persists despite anti-HBe positivity. This state, characterized by continuing viral replication, has been termed as HBeAg-negative CHB, and is the most prevalent form in Italy. At the moment, there are 4 approved antiviral drug classes, with different antiviral efficacy, for the treatment of chronic hepatitis B: interferons, nucleoside analogues, nucleotide analogues, and cyclopents.The primary target of the treatment is a prolonged suppression of viral replication, in order to avoid long term complications and increase survival.

Download Full-text

The Hepatitis B Virus Polymerase Mutation rtV173L Is Selected during Lamivudine Therapy and Enhances Viral Replication In Vitro

Journal of Virology ◽

10.1128/jvi.77.21.11833-11841.2003 ◽

2003 ◽

Vol 77 (21) ◽

pp. 11833-11841 ◽

Cited By ~ 174

Author(s):

William E. Delaney ◽

Huiling Yang ◽

Christopher E. Westland ◽

Kalyan Das ◽

Eddy Arnold ◽

...

Keyword(s):

Hepatitis B Virus ◽

Nucleic Acid ◽

Hepatitis B ◽

Viral Replication ◽

Reverse Transcriptase ◽

Polymerization Reaction ◽

Replication Efficiency ◽

Template Strand ◽

B Virus

ABSTRACT Therapy of chronic hepatitis B virus (HBV) infection with the polymerase inhibitor lamivudine frequently is associated with the emergence of viral resistance. Genotypic changes in the YMDD motif (reverse transcriptase [rt] mutations rtM204V/I) conferred resistance to lamivudine as well as reducing the in vitro replication efficiency of HBV. A second mutation, rtL180M, was previously reported to partially restore replication fitness as well as to augment drug resistance in vitro. Here we report the functional characterization of a third polymerase mutation (rtV173L) associated with resistance to lamivudine and famciclovir. rtV173L was observed at baseline in 9 to 22% of patients who entered clinical trials of adefovir dipivoxil for the treatment of lamivudine-resistant HBV. In these patients, rtV173L was invariably found as a third mutation in conjunction with rtL180M and rtM204V. In vitro analyses indicated that rtV173L did not alter the sensitivity of wild-type or lamivudine-resistant HBV to lamivudine, penciclovir, or adefovir but instead enhanced viral replication efficiency. A molecular model of HBV polymerase indicated that residue rtV173 is located beneath the template strand of HBV nucleic acid near the active site of the reverse transcriptase. Substitution of leucine for valine at this residue may enhance polymerization either by repositioning the template strand of nucleic acid or by affecting other residues involved in the polymerization reaction. Together, these results suggest that rtV173L is a compensatory mutation that is selected in lamivudine-resistant patients due to an enhanced replication phenotype.

Download Full-text

Differential Impact of Immune Escape Mutations G145R and P120T on the Replication of Lamivudine-Resistant Hepatitis B Virus e Antigen-Positive and -Negative Strains

Journal of Virology ◽

10.1128/jvi.01796-09 ◽

2009 ◽

Vol 84 (2) ◽

pp. 1026-1033 ◽

Cited By ~ 29

Author(s):

Samad Amini-Bavil-Olyaee ◽

Mihael Vucur ◽

Tom Luedde ◽

Christian Trautwein ◽

Frank Tacke

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Viral Replication ◽

Immune Escape ◽

Drug Susceptibility ◽

Basal Core Promoter ◽

Wild Type ◽

Differential Impact ◽

B Virus ◽

Selection Of

ABSTRACT Immune escape variants of the hepatitis B virus (HBV) represent an emerging clinical challenge, because they can be associated with vaccine escape, HBV reactivation, and failure of diagnostic tests. Recent data suggest a preferential selection of immune escape mutants in distinct peripheral blood leukocyte compartments of infected individuals. We therefore systematically analyzed the functional impact of the most prevalent immune escape variants, the sG145R and sP120T mutants, on the viral replication efficacy and antiviral drug susceptibility of common treatment-associated mutants with resistance to lamivudine (LAM) and/or HBeAg negativity. Replication-competent HBV strains with sG145R or sP120T and LAM resistance (rtM204I or rtL180M/rtM204V) were generated on an HBeAg-positive and an HBeAg-negative background with precore (PC) and basal core promoter (BCP) mutants. The sG145R mutation strongly reduced HBsAg levels and was able to fully restore the impaired replication of LAM-resistant HBV mutants to the levels of wild-type HBV, and PC or BCP mutations further enhanced viral replication. Although the sP120T substitution also impaired HBsAg secretion, it did not enhance the replication of LAM-resistant clones. However, the concomitant occurrence of HBeAg negativity (PC/BCP), sP120T, and LAM resistance resulted in the restoration of replication to levels of wild-type HBV. In all clones with combined immune escape and LAM resistance mutations, the nucleotide analogues adefovir and tenofovir remained effective in suppressing viral replication in vitro. These findings reveal the differential impact of immune escape variants on the replication and drug susceptibility of complex HBV mutants, supporting the need of close surveillance and treatment adjustment in response to the selection of distinct mutational patterns.

Download Full-text