Variant of hepatitis B virus with primary resistance to adefovir

The unexpected high prevalence of HBV subgenotype D4 in patients with chronic hepatitis B in Galicia, a northwestern Spanish region, reflects strong links with Latin America

BACKGROUND

Hepatitis B virus (HBV) comprises 9 genotypes and multiple subgenotypes that depict differences in geographic distribution, clinical outcome and response to antiviral therapy. However, the molecular epidemiology of HBV geno/subgenotypes is globally scarce. In Spain, HBV genotype D seems to be more prevalent in the northwestern regions compared to the rest of the country for unclear reasons.

METHODS

HBV genotyping was performed using geno2pheno on a S gene fragment amplified from plasma collected from all chronic hepatitis B individuals attended at one reference hospital in Santiago de Compostela, the Galicia's capital town. Phylogenetic and phylogeographic analyses using a fragment of 345 bp were performed in all viremic specimens. To avoid misleading allocation as consequence of short fragment analysis, several bioinformatic controls were used.

RESULTS

A total of 320 individuals with persistent serum HBsAg+ and detectable HBV-DNA were seen between 2000 and 2016 (male 68.4%; median age, 52 years-old; native Spaniards 83.8%). HBV genotype distribution was as follows: A 15.3%; B 1.6%; C 2.5%; D 71.6%; E 3.1%; F 2.2%; G 3.1%; and H 0.6%. HBV genotype D was mostly represented by D4 and D2 subgenotypes (33.4% and 15% of total, respectively). Compared to chronic hepatitis B patients with genotypes B, C, E and G, HBV-D4 carriers tended to be older (54.2% had >50 years-old) and HBeAg-negative (85%). Moreover, 43% were female, 4.7% had cirrhosis, 10.2% hepatitis C and 6.4% HIV coinfection. Phylogenetic analyses could be performed on 82 HBV-D4 specimens; and 79 were confirmed as HBV-D4 using PhyML. Phylogeography using FasTree suggested at least two distinct introductions of HBV-D4 in Galicia, one from the Caribbean and South America, and another from India.

CONCLUSIONS

HBV subgenotype D4 is the most prevalent HBV variant in chronic hepatitis B patients living in the northwest of Spain, representing 33.4% (107/320) of all chronic hepatitis B infections. This rate of HBV-D4 is among the highest reported worldwide. Epidemiological and phylogenetic analyses suggest a strong association with historical migrant exchanges with Latin America, and especially with the Caribbean basin.

Adefovir for lamivudine-resistant hepatitis B

Adefovir, a nucleotide analog developed by John Martin, was a major breakthrough in the treatment of chronic Hepatitis B. Prior to adefovir, Hepatitis B treatment was limited to two therapeutic modalities, either interferon, which carried significant side effects and was efficacious in a minority of patients, or lamivudine which showed no durable effects with short-term use and a high rate of resistance with long-term use. Adefovir was found to be effective in suppressing viral replication and in resolving the hepatic inflammation associated with hepatitis B with only rare instances of resistance. In this article, we appreciate John Martin’s contribution to science and medicine as we review the landmark trials of adefovir that brought forth a new era of treatment of Hepatitis B.

COLD-PCR Method for Early Detection of Antiviral Drug-Resistance Mutations in Treatment-Naive Children with Chronic Hepatitis B

We investigated Nucleos(t)ide-analogue (NA)-resistance mutations (mt) in 142 treatment-naive children with Chronic Hepatitis B (CHB), using a sensitive co-amplification at lower denaturation temperature (COLD)-PCR with Sanger DNA sequencing. An NA resistance-associated mt in the hepatitis B virus (HBV) reverse transcriptase (RT) was found in 66.2% of the patients, with nonclassical mt contributing the most (64.8%). Significantly higher frequencies of Lamivudine (LMV) and Adefovir dipivoxil (ADF) resistance-associated mt were found in genotypes B and C, respectively (OR_LMV/ADF: 1495.000; 95% CI: 89.800–24,889.032; p < 0.001). Single-point mt associated to LMV and ADF resistance were detected in 59.9% of the tested children with rtV207M (38.0%) and rtN238T (9.9%) being the most frequent. Multiple-point mt were found only in 8 cases (5.6%): 6 children carried double mt (rtV207M + rtL229V; rtV207M + rtI233V; rtV207I + rtV207M × 2 cases; rtV207M + rtS213T; rtN238A + rtS256G) relating to LMV or/and ADF resistance and 3 children carried triple mt (rtL180M + rtM204I + rtN238T; rtV207M + rtS213T + rtS256G) or quadruple mt (rtL180M + rtM204V + rtV207I/M) for LMV-ADF resistance and Entecavir-reduced susceptibility. Our data indicate that significantly higher frequencies of LMV and ADF-associated mutations were found in treatment-naïve children infected with HBV genotypes B and C, respectively. The developed COLD-PCR method and obtained data may contribute to the development of suitable treatments for children with CHB.

Coevolution analysis of amino-acids reveals diversified drug-resistance solutions in viral sequences: a case study of hepatitis B virus

The study of mutational landscapes of viral proteins is fundamental for the understanding of the mechanisms of cross-resistance to drugs and the design of effective therapeutic strategies based on several drugs. Antiviral therapy with nucleos(t)ide analogues targeting the hepatitis B virus (HBV) polymerase protein (Pol) can inhibit disease progression by suppression of HBV replication and makes it an important case study. In HBV, treatment may fail due to the emergence of drug-resistant mutants. Primary and compensatory mutations have been associated with lamivudine resistance, whereas more complex mutational patterns are responsible for resistance to other HBV antiviral drugs. So far, all known drug-resistance mutations are located in one of the four Pol domains, called reverse transcriptase. We demonstrate that sequence covariation identifies drug-resistance mutations in viral sequences. A new algorithmic strategy, BIS2TreeAnalyzer, is designed to apply the coevolution analysis method BIS2, successfully used in the past on small sets of conserved sequences, to large sets of evolutionary related sequences. When applied to HBV, BIS2TreeAnalyzer highlights diversified viral solutions by discovering thirty-seven positions coevolving with residues known to be associated with drug resistance and located on the four Pol domains. These results suggest a sequential mechanism of emergence for some mutational patterns. They reveal complex combinations of positions involved in HBV drug resistance and contribute with new information to the landscape of HBV evolutionary solutions. The computational approach is general and can be applied to other viral sequences when compensatory mutations are presumed.

Current state-of-the-art pharmacotherapy for the management of hepatitis B infection

INTRODUCTION

Hepatitis B virus (HBV) infection remains a global challenge with several hundred million infected individuals. Disease activity can be controlled, and adverse outcomes prevented when treatment can be provided. Frequently life-long therapy is required instead of defined treatment periods such as with the case of Hepatitis C Virus (HCV) infection.

AREAS COVERED

In this review, the authors provide an overview of current start of the art therapy for HBV and indicate where variation from the current guidelines could be considered. Certain patients may be eligible for treatment with suboptimal therapies when their baseline viral load is low. Identifying ideal candidates for interferon therapy will result in good sustained responses for some patients.

EXPERT OPINION

The biggest challenge remains linking patients to care and therapy. Patients can nowadays be sufficiently treated before the disease advances to a more progressed phase. However, future therapies must be extremely safe and ideally limit the required treatment period. Given Hepatitis D Virus's dependence on HBV and being a disease with an unmet clinical need, HDV may be the best target group for the development of a functional cure for hepatitis B.

Clinical Implications of Hepatitis B Virus RNA and Covalently Closed Circular DNA in Monitoring Patients with Chronic Hepatitis B Today with a Gaze into the Future: The Field Is Unprepared for a Sterilizing Cure

. Chronic hepatitis B virus (HBV) infection has long remained a critical global health issue. Covalently closed circular DNA (cccDNA) is a persistent form of the HBV genome that maintains HBV chronicity. Decades of extensive research resulted in the two therapeutic options currently available: nucleot(s)ide analogs and interferon (IFN) therapy. A plethora of reliable markers to monitor HBV patients has been established, including the recently discovered encapsidated pregenomic RNA in serum, which can be used to determine treatment end-points and to predict the susceptibility of patients to IFN. Additionally, HBV RNA splice variants and cccDNA and its epigenetic modifications are associated with the clinical course and risks of hepatocellular carcinoma (HCC) and liver fibrosis. However, new antivirals, including CRISPR/Cas9, APOBEC-mediated degradation of cccDNA, and T-cell therapies aim at completely eliminating HBV, and it is clear that the diagnostic arsenal for defining the long-awaited sterilizing cure is missing. In this review, we discuss the currently available tools for detecting and measuring HBV RNAs and cccDNA, as well as the state-of-the-art in clinical implications of these markers, and debate needs and goals within the context of the sterilizing cure that is soon to come.

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.

Polypharmacology in HIV inhibition: can a drug with simultaneous action against two relevant targets be an alternative to combination therapy?

HIV infection still has a serious health and socio-economical impact and is one of the primary causes of morbidity and mortality all over the world. HIV infection and the AIDS pandemic are still matters of great concern, especially in less developed countries where the access to highly active antiretroviral therapy (HAART) is limited. Patient compliance is another serious drawback. Nowadays, HAART is the treatment of choice although it is not the panacea. Despite the fact that it suppresses viral replication at undetectable viral loads and prevents progression of HIV infection into AIDS HAART has several pitfalls, namely, long-term side-effects, drug resistance development, emergence of drug-resistant viruses, low compliance and the intolerance of some patients to these drugs. Moreover, another serious health concern is the event of co-infection with more than one pathogen at the same time (e.g. HIV and HCV, HBV, herpes viruses, etc). Currently, the multi-target drug approach has become an exciting strategy to address complex diseases and overcome drug resistance development. Such multifunctional molecules combine in their structure pharmacophores that may simultaneously interfere with multiple targets and their use may eventually be more safe and efficacious than that involving a mixture of separate molecules because of avoidance or delay of drug resistance, lower incidence of unwanted drug-drug interactions and improved compliance. In this review we focus on multifunctional molecules with dual activity against different targets of the HIV life cycle or able to block replication, not only of HIV but also of other viruses that are often co-pathogens of HIV. The different approaches are documented by selected examples.

Profile of Mutations in the Reverse Transcriptase and Overlapping Surface Genes of Hepatitis B Virus (HBV) in Treatment-Naïve Indonesian HBV Carriers

Mutations in the reverse transcriptase (RT) region of the hepatitis B virus (HBV) genome are an important factor in low therapeutic effectiveness. Nonetheless, the prevalence of these mutations in HBV strains isolated previously in Indonesia has not been systematically examined. Therefore, in this study, we investigated the profile of mutations in the RT region and the associations of these mutations with amino acid changes in the surface protein in the virus of treatment-naïve Indonesian HBV carriers. Overall, 96 sequences of the full-length Indonesian HBV genomes (genotype B, n = 54; genotype C, n = 42) were retrieved from the National Center for Biotechnology Information. Naturally occurring primary and/or compensatory drug resistance mutations were found in 6/54 (11.1%) genotype B strains and in 1/42 (2.4%) genotype C strains. The potential mutations underlying resistance to a nucleos(t)ide analog and/or pretreatment mutations were more frequent in both genotypes but more frequent in genotype C strains than in genotype B strains. The A-B interdomain region in the RT gene was more frequently mutated in genotype C than in genotype B (3.51 ± 2.53 vs. 1.08 ± 1.52, P ＜ 0.001). Knowledge about the mutational profiles of the RT gene and changes in the surface protein may help clinicians to select the most appropriate antiviral drug and vaccination or HBV immunoglobulin regimen for management of HBV infection in Indonesia.

Hepatitis B reactivation characterized by HBsAg negativity and anti-HbsAg antibodies persistence in haematopoietic stem cell transplanted patient after lamivudine withdrawal

Background

HBV reactivation is associated with high mortality rates in hematopoietic stem cell transplantation (HSCT) and prophylactic lamivudine (LMV) treatment is suggested to prevent this phenomenon. However, the duration of LMV treatment in HSCT patients is not fully defined and the time of immune recovery is considered the best parameter for a drug to be safely interrupted. In patients undergoing allogeneic HSCT, the time of immune recovery is not easy to define and may take years after transplantation and prolonged LMV treatments, which can lead to drug-resistant viral strains.

Case presentation

An anti-HBc-positive hematological patient who was undergoing prolonged immunosuppression and who experienced HBV reactivation 3 months after the suspension of a prolonged LMV prophylaxis is described. HBV-DNA matching an atypical serological profile characterized by HbsAg negativity and anti-HBs positivity was detected in the patient. The genotypic analysis of the HBV strain identified T127P, F170FL and S204R mutations of HbsAg, which can hinder HBsAg recognition in a diagnostic assay.

Conclusions

HBV reactivation in the HSCT host can be sustained by HBsAg viral variants with characteristics of altered immunogenicity that cannot be detected by usual laboratory tests. This clinical case description suggests the importance of screening for serum HBV-DNA levels in the diagnosis of HBV reactivation and monitoring HBV-DNA after prophylaxis suspension, particularly in HSCT subjects who have undergone prolonged periods of LMV treatment.

Hepatitis B Virus Immunopathology, Model Systems, and Current Therapies

Most people develop acute hepatitis B virus (HBV)-related hepatitis that is controlled by both humoral and cellular immune responses following acute infection. However, a number of individuals in HBV-endemic areas fail to resolve the infection and consequently become chronic carriers. While a vaccine is available and new antiviral drugs are being developed, elimination of persistently infected cells is still a major issue. Standard treatment in HBV infection includes IFN-α, nucleoside, or nucleotide analogs, which has direct antiviral activity and immune modulatory capacities. However, immunological control of the virus is often not durable. A robust T-cell response is associated with control of HBV infection and liver damage; however, HBV-specific T cells are deleted, dysfunctional, or become exhausted in chronic hepatitis patients. As a result, efforts to restore virus-specific T-cell immunity in chronic HBV patients using antiviral therapy, immunomodulatory cytokines, or therapeutic vaccination have had little success. Adoptive cell transfer of T cells with specificity for HBV antigen⁺ cells represents an approach aiming to ultimately eliminate residual hepatocytes carrying HBV covalently closed circular DNA (cccDNA). Here, we discuss recent findings describing HBV immunopathology, model systems, and current therapies.

Association between hepatitis B co-infection and elevated liver stiffness among HIV-infected adults in Lusaka, Zambia

OBJECTIVE

To describe liver disease epidemiology among HIV-infected individuals in Zambia.

METHODS

We recruited HIV-infected adults (≥18 years) at antiretroviral therapy initiation at two facilities in Lusaka. Using vibration controlled transient elastography, we assessed liver stiffness, a surrogate for fibrosis/cirrhosis, and analysed liver stiffness measurements (LSM) according to established thresholds (>7.0 kPa for significant fibrosis and >11.0 kPa for cirrhosis). All participants underwent standardised screening for potential causes of liver disease including chronic hepatitis B (HBV) and C virus co-infection, herbal medicine, and alcohol use. We used multivariable logistic regression to identify factors associated with elevated liver stiffness.

RESULTS

Among 798 HIV-infected patients, 651 had a valid LSM (median age, 34 years; 53% female). HBV co-infection (12%) and alcohol use disorders (41%) were common and hepatitis C virus co-infection (<1%) was rare. According to LSM, 75 (12%) had significant fibrosis and 13 (2%) had cirrhosis. In multivariable analysis, HBV co-infection as well as male sex, increased age and WHO clinical stage 3 or 4 were independently associated with LSM >7.0 kPa (all P < 0.05). HBV co-infection was the only independent risk factor for LSM >11.0 kPa. Among HIV-HBV patients, those with elevated ALT and HBV viral load were more likely to have significant liver fibrosis than patients with normal markers of HBV activity.

CONCLUSIONS

HBV co-infection was the most important risk factor for liver fibrosis and cirrhosis and should be diagnosed early in HIV care to optimise treatment outcomes.

Hepatitis B Infection, Viral Load and Resistance in HIV-Infected Patients in Mozambique and Zambia

Background

Few data on the virological determinants of hepatitis B virus (HBV) infection are available from southern Africa.

Methods

We enrolled consecutive HIV-infected adult patients initiating antiretroviral therapy (ART) at two urban clinics in Zambia and four rural clinics in Northern Mozambique between May 2013 and August 2014. HBsAg screening was performed using the Determine^® rapid test. Quantitative real-time PCR and HBV sequencing were performed in HBsAg-positive patients. Risk factors for HBV infection were evaluated using Chi-square and Mann-Whitney tests and associations between baseline characteristics and high level HBV replication explored in multivariable logistic regression.

Results

Seventy-eight of 1,032 participants in Mozambique (7.6%, 95% confidence interval [CI]: 6.1–9.3) and 90 of 797 in Zambia (11.3%, 95% CI: 9.3–13.4) were HBsAg-positive. HBsAg-positive individuals were less likely to be female compared to HBsAg-negative ones (52.3% vs. 66.1%, p<0.001). Among 156 (92.9%) HBsAg-positive patients with an available measurement, median HBV viral load was 13,645 IU/mL (interquartile range: 192–8,617,488 IU/mL) and 77 (49.4%) had high values (>20,000 UI/mL). HBsAg-positive individuals had higher levels of ALT and AST compared to HBsAg-negative ones (both p<0.001). In multivariable analyses, male sex (adjusted odds ratio: 2.59, 95% CI: 1.22–5.53) and CD4 cell count below 200/μl (2.58, 1.20–5.54) were associated with high HBV DNA. HBV genotypes A1 (58.8%) and E (38.2%) were most prevalent. Four patients had probable resistance to lamivudine and/or entecavir.

Conclusion

One half of HBsAg-positive patients demonstrated high HBV viremia, supporting the early initiation of tenofovir-containing ART in HIV/HBV-coinfected adults.

The Association of Pre-S/S Gene Mutations and Hepatitis B Virus Vertical Transmission

BACKGROUND

HBV Pre-S/S gene mutations can occur before or after implementation of combined vaccination program. HBV Prs-S/S gene mutation is a risk factor of vaccination failure and frequently causes HBV vertical transfection.

OBJECTIVES

To assess the association of hepatitis B virus (HBV) S gene mutations with vertical transmission.

PATIENTS AND METHODS

In this prospective nested case-control study, a total of 60 pregnant women with positive serum HBsAg and HBV DNA ≥ 10(7) IU/mL were divided into a case group (15 cases with vaccination failure) and a control group (45 cases with vaccination success) according to whether their infants tested positive for HBV infection. Mothers and their children in the case group were further sub-divided into groups including mothers, newborns and infant (the same newborns at age of seven months). The pre-S/S gene mutations were detected by PCR and sequenced and its association with vertical transmission of HBV was analyzed.

RESULTS

HBV genotype B was the dominant genotype in the both groups' mothers. Each mother-child pair in case group had the same HBV genotype. There were no significant differences in mutation frequencies of HBV Pre-S/S gene between case and control groups' mothers (Fragment 1 (M): 2 vs. 4, P > 0.05; Fragment 2 (M): 10 vs. 10, P > 0.05), or among the mothers, newborns and infants in the case group (Fragment 1 (M): 2, 2, and 3, respectively, P > 0.05; Fragment 2 (M): 10, 10 and 10 respectively, P > 0.05). Mutation site analysis of the both groups' mothers demonstrated 108 different mutation sites in the HBV pre-S/S gene, with 105 silent mutations and 5 missense mutations including ntA826G, ntC531T, ntT667C, ntC512T and ntC546A. Among 15 mother-newborn-infant pairs with successful PCR and sequence in case group, 7 (41.17%) mother-newborn pairs, 9 (60.00%) mother-infant pairs and 3 (20.00%) infant-newborn pairs had different mutation sites.

CONCLUSIONS

HBV in children due to vaccination failure was resulted from vertical transmission. HBV Pre-S/S gene mutations were prevalent and could occur before or after vaccination. Therefore, simply analyzing mutation frequency of HBV gene was not of value. To advance blocking HBV vertical transmission, future studies should focus on specific mutation sites, potentially associated with vaccination failure.

Genetic variation of hepatitis B virus and its significance for pathogenesis

Hepatitis B virus (HBV) has a worldwide distribution and is endemic in many populations. Due to its unique life cycle which requires an error-prone reverse transcriptase for replication, it constantly evolves, resulting in tremendous genetic variation in the form of genotypes, sub-genotypes, and mutations. In recent years, there has been considerable research on the relationship between HBV genetic variation and HBV-related pathogenesis, which has profound implications in the natural history of HBV infection, viral detection, immune prevention, drug treatment and prognosis. In this review, we attempted to provide a brief account of the influence of HBV genotype on the pathogenesis of HBV infection and summarize our current knowledge on the effects of HBV mutations in different regions on HBV-associated pathogenesis, with an emphasis on mutations in the preS/S proteins in immune evasion, occult HBV infection and hepatocellular carcinoma (HCC), mutations in polymerase in relation to drug resistance, mutations in HBV core and e antigen in immune evasion, chronicalization of infection and hepatitis B-related acute-on-chronic liver failure, and finally mutations in HBV x proteins in HCC.

Molecular epidemiology of hepatitis B virus infection in Switzerland: a retrospective cohort study

BACKGROUND

Chronic hepatitis B virus (HBV) infection affects up to 7% of the European population. Specific HBV genotypes are associated with rapid progression to end-stage liver disease and sub-optimal interferon treatment responses. Although the geographic distribution of HBV genotypes differs between regions, it has not been studied in Switzerland, which lies at the crossroads of Europe.

METHODS

In a retrospective analysis of 465 HBV samples collected between 2002 and 2013, we evaluated the HBV genotype distribution and phylogenetic determinants, as well as the prevalence of serological evidence of hepatitis delta, hepatitis C and HIV infections in Switzerland. Baseline characteristics of patients were compared across their region of origin using Fisher's exact test and ANOVA, and risk factors for HBeAg positivity were assessed using logistic regression.

RESULTS

The Swiss native population represented 15.7% of HBV-infected patients living in Switzerland. In the overall population, genotype D was most prevalent (58.3%), whereas genotype A (58.9%) was the predominant genotype among the Swiss native population. The prevalence of patients with anti-HDV antibodies was 4.4%. Patients of Swiss origin were most likely to be HBeAg-positive (38.1%). HBV genotypes of patients living in Switzerland but sharing the same original region of origin were consistent with their place of birth.

CONCLUSIONS

The molecular epidemiology of HBV infection in Switzerland is driven by migration patterns and not by the genotype distribution of the native population. The prevalence of positive anti-HDV antibodies in our cohort was very low.

Hepatitis B viral load in dried blood spots: A validation study in Zambia

BACKGROUND

Access to hepatitis B viral load (VL) testing is poor in sub-Saharan Africa (SSA) due to economic and logistical reasons.

OBJECTIVES

To demonstrate the feasibility of testing dried blood spots (DBS) for hepatitis B virus (HBV) VL in a laboratory in Lusaka, Zambia, and to compare HBV VLs between DBS and plasma samples.

STUDY DESIGN

Paired plasma and DBS samples from HIV-HBV co-infected Zambian adults were analyzed for HBV VL using the COBAS AmpliPrep/COBAS TaqMan HBV test (Version 2.0) and for HBV genotype by direct sequencing. We used Bland-Altman analysis to compare VLs between sample types and by genotype. Logistic regression analysis was conducted to assess the probability of an undetectable DBS result by plasma VL.

RESULTS

Among 68 participants, median age was 34 years, 61.8% were men, and median plasma HBV VL was 3.98logIU/ml (interquartile range, 2.04-5.95). Among sequenced viruses, 28 were genotype A1 and 27 were genotype E. Bland-Altman plots suggested strong agreement between DBS and plasma VLs. DBS VLs were on average 1.59logIU/ml lower than plasma with 95% limits of agreement of -2.40 to -0.83log IU/ml. At a plasma VL ≥2,000IU/ml, the probability of an undetectable DBS result was 1.8% (95% CI: 0.5-6.6). At plasma VL ≥20,000IU/ml this probability reduced to 0.2% (95% CI: 0.03-1.7).

CONCLUSIONS

In a Zambian laboratory, we observed strong agreement between DBS and plasma VLs and high sensitivity in DBS at plasma VL ≥2,000IU/ml. As HBV treatment expands, DBS could increase access to HBV VL testing and care in SSA settings.

Performance of HBsAg point-of-care tests for detection of diagnostic escape-variants in clinical samples

BACKGROUND

Hepatitis B viruses (HBV) harboring mutations in the a-determinant of the Hepatitis B surface antigen (HBsAg) are associated with reduced reactivity of HBsAg assays.

OBJECTIVES

To evaluate the sensitivity and specificity of three HBsAg point-of-care tests for the detection of HBsAg of viruses harboring HBsAg mutations.

STUDY DESIGN

A selection of 50 clinical plasma samples containing HBV with HBsAg mutations was used to evaluate the performance of three HBsAg point-of-care tests (Vikia(®), bioMérieux, Marcy-L'Étoile, France. Alere Determine HBsAg™, Iverness Biomedical Innovations, Köln, Germany. Quick Profile™, LumiQuick Diagnostics, California, USA) and compared to the ARCHITECT HBsAg Qualitative(®) assay (Abbott Laboratories, Sligo, Ireland).

RESULTS

The sensitivity of the point-of-care tests ranged from 98% to 100%. The only false-negative result occurred using the Quick Profile™ assay with a virus harboring a D144A mutation.

CONCLUSIONS

The evaluated point-of-care tests revealed an excellent sensitivity in detecting HBV samples harboring HBsAg mutations.

Prevalence and types of drug-resistant variants in Chinese patients with acute hepatitis B

The presence of therapy-associated hepatitis B virus (HBV) variants is the main drawback of antiviral therapy for HBV infection. Moreover, drug-resistant variants are more insensitive to a second agent and more therapy-associated mutations will be present. To apply better nucleos(t)ide analogues (NA) and reduce the occurrence of resistance, the prevalence and types of drug-resistant mutations in acute hepatitis B patients were investigated in this study. One hundred three HBV DNA-positive patients with symptomatic acute hepatitis B that were observed from 2011 to 2013 were enrolled. Direct polymerase chain reaction sequencing was used firstly to screen HBV reverse-transcriptase domain to detect HBV mutants. Five lamivudine-resistant variants were identified. Clonal sequencing was performed for 5 resistance-positive samples and 10 other random samples. Interestingly, all detected samples harbored drug-resistant mutations, although with different percentage. Thirteen harbored lamivudine-related alone (five) or together with other NA related mutations (five with adefovir, one with entecavir, and one with telbivudine), and two of them harbored adefovir-related mutations. Also, mutations associated with four currently used NA were all detected, and the frequency is in accordance with the popularity of NA used in clinical practice. These data suggest that drug-resistant variants are present in patients with acute hepatitis B and NA should be applied more carefully for chronic hepatitis B patients developed from acute hepatitis B.

The rtA181S mutation of hepatitis B virus primarily confers resistance to adefovir dipivoxil

The study aimed to clarify clinical significance of hepatitis B virus (HBV) rtA181S mutation in Chinese HBV-infected patients. A total of 18 419 patients with chronic HBV infection from Beijing 302 Hospital were investigated. HBV complete reverse transcriptase region of polymerase was screened by direct sequencing, and the results were verified by clonal sequencing. Replication-competent mutant and wild-type HBV genomic amplicons were constructed and transfected into the HepG2 cells and cultured in the presence or absence of serially diluted nucleos(t)ide analogues. Intracellular HBV replicative intermediates were quantitated for calculating the 50% effective concentration of the drug (EC(50)). The rtA181S was detected in 98 patients with 12 kinds of mutational patterns. Genotype C and genotype B HBV infection occupied 91.8% and 8.2% in rtA181S-positive patients, in contrast to 84.6% and 15.4% in rtA181S-negative patients (P < 0.01). All rtA181S-positive patients had received nucleos(t)ide analogues. rtA181S was detected in multiple patients with virologic breakthrough. Phenotypic analysis of patient-derived viral strains showed that rtA181S, rtA181S+N236T, rtN236T and rtA181V strains had 68.5%, 49.9%, 71.4% and 66.2% of natural replication capacity of wild-type strain, and 3.7-fold, 9.8-fold, 7.9-fold and 5.6-fold increased EC(50) to adefovir dipivoxil (ADV). The rtA181S strain remained susceptible to lamivudine, entecavir and tenofovir, and ADV susceptibility was restored after the mutation was eliminated through site-directed mutagenesis. Rescue therapy with entecavir or combination therapy was effective in rtA181S-related ADV-refractory patients. The rtA181S mutation confers moderate resistance to ADV. It could be induced by either lamivudine or ADV and contribute ADV treatment failure.

Hepatitis B outbreak in a nursing home associated with reusable lancet devices for blood glucose monitoring, Northern Germany 2010

In September 2010, an outbreak of acute hepatitis B virus (HBV) infections in a nursing home was notified to public health authorities in Northern Germany. To identify the route of transmission and prevent further cases a retrospective cohort study was conducted. Blood samples of residents were tested for serologic markers of HBV infection and HBV subgenotypes and sequences were analyzed. Outbreak-related cases were defined as residents of the nursing home with detection of hepatitis B surface antigen (HBsAg) and the HBV DNA sequence of the outbreak strain in 2010. Information on possible risk factors as patient care, invasive diagnostic, and therapeutical procedures was collected using a standardized questionnaire. Risk ratios (RR) and 95% confidence intervals (CI) were estimated with exact Poisson regression and binomial regression. Sixty-four residents were included in the study, 5 of them were outbreak-related cases, 12 had a past HBV infection. The outbreak strain belonged to HBV genotype D2 (HBsAg subtype ayw3, Ala118) which is not prevalent in Germany but in Eastern Europe. All cases (median age 81) were female, had diabetes, blood glucose monitoring, and chiropody. In multivariable analysis only blood glucose monitoring was associated with HBV infection (RR = 22, 95%CI 3.0-∞). Blood glucose monitoring was reported to be done by nursing home staff with patient-based reusable lancet devices. In nursing home settings the use of single use lancets for blood glucose monitoring is recommended strongly to prevent transmission. National guidelines on the handling of point-of-care devices and reusable equipment in long-term care facilities should be developed.

Visualizing hepatitis B virus with biarsenical labelling in living cells

BACKGROUND

Study on viruses has greatly benefited from visualization of viruses tagged with green fluorescent protein (GFP) in living cells. But GFP tag, as a large inserted fragment, is not suitable for labelling Hepatitis B virus (HBV) that is a compact virion with limited internal space.

AIM

To visualize HBV in living cells, we constructed several recombinant HBV fluorescently labelled with biarsenical dye to track the behaviour of HBV in the cytoplasm of infected cells.

METHODS

By mutagenesis, a smaller size tetracysteine (TC) tag (C-C-P-G-C-C) that could be bound with a biarsenical fluorescent dye was genetically inserted at different cell epitopes of HBV core protein expressed in transfected cells.

RESULT

Confocal microscopy and transmission electron microscopy (TEM) observations showed that TC-tagged core proteins bound with biarsenical dye could specifically fluoresce in cells and be incorporated into nucleocapsid to form fluorescent virions. The recombinant fluorescent HBV virions retained their infectivity as wild-type ones. Moreover, tracking of fluorescent HBV particles in living cells reveals microtubule-dependent motility of the intracellular particles.

CONCLUSION

To the best of our knowledge, this is the first time to generate fluorescent HBV virions with biarsenical labelling and to visualize their trafficking in living cells. The fluorescent HBV may become one highly valuable tool for further studying detailed dynamic processes of HBV life cycle and interaction of HBV with host in live-imaging approach.

Management of antiviral drug resistance in chronic hepatitis B

Rescue antiviral treatment for patients with resistance to preexisting nucleos(t)ide analogues remains a clinical challenge. The correct choice of a first-line treatment of high potency and with a high genetic barrier to achieve sustained long-term suppression of viral replication provides the best chance of preventing treatment failure and the emergence of drug resistance. The management of treatment failure and drug resistance requires a precise and accurate clinical and virologic monitoring. Combination treatment with antiviral drugs that belong to different groups is associated with a lower chance of developing resistance to rescue drugs. To guarantee better control of viral replication in patients with drug resistance, the addition of another drug without a cross resistance profile should be given as early as possible, preferably at the time when genotypic resistance emerges. Long-term surveillance for treatment efficacy and possible emergence of drug resistance should be continued to prevent the emergence of multidrug-resistant strains.

Effect of hepatitis B virus reverse transcriptase variations on entecavir treatment response

BACKGROUND

Entecavir therapy often reduces hepatitis B virus (HBV) DNA to an undetectable level, but HBV DNA remain detectable in some patients. We investigated whether baseline HBV reverse transcriptase (rt) polymorphism and quasispecies complexity and diversity were associated with treatment response.

METHODS

Pretreatment HBV DNA levels, HBV rt sequence, serology, and quasispecies complexity and diversity from 305 entecavir-treated patients were determined. These data were tested for their association with year 1 virological outcome, defined by optimal response (undetectable HBV DNA; lower limit of detection, ≤12 IU/mL) or partial response (detectable HBV DNA).

RESULTS

Four rt variants were more frequently detected in the 64 partial responders than in the 241 optimal responders (all P < .05). Multivariate analysis revealed that high baseline HBV DNA level (P < .0001; odds ratio [OR], 2.32), HBV e antigen (HBeAg) positivity (P < .001; OR, 3.70), and rt124N (P = .002; OR, 3.06) were associated with a partial entecavir response. Compared with the optimal responders, the partial responders had a lower quasispecies complexity and diversity.

CONCLUSIONS

Apart from the known factors (high baseline HBV DNA level and HBeAg positivity), a novel single nucleotide polymorphism (rt124N) and lower quasispecies complexity and diversity were associated with partial entecavir response at year 1.

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

BACKGROUND & AIMS

Prior studies have detected hepatitis B virus (HBV) DNA polymerase mutations in treatment-naive patients. However, most of these studies used either direct polymerase chain reaction sequencing, which detects these mutations with low levels of sensitivity, or patient cohorts that were not well-characterized. We investigated the prevalence of HBV mutations in DNA polymerase by using a line probe assay.

METHODS

In a prospective, cross-sectional study, we enrolled 198 treatment-naive patients with chronic hepatitis B (52.5% male; mean age, 41 years) from February 2009 to May 2011 from 3 gastroenterology and liver clinics in Northern California. Exclusion criteria included infection with hepatitis C or D viruses or human immunodeficiency virus. All patients completed a questionnaire (to determine demographics, history of liver disease, prior treatments, family medical history, drug and alcohol use, and environmental risk factors for hepatitis) that was administered by a research coordinator; mutations in HBV DNA polymerase were detected by using the INNO-LiPA HBV DR v.3 assay.

RESULTS

Most patients were Vietnamese (48.5%) or Chinese (36.4%) and were infected with HBV genotypes B (67.5%) or C (24.2%). Mutations in HBV DNA polymerase were found in 2 patients (1%), rtI233V (n = 1) and rtM250M/L (n = 1).

CONCLUSIONS

In a multicenter prospective study of treatment-naive patients with chronic hepatitis B, we detected mutations in HBV DNA polymerase in only 1%. Because of the low prevalence of these mutations and the uncertain clinical significance of such quasispecies, routine HBV DNA polymerase mutation analysis cannot be recommended before initiation of antiviral therapy for treatment-naive patients with chronic hepatitis B. The analysis requires further molecular and clinical studies.

Hepatitis B virus drug resistance tools: one sequence, two predictions

Drug resistance testing, genotype analysis, and the determination of immune and vaccine escape variants support personalized antiviral treatment for hepatitis B patients. As phenotypic drug resistance testing for hepatitis B virus (HBV) is especially labor-intensive, due to the lack of simple cell culture systems, genotypic methods play a very pronounced role. The genetic structure of HBV allows the simultaneous analysis of two different genes by examination of a single region in the genome of HBV. Nevertheless, the overlapping open reading frames of the hepatitis B surface antigen (HBsAg) and the reverse transcriptase (RT) have to be interpreted separately. In diagnostic procedures, standard Sanger type sequencing (mostly performed as a dye-dideoxynucleotide terminator system) is still the most commonly used method. This allows using established techniques for interpreting those types of genetic information. Besides reviewing the foundation of drug resistance interpretation for HBV, different interpretation systems, either commercially available (TRUGENE, Abbott, ViroScore) or free to use (geno2pheno[HBV], HIV-GRADE HBV tool), are compared in this article.

Clinical implications of hepatitis B virus mutations: Recent advances

Hepatitis B virus (HBV) infection is a major cause of acute and chronic hepatitis, and of its long-term complications. It is the most variable among DNA viruses, mostly because of its unique life cycle which includes the activity of error-prone enzyme, reverse transcriptase, and the very high virion production per day. In last two decades, numerous research studies have shown that the speed of disease progression, reliability of diagnostic methods and the success of antiviral therapy and immunization are all influenced by genetic variability of this virus. It was shown that mutations in specific regions of HBV genome could be responsible for unwanted clinical outcomes or evasion of detection by diagnostic tools, thus making the monitoring for these mutations a necessity in proper evaluation of patients. The success of the vaccination programs has now been challenged by the discovery of mutant viruses showing amino acid substitutions in hepatitis B surface antigen (HBsAg), which may lead to evasion of vaccine-induced immunity. However, the emergence of these mutations has not yet raised concern since it was shown that they develop slowly. Investigations of HBV genetic variability and clinical implications of specific mutations have resulted in significant advances over the past decade, particularly in regard to management of resistance to antiviral drugs. In the era of drugs with high genetic barrier for resistance, on-going monitoring for possible resistance is still essential since prolonged therapy is often necessary. Understanding the frequencies and clinical implications of viral mutations may contribute to improvement of diagnostic procedures, more proper planning of immunization programs and creating the most efficient therapeutic protocols.

Prevelance of common YMDD motif mutations in long term treated chronic HBV infections in a Turkish population

In the current study we aimed to show the common YMDD motif mutations in viral polymerase gene in chronic hepatitis B patients during lamivudine and adefovir therapy. Forty-one serum samples obtained from chronic hepatitis B patients (24 male, 17 female; age range: 34-68 years) were included in the study. HBV-DNA was extracted from the peripheral blood of the patients using an extraction kit (Invisorb, Instant Spin DNA/ RNA Virus Mini Kit, Germany). A line probe assay and direct sequencing analyses (INNO-LIPA HBV DR v2; INNOGENETICS N.V, Ghent, Belgium) were applied to determine target mutations of the viral polymerase gene in positive HBV-DNA samples. A total of 41 mutations located in 21 different codons were detected in the current results. In 17 (41.5%) patients various point mutations were detected leading to lamivudin, adefovir and/ or combined drug resistance. Wild polymerase gene profiles were detected in 24 (58.5%) HBV positive patients of the current cohort. Eight of the 17 samples (19.5%) having rtM204V/I/A missense transition and/or transversion point mutations and resistance to lamivudin. Six of the the mutated samples (14.6%) having rtL180M missense transversion mutation and resistance to combined adefovir and lamivudin. Three of the mutated samples (7.5%) having rtG215H by the double base substituation and resistance to adefovir. Three of the mutated samples (7.5%) having codon rtL181W due to the missense transversion point mutations and showed resistance to combined adefovir and lamivudin. Unreported novel point mutations were detected in the different codons of polymerase gene region in the current HBV positive cohort fromTurkish population. The current results provide evidence that rtL180M and rtM204V/I/A mutations of HBV-DNA may be associated with a poor antiviral response and HBV chronicity during conventional therapy in Turkish patients.

The impact of the hepatitis B virus polymerase rtA181T mutation on replication and drug resistance is potentially affected by overlapping changes in surface gene

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

IMPORTANCE

The emergence of drug-resistant HBV that are no longer susceptible to nucleos(t)ide analogues is a major problem for antiviral treatment in chronic hepatitis B infection. Among drug-resistant mutations, the single rtA181T mutation is known to confer cross-resistance to antiviral drugs. This mutation causes intermediate or reduced susceptibility to tenofovir. Moreover, the clinical occurrence of the rtA181T mutation during antiviral therapy is also high. Our study revealed that the effect of the rtA181T mutation on viral replication and drug resistance is dependent on the mutations in the overlapping surface gene. This observation suggests the need for genotypic analysis of overlapping surface genes to manage antiviral drug resistance if clinical isolates harbor the rtA181T mutation. We believe that our study will not only extend the understanding of the drug resistance mechanism, but it will also ultimately provide new treatment options for patients with multidrug resistant HBV.

An initial assessment of correlations between host- and virus-related factors affecting analogues antiviral therapy in HBV chronically infected patients

BACKGROUND

Success in treating hepatitis B virus (HBV) infection with nucleoside analogues drugs is limited by the emergence of drug-resistant viral strains upon prolonged therapy. In addition to mutation patterns in the viral polymerase gene, host factors are assumed to contribute to failure of treatment in chronic HBV infections. The aim of this study was to analyze the correlation between efficacy of antiviral therapy and the prevalence of HBV pretreatment drug-resistant variants. We also analyzed the role of heterogeneity in the promoter region of the IL-10 on the HBV pol/s gene polymorphisms and efficacy of analogues-driven therapy.

MATERIAL AND METHODS

HBV DNA was extracted from 54 serum samples from chronic hepatitis B (CHB) patients. Drug-resistance mutations were analyzed using MALDI-TOF mass spectrometry technology (MALDI-TOF MS) and Multi-temperature single-strand conformation polymorphism (MSSCP). IL-10 gene promoter region polymorphisms at positions -1082, -819, and -592 were determined in allele-specific PCR reactions (AS-PCR).

RESULTS

Drug-resistance mutations were detected in 74% of naïve and 93% of experienced patients, but the effect of pre-existence of drug-resistant HBV variants on antiviral therapy was not statistically significant (p=0.86). The role of polymorphisms at positions -1082 (p=0.88), -819 (p=0.26), and -592 (p=0.26) of IL-10 promoter region polymorphisms was excluded from the response-predicting factors. The main host factors predicting successful response to antiviral therapy were female sex (p=0.007) and young age (p=0.013).

CONCLUSIONS

The presence of drug-resistant HBV variants in baseline is not a viral predictor of good response to nucleoside/nucleotide analogues therapy. Only low HBV viral load predicted positive response to antiviral therapy. The ideal candidate for antiviral therapy is an immunocompetent, young female with low HBV viral load and elevated ALT activity.

Drug-resistance associated mutations in polymerase (p) gene of hepatitis B virus isolated from malaysian HBV carriers

BACKGROUND

Mutations in the polymerase (P) gene of hepatitis B virus are often associated with drug resistance. The pattern of mutations varies geographically, thus giving rise to genotypes diversity.

OBJECTIVES

This study was carried out to detect mutations in P gene of hepatitis B virus isolated from Malaysian HBV carriers.

MATERIALS AND METHODS

A total of 58 sera samples were analyzed by PCR and sequencing, of which the P gene of isolated HBV was successfully amplified and sequenced from 40 samples.

RESULTS

Genotyping of these samples revealed that the predominant genotype was genotype C (22/40, 55.0%), followed by genotype B (17/40, 42.5%), and only 1 sample showed genotype D (2.5%). A number of significant drug resistant mutations were found in five patients including S202I, N236T, M250L, L180M/V, M204I, A181T, T184G, M250V, and V173L. Of these, L180M/V and M204I were most frequently detected (80%) and associated with lamivudine in combination with emtricitabine and telbivudine drug resistance. Association with age, sex, and clinical symptoms revealed that these patients were all male, mid to elderly age and almost all hadcirrhotic liver disease.

CONCLUSIONS

Detection and surveillance of the significant sites of mutations in HBV is crucial for clinicians to decide on the choice of antiviral treatment and further management of hepatitis B carriers.

Quasispecies structure, cornerstone of hepatitis B virus infection: Mass sequencing approach

Hepatitis B virus (HBV) is a DNA virus with complex replication, and high replication and mutation rates, leading to a heterogeneous viral population. The population is comprised of genomes that are closely related, but not identical; hence, HBV is considered a viral quasispecies. Quasispecies variability may be somewhat limited by the high degree of overlapping between the HBV coding regions, which is especially important in the P and S gene overlapping regions, but is less significant in the X and preCore/Core genes. Despite this restriction, several clinically and pathologically relevant variants have been characterized along the viral genome. Next-generation sequencing (NGS) approaches enable high-throughput analysis of thousands of clonally amplified regions and are powerful tools for characterizing genetic diversity in viral strains. In the present review, we update the information regarding HBV variability and present a summary of the various NGS approaches available for research in this virus. In addition, we provide an analysis of the clinical implications of HBV variants and their study by NGS.

High-throughput matrix-assisted laser desorption ionization-time of flight mass spectrometry as an alternative approach to monitoring drug resistance of hepatitis B virus

Long-term antiviral therapy of chronic hepatitis B virus (HBV) infection can lead to the selection of drug-resistant HBV variants and treatment failure. Moreover, these HBV strains are possibly present in treatment-naive patients. Currently available assays for the detection of HBV drug resistance can identify mutants that constitute ≥5% of the viral population. Furthermore, drug-resistant HBV variants can be detected when a viral load is >10(4) copies/ml (1,718 IU/ml). The aim of this study was to compare matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and multitemperature single-strand conformation polymorphism (MSSCP) with commercially available assays for the detection of drug-resistant HBV strains. HBV DNA was extracted from 87 serum samples acquired from 45 chronic hepatitis B (CHB) patients. The 37 selected HBV variants were analyzed in 4 separate primer extension reactions on the MALDI-TOF MS. Moreover, MSSCP for identifying drug-resistant HBV YMDD variants was developed and turned out to be more sensitive than INNOLiPA HBV DR and direct sequencing. MALDI-TOF MS had the capability to detect mutant strains within a mixed viral population occurring with an allelic frequency of approximately 1% (with a specific value of ≥10(2) copies/ml, also expressed as ≥17.18 IU/ml). In our study, MSSCP detected 98% of the HBV YMDD variants among strains detected by the MALDI-TOF MS assay. The routine tests revealed results of 40% and 11%, respectively, for INNOLiPA and direct sequencing. The commonly available HBV tests are less sensitive than MALDI-TOF MS in the detection of HBV-resistant variants, including quasispecies.

Short hairpin RNAs with a 2- or 3-base mismatch inhibit HBV expression and replication in HepG2 cells

PURPOSE

To assess the functions of mismatched short hairpin RNAs (shRNAs) that inhibit replication and the expression of hepatitis B virus (HBV), two shRNAs possessing a 2- or 3-base mismatch that targeted HBV were studied.

METHODS

shRNAs and pHY106-HBV were cotransfected into HepG2 cells. The culture supernatants were collected and used in hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) assays. The levels of HBsAg and HBcAg mRNA were detected by reverse-transcriptase PCR (RT-PCR). HBV DNA replication intermediates were extracted for Southern blot hybridization.

RESULTS

The results demonstrate that mismatched shRNA-458 and shRNA-635 can significantly inhibit HBsAg and HBeAg protein expression, and the maximal inhibition ratio for both proteins was found at 72 h after cotransfection: 80 and 50 %, respectively. Similar inhibitory effects were found on HBsAg and HBcAg mRNA levels and HBV DNA replication intermediates at 72 h after cotransfection, and the inhibition ratio was found to be approximately 70 and 90 %, respectively.

CONCLUSIONS

Despite the 2- or 3-base mismatch between the shRNAs and the HBV target sequences, shRNA-458 and shRNA-635 exerted a significant inhibitory effect on HBsAg and HBeAg expression and HBV replication. This indicates that mismatched shRNAs could be a promising therapy for HBV.

Impact of rtI233V mutation in hepatitis B virus polymerase protein and adefovir efficacy: Homology modeling and molecular docking studies

Adefovir is an adenosine analogue approved by the Food and Drug Administration for the treatment of chronic hepatitis B. Mutations occurring in the hepatitis B virus (HBV) reverse transcriptase (rt) domains are shown to confer resistance to antiviral drugs. The role of the rtI233V mutation and adefovir resistance remains contradictory. In this study, it was attempted to evaluate the impact of putative rtI233V substitution on adefovir action by homology modeling and docking studies. The HBVrt nucleotide sequence containing rtI233V mutation was obtained from the treatment-naive chronic hepatitis B subject. The three dimensional model of HBV polymerase/rt was constructed using the HIV-1rt template (PDB code: 1RTD A) and the model was evaluated by the Ramachandran plot. Autodock was employed to dock the HBV polymerase/rt and adefovir. The modelled structure showed the amino acid rtI233 to be located away from the drug interactory site. The substitution of isoleucine to valine did not appear to affect the catalytic sites of the protein. In addition, it does not alter the conformation of bent structure formed by residues 235 to 240 that stabilizes the binding of dNTPs. Therefore, it was predicted that rtI233V substitution may not independently affect the antiviral action of adefovir and incoming dNTP binding.

Efficacy of lamivudine or entecavir against virological rebound after achieving HBV DNA negativity in chronic hepatitis B patients

Nucleos(t)ide analogues (NAs) lead to viral suppression and undetectable hepatitis B virus (HBV) DNA in some individuals infected with HBV, but the rate of virological rebound has been unknown in such patients. We examined the prevalence of virological rebound of HBV DNA among NA-treated patients with undetectable HBV DNA. We retrospectively analyzed 303 consecutive patients [158 entecavir (ETV)- and 145 lamivudine (LAM)-treated] who achieved HBV DNA negativity, defined as HBV DNA < 3.7 log IU/mL for at least 3 months. They were followed up and their features, including their rates of viral breakthrough, were determined. Viral rebound after HBV DNA negativity was not observed in the ETV-group. Viral rebound after HBV DNA negativity occurred in 38.7% of 62 HBe antigen-positive patients in the LAM-group. On multivariate analysis, age was an independent factor for viral breakthrough among these patients (P = 0.035). Viral rebound after HBV DNA negativity occurred in 29.1% of 79 HBe antigen-negative patients in the LAM-group. Differently from LAM, ETV could inhibit HBV replication once HBV DNA negativity was achieved. In contrast, LAM could not inhibit HBV replication even if HBV negativity was achieved in the early phase. Attention should be paid to these features in clinical practice.

Antiviral treatment to prevent chronic hepatitis B or C-related hepatocellular carcinoma

Antiviral treatment is the only option to prevent or defer the occurrence of hepatocellular carcinoma (HCC) in patients chronically infected with hepatitis B virus (HBV) or hepatitis C virus (HCV). The approved medication for the treatment of chronic HBV infection is interferon-α (IFNα) and nucleos(t)ide analogues (NAs), including lamivudine, adefovir dipivoxil, telbivudine, entecavir and tenofovir disoproxil fumarate. IFNα is the most suitable for young patients with less advanced liver diseases and those infected with HBV genotype A. IFNα treatment significantly decreases the overall incidence of HBV-related HCC in sustained responders. However, side effects may limit its long-term clinical application. Orally administered NAs are typically implemented for patients with more advanced liver diseases. NA treatment significantly reduces disease progression of cirrhosis and therefore HCC incidence, especially in HBV e antigen-positive patients. NA-resistance due to the mutations in HBV polymerase is a major limiting factor. Of the NA resistance-associated mutants, A181T mutant significantly increases the risk of HCC development during the subsequent course of NA therapy. It is important to initiate treatment with NAs that have a high genetic barrier to resistance, to counsel patients on medication adherence and to monitor virological breakthroughs. The recommended treatment for patients with chronic HCV infection is peg-IFN plus ribavirin that can decrease the occurrence of HCC in those who achieve a sustained virological response and have not yet progressed to cirrhosis. IFN-based treatment is reserved for patients with decompensated cirrhosis who are under evaluation of liver transplantation to reduce post-transplant recurrence of HCV. More effective therapeutic options such as direct acting antiviral agents will hopefully increase the response rate in difficult-to-treat patients with HCV genotype 1. However, the risk of HCC remains in cirrhotic patients (both chronic HBV and HCV infection) if treatment is initiated after cirrhosis is established. Future research should focus on investigating new agents, especially for those patients with hepatic decompensation or post-transplantation.

Clonal evolution of hepatitis B virus polymerase gene mutations during lamivudine-adefovir combination treatment

AIM: To identify hepatitis B virus polymerase gene mutations during antiviral therapy using lamivudine-adefovir sequential monotherapy followed by lamivudine-adefovir combination therapy.

METHODS: The patient cohort included four adult chronic hepatitis B patients who had undergone sequential monotherapy, first with lamivudine (LMV) and then, after developing viral breakthrough, with adefovir (ADV) therapy. All of the patients had non-response or viral breakthrough after LMV-ADV sequential monotherapy, which resulted in the switching of their antiviral regimen to LMV-ADV combination therapy. Eleven serum samples from the four patients who showed non-response to rescue LMV-ADV combination therapy were collected sequentially at a time before the antiviral treatment and then during the LMV monotherapy, ADV monotherapy, and LMV-ADV combination therapy. For the genotypic analysis, the whole 1310-bp polymerase gene region was amplified, cloned and sequenced.

RESULTS: All patients had been previously treated with 100 mg of LMV once daily for a 15- to 26-mo period. The emergence of resistance mutations to LMV, such as rtM204V/I and/or rtL180M, were found in all patients. Their antiviral regimens were switched to ADV monotherapy as the second line treatment. All patients had viral breakthrough or non-response after the LMV-ADV sequential monotherapy. ADV-resistant mutations were detected after 13 to 19 mo of LMV-ADV sequential monotherapy. The rtA181V/T mutations were predominantly identified during the ADV treatment in the LMV-resistant patients. Twenty-seven of 38 clones were combined with an amino acid change at rt181; three clones had mutations in rt236 and one clone had a combined mutation. The rtA181V/T mutations were not suppressed by the LMV-ADV combination therapy. Thirty-nine of 64 clones showed an rtA181V/T mutation and six clones showed combined mutations in rt181 and rt236. Mutations in rt204 re-emerged during the combination treatment. The rt181 and rt204 mutations did not co-exist in one clone.

CONCLUSION: Add-on lamivudine therapy with adefovir for adefovir resistance may not suppress the pre-existing adefovir-resistant mutation that develops during lamivudine-adefovir sequential monotherapy.

Comparison of the Mechanisms of Drug Resistance among HIV, Hepatitis B, and Hepatitis C

Human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) are the most prevalent deadly chronic viral diseases. HIV is treated by small molecule inhibitors. HBV is treated by immunomodulation and small molecule inhibitors. HCV is currently treated primarily by immunomodulation but many small molecules are in clinical development. Although HIV is a retrovirus, HBV is a double-stranded DNA virus, and HCV is a single-stranded RNA virus, antiviral drug resistance complicates the development of drugs and the successful treatment of each of these viruses. Although their replication cycles, therapeutic targets, and evolutionary mechanisms are different, the fundamental approaches to identifying and characterizing HIV, HBV, and HCV drug resistance are similar. This review describes the evolution of HIV, HBV, and HCV within individuals and populations and the genetic mechanisms associated with drug resistance to each of the antiviral drug classes used for their treatment.

Factors influencing inadequate or suboptimal response to adefovir with or without genotypic resistance

The aim of the study was to explore the factors in inadequate-responders to treatment with adefovir (ADV) with or without genotypic resistance. The reverse-transcriptase (RT) gene of hepatitis B virus (HBV) was sequenced in 161 patients with inadequate-response to ADV and analyzed for HBV genotypes using a phylogenetic approach. Seventy-six patients (47.2%) were found to carry the rtA181V/T/S or rtN236T residue substitution, and most of them had viral rebound. In the patients with viral rebound and ADV genotypic resistance, 19 (25.7%) showed rtA181V/T/S + rtN236T substitutions. In the other patients, it was found that HBV genotypes and cirrhosis influenced the selection of ADV-resistant positions by univariate analysis and multiple logistic regression analysis. The rtN236T was more frequent in patients with genotype B, and the rtA181V/T/S was more common in patients with genotype C (χ(2)  = 11.543, P = 0.001). Multiple logistic regression analysis showed that the rtN236T and time resistant strains occurred during ADV-treatment were statistically significant for influencing rtA181 variation types (P = 0.007 and P = 0.024, respectively), and the occurrence of rtA181T was found to be significantly earlier than rtA181V. In conclusion, genotypic resistance was not detected in the majority of primary nonresponders to ADV when compared to the patients with viral rebound. The different HBV genotypes influence the selection of ADV-resistant mutation positions. The rtA181T occurs more frequently in patients with the rtN236T and it occurs earlier when compared to the rtA181V. These findings suggest that early judgment of adequate response and making a decision for interference in patients treated with ADV are of importance in clinical practice.

Management of treatment failure in chronic hepatitis B

Antiviral therapy of chronic hepatitis B remains a clinical challenge. The primary goal of therapy is to prevent liver disease progression. Because of the mechanism of viral persistence in infected hepatocytes, long-term antiviral therapy is needed in the majority of patients. Incomplete viral suppression and emergence of drug resistance is a major concern. The correct choice of a first-line potent therapy to achieve sustained long-term suppression of viral replication provides the best chance of preventing treatment failure and drug resistance. Clinical studies have demonstrated that drugs with a high barrier to resistance, such as entecavir and tenofovir, have significantly lower rates of resistance when compared with those with a low barrier to resistance such as lamivudine, adefovir, or telbivudine. Management of treatment failure requires a precise clinical and accurate virologic monitoring as well as an early treatment intervention with appropriate complementary drugs with respect to their cross-resistance profile. Long-term surveillance for treatment efficacy and possible emergence of drug resistance is necessary for those patients who have been sequentially treated with multiple antivirals. Finally, the identification of novel treatment targets remains a major research challenge to improve the efficacy of current antiviral therapy.

Antiviral therapies: focus on hepatitis B reverse transcriptase

Hepatitis B virus (HBV) is the etiologic agent of mankind's most serious liver disease. While the availability of a vaccine has reduced the number of new HBV infections, the vaccine does not benefit the approximately 350 million people already chronically infected by the virus. Most of the drugs approved by the FDA for the treatment of hepatitis B target the reverse transcriptase (RT or P gene product) and are nucleoside RT inhibitors (NRTIs) that suppress viral replication. However, prolonged monotherapies directed against a single target result in the emergence of viral resistance. HBV genotypic differences affect NRTI resistance, and because the reading frames of the S (surface antigen) and P genes partially overlap, genomic differences that affect the surface of the virus may also alter the viral polymerase sequence, function and drug susceptibility. The scope of this review is to assess the effects of HBV genotypic variation on the development of drug resistance to NRTIs. Some RT residues that vary among different genotypes are in the vicinity of residues that mutate and give rise to NRTI resistance. Interactions between these amino acids can help explain the effect of HBV genotype on the development of NRTI resistance during antiviral therapies, and might help in the design of improved therapeutic strategies.

Molecular characterization of a novel entecavir mutation pattern isolated from a multi-drug refractory patient with chronic hepatitis B infection

BACKGROUND

Prolonged antiviral treatment results in selection and accumulation of resistant strains in quasispecies pool in hepatitis B virus (HBV) infection.

OBJECTIVES

The aim of this study was to characterise a novel HBV pattern which shows resistance to lamivudine, adefovir dipivoxil and entecavir using in vitro phenoyping assay.

STUDY DESIGN

A male 36 years old patient diagnosed with anti HBe-positive chronic hepatitis B (CHB) had received lamivudine treatment for 7 years following an initial unsuccessfull interferon treatment. The therapy had been switched to adefovir and then to entecavir when breakthrough occcured during each treatment. This led only to a temporary HBV DNA decline which soon was followed by viral breakthrough despite the lack of known entecavir resistance mutations. Patient died after 9 months of entecavir treatment from liver failure. A total of 434 clones from 6 different serum samples were analysed retrospectively. HBV genomes bearing mutation patterns suggestive of antiviral resistance were analysed by in vitro phenotyping assay.

RESULTS

Dominance of a clone carrying L80LV, L91I, M204I, S219A, N238D, Y245H changes was detected in the last serum sample of the patient just before his death. This pattern displayed 30.4 fold resistance to entecavir when compared with the wild type HBV by in vitro phenotyping assay.

CONCLUSION

A novel mutation pattern showing a high degree of resistance to entecavir was documented. In this pattern, the S219A and Y245H mutations mainly seem to contribute to the emergence of ETV resistance.

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.