Hepatitis B virus resistance to nucleos(t)ide analogues

Design, synthesis, and molecular hybrids of caudatin and cinnamic acids as novel anti-hepatitis B virus agents

Forty-six conjugated derivatives of caudatin with substituted cinnamic acids were synthesized, and their anti-hepatitis B virus (HBV) activity was evaluated in HepG 2.2.15 cells. Most of the derivatives exhibited potent anti-HBV activity, especially inhibiting the HBV DNA replication with the IC(50) values from 2.44 to 22.89 μΜ. Compound 18 showed significant activity against the secretion of HBsAg, HBeAg, and HBV DNA replication with IC(50) values of 5.52, 5.52, 2.44 μΜ, respectively, and had good safety (LD(50) > 1250 mg/kg) according to the acute toxicity study. Preliminary mechanism investigation suggested that compound 18 exerted antivirus effects via interfering HBV X promoter and enhancer I to influence HBV transcriptions.

Extensive mutagenesis of the conserved box E motif in duck hepatitis B virus P protein reveals multiple functions in replication and a common structure with the primer grip in HIV-1 reverse transcriptase

Hepadnaviruses, including the pathogenic hepatitis B virus (HBV), replicate their small DNA genomes through protein-primed reverse transcription, mediated by the terminal protein (TP) domain in their P proteins and an RNA stem-loop, ε, on the pregenomic RNA (pgRNA). No direct structural data are available for P proteins, but their reverse transcriptase (RT) domains contain motifs that are conserved in all RTs (box A to box G), implying a similar architecture; however, experimental support for this notion is limited. Exploiting assays available for duck HBV (DHBV) but not the HBV P protein, we assessed the functional consequences of numerous mutations in box E, which forms the DNA primer grip in human immunodeficiency virus type 1 (HIV-1) RT. This substructure coordinates primer 3'-end positioning and RT subdomain movements during the polymerization cycle and is a prime target for nonnucleosidic RT inhibitors (NNRTIs) of HIV-1 RT. Box E was indeed critical for DHBV replication, with the mutations affecting the folding, ε RNA interactions, and polymerase activity of the P protein in a position- and amino acid side chain-dependent fashion similar to that of HIV-1 RT. Structural similarity to HIV-1 RT was underlined by molecular modeling and was confirmed by the replication activity of chimeric P proteins carrying box E, or even box C to box E, from HIV-1 RT. Hence, box E in the DHBV P protein and likely the HBV P protein forms a primer grip-like structure that may provide a new target for anti-HBV NNRTIs.

Convergence and coevolution of hepatitis B virus drug resistance

Treatment with lamivudine of patients infected with hepatitis B virus (HBV) results in a high rate of drug resistance, which is primarily associated with the rtM204I/V substitution in the HBV reverse transcriptase domain. Here we show that the rtM204I/V substitution, although essential, is insufficient for establishing resistance against lamivudine. The analysis of 639 HBV whole-genome sequences obtained from 11 patients shows that rtM204I/V is independently acquired by more than one intra-host HBV variant, indicating the convergent nature of lamivudine resistance. The differential capacity of HBV variants to develop drug resistance suggests that fitness effects of drug-resistance mutations depend on the genetic structure of the HBV genome. An analysis of Bayesian networks that connect rtM204I/V to many sites of HBV proteins confirms that lamivudine resistance is a complex trait encoded by the entire HBV genome rather than by a single mutation. These findings have implications for public health and offer a more general framework for understanding drug resistance.

Dynamics of hepatitis B virus quasispecies in association with nucleos(t)ide analogue treatment determined by ultra-deep sequencing

BACKGROUND AND AIMS

Although the advent of ultra-deep sequencing technology allows for the analysis of heretofore-undetectable minor viral mutants, a limited amount of information is currently available regarding the clinical implications of hepatitis B virus (HBV) genomic heterogeneity.

METHODS

To characterize the HBV genetic heterogeneity in association with anti-viral therapy, we performed ultra-deep sequencing of full-genome HBV in the liver and serum of 19 patients with chronic viral infection, including 14 therapy-naïve and 5 nucleos(t)ide analogue(NA)-treated cases.

RESULTS

Most genomic changes observed in viral variants were single base substitutions and were widely distributed throughout the HBV genome. Four of eight (50%) chronic therapy-naïve HBeAg-negative patients showed a relatively low prevalence of the G1896A pre-core (pre-C) mutant in the liver tissues, suggesting that other mutations were involved in their HBeAg seroconversion. Interestingly, liver tissues in 4 of 5 (80%) of the chronic NA-treated anti-HBe-positive cases had extremely low levels of the G1896A pre-C mutant (0.0%, 0.0%, 0.1%, and 1.1%), suggesting the high sensitivity of the G1896A pre-C mutant to NA. Moreover, various abundances of clones resistant to NA were common in both the liver and serum of treatment-naïve patients, and the proportion of M204VI mutants resistant to lamivudine and entecavir expanded in response to entecavir treatment in the serum of 35.7% (5/14) of patients, suggesting the putative risk of developing drug resistance to NA.

CONCLUSION

Our findings illustrate the strong advantage of deep sequencing on viral genome as a tool for dissecting the pathophysiology of HBV infection.

Synthesis, biological evaluation and structure-activity relationships of glycyrrhetinic acid derivatives as novel anti-hepatitis B virus agents

Fifty-seven derivatives of glycyrrhetinic acid (GA) were synthesized, and their anti-hepatitis B virus (HBV) activity was evaluated in HepG 2.2.15 cells. Among them, sixteen compounds showed greater anti-HBV activity than GA, especially, compounds 29, 32, 35, 41 exhibited significantly inhibitory activities against HBV DNA replication with IC(50) values of 5.71, 5.36, 8.90 and 9.08 μM, respectively. The structure-activity relationships (SARs) of GA derivatives were discussed for exploring novel anti-HBV agents.

Hepatitis B surface antigen seroconversion is associated with favourable long-term clinical outcomes during lamivudine treatment in HBeAg-negative chronic hepatitis B patients

The aims of this study were to assess hepatitis B surface antigen (HBsAg) seroconversion and to determine its impact on the natural course of the disease in patients with HBeAg-negative chronic hepatitis B (CHB) during lamivudine (LMV) treatment. A total of 183 consecutive patients with HBeAg-negative CHB who were treated with LMV were included in the study. Data were retrospectively collected from outpatient visit charts. The primary endpoint was HBsAg seroconversion to anti-HBs. The secondary endpoint was to determine the development of cirrhosis. Loss of HBsAg was confirmed in 10 patients and seroconversion to anti-HBs in nine patients during LMV treatment or after its discontinuation. HBsAg seroconversion was achieved on-treatment in four patients after a median treatment duration of 30 months and off-treatment in the remaining five patients in a median 61 months after LMV discontinuation. The cumulative probability of HBsAg seroconversion increased from 0.6% at 1 year and 1.9% at 5 years to 21.5% at 10 years of LMV during and after LMV treatment. HBsAg clearance was preceded by undetectable serum hepatitis B virus (HBV) DNA. The majority of the patients responding to treatment had undetectable HBV DNA levels at 24 weeks of treatment. The cumulative probability of LMV resistance increased from 2.2% at 1 year to 37.3% at 5 years. No baseline parameter predicting either HBsAg seroconversion or the emergence of LMV resistance was identified. None of the patients with HBsAg seroconversion experienced virological breakthrough or disease progression during the follow-up period. These results indicate that HBsAg seroclearance can occur in patients with HBeAg-negative CHB under LMV therapy and predicts better clinical outcome.

Entecavir plus tenofovir combination as rescue therapy in pre-treated chronic hepatitis B patients: an international multicenter cohort study

BACKGROUND & AIMS

Long-term viral suppression is a major goal to prevent disease progression in patients with HBV. Aim of this study was to investigate the efficacy and safety of entecavir plus tenofovir combination in 57 CHB partial responders or multidrug resistant patients.

METHODS

Investigator-initiated open-label cohort study. Quantitative HBV-DNA measurement and resistance testing (line-probe-assays and direct-sequencing) at baseline and every 3 months.

RESULTS

Fifty seven patients (37 HBeAg+), median age 45 years, previously treated with a median of three lines of antiviral therapy (range 1-6), 24/57 with advanced liver disease, were included. Median ALT at baseline was 1.0 ULN (range 0.3-22) and HBV-DNA 1.5 × 10(4)IU/ml (range 500-1 × 10(11)IU/ml). Median treatment duration of combination therapy was 21 months. HBV-DNA level dropped 3 logs (median, range 0-8 log; p<0.0001), 51/57 patients became HBV-DNA undetectable, median after 6 months (95% CI, 4.6-7). The probability for HBV DNA suppression was not reduced in patients with adefovir or entecavir resistance or in patients with advanced liver disease. Viral suppression led to decline in ALT (median 0.7 ULN; range 0.2-2.4; p=0.001). Five patients lost HBeAg (after 15, 18, 20, 21, and 27 months, respectively), one patient showed HBs-seroconversion. Patients with advanced disease did not show clinical decompensation, two patients with cirrhosis and undetectable HBV DNA developed HCCs. No death, newly induced renal impairment or lactic acidosis were reported.

CONCLUSIONS

Rescue therapy with entecavir and tenofovir in CHB patients harboring viral resistance patterns or showing only partial antiviral responses to preceding therapies was efficient, safe, and well tolerated in patients with and without advanced liver disease (249).

Evaluation of adherence to oral antiviral hepatitis B treatment using structured questionnaires

AIM

To assess adherence rates to nucleos(t)ide analogues (NUCs) therapy in patients with chronic hepatitis B virus infection and determine factors associated with adherence.

METHODS

The questionnaire study was conducted in the liver clinics at Concord Repatriation General Hospital. All patients who were currently taking one or more NUCs were asked to complete a structured, self-administered 32-item questionnaire. Adherence was measured using visual analogue scales. The patient's treating clinician was also asked to assess their patient's adherence via a structured questionnaire.

RESULTS

A total of 80 patients completed the questionnaire. Sixty six percent of the patients (n = 49) reported optimal adherence whilst 25 (33.8%) graded their adherence to NUCs as suboptimal. Thirty four (43%) patients reported to have omitted taking their NUCs sometime in the past. Recent non-adherence was uncommon. Amongst the patients who reported skipping medications, the most common reason cited was "forgetfulness" (n = 27, 56.25%). Other common reasons included: ran out of medications (n = 5, 10.42%), being too busy (n = 4, 8.33%) and due to a change in daily routine (n = 5, 10.42%). Patients who reported low adherence to other prescription pills were also more likely to miss taking NUCs (P = 0.04). Patients who were under the care of a language-discordant clinician were also more likely to report suboptimal adherence to NUCs (P = 0.04).

CONCLUSION

Adherence rates were much less than that expected by the physician and has potential adverse affect on long term outcome. Communication and education appear central and strategies need to be implemented to improve ongoing adherence.

Selection of chronic hepatitis B therapy with high barrier to resistance

Antiviral drug resistance is a crucial factor that frequently determines the success of long-term therapy for chronic hepatitis B. The development of resistance to nucleos(t)ide analogues has been associated with exacerbations in liver disease and increased risk of emergence of multidrug resistance. The selection of a potent nucleos(t)ide analogue with a high barrier to resistance as a first-line therapy, such as entecavir or tenofovir, provides the best chance of achieving long-term treatment goals and should be used wherever possible. The barrier to resistance of a given nucleos(t)ide analogue is influenced by genetic barrier, drug potency, patient adherence, pharmacological barrier, viral fitness, mechanism of action, and cross-resistance. In countries with limited health-care resources, the selection of a therapy with a high barrier to resistance is not always possible and alternative strategies for preventing resistance might be needed, although limited data are available to support these strategies.

Frequency and risk factors of renal impairment during long-term adefovir dipivoxil treatment in chronic hepatitis B patients

BACKGROUND AND AIM

There are insufficient data on renal safety during long-term adefovir dipivoxil (ADV) treatment. We aimed to elucidate the incidence and risk factors of renal impairment in chronic hepatitis B (CHB) patients treated with ADV.

METHODS

We retrospectively enrolled 687 CHB patients (51.4% with compensated cirrhosis) treated with ADV alone (18.2%) or in combination with lamivudine (81.8%) for more than 12 months. Renal function was measured using the estimated glomerular filtration rate (eGFR), and renal dysfunction was defined as mild (20-30% decrease), moderate (30-50%), or severe (more than 50%).

RESULTS

During the median treatment duration of 27 months, 72 patients (10.5%) developed renal impairment, which was mild in 77.8% of cases, moderate in 20.8% of cases, and severe in one patient. The cumulative incidence of renal impairment at 1, 3, and 5 years was 2.6%, 14.8%, and 34.7%, respectively. Modification of the dosing interval or discontinuation of ADV was required in seven and three patients, respectively, and none of them showed a further decline in the eGFR. Although a univariate analysis revealed age, the number of exposure to radio-contrast dye, liver cirrhosis, and hepatocellular carcinoma as risk factors of renal impairment, age was the only significant risk factor identified in the multivariate analysis (odds ratio = 1.048, 95% confidence interval = 1.019-1.076, P = 0.001).

CONCLUSIONS

Renal impairment in long-term ADV users was relatively frequent, but serious renal toxicity was rare, and all cases were safely managed. Careful monitoring of renal function is required, especially in older patients.

Consequences of persistent HBV infection in HIV: the double-edged sword of nucleos(t)ide analogs

A variety of nucleos(t)ide analogs (NA) are available to treat HBV infection, the majority of which are also active against HIV, and when alone or in combination, have proven to actively suppress circulating HBV. However during treatment, especially among HIV-infected patients, the persistent nature of replicating intracellular DNA and lack of HBsAg loss indicates the potential for NA resistance and hence changes in HBV genetic variability. Meanwhile, cytotoxic CD8+ T cells responsible for clearing infected hepatocytes appear to become exhausted and anti-HBV immunoglobulin-producing B cells become deficient; both of which can be altered during HIV infection. Furthermore, host-determinants, specifically regulation of HBV integration into the host genome and polymorphisms on the HLA allele, have been shown to affect HBV replication. Studies on how these selective pressures influence HBV genetic variability are sparse, yet lead to important considerations on NA resistance during persistent infection.

High-resolution melting and real-time PCR for quantification and detection of drug-resistant HBV mutants in a single amplicon

BACKGROUND

Antiviral therapy by nucleoside/nucleotide analogues (NAs) effectively reduces HBV replication in chronic hepatitis B (CHB) patients. Because long-term NA treatments will eventually select for drug-resistant mutants, early detection of mutants and frequent monitoring of viral loads is crucial for successful NA therapy. Because no efficient test for one-tube quantification and qualification of various HBV-resistant mutants exists, we propose to use high-resolution melting (HRM) analysis in combination with real-time PCR to achieve this unmet need.

METHODS

We developed a single amplicon for detecting HBV mutants resistant to lamivudine (LMV), adefovir (ADV) and entecavir (ETV), which are commonly used for CHB treatment. Our design consists of two steps: real-time PCR for viral quantification, and hybridization probe HRM analysis for detection of specific drug-resistant mutants.

RESULTS

Assay quantification was accurate (R=0.98) for viral loads from 10(3) to 10(9) copies/ml. HRM analysis produced distinct melting temperatures that clearly distinguished the mutants, rtM204V/I (LMV), rtA181V and rtN236T (ADV), and rtT184G and rtM250V (ETV), from their respective wild types. The assay detected mutants at only 10-25% of the HBV population. The clinical applicability of this assay was tested in a pilot study with serial samples from patients receiving LMV treatment.

CONCLUSIONS

Flexibility, speed and cost-efficiency are additional benefits unique to our assay. The clinical sample results further support the feasibility of applying our design to frequent and long-term monitoring of CHB patients receiving NA treatments in the clinical setting.

Role of hepatitis B virus genetic barrier in drug-resistance and immune-escape development

BACKGROUND

Impact of hepatitis B virus genetic barrier, defined as the number and type of nucleotide substitutions required to overcome drug/immune selective pressure, on drug-resistance/immune-escape development is unknown.

METHODS

Genetic barrier was calculated according to Van de Vijver (2006) in 3482 hepatitis B virus-reverse transcriptase/HBV surface antigen sequences from 555 drug-naïve patients and 2927 antiviral-treated patients infected with hepatitis B virus genotypes A-G.

RESULTS

Despite high natural variability, genetic barrier for drug-resistance development is identical amongst hepatitis B virus genotypes, but varies according to drug-resistance mutation type. Highest genetic barrier is found for secondary/compensatory mutations (e.g. rtL80I/V-rtL180M-rtV173L), whilst most primary mutations (including rtM204V-rtA181T/V-rtI169T-rtA194T) are associated with low genetic barrier. An exception is rtM204I, which can derive from a transition or a transversion. Genotypes A and G are more prone to develop immune/diagnostic-escape mutations sT114R and sG130N. Vaccine-escape associated sT131N-mutation is a natural polymorphism in both A and G genotypes.

CONCLUSION

Genetic barrier and reverse transcriptase/HBV surface antigen overlapping can synergistically influence hepatitis B virus drug-resistance/immune-escape development. The different immune-escape potential of specific hepatitis B virus genotypes could have important clinical consequences in terms of disease progression, vaccine strategies and correct HBV surface antigen detection.

Current Antiviral Therapy of Chronic Hepatitis B: Efficacy and Safety

The treatment of chronic hepatitis B is in constant evolution. Interferon, the first agent licensed for chronic hepatitis B treatment, has been superseded by the growing popularity of nucleoside/nucleotide analogues (NA). However, resistance to these agents is a major challenge. Newer NAs, such as entecavir and tenofovir dipivoxil fumarate, have very low resistance rates and favorable safety profiles. Long-term use of these agents can effectively suppress hepatitis B virus DNA, leading to decrease in incidence of hepatitic flares, as well as in the development of cirrhosis and hepatocellular carcinoma. The efficacy and safety of various antiviral agents is discussed in this review.

Hepatitis B virus drug resistance to current nucleos(t)ide analogs: Mechanisms and mutation sites

Nucleos(t)ide analogs (NAs) have become the mainstream drugs for the treatment of chronic hepatitis B virus infection. Drug resistance to NAs, however, has posed a major obstacle in obtaining sustained viral suppression. Standardized definitions of terms and nomenclature in discussing NAs resistance have been proposed. Drug resistance to NAs is produced by a combination of viral, host and antiviral drug factors. A detailed understanding of the mechanisms and effects of mutation sites that cause resistance to NAs is important for the design of rational treatment and management of patients with existing drug resistance.

High rate of complete viral suppression with combination therapy in patients with chronic hepatitis B and prior treatment failure

BACKGROUND

Combination therapy for chronic hepatitis B virus (HBV) infection is recommended for patients with antiviral resistance (AVR) or partial response (PR) to earlier antiviral therapy; however, data on outcomes are limited.

GOALS

To determine the rate of complete viral suppression (CVS) with combination therapy and to compare CVS among different indications and treatment regimens.

METHODS

A cohort of 109 consecutive patients with chronic hepatitis B from 3 liver clinics in Northern California was retrospectively studied. All patients started combination therapy between April 2004 and August 2009 for the following indications: AVR (n = 29), PR (n = 60), or others (n = 20). Combination treatments included lamivudine (LAM), adefovir (ADV), telbivudine (LdT), entecavir (ETV), tenofovir (TDF), and emtricitabine (FTC). CVS was defined as undetectable serum HBV DNA <100 IU/mL.

RESULTS

Among the patients, who were nearly all Asian (99%), 73% had ≥ 2 prior treatments and 82% had treatment failure (AVR or PR). Median treatment duration of combination therapy was 21 months (range, 6 to 50 mo). The majority (77%) achieved CVS after 6 months of various combination regimens: 80% for ETV+TDF, 76% for TDF+LAM or FTC or LdT, 75% for ETV+ADV, and 69% for ADV+LAM or LdT (P = 0.86). After 6 months of therapy, CVS was observed in a similar proportion of patients treated for PR and AVR (72% and 74%, respectively).

CONCLUSIONS

Although the majority of 109 treatment-experienced patients had prior treatment failure, high rates of CVS were rapidly achieved and did not significantly differ between indications of AVR and PR or between ETV-based and TDF-based regimens.

HBV primary drug resistance in newly diagnosed HIV-HBV-coinfected individuals in Spain

BACKGROUND

The wide use of lamivudine (3TC) as oral therapy for chronic HBV infection has favoured the selection and circulation of 3TC-resistant HBV strains worldwide. Although transmission of 3TC-resistant HBV variants has been reported only sporadically, few studies have been conducted in the HIV population where exposure to 3TC has been greater forming part of antiretroviral therapy (ART) regimens.

METHODS

All individuals positive for serum hepatitis B surface antigen (HBsAg), newly diagnosed with HIV-1 infection, naive to ART and enrolled in the Spanish HIV cohort (CoRIS) since 2004 were identified. The HBV polymerase gene was sequenced and drug resistance mutations were characterized retrospectively in stored frozen plasma specimens.

RESULTS

From 4,419 ART-naive HIV-1-infected individuals, 223 (5.1%) were positive for serum HBsAg. Baseline stored sera were available for 84 patients, of whom 73 could be characterized virologically. This population was mainly represented by men who had sex with men (52.1%), native Spaniards (65.7%) and Latin Americans (16.4%). The mean age was 36 years, mean CD4(+) T-cell count 375 cells/mm(3) and mean plasma HIV RNA 4.5 log(10) copies/ml. The HBV genotype distribution was 64% A, 20% F, 12% D and 4% others. Drug-resistant mutations in the HBV polymerase were found in four (5.5%) patients: two harboured rtL180M, one rtL80V and one rtV173L.

CONCLUSIONS

The rate of primary drug resistance in HBV among newly diagnosed HIV-HBV-coinfected patients in Spain is currently low (5.5%) and restricted to 3TC. Thus, HBV drug resistance testing before prescription of oral antiviral therapy is not warranted, although periodic surveillance might be recommended.

Nucleoside analogues improve the short-term and long-term prognosis of patients with hepatitis B virus-related acute-on-chronic liver failure

Hepatitis B virus (HBV) infection is a major public health problem, and HBV-related acute-on-chronic liver failure (ACLF) has an extremely poor prognosis. There is no standard approach for managing ACLF. Nucleos(t)ide analogue has been proven effective in suppressing viral replication, improving histology and biochemical, and decreasing the inflammatory response in patients with chronic hepatitis B. This study was designed to evaluate the short-term and long-term efficacy of nucleoside analogue treatment of patients with HBV-related ACLF. One hundred and six consecutive subjects were recruited from 2,308 patients with elevated alanine aminotransferase activity. Forty-two patients were treated with 0.5 mg entecavir (ETV) daily (ETV group); 30 patients received 100 mg lamivudine (LAM) daily (LAM group); 34 patients did not take any nucleos(t)ide analogues (non-NAs group). All eligible patients were given standard medical treatment. All the patients were followed up until death or until October 2010. The HBV DNA levels and the short-term and long-term efficacy of the drugs were evaluated. After 3 weeks of nucleoside analogue treatment and/or supportive therapy, HBV DNA levels were decreased when compared with the baseline level in the ETV group (7.04 ± 1.58 log(10) IU/mL vs. 4.03 ± 2.04 log(10) IU/mL, P = 0.001), the LAM group (7.25 ± 0.89 log(10) IU/mL vs. 4.33 ± 2.48 log(10) IU/mL, P = 0.01), and the non-NAs group (5.73 ± 0.96 log(10) IU/mL vs. 4.21 ± 1.47 log(10) IU/mL, P = 0.01). The ETV and LAM groups showed a similar accumulative mortality in the first 3 months of treatment (33.3% vs. 40%, χ(2) = 0.568, P = 0.374). The non-NAs group had a significantly high mortality, compared with the ETV group (64.7% vs. 33.3%, χ(2) = 7.163, P = 0.007), the LAM group (64.7% vs. 40%, χ(2) = 3.906, P = 0.042), and the nucleoside analogue group (ETV group + LAM group) (64.7% vs. 36.2%, χ(2) = 7.443, P = 0.006). All the 56 patients survived were followed up to October 2010. The median follow-up period was 7.3 months. Recurrence was observed in a total of 6 patients (10.72%), of whom 4 patients (33.33%) were from the non-NAs group, 2 (11.11%) from the LAM group after cessation LAM therapy by patients himself, and 0 from the ETV group (P = 0.003). Nucleoside analogue may improve the short-term and long-term prognosis of patients with HBV-related ACLF.

Easy-to-use phylogenetic analysis system for hepatitis B virus infection

AIM

  The molecular phylogenetic analysis has been broadly applied to clinical and virological study. However, the appropriate settings and application of calculation parameters are difficult for non-specialists of molecular genetics. In the present study, the phylogenetic analysis tool was developed for the easy determination of genotypes and transmission route.

METHODS

  A total of 23 patients of 10 families infected with hepatitis B virus (HBV) were enrolled and expected to undergo intrafamilial transmission. The extracted HBV DNA were amplified and sequenced in a region of the S gene.

RESULTS

  The software to automatically classify query sequence was constructed and installed on the Hepatitis Virus Database (HVDB). Reference sequences were retrieved from HVDB, which contained major genotypes from A to H. Multiple-alignments using CLUSTAL W were performed before the genetic distance matrix was calculated with the six-parameter method. The phylogenetic tree was output by the neighbor-joining method. User interface using WWW-browser was also developed for intuitive control. This system was named as the easy-to-use phylogenetic analysis system (E-PAS). Twenty-three sera of 10 families were analyzed to evaluate E-PAS. The queries obtained from nine families were genotype C and were located in one cluster per family. However, one patient of a family was classified into the cluster different from her family, suggesting that E-PAS detected the sample distinct from that of her family on the transmission route.

CONCLUSIONS

  The E-PAS to output phylogenetic tree was developed since requisite material was sequence data only. E-PAS could expand to determine HBV genotypes as well as transmission routes.

Long-term efficacy of entecavir in adefovir-refractory chronic hepatitis B patients with prior lamivudine resistance

This study aimed to evaluate the long-term efficacy of entecavir (ETV) in adefovir (ADV)-refractory chronic hepatitis B (CHB) patients with prior lamivudine (LMV) resistance. A total of 55 ADV-refractory CHB patients with prior LMV resistance, who received rescue therapy with ETV 1 mg daily for at least 12 months, were consecutively enrolled and analysed. Forty-four patients were men, and their median age was 47 (25-69). Ten patients had liver cirrhosis and 46 patients were positive for hepatitis B e antigen (HBeAg). Median hepatitis B virus DNA levels were 6.6 (4.3-8.0) log(10) copies/mL, and the median duration of ETV therapy was 24 (12-47) months. Cumulative virologic response rates at 6, 12, 24 and 36 months were 18%, 29%, 58% and 75%, respectively. HBeAg loss occurred in 10 (21.7%) of 46 HBeAg-positive patients. In multivariate analysis, only initial virologic response at 3 months remained as an independent predictor for virologic response (RR 3.143; 95% CI 1.387-7.120; P = 0.006). The patients with a virological response at 3 months had not only a significantly higher probability of achieving a virologic response (P < 0.001) but also lower probability of experiencing a virologic breakthrough (P = 0.043) than the patients without an early response. Viral breakthrough was observed in 29 patients during the follow-up period. Cumulative breakthrough rates at 6, 12, 24 and 36 months were 0%, 15%, 45% and 73%, respectively. ETV monotherapy may be considerably efficacious in cases with an initial virological response but its efficacy is attenuated by frequent emergence of ETV resistance in ADV-refractory CHB patients with prior LMV resistance.

Virologic and clinical characteristics of HBV genotypes/subgenotypes in 487 Chinese pediatric patients with CHB

Background

The association of hepatitis B virus (HBV) genotypes/subgenotypes with clinical characteristics is increasingly recognized. However, the virologic and clinical features of HBV genotypes/subgenotypes in pediatric patients remain largely unknown.

Methods

Four hundred and eighty-seven pediatric inpatients with CHB were investigated, including 217 nucleos(t)ide analog-experienced patients. HBV genotypes/subgenotypes and reverse transcriptase (RT) mutations were determined by direct sequencing. The stage of fibrosis and degree of inflammatory activity were evaluated by the Metavir score system.

Results

Among 487 enrolled pediatric patients, HBV genotype C2 and B2 were the most two prevalent (73.7% and 21.1%). Comparing with HBV/B2 infected patients, no significant difference was observed in the incidence rate and mutant patterns of lamivudine- or adefovir-resistant mutations in HBV/C2 infected patients (P > 0.05). Importantly, we found that the degree of hepatic inflammation degree, fibrosis stage and ALT level were significantly higher in HBV/C2-infected HBeAg positive patients than it was in HBV/B2-infected ones.

Conclusions

The pediatric patients with HBV/C2 infection might be more susceptible to develop severe liver pathogenesis.

Characterization of drug-resistance mutations in HBV D-genotype chronically infected patients, naïve to antiviral drugs

Presence of drug-resistance mutations in drug-naïve hepatitis B virus (HBV) infected patients can seriously compromise response to antiviral treatment. Therefore, our study was aimed at defining the prevalence of HBV drug-resistance in a population of 140 patients, all infected with HBV-D-genotype (the most common HBV-genotype in Eastern Europe, Mediterranean countries and Middle East) and naïve to antiviral therapy. HBV reverse-transcriptase (RT) region was sequenced and analyzed for 20 mutations, confirmed by in vitro studies as associated with resistance to nucleos(t)ide HBV-RT inhibitors (rtL80I/V-rtI169T-rtV173L-rtL180M-rtA181T/V/S-rtT184A/S/G/C-rtA194T-rtS202C/G/I-rtM204V/I-rtN236T-rtM250V). Amino acid changes at other six RT positions, potentially associated with resistance, were also analyzed (rtV84M-rtV191I-rtV207L-rtV214A-rtQ215S-rtI233V). Overall, only 2/140 (1.4%) patients carried primary drug-resistance mutations [rtA181V (0.7%), and rtA194T (0.7%)], while 3/140 (2.1%) patients harbored the secondary mutations rtV173L (1.4%) and rtL180M (0.7%). Additionally, five polymorphic mutations, with a suggested role in drug resistance, were detected [rtQ215S (12.8%), rtI233V (4.3%), rtV214A (3.6%), rtV191I (0.7%), rtV207L (0.7%)]. Notably, no YMDD mutations, namely rtM204V/I, were found. Taken together, the rate of important drug resistance mutations in naïve HBV D-genotype infected patients is today very low, and suggests the potential full efficacy of new-generation antiviral drugs used in first line therapy. Whether such low rate can be extrapolated to non HBV-D subtypes, requires a detailed investigation to be performed in a different cohort of patients.

Entecavir treatment for chronic hepatitis B: adaptation is not needed for the majority of naïve patients with a partial virological response

Entecavir (ETV) is a potent inhibitor of viral replication in nucleos(t)ide analogue (NA)-naïve chronic hepatitis B (CHB) patients. The aim of this study was to investigate the long term efficacy and safety of ETV in NA-naïve CHB patients, particularly in those with detectable hepatitis B virus (HBV) DNA after 48 weeks, in whom treatment adaptation is suggested by current guidelines. In a multicenter cohort study, we investigated 333 CHB patients treated with entecavir monotherapy. The NA-naïve population consisted of 243 patients, whereas 90 were NA-experienced. Virological response (VR) (HBV DNA<80 IU/mL) was achieved in 48%, 76%, and 90% of hepatitis B e antigen (HBeAg)-positive and in 89%, 98%, and 99% of HBeAg-negative NA-naïve patients at weeks 48, 96, and 144, respectively. Thirty-six of 175 (21%) NA-naïve patients with at least 48 weeks of follow-up had a detectable load at week 48 (partial virological response [PVR]). Twenty-nine (81%) patients with PVR reached VR during prolonged ETV monotherapy, and none of them developed ETV-resistance. Among 22 patients with HBV DNA<1,000 IU/mL at week 48, VR was achieved in 21 (95%) patients, compared with eight of 14 (57%) patients with HBV DNA≥1,000 IU/mL. Continuous HBV DNA decline was observed in most patients without VR during follow-up, and in three patients adherence was suboptimal according to the treating physician. ETV was safe and did not affect renal function or cause lactic acidosis.

CONCLUSION

ETV monotherapy can be continued in NA-naïve patients with detectable HBV DNA at week 48, particularly in those with a low viral load because long-term ETV leads to a virological response in the vast majority of patients.

Randomised clinical trial: efficacy of peginterferon alfa-2a in HBeAg positive chronic hepatitis B patients with lamivudine resistance

BACKGROUND

Previous studies suggested that a finite course of peginterferon alfa-2a may offer an alternative rescue therapy for patients with lamivudine resistance. However, because of the limitation of study design and small sample size, it is difficult to make definitive conclusion.

AIM

To explore the role of peginterferon alfa-2a, in the rescue treatment of HBeAg-positive chronic hepatitis B patients with lamivudine resistance.

METHODS

In this randomised study, chronic hepatitis B patients with lamivudine resistance were treated with peginterferon alfa-2a for 48 weeks (n=155) or adefovir for 72 weeks (n=80). All enrolled patients were treated with lamivudine for the first 12weeks.

RESULTS

At 6 months posttreatment, 14.6% (18/123) of peginterferon alfa-2a-treated patients achieved HBeAg seroconversion, in contrast to 3.8% (3/80) of adefovir-treated patients after 72 weeks continuous therapy (P=0.01). For peginterferon alfa-2a-treated patients, the rate of HBeAg seroconversion at week 72 was significantly higher in patients who had HBsAg decline >0.5 Log(10) IU/mL from baseline at week 24, compared with patients with HBsAg decline ≤0.5 Log(10) IU/mL from baseline at week 24 (25.5% vs. 7.7%, P=0.01). After 72 weeks continuous adefovir treatment, 22.5% of patients achieved HBV DNA <80 IU/mL, compared with 10.6% in peginterferon alfa-2a-treated patients at 6months off-treatment (P=0.02).

CONCLUSIONS

Overall, the response to peginterferon alfa-2a among patients with lamivudine resistance was suboptimal. HBeAg seroconversion rate at week 72 by 48 weeks peginterferon alfa-2a treatment was higher than continuous adefovir therapy. Monitoring HBsAg levels can help to predict response to peginterferon alfa-2a.

HIV and hepatitis virus resistance to antivirals: review of data from the XIX International HIV and Hepatitis Virus Drug Resistance Workshop and curative strategies

The XIX International HIV and Hepatitis Virus Drug Resistance Workshop offered scientists, clinical investigators, physicians and others an opportunity to present study results selected in a rigorous peer-review process and to discuss those data in an open forum. In 2010, Workshop organizers expanded the programme to include hepatitis B and C viruses, reasoning that workers in all three fields could benefit from shared experience, positive and negative. Slide sessions at the 2010 Workshop focused on hepatitis virus resistance to current and experimental antivirals; epidemiology of HIV resistance; HIV pathogenesis, fitness and resistance; resistance to new antiretrovirals; markers of response to HIV entry inhibitors; HIV persistence, reservoirs and elimination strategies; application of new viral sequencing techniques; and mechanisms of HIV drug resistance. This article summarizes all slide presentations at the Workshop.

A high level of mutation tolerance in the multifunctional sequence encoding the RNA encapsidation signal of an avian hepatitis B virus and slow evolution rate revealed by in vivo infection

In all hepadnaviruses, protein-primed reverse transcription of the pregenomic RNA (pgRNA) is initiated by binding of the viral polymerase, P protein, to the ε RNA element. Universally, ε consists of a lower stem and an upper stem, separated by a bulge, and an apical loop. Complex formation triggers pgRNA encapsidation and the ε-templated synthesis of a DNA oligonucleotide (priming) that serves to generate minus-strand DNA. In vitro systems for duck hepatitis B virus (DHBV) yielded important insights into the priming mechanism, yet their relevance in infection is largely unexplored. Moreover, additional functions encoded in the DHBV ε (Dε) sequence could affect in vivo fitness. We therefore assessed the in vivo performances of five recombinant DHBVs bearing multiple mutations in the upper Dε stem. Three variants with only modestly reduced in vitro replication competence established chronic infection in ducks. From one variant but not another, three adapted new variants emerged upon passaging, as demonstrated by increased relative fitness in coinfections with wild-type DHBV. All three showed enhanced priming and replication competence in vitro, and in one, DHBV e antigen (DHBeAg) production was restored. Pronounced impacts on other Dε functions were not detected; however, gradual, synergistic contributions to overall performance are suggested by the fact of none of the variants reaching the in vivo fitness of wild-type virus. These data shed more light on the P-Dε interaction, define important criteria for the design of future in vivo evolution experiments, and suggest that the upper Dε stem sequences provided an evolutionary playground for DHBV to optimize in vivo fitness.

Efficacy and tolerance of a combination of tenofovir disoproxil fumarate plus emtricitabine in patients with chronic hepatitis B: a European multicenter study

BACKGROUND AND AIMS

The combination of tenofovir disoproxil fumarate (TDF) plus emtricitabine (FTC) is used extensively to treat HIV infection and also has potent activity against hepatitis B virus (HBV) infection. The aim of this study was to assess the efficacy and tolerance of TDF + FTC in patients with chronic hepatitis B (CHB).

METHODS

Seventy eight consecutive CHB patients from five European centers were included. All started a TDF + FTC combination between October 2005 and March 2010. Virological, biochemical, and clinical data were recorded during follow-up. Tolerance was also monitored. Patients were classified into either treatment simplification (TS), where efficacy of the previous treatment was obtained at TDF + FTC initiation, and treatment intensification (TI), where the previous line of therapy had failed.

RESULTS

TDF + FTC was given as a TI to 54 patients (69%) and as a TS to 24 (31%). Among patients with TI, 83% were males. The median baseline HBV-DNA was 4.4 log10 IU/mL, and median alanine-transaminase (ALT) was 1.10 × ULN. Sixty percent were HBeAg positive, 47% had significant fibrosis (≥ F3 Metavir equivalent), and 29% had confirmed cirrhosis. Median treatment duration was 76 weeks (interquartile range 60-116). Kaplan-Meier analysis showed that, 48 weeks after TI, the probability of being HBV-DNA becoming undetectable was 76%, and reached 94% at week 96. No viral breakthrough occurred. Patients with TS (87% males, median baseline HBV-DNA 1.1 log10 IU/mL, median ALT 0.79 × ULN, 33% HBeAg positive, 61% with significant fibrosis) were treated for a median duration of 76 weeks. In this subgroup, all patients but one remained HBV-DNA undetectable and no ALT flare-up occurred during follow-up. Creatinine levels did not show kidney-function deterioration in either group of patients.

CONCLUSIONS

After a median follow-up of > 76 weeks, the TDF + FTC combination showed encouraging antiviral efficacy and a good safety profile in all patients with CHB. TDF + FTC may represent an interesting clinical option to simplify therapy and increase the barrier to resistance, which should be assessed in the long term.

[Interferon-based versus direct antiviral therapy in patients with chronic hepatitis B]

Treatment of chronic hepatitis B is still challenging. Lots of parameters are needed to be considered before and during the therapy. There are several possible endpoints and their durability is very much variable. Patients with HBeAg-positive and HBeAg-negative hepatitis B need treatment. Two different strategies are available. Interferon-based therapy is a limited treatment, which might result in a sustained immune response in about one third of the patients, leading to an induced remission, sometimes years after the end of the treatment. According to the other strategy a continuous, indefinite oral nucleoside/nucleotide analogue (NA) treatment is administered to maintain a remission. However, relapse is rather frequent after the cessation of this therapy. During the long-term NA treatment drug resistance can lead to the loss of antiviral effect. Three first-line drugs are recommended, pegylated interferon alfa-2a, entecavir and tenofovir. If there is no contraindication to interferon, it is worth trying to achieve immune control and an induced remission. In patients, who do not respond to interferon, a sequential NA therapy is indicated.

Large-scale survey of naturally occurring HBV polymerase mutations associated with anti-HBV drug resistance in untreated patients with chronic hepatitis B

Drug resistance is a major limitation for the long-term efficacy of antiviral therapy with nucleos(t)ide analogues (NAs) in chronic hepatitis B (CHB). Antiviral resistance mutations may pre-exist in the overall viral population of untreated patients. We aimed to assess the prevalence of such hepatitis B virus (HBV) variants in a large cohort of NAs-naïve patients with CHB and to explore possible association with viral and host variables. Serum samples from 286 NAs-naïve consecutive patients with CHB were tested for serum HBV-DNA, and 255 of them having HBV-DNA > 1000 IU/mL were further analysed for drug resistance mutations by INNO-LiPA HBV DRv2/v3. NAs-naïve patients analysed were mainly men (73%), Caucasians (85%), hepatitis B e Antigen (HBeAg) negative (79%) and genotype D (69%), with a mean age of 43.2 ± 13.4 years. HBV mutations associated with antiviral drug resistance were detected in 13 (5%) patients: three patients infected with HBV genotype C had the rtM204V + rtL180M mutations associated with lamivudine (LMV) resistance. Four patients had the rtI233V mutation that may reduce sensitivity to adefovir, and three patients had the rtM250L/V mutation typical of entecavir resistance. LMV compensatory mutations rtL80V and rtV173L were seen in two and one patients, respectively. No relationship was seen between presence of resistant or compensatory mutations and HBV-DNA levels, HBeAg/anti-HBe status or previous IFN therapy. These results confirm that HBV mutations, which confer resistance against currently available anti-HBV NAs, may already exist in patients who have never received the drug.

Adefovir serum levels do not differ between responders and nonresponders

Primary or secondary failure of adefovir dipivoxil (ADV) therapy of chronic hepatitis B is not infrequent. The reasons for suboptimal responses are not well defined. In HIV and hepatitis C virus infection, failure of antiviral drug therapy has been linked with low blood drug levels. We have studied 20 well-defined patients with chronic hepatitis B who were treated with ADV for drug and virus kinetics. Importantly, neither Cmax levels (mean 26 ng/mL, range 14-59 ng/mL) nor the time to maximal drug levels (mean 4 h, range 2-8 h) differed between patients showing a complete virological response to adefovir (n = 10), patients with secondary treatment failure (n = 7) and patients with suboptimal primary response (hepatitis B virus-DNA >10,000 IU/mL after 6 months of treatment; n = 3). Thus, adefovir treatment failure is unlikely to be due to an inability to mount sufficient drug levels in the blood.

Long-term effects of lamivudine treatment in Japanese chronic hepatitis B patients

AIM: To analyze the association between the emergence of tyrosine-methionine-asparatate-asparatate (YMDD) mutants (reverse transcription; rtM204I/V) and deterioration of liver function during long-term lamivudine treatment of Japanese patients with chronic hepatitis B virus (HBV) infection.

METHODS: The data of 61 consecutive Japanese patients with chronic hepatitis B who underwent continuous lamivudine treatment for more than 24 mo and had a virological response were analyzed. Analysis of YMDD mutants was done by real-time polymerase chain reaction with LightCycler probe hybridization assay for up to 90 mo (mean, 50.8 mo; range, 24-90 mo).

RESULTS: A mixed mutant-type (YMDD + tyrosine-isoleucine-asparatate-asparatate: YIDD or tyrosine-valine-asparatate-asparatate: YVDD) or a mutant-type (YIDD or YVDD) were found in 57.4% of 61 patients at 1 year, 78.7% of 61 patients at 2 years, 79.6% of 49 patients at 3 years, 70.5% of 34 patients at 4 years, 68.4% of 19 patients at 5 years, 57.1% of 14 patients at 6 years, and 33.3% of 6 patients at 7 years. Of the 61 patients, 56 (92%) had mixed mutant- or a mutant-type. Only 5 (8%) had no mutants at each observation point. Virological breakthrough was found in 26 (46.4%) of 56 patients with YMDD mutants, 20 of whom had a hepatitis flare-up: the remaining 30 (53.6%) had neither a virological breakthrough nor a flare-up. All 20 patients who developed a hepatitis flare-up had a biochemical and virological response after adefovir was added to the lamivudine treatment.

CONCLUSION: Our results suggest that it is possible to continue lamivudine treatment, even after the emergence of YMDD mutants, up to the time that the patients develop a hepatitis flare-up.

Therapeutic vaccines and immune-based therapies for the treatment of chronic hepatitis B: perspectives and challenges

The treatment of chronic hepatitis B virus (HBV) infection has greatly improved over the last 10 years, but alternative treatments are still needed. Therapeutic vaccination is a promising new strategy for controlling chronic infection. However, this approach has not been as successful as initially anticipated for chronic hepatitis B. General impairment of the immune responses generated during persistent HBV infection, with exhausted T cells not responding correctly to therapeutic vaccination, is probably responsible for the poor clinical responses observed to date. Intensive research efforts are now focusing on increasing the efficacy of therapeutic vaccination without causing liver disease. Here we describe new approaches to use with therapeutic vaccination, in order to overcome the inhibitory mechanisms impairing immune responses. We also describe innovative strategies for generating functional immune responses and inducing sustained control of this persistent infection.

Heat shock protein gp96 enhances humoral and T cell responses, decreases Treg frequency and potentiates the anti-HBV activity in BALB/c and transgenic mice

More than 350 million people worldwide are chronically infected with hepatitis B virus (HBV). Broad repertoire and strong magnitude of HBV-specific T cell responses are thought to play key roles for virus control and clearance. Previous studies together with ours showed that heat shock protein gp96 as adjuvant induces antigen specific T cell responses, yet little is known for its anti-viral properties. Here, we investigated the role of gp96 mediated cellular and humoral immunity in antiviral effects in HBV transgenic mice. Immunization with HBV surface (HBsAg) and core (HBcAg) antigens combined formulation along with gp96 induced robust antiviral T-cell and antibody immunity against HBsAg and HBcAg. Compared with non-immunized control, immunization with gp96 adjuvant vaccine led to decrease of serum HBs level and HBc expression in hepatocyte by 45% and 90% at maximum, respectively, and decreased serum HBV-DNA level to below or close to the detection limit 4 weeks after the last immunization, suggesting the therapeutic effect. A significant enhancement in cellular responses towards HBcAg and increased infiltration of CD8+ T cells in liver of transgenic were observed under treatment with gp96 compared with no treatment (P<0.05 or 0.01). Treatment with gp96 was capable of reducing Tregs by overall 30-40%. The superior immune responses induced with the aid of gp96 correlated with improved antiviral effect by vaccination with HBsAg and HBcAg. We conclude that gp96 may contribute to enhanced antiviral immunity in transgenic mice at least partly by Treg down-regulation. HBcAg may act as potent adjuvant for Th1 response. Our study reveals the novel property of gp96 in immune modulation and its potential use for breaking immunotolerance in immunotherapy of chronic HBV infection.

A Tyr residue in the reverse transcriptase domain can mimic the protein-priming Tyr residue in the terminal protein domain of a hepadnavirus P protein

Hepadnaviruses are the only known viruses that replicate by protein-primed reverse transcription. Beyond the conserved reverse transcriptase (RT) and RNase H domains, their polymerases (P proteins) carry a unique terminal protein (TP) domain that provides a specific Tyr residue, Tyr96 in duck hepatitis B virus (DHBV), to which the first nucleotide of minus-strand DNA is autocatalytically attached and extended by three more nucleotides. In vitro reconstitution of this priming reaction with DHBV P protein and cellular chaperones had revealed strict requirements for the Dε RNA stem-loop as a template and for catalytic activity of the RT domain plus RNA-binding competence of the TP domain. Chaperone dependence can be obviated by using a truncated P protein (miniP). Here, we found that miniP with a tobacco etch virus (TEV) protease cleavage site between TP and RT (miniP(TEV)) displayed authentic priming activity when supplied with α-(32)P-labeled deoxynucleoside triphosphates; however, protease cleavage revealed, surprisingly, that the RT domain was also labeled. RT labeling had identical requirements as priming at Tyr96 and originated from dNMP transfer to a unique Tyr residue identified as Tyr561 in the presumed RT primer grip motif. Mutating Tyr561 did not affect Tyr96 priming in vitro and only modestly reduced replication competence of an intact DHBV genome; hence, deoxynucleotidylated Tyr561 is not an obligate intermediate in TP priming. However, as a first alternative substrate for the exquisitely complex protein-priming reaction, dNMP transfer to Tyr561 is a novel tool to further clarify the mechanism of hepadnaviral replication initiation and suggests that specific priming inhibitors can be found.

[Current treatment of hepatitis B infection: where do the new nucleos(t)ide analogues fit in?]

One of the most important advances made in the treatment of chronic hepatitis B infection has been the development of nucleos(t)ide analogues. The first antiviral agents used had limited efficacy due to the high resistance rate. However, in the last few years, new agents (tenofovir, entecavir) have been developed with greater antiviral potency and a lower resistance rate. Consequently, these agents are considered to be the treatment of choice in the most recent clinical guidelines. Nevertheless, interferon may still play an important role in the treatment of hepatitis B in selected patients. Moreover, in some contexts, such as renal insufficiency, pregnancy or immunosuppression, the role of the new oral antiviral agents has not been precisely defined. The present review analyzes these aspects, as well as some of the particular features of the management of patients treated with nucleos(t)ide analogues.

A conserved arginine residue in the terminal protein domain of hepatitis B virus polymerase is critical for RNA pre-genome encapsidation

Hepadnaviruses, including human hepatitis B virus (HBV) and duck hepatitis B virus (DHBV), replicate their DNA genome through reverse transcription. Although hepadnaviral polymerase (Pol) is distantly related to retroviral reverse transcriptases, some of its features are distinct. In particular, in addition to the reverse transcriptase and RNase H domains, which are commonly encoded by retroviral reverse transcriptases, the N-terminally extended terminal protein (TP) domain confers unique features such as protein-priming capability. Importantly, the TP domain is also essential for encapsidation of the viral RNA pre-genome. To gain further insight into the TP domain, this study used clustered charged residue-to-alanine mutagenesis of HBV Pol. Of the 20 charged residues examined, only one arginine (R105) was critical for RNA encapsidation. This result contrasts with previous findings for DHBV Pol regarding the critical residue of the TP domain required for RNA binding. Firstly, R128 of DHBV Pol, which corresponds to R105 of HBV Pol, was reportedly tolerable to alanine substitution for RNA binding. Secondly, the C-terminal arginine residue of the DHBV Pol TP domain (R183) was shown to be critical for RNA binding, whereas alanine substitution of the corresponding arginine residue of the HBV Pol TP domain (R160) remained able to support RNA encapsidation. Together, these data highlight the divergence between avian and mammalian hepadnaviral Pols with respect to an arginine residue critical for RNA encapsidation.

Detection of lamivudine- or adefovir-resistant hepatitis B virus mutations by a liquid array

A novel polymerase chain reaction (PCR)-Luminex assay was developed for rapid, accurate, and high-throughput detection of the most important hepatitis B virus (HBV) variants, including those with reverse transcriptase (RT) domain L180M, M204I/V, A181T/V/S, I233V and N236T mutations associated with resistance to lamivudine (LAM) or adefovir (ADV). Using mixtures of mutant and wild-type HBV, this method was sufficiently sensitive for detecting 10(3)HBV ml(-1) and could detect minor mutants when they comprised 5% of the total viral population. Comparison of the PCR-Luminex assay with INNO-LiPA for detecting clinical LAM- or ADV-resistant chronic hepatitis B virus infection in 64 patients confirmed the following: the 2 methods were 97.9% (48 of 49) and 93.3% (14 of 15) concordant for detecting LAM- or ADV-resistance mutations, respectively. The agreement with direct sequencing was 70.3% (45 of 64). The PCR-Luminex assay or multi-analyte suspension array can detect simultaneously and efficiently minor populations HBV mutants early during infection in many clinical samples. It is a simple, cost-effective method for resistance surveillance or selecting appropriate antiviral agents and initiating timely rescue treatment before the development drug-resistance related virus or biochemical breakthrough.

Evolution and suppression of HBV strains with multidrug resistance to lamivudine, adefovir dipivoxil and entecavir in a patient with chronic hepatitis B

Here, we report a case of multidrug resistance in a patient with chronic hepatitis B. The patient sequentially received lamivudine, adefovir dipivoxil and entecavir, and subsequently developed single-, double- and triple-drug-resistant HBV strains. We consider this case report important because it documents, for the first time, that triple-drug-resistant HBV strains identified in a clinical setting were suppressible by lamivudine add-on adefovir dipivoxil when tenofovir disoproxil fumarate was not available.