Screening and identification of a novel adefovir dipivoxil resistance associated mutation, rtN236V, of HBV from a large cohort of HBV-infected patients

Investigation of multidrug-resistance mutations of hepatitis B virus (HBV) in a large cohort of chronic HBV-infected patients with treatment of nucleoside/nucleotide analogs

Multidrug-resistance hepatitis B virus (MDR HBV), defined as those with mutations resistant to both nucleoside analogs lamivudine/telbivudine/entecavir (LAM/LdT/ETV) and nucleotide analog adefovir (ADV), has potential to cause treatment difficulty. To clarify clinical prevalence and virological features of MDR HBV, we investigated serum samples from 28,236 chronic HBV-infected patients with treatment of nucleoside/nucleotide analogs. All patients underwent resistance testing in the Fifth Medical Center of Chinese PLA General Hospital between 2007 and 2019. MDR mutations were screened by direct sequencing; MDR strains (with mutations co-located on the same viral genome) were verified by clonal sequencing (≥20 clones/sample) and subjected to phenotypic analysis if necessary. MDR mutations were detected in 0.81% (229/28,236) patients. MDR strains were verified in 83.0% (190/229) of MDR mutation-positive patients. As ETV-resistance mutation (ETVr) had additional mutation(s) on LAMr conferring more resistance, MDR mutations fell into LAMr + ADVr and ETVr + ADVr subsets. Sixteen mutation patterns of MDR strains were verified, including eight with LAMr + ADVr and eight with ETVr + ADVr. Refractory to sequential therapies of LAM/LdT/ETV and ADV were closely linked with MDR HBV development. Ten representative MDR strains (five LAMr + ADVr and five ETVr + ADVr) tested all had decrease in replication capacity compared to wild-type strains and decrease extent was positively related with the number of primary resistance on viral genome. Compared to ADV + ETV, TDF/TDF + ETV showed higher inhibitory rates on MDR HBV, especially for the five ETVr + ADVr strains (74.5%-97.6% vs. 60.2%-79.5%, all P < 0.05). This study significantly extends the knowledge on MDR HBV and has clinical implications for resistance management.

Entecavir resistance mutations rtL180M/T184L/M204V combined with rtA200V lead to tenofovir resistance

BACKGROUND

Tenofovir disoproxil fumarate (TDF) imposes a high genetic barrier to drug resistance and potently inhibits replication of multidrug-resistant hepatitis B virus. Few clinical cases with confirmed TDF-resistance have been reported to date.

METHODS AND RESULTS

Here, we report viral rebound in a patient with chronic hepatitis B who underwent TDF monotherapy and harboured a quadruple mutant consisting of classic entecavir (ETV)-resistance mutations (rtL180M/T184L/M204V) together with an rtA200V mutation in the reverse transcriptase gene. Sequencing analysis revealed that this quadruple mutant emerged as a major viral population. In vitro phenotyping demonstrated that the rtL180M/T184L/A200V/M204V mutant had moderate resistance to TDF treatment, with a 4.52-fold higher half maximal effective concentration than that of wild-type virus. Importantly, this patient with TDF resistance achieved virological suppression after TDF/ETV combination rescue therapy.

CONCLUSION

An rtL180M/T184L/A200V/M204V mutant with moderate resistance to TDF monotherapy was selected during sequential nucleoside analogue (NA) treatment in a stepwise manner. ETV/TDF combination therapy effectively suppressed replication of this TDF-resistant mutant. Our studies provide novel insights into the treatment of NA-naïve patients as well as patients with TDF resistance.

Hepatitis B virus mutation pattern rtL180M+A181C+M204V may contribute to entecavir resistance in clinical practice

Background and Aims: Entecavir (ETV) resistance of hepatitis B virus (HBV) conventionally requires rt184, 202, or 250 mutations plus lamivudine-resistance mutation (rtM204V/I ± L180M). This study aimed to clarify whether rtL180M+A181C+M204V mutations may contribute to HBV ETV resistance.

Methods: Serum samples were collected from 22,009 patients who underwent resistance testing in Beijing 302 Hospital from 2007 to 2016. HBV reverse transcriptase (RT) gene was screened by direct sequencing and verified by clonal sequencing. Phenotypic analysis was performed for evaluating replication capacity and drug susceptibility.

Results: Classical ETV-resistance mutations of HBV were detected in 1252 patients who were receiving ETV therapy. The rtA181C mutation was detected with rtL180M+M204V mutations in 18 lamivudine-experienced ETV-treated patients, and the emergence of the mutations was associated with virological breakthrough or inadequate virological response to ETV. Patient-derived representative rtA181C-containing mutants, rtL180M+A181C+M204V, rtL180M+A181C+M204V+M250V, and rtL180M+A181C+S202G+M204V, exhibited 45.7%, 25.9%, and 25.0% replication capacity and 85.6-, 356.1-, and 307.1-fold decreased susceptibility to ETV respectively compared to the wild-type strain, while the three mutants remained sensitive to tenofovir (TDF). Artificial elimination of rtA181C largely restored the rtL180M+A181C+M204V mutant’s sensitivity to ETV. Molecular modelling of viral RT binding to ETV showed that the rtL180M+A181C+M204V mutant had a less stable conformation compared to rtL180M+M204V mutant. In clinical practice, undetectable serum HBV DNA was achieved in two of five longitudinally followed rtA181C-positive patients who received switching-to TDF therapy, but not in the other three who received add-on adefovir therapy during observation.

Conclusions: Both clinical and experimental data support rtL180M+A181C+M204V as a novel non-classical ETV-resistance mutation pattern.

Prevalence of the entecavir-resistance-inducing mutation rtA186T in a large cohort of Chinese hepatitis B virus patients

This study aimed to clarify whether rtA186T and rtI163V substitutions of hepatitis B virus (HBV) contributed to entecavir (ETV) resistance. A total of 22,009 Chinese patients with chronic HBV infection who received resistance testing at Beijing 302 Hospital from 2007 to 2016 were enrolled. Among them, 6170 patients had been treated with ETV. The HBV reverse transcriptase gene was screened by direct sequencing and verified by clonal sequencing. Phenotypic analysis was performed for evaluating replication capacity and drug susceptibility. Classical ETV-resistance mutations rtT184/S202/M250substitution+rtM204V/I±L180M (LAM-r), rtA186T, and rtI163V were detected in 1252 (5.69%), 14 (0.06%), and 230 (1.05%) of the 22,009 patients, respectively. The rtA186T mutation always coexisted with LAM-r, but not with rtI163V. The 14 rtA186T-positive patients were all treated with LAM and ETV, and the emergence of the rtA186T+LAM-r was closely associated with virological breakthrough or inadequate virological response to ETV. By contrast, the emergence of rtI163V was not related to ETV treatment. Six rtA186T-positive patients were followed up longitudinally, showing that these patients all had received sequential adefovir and LAM monotherapies prior to ETV treatment. Compared to wild-type strain, two patient-derived mutants' rtL180M+A186T+M204V and rtL180M+T184S+A186T+M204V had 86.7% and 89.2% decreased replication capacity, 210- and 555-fold increased ETV resistance, respectively; and artificial elimination of rtA186T largely restored their ETV sensitivity. The rtA186T mutants remained sensitive to tenofovir. In conclusion, our study confirmed that rtA186T plus LAM-r is a novel ETV-resistance mutation pattern which conferred ETV resistance in multiple Chinese patients.

Clinical and virological implications of A1846T and C1913A/G mutations of hepatitis B virus genome in severe liver diseases

OBJECTIVE

Mutations occurring within different genes of hepatitis B virus (HBV) genome may have different clinical implications. This study aimed to observe the clinical and virological implications of the A1846T and C1913A/G mutations of HBV genome in the development and treatment outcome of severe liver diseases, which has not been previously determined.

MATERIALS AND METHODS

A total of 438 cases of patients with liver diseases were retrospectively reviewed, including 146 with mild chronic hepatitis B infection (CHB-M), 146 with severe chronic hepatitis B infection (CHB-S), and 146 with acute-on-chronic liver failure (ACLF). Partial or full-length HBV genome was directly sequenced. Replicons containing A1846T, C1913A or other mutant sequences, or the wild-type counterparts were constructed respectively, and then transfected into HepG2 cells for phenotype analysis.

RESULTS

There was significant difference in the detection rates of A1846T (30.82%, 40.41% and 55.48%, respectively) and C1913A/G (15.52%, 28.77%, and 35.62%, respectively) among patients with CHB-M, those with CHB-S, and those with ACLF (p < .01). A1846T was significantly associated with the mortality of ACLF patients within six months after the disease onset (OR 1.704, p = .041). In vitro experiment revealed that A1846T mutant resulted in 3.20-fold and 1.85-fold increase of replication capacity and promoter activity, respectively compared with wild type counterpart (p < .001), while C1913A led to a significant decrease of core protein expression (p < .05).

CONCLUSION

Occurrence of A1846T and C1913A is positively associated with clinical presentations of severe liver disease. A1846T mutation is significantly associated with poor prognosis of ACLF.

HBV Drug Resistance Substitutions Existed before the Clinical Approval of Nucleos(t)ide Analogues: A Bioinformatic Analysis by GenBank Data Mining

Naturally occurring nucleos(t)ide analogue resistance (NUCr) substitution frequencies in the reverse transcriptase (RT) of the hepatitis B virus (HBV) were studied extensively after the clinical approval of nucleos(t)ide analogues (NUCs; year of approval 1998). We aimed to study NUCr substitutions in HBV RT sequences obtained before 1998 and better understand the evolution of RT sequences without NUC pressures. Our strategy was to retrieve HBV sequences from GenBank deposited before 1998. The initial search used the keywords "hepatitis B virus" or "HBV" and 1139 sequences were found. Data analyses included information extraction: sequence quality control and amino acid substitution analysis on 8 primary NUCr and 3 secondary substitution codons. Three hundred and ninety-four RT-containing sequences of 8 genotypes from 25 countries in 4 continents were selected. Twenty-seven (6.9%) sequences were found to harbor substitutions at NUCr-related codons. Secondary substitutions (rtL80V and rtV173G/A/L) occurred more frequently than primary NUCr substitutions (rtI169L; rtA181G; T184A/S; rtS202T/R; rtM204L and rtM250K). Typical amino acid substitutions associated with NUCr were of rtL80V, rtV173L and rtT184A/S. We confirm the presence of naturally occurring typical HBV NUCr substitutions with very low frequencies, and secondary substitutions are more likely to occur than primary NUCr substitutions without the selective pressure of NUCs.

Comparison of Detection Rate and Mutational Pattern of Drug-Resistant Mutations Between a Large Cohort of Genotype B and Genotype C Hepatitis B Virus-Infected Patients in North China

The study aimed to investigate the association of prevalent genotypes in China (HBV/C and HBV/B) with HBV drug-resistant mutations. A total of 13,847 nucleos(t)ide analogue (NA)-treated patients with chronic HBV infection from North China were enrolled. HBV genotypes and resistant mutations were determined by direct sequencing and confirmed by clonal sequencing if necessary. HBV/B, HBV/C, and HBV/D occupied 14.3%, 84.9%, and 0.8% across the study population, respectively. NA usage had no significant difference between HBV/B- and HBV/C-infected patients. Lamivudine-resistant mutations were more frequently detected in HBV/C-infected patients, compared with HBV/B-infected patients (31.67% vs. 25.26%, p < 0.01). Adefovir- and entecavir-resistant mutation detection rates were similar, but the mutational pattern was different between the two genotypes. For adefovir-resistant mutations, HBV/C-infected patients had a higher detection rate of rtA181 V (HBV/C 5.29% vs. HBV/B 1.36%, p < 0.01) and a lower detection rate of rtN236T (2.70% vs. 6.54%, p < 0.01). For entecavir-resistant mutations, HBV/C-infected patients had a higher detection rate of rtM204 V/I+T184 substitution or S202G/C (3.66% vs. 2.16%, p < 0.01) and a lower detection rate of rtM204 V/I+M250 V/I/L substitution (0.67% vs. 1.46%, p < 0.01). Multidrug-resistant mutations (defined as coexistence of mutation to nucleoside and nucleotide analogues) were detected in 104 patients. HBV/C-infected patients had a higher detection rate of multidrug-resistant mutation than HBV/B-infected patients (0.83% vs. 0.35%, p < 0.05). The study for the first time clarified that HBV/C-infected patients had a higher risk to develop multidrug-resistant mutations, compared with HBV/B-infected patients; and HBV/C- and HBV/B-infected patients had different inclinations in the ETV-resistant mutational pattern.

Cost-effectiveness analysis of lamivudine, telbivudine, and entecavir in treatment of chronic hepatitis B with adefovir dipivoxil resistance

The purpose of this study was to analyze the cost-effectiveness of lamivudine (LMV), telbivudine (LdT), and entecavir (ETV) in treatment of chronic hepatitis B with adefovir dipivoxil (ADV) resistance. Two hundred and fifty-two patients were recruited and screened for resistance to ADV and randomly assigned into three groups: LMV + ADV, LdT + ADV, and ETV + ADV. The ratio of biochemical response, virological response, seroconversion of hepatitis Be antigen (HBeAg)/hepatitis Be antibody (HBeAb), viral breakthrough, and the cost and effectiveness of treatments were analyzed. A comparison of the results of the ratio of biochemical response, virological response and seroconversion of HBeAg/HBeAb, showed no statistical difference between the three groups, with the economic cost of LMV + ADV the lowest, LdT + ADV the middle, and ETV + ADV the highest. The side effects of the three plans are all rare and tolerable. LMV + ADV is the optimal rescue strategy, and LdT + ADV the alternative selection in the economically less developed regions, while ETV + ADV was used in the economically developed regions.

Investigation into drug-resistant mutations of HBV from 845 nucleoside/nucleotide analogue-naive Chinese patients with chronic HBV infection

BACKGROUND

This study aimed to clarify the clinical significance of drug-resistant HBV in nucleoside/nucleotide analogue (NA)-naive Chinese patients with chronic HBV infection in real clinical practice.

METHODS

A total of 845 NA-naive patients who were admitted to Beijing 302 Hospital between July 2007 and March 2012 were included in the study. HBV drug-resistant mutations were examined by direct sequencing of the viral reverse transcriptase gene and verified by clonal sequencing. Phenotypic analysis of viral replication capacity and drug susceptibility were performed by measuring viral replicative intermediate level in 1.1-mer mutant or wild-type HBV amplicon-transfected HepG2 cells in absence or presence of serially diluted drugs.

RESULTS

Drug-resistant mutations were detected in 2.01% (17/845) of the patients by direct sequencing, including 15 with lamivudine-resistant mutations (rtM204V, rtM204I), one with adefovir-resistant mutation (rtA181V), and one with both lamivudine- and adefovir-resistant mutations (rtA181V, rtM204I). Clonal sequencing identified 13 drug-resistant HBV strains: rtL80I+M204I, rtL80I+M204V, rtL180M+M204I, rtL180M+M204V, rtM204I, rtM204V, rtL80I+L180M+M204I, rtL80I+L180M+M204V, rtA181V, rtA181V+M204I, rtA181T+N236T, rtA181V+N236T and rtN236T. Phenotypic analysis showed that two pre-existing lamivudine-resistant strains (rtL80I+M204I, rtL180M+M204V) had >1,000-fold resistance to lamivudine, and one pre-existing adefovir-resistant strain (rtA181V+N236T) had 15.4-fold resistance to adefovir compared with the wild-type strain. A follow-up study showed that the presence of pre-existing rtM204I strain in one patient increased from 20% at baseline to 85% after 13 months of entecavir treatment with corresponding recession of wild-type strain in the viral pool.

CONCLUSIONS

The incidence of drug-resistant HBV mutations was low in NA-naive Chinese HBV-infected patients. Pre-existing mutants had similar resistance characteristics to those from NA refractory patients.