Mutations in HBV DNA polymerase associated with nucleos(t)ide resistance are rare in treatment-naive patients

Association of Pre-S/S and Polymerase Mutations with Acute and Chronic Hepatitis B Virus Infections in Patients from Rio de Janeiro, Brazil

Several hepatitis B virus (HBV)-related factors, including the viral load, genotype, and genomic mutations, have been linked to the development of liver diseases. Therefore, in this study we aimed to investigate the influence of HBV genetic variability during acute and chronic infection phases. A real-time nested PCR was used to detect HBV DNA in all samples (acute, n = 22; chronic, n = 49). All samples were sequenced for phylogenetic and mutation analyses. Genotype A, sub-genotype A1, was the most common genotype in the study population. A total of 190 mutations were found in the pre-S/S gene area and the acute profile revealed a greater number of nucleotide mutations (p < 0.05). However, both profiles contained nucleotide mutations linked to immune escape and an increased risk of hepatocellular carcinomas (acute, A7T; chronic, A7Q). Furthermore, 17 amino acid substitutions were identified in the viral polymerase region, including the drug resistance mutations lamivudine and entecavir (rtL180M), with statistically significant differences between the mutant and wild type strains. Owing to the natural occurrence of these mutations, it is important to screen for resistance mutations before beginning therapy.

Differential Effectiveness of Tenofovir and Entecavir for Prophylaxis of Hepatocellular Carcinoma in Chronic Hepatitis B Patients Depending on Coexisting Cirrhosis and Prior Exposure to Antiviral Therapy: A Systematic Review and Meta-analysis

GOALS

This meta-analysis evaluated the comparative effectiveness of tenofovir disoproxil fumarate (TDF) versus entecavir (ETV) in reducing the risk of hepatocellular carcinoma (HCC).

BACKGROUND

It is unclear whether TDF or ETV is more effective in reducing the risk of HCC in chronic hepatitis B (CHB) patients with or without underlying cirrhosis.

METHODS

We searched the MEDLINE database through April 13, 2020, for studies involving CHB treated with TDF and/or ETV. Primary and secondary outcomes were the incidence of HCC and overall survival, respectively, calculated as risk ratios (RRs). Adjusted results were further evaluated by pooling propensity score matched cohorts.

RESULTS

Of the 229 records identified, 17 studies were included in the quantitative analysis. TDF treatment was associated with a significantly lower risk of HCC development [RR, 0.63; 95% confidence interval (CI), 0.43-0.93; P=0.024] and mortality (RR, 0.69; 95% CI, 0.57-0.84; P=0.003) than ETV treatment. Moreover, TDF significantly lowered HCC risk in patients with cirrhosis (RR, 0.69; 95% CI, 0.56-0.84) and antiviral treatment-naive patients (RR, 0.59; 95% CI, 0.35-0.98) compared with ETV. Among treatment-naive patients, TDF significantly prolonged survival compared with ETV (RR, 0.69; 95% CI, 0.52-0.91).

CONCLUSIONS

TDF likely confers a lower risk of HCC development and longer survival in patients with CHB, especially among treatment-naive patients and those with underlying cirrhosis, than ETV.

Mutational characterization of HBV reverse transcriptase gene and the genotype-phenotype correlation of antiviral resistance among Chinese chronic hepatitis B patients

Background and Aims: The drug resistance of hepatitis B virus (HBV) originates from mutations within HBV reverse transcriptase (RT) region during the prolonged antiviral therapy. So far, the characteristics of how these mutations distribute and evolve in the process of therapy have not been clarified yet. Thus we aimed to investigate these characteristics and discuss their contributing factors.

Methods: HBV RT region was direct-sequenced in 285 treatment-naive and 214 post-treatment patients. Mutational frequency and Shannon entropy were calculated to identify the specific mutations differing between genotypes or treatment status. A typical putative resistance mutation rtL229V was further studied using in-vitro susceptibility assays and molecular modeling.

Results: The classical resistance mutations were rarely detected among treatment-naive individuals, while the putative resistance mutations were observed at 8 AA sites. rtV191I and rtA181T/V were the only resistance mutations identified as genotype-specific mutation. Selective pressure of drug usage not only contributed to the classical resistance mutations, but also induced the changes at a putative resistance mutation site rt229. rtL229V was the major substitution at the site of rt229. It contributed to the most potent suppression of viral replication and reduced the in-vitro drug susceptibility to entecavir (ETV) when coexisting with rtM204V, consistent with the hypothesis based on the molecular modeling and clinical data analysis.

Conclusions: The analysis of mutations in RT region under the different circumstances of genotypes and therapy status might pave the way for a better understanding of resistance evolution, thus providing the basis for a rational administration of antiviral therapy.

Cross-sectional retrospective analysis of clinical characteristics of chronic hepatitis B patients with oral antiviral treatment in eastern China

BACKGROUND

In China, more than 20 million patients with chronic hepatitis B need antiviral treatment. Side effects of antiviral treatment such as renal complications can be problematic, particularly in an aging population.

METHODS

The data were retrospectively extracted from the hospital medical charts of five centers in eastern China from January 1 to December 31, 2018.

RESULTS

A total of 8309 patients with CHB was enrolled in this study. The median age of the patients was 46 years. The prevalence of diabetes mellitus, hypertension, and hepatic cirrhosis was respectively 3.49%, 4.42%, and 23.72%. The prevalence of these comorbidities increased with age (P < 0.001). Of the patients with CHB, 5332 had complete renal function results. Among them, patients with an estimated glomerular filtration rate of < 60 mL/min/1.73m² accounted for 4.14%, and those with proteinuria for 8.33%. According to the definition of chronic kidney disease, the proportion of patients with chronic kidney disease was 11.37%. The prevalence of chronic kidney disease increased with age (P < 0.001). In a multivariate analysis, age group [odds ratio (OR) = 2.387], diabetes mellitus (OR = 1.486), hypertension (OR = 2.557), hepatic cirrhosis (OR = 1.295), and a history of exposure to adefovir dipivoxil (OR = 1.644) were significantly associated with CKD (P < 0.05). Among patients with CKD, 17.66% (107/606) had a history of lamivudine exposure, and 34.65% (210/606) had a history of nucleotide analogue exposure CONCLUSION: The management of Chinese patients with CHB should take into consideration age, previous medication history, and renal impairment.

Prevalence of Potential Resistance Related Variants Among Chinese Chronic Hepatitis B Patients Not Receiving Nucleos(T)ide Analogues

Background and Aims

Potential drug resistance (DR) related variants in the hepatitis B virus (HBV) reverse transcriptase (RT) region may be associated with the effectiveness of antiviral drugs and disease progression. The aim of this study was to investigate the prevalence and clinical characteristics of potential DR-related variants in Chinese CHB patients not receiving nucleos(t)ide analogues (NAs).

Patients and Methods

Two hundred and six untreated CHB patients from Huzhou Central Hospital in eastern China were recruited for this study. The serum DNA was extracted and the HBV RT region was amplified using nest polymerase chain reaction (nest-PCR). The 42 potential DR-related variants were analyzed by direct sequencing.

Results

Among these CHB patients, HBV genotype B and genotype C were identified in 121 (58.7%) and 85 (41.3%) patients, respectively. Potential DR-related variants were detected in 42.7% (88/206) of patients. Primary and secondary DR variants were found in 7.3% (15/206) of patients, including rtL80I/V, rtI169T, rtV173L rtL180M, rtA181T/V, rtM204I/V, and rtN236T. The variants at rt53, rt82, rt221, rt233, rt237, and rt256 were specific for genotype B, and those at rt38, rt84, rt126, rt139, rt153, rt191, rt214, rt238, and rt242 were specific for genotype C. Moreover, the variation frequency in the A-B interdomain (3.96%) was significantly higher than that in the functional domains (1.17%) and non-A-B interdomains (1.11%). Multivariate logistic regression analysis showed that lower HBV-DNA load (<10⁶ IU/mL) was an independent factor associated with potential DR-related variants in untreated CHB patients (P <0.05).

Conclusion

Potential DR-related variants were frequent and complex in untreated Chinese CHB patients. Furthermore, the variants may contribute to decreased serum HBV-DNA loads. However, the effects of potential DR-related variants on the antiviral therapy and liver disease progression require further study.

Hepatitis B virus reverse transcriptase polymorphisms between treated and treatment-naïve chronically infected patients

The aim of this study was investigation of variation(s) in the Hepatitis B virus (HBV) reverse transcriptase domain. 120 patients with chronic HBV infection recruited. 104 patients were received nucleos(t)ide analogs treatments. DNA extractions were done from plasma samples. Direct sequencing and alignment of Polymerase Chain Reaction products were applied for further analysis. HBV genotypes determined by NCBI's Genotyping Tool. Polymorphism(s) were detected by using DnaSP software. Of 120 samples, 98 were sequenced. All of products were HBV genotype D. 13/98 (13.27%) of patients had M539I/V substitutions corresponding to YMDD motif. FLLAQ to FLMAQ was observed among 22/98 (22.98) patients. Two substitutions N459Y and L515M were significantly correlated (R2 = 0.486 and R2 = 0.941 respectively) with FLLAQ motif variation. Mutation ratio among treatment-received patients to treatment-naïve patients was 0.2-0.6. Drug resistance conferring substitutions (DRCSs) were rtL180M (22/98), rtA194V (11/98), rtM204V (1/98), and rtM204I (11/98). Furthermore, six variants were observed among all patients. Appearance of DRCSs in HBV polymerase is a major obstacle to the virus treatments. In the present study, it was shown that DRCSs are more prevalent among treated patients. Therefore, replacement of current anti-viral regimen with novel anti-HBV drugs is warranted in the future.

Molecular epidemiology of hepatitis B virus mutants associated with vaccine escape, drug resistance and diagnosis failure

The massive implementation of the vaccine and antiviral agents against hepatitis B virus (HBV), targeting the envelope and viral polymerase genes, induces a selection pressure that might lead to the emergence of variants that impair the effectiveness of the vaccine, diagnostic methods and antiviral therapy. The aim of this study was to evaluate the prevalence of HBV vaccine escape mutants (VEMs), diagnostic failure mutants (DFMs) and treatment resistance mutants (ARMs) among individuals from Buenos Aires, Argentina. HBV surface antigen and polymerase sequences obtained from serum samples of 530 HBV-infected individuals were analysed. Samples belonged to genotypes A (28.1%), D (13.6%) and F (58.3%). VEMs, DMFs and ARMs were present in 40 (7.5%), 57 (10.7%) and 27 (5.1%) samples within the studied population. Additionally, eight nonpreviously reported VEMs and nine DFMs were identified. VEMs and DFMs were biased by genotype, being higher in genotype D (33.3% and 33.3%) compared to genotype A (6% and 17.4%) and genotype F (2.3% and 2.3%) (P > 0.001). On the contrary, there was no association between the presence of ARMs and HBV genotype (P = 0.324). VEMs, DFMs and ARMs create public health concerns. The current study provided valuable information about mutants in surface antigen and polymerase in HBV-infected patients from Argentina where HBV-F is the most prevalent genotype. Consequently, it constitutes an important reference for Latin American clinicians in order to optimize the management of HBV-infected patients.

Naturally occurring hepatitis B virus reverse transcriptase mutations related to potential antiviral drug resistance and liver disease progression

The annual number of deaths caused by hepatitis B virus (HBV)-related disease, including cirrhosis and hepatocellular carcinoma (HCC), is estimated as 887000. The reported prevalence of HBV reverse transcriptase (RT) mutation prior to treatment is varied and the impact of preexisting mutations on the treatment of naïve patients remains controversial, and primarily depends on geographic factors, HBV genotypes, HBeAg serostatus, HBV viral loads, disease progression, intergenotypic recombination and co-infection with HIV. Different sensitivity of detection methodology used could also affect their prevalence results. Several genotype-dependent HBV RT positions that can affect the emergence of drug resistance have also been reported. Eight mutations in RT (rtL80I, rtD134N, rtN139K/T/H, rtY141F, rtM204I/V, rtF221Y, rtI224V, and rtM309K) are significantly associated with HCC progression. HBeAg-negative status, low viral load, and genotype C infection are significantly related to a higher frequency and prevalence of preexisting RT mutations. Preexisting mutations are most frequently found in the A-B interdomain of RT which overlaps with the HBsAg “a” determinant region, mutations of which can lead to simultaneous viral immune escape. In conclusion, the presence of baseline RT mutations can affect drug treatment outcomes and disease progression in HBV-infected populations via modulation of viral fitness and host-immune responses.

An Overview of Hepatitis B Virus Surface Antigen Secretion Inhibitors

Current anti-hepatitis B virus (HBV) regimen do not meet ideal result due to emerging resistance strains, cytotoxicity, and unfavorable adverse effects. In chronic HBV infection, high rates of sub-viral particles (SVPs) bearing HBV surface antigen (HBsAg) is a major obstacle regarding to raise effective immune responses and subsequently virus clearance. Development of potent HBsAg secretion inhibitors would provide a better insight into HBV immunopathogenesis and therapy. Investigating new non-toxic HBsAg secretion inhibitors targeting either viral or cellular factors could restore the immune response to remove virally infected hepatocytes after inhibiting SVPs. In this study, we overview several classes of HBV inhibitors with focus on their limitations and advantages over anti-HBsAg secretion potential.

Prevalence of hepatitis B antiviral drug resistance variants in North American patients with chronic hepatitis B not receiving antiviral treatment

Antiviral drug resistance hepatitis B virus (HBV) variants (HBV-DR) occur spontaneously in chronic hepatitis B (CHB) patients and after exposure to nucleos(t)ide analogues (NUCs). We determined the prevalence of HBV-DR variants among participants of the Hepatitis B Research Network (HBRN) Cohort Study conducted at 21 sites in the United States (US) and Canada. Samples obtained from 1342 CHB participants aged ≥18 years, and who were currently not receiving NUCs, were tested for HBV-DR variants by Sanger sequencing. In addition, next generation sequencing (NGS) was used to characterize HBV-DR variants from 66 participants with and 66 participants with no prior NUC exposure matched for HBV genotype and HBV DNA level. Half the participants were men, 75% Asian, 26% HBeAg positive. Primary HBV-DR variants were detected by Sanger sequencing in 16 (1.2%) participants: 2/142 (1.4%) with and 14/1200 (1.2%) without prior NUC exposure; only 1 of these 16 had a secondary variant. In total, 23 (1.7%) participants had secondary variants, including 1 with prior NUC experience. In the subset of 132 participants, NGS detected HBV-DR variants in a higher proportion of participants: primary variants in 18 (13.6%) (8 [12.1%] with, and 10 [15.2%] without prior NUC therapy) and secondary variants in 10 (7.6%) participants. Based on Sanger sequencing, prevalence of primary HBV-DR variants is low (1.2%) among adults with CHB in US/Canada. The similar low prevalence of HBV-DR variants in participants with and without NUC treatment suggests transmission of these variants is uncommon.

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.

Naturally occurring mutations in the reverse transcriptase region of hepatitis B virus polymerase from treatment-naïve Korean patients infected with genotype C2

AIM

To report naturally occurring mutations in the reverse transcriptase region (RT) of hepatitis B virus (HBV) polymerase from treatment naïve Korean chronic patients infected with genotype C2.

METHODS

Here, full-length HBV reverse transcriptase RT sequences were amplified and sequenced from 131 treatment naïve Korean patients chronically infected with hepatitis B genotype C2. The patients had two distinct clinical statuses: 59 patients with chronic hepatitis (CH) and 72 patients with hepatocellular carcinoma (HCC). The deduced amino acids (AAs) at 42 previously reported potential nucleos(t)ide analog resistance (NAr) mutation positions in the RT region were analyzed.

RESULTS

Potential NAr mutations involving 24 positions were found in 79 of the 131 patients (60.3%). Notably, AA substitutions at 2 positions (rt184 and rt204) involved in primary drug resistance and at 2 positions (rt80 and rt180) that functioned as secondary/compensatory mutations were detected in 10 patients (1 CH patient and 9 HCC patients) and 7 patients (1 CH and 6 HCC patients), respectively. The overall mutation frequencies in the HCC patients (3.17%, 96/3024 mutations) were significantly higher than the frequencies in the CH patients (2.09%, 52/2478 mutations) (P = 0.003). In addition, a total of 3 NAr positions, rt80, rt139 and rt204 were found to be significantly related to HCC from treatment naïve Korean patients.

CONCLUSION

Our data showed that naturally occurring NAr mutations in South Korea might contribute to liver disease progression (particularly HCC generation) in chronic patients with genotype C2 infections.

Relationship between pre-existing resistance mutations and HBV genotype in patients with HBV related liver cirrhosis

AIM

To investigate the relationship between hepatitis B virus (HBV)-related drug resistance mutations and HBV genotype in patients with HBV-related liver cirrhosis (LC).

METHODS

Serum samples were collected from 112 patients with HBV-related LC who did not receive prior anti-viral treatment. HBV reverse transcriptase regions were amplified by PCR, and PCR products were directly sequenced.

RESULTS

Among 112 HBV-related LC patients, 13 (11.61%, 13/112) had lamivudine resistance associated mutations, 15 (13.39%, 15/112) had adefovir resistance associated mutations, and 1 had mutations associated with both lamivudine and adefovir resistance. All of these resistance mutations occurred in patients infected with HBV genotype C, and there was no mutation in patients infected with HBV genotype B.

CONCLUSION

Adefovir/lamivudine resistance associated mutations exist in patients with HBV-related LC, and the mutations are related to HBV genotype. Compared with patients infected with HBV genotype B, those infected with HBV genotype C are prone to resistance mutations.

Prevalence of mutations in HBV DNA polymerase gene associated with nucleos(t)ide resistance in treatment-naive patients with Chronic Hepatitis B in Central China

Objective

There are a lot of disagreements in the studies on hepatitis B virus (HBV) DNA polymerase mutation rate associated with nucleos(t)ide analogues (NAs) in treatment-naive chronic hepatitis B (CHB) patients. This is the first study aimed to investigate the prevalence of spontaneous HBV resistance mutations in Central China.

Methods

This study included treatment-naive patients with CHB from June 2012 to May 2015 receiving care at the Institute of Liver Disease in Central China. All patients completed a questionnaire covering different aspects, such as family medical history, course of liver disease, medication history, alcohol use, among others. Mutations in HBV DNA polymerase associated with NAs resistance were detected using INNO-LiPA assay.

Results

269 patients were infected with HBV genotype B (81.4%), C (17.9%), and both B and C (0.7%). Mutations in HBV DNA polymerase were detected in 24 patients (8.9%) including rtM204I/V (n = 6), rtN236T (n = 5), rtM250V (n = 2), rtL180M (n = 2), rtT184G (n = 1), rtM207I (n = 1), rtS202I (n = 1), rtM204V/I & rtL180M (n = 5), and rtM204I & rtM250V (n = 1).

Conclusion

Spontaneous HBV resistance mutations in HBV DNA polymerase were found in treatment-naive patients with CHB in Central China. These findings suggest that we should analyze HBV DNA polymerase resistance mutation associated with NAs before giving antiviral therapy such as lamivudine (LAM), adefovir (ADV), and telbivudine (LdT).

Response to potent anti-HBV agents in chronic hepatitis B and combined effect of HBV reverse transcriptase mutations

BACKGROUND AND AIM

Response to nucleos(t)ide analogue therapy against HBV infection depends on a number of factors. One of them is appearance of drug resistance mutations. The present study aimed to investigate the efficacy of ETV and TDF as anti-HBV agents and to analyze the role of HBV-RT mutations in reducing the efficacy of mentioned drugs.

MATERIAL AND METHODS

Sixty nine treatment naïve CHB patients (mean age 33.8 ± 11.9 years) were enrolled and treated with ETV or TDF for one year. Complete virological response (CVR) was defined as undetectable serum HBV DNA after 12 months of therapy. Amino acid and nucleotide sequence analyses of HBV-RT region were performed using Geno2pheno HBV drug resistance tool. The 3D model of HBV-RT protein was built by I-TASSER server and RMSD was calculated between wild type and mutated HBV-RT protein.

RESULTS

After 12 months of treatment, four CHB patients did not achieve CVR and all of them were with HBV genotype D. HBeAg seroconversion was achieved in 56% HBeAg positive patients after 12 months of antiviral therapy. The HBV-RT amino acid sequences from these four patients were used for in-silico analysis. It was found that the presence of many mutations in HBV-RT region of HBV isolated from these patients led to a high degree of variation in configuration of atoms of HBV-RT protein and also caused displacement of active site of this protein.

CONCLUSION

The efficacy of antiviral drugs in inhibiting HBV replication may be reduced by combined effect of many HBV-RT mutations; however, an in vitro study is needed to validate the findings.

Incidence of natural resistance mutations in naïve chronic hepatitis B patients: a systematic review and meta-analysis

BACKGROUND AND AIM

Studies focused on the naturally occurring resistance mutation rate in treatment-naïve chronic hepatitis B (CHB) patients have set off a furious dispute. We conduct this meta-analysis to appraise the pooled incidence of spontaneous hepatitis B virus resistance mutations worldwide and its distribution.

METHODS

We searched PubMed, EMBASE, Chinese Biomedical Literature Database, and China National Knowledge Infrastructure until December 31, 2013. Cross-sectional or case-control studies reporting incidence of natural resistance mutations in untreated CHB patients were included. Pooled incidence was performed in fixed- or random-effects models, and heterogeneity among studies was assessed.

RESULTS

A total of 106 studies were included involving 12,212 naive CHB patients. The summarized incidence of natural mutations worldwide was 5.73% (95% confidence interval [CI]: 4.85-6.61%), primary mutation rate 5.39% (95%CI: 4.54-6.24%), and secondary mutation rate 2.94% (95%CI: 1.59-4.29%). The pooled incidence reached up to 8.00% (95%CI: 6.63-9.38%) in China, higher than that in other countries (1.88% [95%CI: 1.06-2.69%]). Mutation rtM204V/I had the highest incidence of 4.89% (95%CI: 4.13-5.65%), and other primary mutations seldom spontaneously occurred. In subgroup analysis, genotype C hepatitis B virus infection, male, and hepatitis B antigen (HBeAg) negative patients had a slightly higher natural mutation rate.

CONCLUSION

The resistance mutations occurred frequently in untreated CHB patients, especially in China. The lamivudine resistance had the highest natural prevalence rate, while other nucleos(t)ide analogues showed rarely spontaneous resistance. Detecting the spontaneous resistance mutations will benefit the clinical management of CHB patients.

Advances in treating drug-resistant hepatitis B virus in HIV-infected patients

INTRODUCTION

Treatment of HIV infection with nucleos(t)ide analogs active against hepatitis B virus (HBV) highly improves hepatic outcomes in HIV-HBV coinfected patients, especially when tenofovir (TDF) is part of the antiviral regimen. Drug resistance has been the major drawback and must remain as the most important caveat when planning to treat dually or HIV and HBV independently in coinfected patients.

AREAS COVERED

The use of lamivudine (LAM) as the only active anti-HBV agent should strongly be discouraged in HIV-HBV coinfected patients, although it might be considered for individuals with low serum HBV-DNA and in the absence of liver cirrhosis as an exception. In any other case drug resistance may cause any clinical benefit of this antiviral HBV therapy to disappear, and lead to cross-resistance with other antivirals and even occasionally select for HBV vaccine escape mutants. In cirrhotics, liver enzyme flares may be accompanied by life-threatening decompensation. Entecavir is generally not recommended as an anti-HBV agent in HIV-HBV coinfected patients given its low residual antiretroviral activity and potential for selection of resistance mutations in HIV. Adefovir is not active against HIV using HBV dosing and is no longer recommended as HBV therapy given its limited antiviral effect. Finally, telbivudine is not active against HIV, it is less potent than TDF against HBV and depicts low barrier to resistance and cross-resistance to LAM or emtricitabine.

EXPERT OPINION

The introduction of TDF has drastically reduced the clinical relevance of hepatitis B drug resistance in HIV-HBV coinfected individuals. The use of LAM as the only active anti-HBV agent should strongly be discouraged in this population.

Different mechanism of selection of adefovir-resistant mutant viruses during adefovir monotherapy in patients with lamivudine-resistant chronic hepatitis B

BACKGROUND

Adefovir (ADV) resistance is more frequent in lamivudine (LMV)-resistant chronic hepatitis B (CHB) patients than in nucleos(t)ide analogue-naïve patients. The majority of LMV-resistant mutants harbor the rtM204V/I mutation, while a minor fraction harbor the rtA181V/T mutation. We aimed to elucidate the mechanism of the high rate of ADV resistance in LMV-resistant patients during ADV therapy.

METHODS

We performed a clonal analysis of HBV reverse transcriptase in treatment-naïve (n = 3) and LMV-resistant patients before ADV therapy (n = 14). Dynamic changes in the viral population (n = 9) during ADV therapy were also analyzed.

RESULTS

Before ADV therapy, rtA181V/T was observed in 30 of 680 clones (4.4%) from 7 patients with LMV resistance under dominant rt204V/I mutation and in one of 150 clones in treatment-naïve patients. The rtA181V/T mutation was more frequently found in clones from LMV-resistant patients than in treatment-naïve patients (p = 0.029). The rtN236T mutation was not observed in any clone. During ADV therapy, most rtM204V/I mutants were replaced by wild type in all 3 patients without the rtA181V/T mutation and in one patient with the rtA181V/T mutation. Subsequently, wild type was replaced by the rtN236T and/or rtA181V/T mutant. In patients with the rtA181V/T mutation (n = 6), the rtA181V/T mutant overtook the rtM204V/I mutant in 3 of 4 patients with ADV resistance. In 2 patients without ADV resistance, most of the viral population was replaced by wild type by the last follow-up.

CONCLUSION

The high rate of ADV resistance in patients with LMV-resistance might be attributable to preexisting rtA181V/T mutant virus.

Management and treatment of chronic hepatitis B in HIV-positive patients

Chronic hepatitis B virus (HBV) infection is common in HIV-positive individuals, mainly among those with sexually risky behaviors. Although HBV vaccination is mandatory in all HIV-infected persons with negative HBV markers, lower rates of protection due to abnormal immune responses are achieved. HIV accelerates the course of liver disease caused by chronic HBV infection, leading rapidly to end-stage hepatic illness and increasing the risk of hepatocellular carcinoma. Treatment of HIV including nucleos(t)ide analogues active against HBV highly improves outcomes, especially when tenofovir is part of the antiviral regimen. The use of lamivudine as the only active anti-HBV agent in HIV-HBV co-infected patients should be limited to individuals with low serum HBV-DNA levels. Otherwise, selection of drug resistance may eliminate any clinical benefit, produce cross-resistance to other antivirals, and favor the emergence of HBV vaccine escape mutants.

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.

Molecular diagnosis and treatment of drug-resistant hepatitis B virus

Oral antiviral agents have been developed in the last two decades for the treatment of chronic hepatitis B (CHB). However, antiviral resistance remains an important challenge for long-term CHB therapy. All of the clinically available oral antiviral agents are nucleoside or nucleotide analogues that target the activity of viral reverse transcriptase (RT), and all are reported to have resistant mutations. Since the hepatitis B virus (HBV) RT, like other viral polymerases, lacks proofreading activity, the emergence of drug-resistance occurs readily under selective pressure from the administration of antiviral agents. The molecular diagnosis of drug-resistant HBV is based on sequence variations, and current diagnostic methods include sequencing, restriction fragment polymorphism analysis, and hybridization. Here, we will discuss the currently available molecular diagnosis tools, in vitro phenotypic assays for validation of drug-resistant HBV, and treatment options for drug-resistant HBV.