Cellular and virological mechanisms of HBV drug resistance

Molecular detection of hepatitis B virus genotype E with immune escape mutations in chronic hepatitis B patients on long-term antiviral therapy in Jos, Nigeria

Background

Previous studies in Nigeria have reported the presence of hepatitis B virus (HBV) genotype E and the availability of immune escape mutants. There is a paucity of data on chronic patients on long-term antiviral therapy for HBV infection.

Objective

This study assessed HBV genotypes and drug resistance variants among patients with chronic HBV infection receiving tenofovir in Jos, Nigeria.

Methods

This cross-sectional study consecutively enrolled 101 patients (51 with HIV/HBV co-infection and 50 with HBV infection only) on antiviral therapy from February 2018 to May 2019 at four hospitals in Jos, Nigeria. DNA quantification of HBV was performed on all samples; 30 samples with detectable viral load were selected for genotyping using Sanger sequencing by targeting the full-length sequences of reverse transcriptase gene of the HBV genome. Phylogenetic analysis was performed with reference sequences from GenBank. Escape mutant and drug resistance analysis were performed using HBV drug resistance interpretation and Geno2pheno.

Results

Only 30 (29.7%) of the 101 study participants had detectable HBV DNA. Of these, six (20.0%) isolates were successfully amplified and sequenced. The identified genotype was E, including escape mutations L127R (16.7%) and G145A (16.7%).

Conclusion

This study revealed exclusive dominance of genotype E in Nigeria. The S gene mutations G145A and L271R are known to be associated with modified antigenicity and impaired serologic assays, which may cause false negatives in the detection of anti-HBV surface antigen. The presence of mutants that are associated with vaccine immune escape may also have diagnostic and vaccine immune response implications.

Whole genome analysis of hepatitis B virus before and during long-term therapy in chronic infected patients: Molecular characterization, impact on treatment and liver disease progression

Hepatitis B virus (HBV) infection remains a serious public health concern worldwide despite the availability of an efficient vaccine and the major improvements in antiviral treatments. The aim of the present study is to analyze the mutational profile of the HBV whole genome in ETV non-responder chronic HBV patients, in order to investigate antiviral drug resistance, immune escape, and liver disease progression to Liver Cirrhosis (LC) or Hepatocellular Carcinoma (HCC). Blood samples were collected from five chronic hepatitis B patients. For each patient, two plasma samples were collected, before and during the treatment. Whole genome sequencing was performed using Sanger technology. Phylogenetic analysis comparing the studied sequences with reference ones was used for genotyping. The mutational profile was analyzed by comparison with the reference sequence M32138. Genotyping showed that the studied strains belong to subgenotypes D1, D7, and D8. The mutational analysis showed high genetic variability. In the RT region of the polymerase gene, 28 amino acid (aa) mutations were detected. The most significant mutations were the pattern rtL180M + rtS202G + rtM204V, which confer treatment resistance. In the S gene, 35 mutations were detected namely sP120T, sT126S, sG130R, sY134F, sS193L, sI195M, and sL216stop were previously described to lead to vaccine, immunotherapy, and/or diagnosis escape. In the C gene, 34 mutations were found. In particular, cG1764A, cC1766G/T, cT1768A, and cC1773T in the BCP; cG1896A and cG1899A in the precore region and cT12S, cE64D, cA80T, and cP130Q in the core region were associated with disease progression to LC and/or HCC. Other mutations were associated with viral replication increase including cT1753V, cG1764A/T, cC1766G/T, cT1768A, and cC1788G in the BCP as well as cG1896A and cG1899A in the precore region. In the X gene, 30 aa substitutions were detected, of which substitutions xT36D, xP46S, xA47T, xI88F, xA102V, xI127T, xK130M, xV131I, and xF132Y were previously described to lead to LC and/or HCC disease progression. In conclusion, our results show high genetic variability in the long-term treatment of chronic HBV patients causing several effects. This could contribute to guiding national efforts to optimize relevant HBV treatment management in order to achieve the global hepatitis elimination goal by 2030.

The underlying mechanisms of anti-hepatitis B effects of formula Le-Cao-Shi and its single herbs by network pharmacology and gut microbiota analysis

Formula Le-Cao-Shi (LCS), a traditional Chinese medicine (TCM), has been used as folk remedy for treating hepatitis B for a long time. In our previous study, the anti-hepatitis B effects of LCS have been verified. In the present study, the anti-hepatitis B activities of LCS and its three single herbs were investigated in vitro by HepG2.2.15 cellular model, and the mechanisms against hepatitis B were deciphered via network pharmacology and gut microbiota analysis. By network pharmacology method, twelve key compounds that played a vital role in LCS were filtered from 213 ingredients. The targets RORA, CDK2, RELA, AKT1, IKBKG, PRKCβ and CASP3 were directly related to hepatitis B pathway, which indicated that LCS could exert anti-hepatitis B effect by co-regulating cell cycle and inflammatory pathways. The interactions between candidate compounds and target proteins that were directly involved in hepatitis B pathway were validated by molecular docking simulation and RT-PCR. By gut microbiota analysis, it was revealed that LCS could alter the disordered microbial composition in the infected ducks towards normal, especially the restoration of three key strains, namely Streptococcus alactolyticus, Enterococcus cecorum and Bacteroides fragilis. The above findings could provide a scientific basis for further development and utilization of LCS against hepatitis B.

Rapid Turnover of Hepatitis B Virus Covalently Closed Circular DNA Indicated by Monitoring Emergence and Reversion of Signature-Mutation in Treated Chronic Hepatitis B Patients

BACKGROUND AND AIMS

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) plays a pivotal role in the establishment and persistence of HBV infection. Understanding the turnover time of preexisting cccDNA pools would be helpful in designing strategies to clear HBV by fully blocking the de novo generation of cccDNA.

APPROACH AND RESULTS

In this study, we retrospectively monitored the emergence and reversion of the rtM204I/V mutant, a signature lamivudine resistance (LAMR ) mutation serving as a biomarker of cccDNA turnover in liver biopsies and longitudinal serum samples from two clinical trials. Methodologies were optimized to differentially isolate and sequence HBV virion DNA, cccDNA, and HBV RNA from clinical samples. A strong correlation was observed between LAMR composition of cccDNA with that of serum and intrahepatic HBV RNA in paired liver and serum samples (r = 0.96 and 0.90, respectively), suggesting that serum HBV RNA can serve as a surrogate marker of cccDNA genetic composition when liver biopsies are unavailable. LAMR mutations emerged and increased from undetectable to 40%-90% within 16-28 weeks in serum HBV RNA from telbivudine-treated patients experiencing virological breakthrough. Similarly, in lamivudine-resistant patients who switched to interferon therapy, serum HBV-RNA population bearing 100% LAMR mutations fully reversed back to wild type within 24-48 weeks.

CONCLUSIONS

The genetic composition dynamics of serum HBV RNA and biopsy cccDNA in treated HBV patients indicates that cccDNA turnover occurs relatively rapidly (several months), offering a possibility of HBV cure with finite therapy through completely blocking cccDNA replenishment.

ATI-2173, a Novel Liver-Targeted Non-Chain-Terminating Nucleotide for Hepatitis B Virus Cure Regimens

ATI-2173 is a novel liver-targeted molecule designed to deliver the 5′-monophosphate of clevudine for the treatment of chronic hepatitis B infection. Unlike other nucleos(t)ides, the active clevudine-5′-triphosphate is a noncompetitive, non-chain-terminating inhibitor of hepatitis B virus (HBV) polymerase that delivers prolonged reduction of viremia in both a woodchuck HBV model and in humans for up to 6 months after cessation of treatment. However, long-term clevudine treatment was found to exhibit reversible skeletal myopathy in a small subset of patients and was subsequently discontinued from development.

ATI-2173 is a novel liver-targeted molecule designed to deliver the 5′-monophosphate of clevudine for the treatment of chronic hepatitis B infection. Unlike other nucleos(t)ides, the active clevudine-5′-triphosphate is a noncompetitive, non-chain-terminating inhibitor of hepatitis B virus (HBV) polymerase that delivers prolonged reduction of viremia in both a woodchuck HBV model and in humans for up to 6 months after cessation of treatment. However, long-term clevudine treatment was found to exhibit reversible skeletal myopathy in a small subset of patients and was subsequently discontinued from development. ATI-2173 was designed by modifying clevudine with a 5′-phosphoramidate to deliver the 5′-monophosphate to the liver. Bypassing the first phosphorylation step of clevudine, the 5′-monophosphate is converted to the active 5′-triphosphate in the liver. ATI-2173 is a selective inhibitor of HBV with an anti-HBV 50% effective concentration (EC₅₀) of 1.31 nM in primary human hepatocytes, with minimal to no toxicity in hepatocytes, skeletal muscle, liver, kidney, bone marrow, and cardiomyocytes. ATI-2173 activity was decreased by viral polymerase mutations associated with entecavir, lamivudine, and adefovir resistance, but not capsid inhibitor resistance mutations. A single oral dose of ATI-2173 demonstrated 82% hepatic extraction, no food effect, and greatly reduced peripheral exposure of clevudine compared with equimolar oral dosing of clevudine. Despite reduced plasma clevudine exposure, liver concentrations of the 5′-triphosphate were equivalent following ATI-2173 versus clevudine administration. By selectively delivering the 5′-monophosphate to the liver, while retaining the unique anti-HBV activity of the 5′-triphosphate, ATI-2173 may provide an improved pharmacokinetic profile for clinical use, reducing systemic exposure of clevudine and potentially eliminating skeletal myopathy.

7-Deaza-7-fluoro modification confers on 4'-cyano-nucleosides potent activity against entecavir/adefovir-resistant HBV variants and favorable safety

We designed, synthesized and identified a novel nucleoside derivative, 4'-C-cyano-7-deaza-7-fluoro-2'-deoxyadenosine (CdFA), which exerts potent anti-HBV activity (IC50 ~26 nM) with favorable hepatocytotoxicity (CC50 ~56 μM). Southern blot analysis using wild-type HBV (HBVWT)-encoding-plasmid-transfected HepG2 cells revealed that CdFA efficiently suppresses the production of HBVWT (IC50 = 153.7 nM), entecavir (ETV)-resistant HBV carrying L180M/S202G/M204V substitutions (HBVETVR; IC50 = 373.2 nM), and adefovir dipivoxil (ADV)-resistant HBV carrying A181T/N236T substitutions (HBVADVR; IC50=192.6 nM), whereas ETV and ADV were less potent against HBVETVR and HBVADVR (IC50: >1,000 and 4,022.5 nM, respectively). Once-daily peroral administration of CdFA to human-liver-chimeric mice over 14 days (1 mg/kg/day) comparably blocked HBVWT and HBVETVR viremia by 0.7 and 1.2 logs, respectively, without significant changes in body-weight or serum human-albumin levels, although ETV only slightly suppressed HBVETVR viremia (CdFA vs ETV; p = 0.032). Molecular modeling suggested that ETV-TP has good nonpolar interactions with HBVWT reverse transcriptase (RTWT)'s Met204 and Asp205, while CdFA-TP fails to interact with Met204, in line with the relatively inferior activity against HBVWT of CdFA compared to ETV (IC50: 0.026 versus 0.003 nM). In contrast, the 4'-cyano of CdFA-TP forms good nonpolar contacts with RTWT's Leu180 and RTETVR's Met180, while ETV-TP loses interactions with RTETVR's Met180, explaining in part why ETV is less potent against HBVETVR than CdFA. The present results show that CdFA exerts potent activity against HBVWT, HBVETVR and HBVADVR with enhanced safety and that 7-deaza-7-fluoro modification confers potent activity against drug-resistant HBV variants and favorable safety, shedding light to further design more potent and safer anti-HBV nucleoside analogs.

Characterization of the molecular events of covalently closed circular DNA synthesis in de novo Hepatitis B virus infection of human hepatoma cells

Despite the utmost importance of cccDNA in HBV biology, the mechanism by which cccDNA synthesis is regulated is not completely understood. Here we explored HepG2-NTCP cell line and performed a time-course HBV infection experiment (up to 30 days) to follow the conversion of the input viral DNA into cccDNA. We found that a protein-free RC DNA (PF-RC DNA) become detectable as early as 12 h post infection (hpi) prior to the detection of cccDNA, which become evident only at 2-3 dpi. Intriguingly, the PF-RC DNA detected at 12 hpi was abundantly located in the cytoplasm, implicating that the protein-removal from the input viral DNA takes place in the cytoplasm, perhaps inside the nucleocapsid. Notably, during the early time points of HBV infection, the PF-RC DNA accumulated at significantly higher levels and appeared in a peak followed by a plateau at late time points with dramatically lower levels, implicating the presence of two distinct populations of the PF-RC DNA. Importantly, the PF-RC DNA at earlier peak is entecavir (ETV)-resistant, whereas the PF-RC DNA at posterior days is ETV-sensitive. An interpretation is that the PF-RC DNA at earlier peak represents "input viral DNA" derived from HBV inoculum, whereas the PF-RC DNA at late time points represents the de novo product of the viral reverse transcription. The existence of two populations of the PF-RC DNA having a distinct kinetic profile and ETV-sensitivity implicated that intracellular amplification via the viral reverse transcription greatly contributes to the maintenance of cccDNA pool during HBV infection. As such, we concluded that the cccDNA level is stably maintained by continuing replenishment of cccDNA primarily through intracellular amplification in the HepG2-NTCP cell line.

Understanding of human ATP binding cassette superfamily and novel multidrug resistance modulators to overcome MDR

Indeed, multi-drug resistance (MDR) is a significant obstacle to effective chemotherapy. The overexpression of ATP-binding cassette (ABC) membrane transporters is a principal cause of enhanced cytotoxic drug efflux and treatment failure in various types of cancers. At cellular level, the pumps of ABC family regulate the transportation of numerous substances including drugs in and out of the cells. In past, the overexpression of ABC pumps suggested a well-known mechanism of drug resistance in cancers as well as infectious diseases. In oncology, the search for new compounds for the inhibition of these hyperactive ABC pumps either genetically or functionally, growing interest to reverse multi-drug resistance and increase chemotherapeutic effects. Several ABC pump inhibitor/modulators has been explored to address the cancer associated MDR. However, the clinical results are still disappointing and conventional chemotherapies are constantly failed in successful eradication of MDR tumors. In this context, the structural and functional understanding of different ATP pumps is most important. In this concise review, we elaborated basic crystal structure of ABC transporter proteins as well as its critical elements such as different domains, motifs as well as some important amino acids which are responsible for ATP binding and drug efflux as well as demonstrated an ATP-switch model employed by various ABC membrane transporters. Furthermore, we briefly summarized different newly identified MDR inhibitors/modulators, deployed alone or in combination with cytotoxic agents to deal with MDR in different types of cancers.

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.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Molecular epidemiology of hepatitis B virus isolated from Bangladesh

BACKGROUND

Hepatitis B virus (HBV) is highly contagious and causes liver diseases. Globally more than 350 million people are chronically infected and among them above 80 % are from developing countries like Bangladesh. Resistance to existing drugs and vaccines are common phenomenon due to mutations in HBsAg 'a' determinant. Due to lack of data about mutations and subtypes of HBV in Bangladesh, this study strongly demands to be documented. Here, we determined the genotypes and subtypes of HBV prevalent in Bangladesh, and their genomic mutations associated with vaccine and drug resistance.

RESULTS

Among 385 samples, a total of 54 (14 %) were found HBV positive, of which 19 samples were subjected to be sequenced. After bioinformatic analysis, we found Genotype D as predominant genotype (73.7 %) with subtypes ayw3 (64.3 %) and ayw2 (35.7 %), followed by genotype A with subtype adw2 (15.8 %), and then genotype C with subtype adr (10.5 %). A significant number of mutations (Thr118Val, Thr125Met, Thr126Ile, Pro127Thr, Ala128Val, Thr131Asn/Ser, Thr/Ser143Leu/Met) were found in 'a' determinant region which may admit resistance to the available vaccines and failure of HBsAg detection.

CONCLUSIONS

This comprehensive study have clinical importance like disease diagnosis and treatment. It emphasizes HBV infected patients to do molecular diagnosis for choice of anti-viral drugs and effectiveness of vaccines for proper treatment.

A Thermodynamic Model for Genome Packaging in Hepatitis B Virus

Understanding the fundamentals of genome packaging in viral capsids is important for finding effective antiviral strategies and for utilizing benign viral particles for gene therapy. While the structure of encapsidated genomic materials has been routinely characterized with experimental techniques such as cryo-electron microscopy and x-ray diffraction, much less is known about the molecular driving forces underlying genome assembly in an intracellular environment and its in vivo interactions with the capsid proteins. Here we study the thermodynamic basis of the pregenomic RNA encapsidation in human Hepatitis B virus in vivo using a coarse-grained molecular model that captures the essential components of nonspecific intermolecular interactions. The thermodynamic model is used to examine how the electrostatic interaction between the packaged RNA and the highly charged C-terminal domains (CTD) of capsid proteins regulate the nucleocapsid formation. The theoretical model predicts optimal RNA content in Hepatitis B virus nucleocapsids with different CTD lengths in good agreement with mutagenesis measurements, confirming the predominant role of electrostatic interactions and molecular excluded-volume effects in genome packaging. We find that the amount of encapsidated RNA is not linearly correlated with the net charge of CTD tails as suggested by earlier theoretical studies. Our thermodynamic analysis of the nucleocapsid structure and stability indicates that ∼10% of the CTD residues are free from complexation with RNA, resulting in partially exposed CTD tails. The thermodynamic model also predicts the free energy of complex formation between macromolecules, which corroborates experimental results for the impact of CTD truncation on the nucleocapsid stability.

Gluconeogenesis, lipogenesis, and HBV replication are commonly regulated by PGC-1α-dependent pathway

PGC-1α, a major metabolic regulator of gluconeogenesis and lipogenesis, is strongly induced to coactivate Hepatitis B virus (HBV) gene expression in the liver of fasting mice. We found that 8-Br-cAMP and glucocorticoids synergistically induce PGC-1α and its downstream targets, including PEPCK and G6Pase. Also, HBV core promoter activity was synergistically enhanced by 8-Br-cAMP and glucocorticoids. Graptopetalum paraguayense (GP), a herbal medicine, is commonly used in Taiwan to treat liver disorders. Partially purified fraction of GP (named HH-F3) suppressed 8-Br-cAMP/glucocorticoid-induced G6Pase, PEPCK and PGC-1α expression and suppressed HBV core promoter activity. HH-F3 blocked HBV core promoter activity via inhibition of PGC-1α expression. Ectopically expressed PGC-1α rescued HH-F3-inhibited HBV surface antigen expression, HBV mRNA production, core protein levels, and HBV replication. HH-F3 also inhibited fatty acid synthase (FASN) expression and decreased lipid accumulation by down-regulating PGC-1α. Thus, HH-F3 can inhibit HBV replication, gluconeogenesis and lipogenesis by down-regulating PGC-1α. Our study indicates that targeting PGC-1α may be a therapeutic strategy for treatment of HBV infections. HH-F3 may have potential use for the treatment of chronic hepatitis B patients with associated metabolic syndrome.

The enzymes LSD1 and Set1A cooperate with the viral protein HBx to establish an active hepatitis B viral chromatin state

With about 350 million people chronically infected around the world hepatitis B is a major health problem. Template for progeny HBV synthesis is the viral genome, organized as a minichromosome (cccDNA) inside the hepatocyte nucleus. How viral cccDNA gene expression is regulated by its chromatin structure; more importantly, how the modulation of this structure impacts on viral gene expression remains elusive. Here, we found that the enzyme SetDB1 contributes to setting up a repressed cccDNA chromatin state. This repressive state is activated by the histone lysine demethylase-1 (LSD1). Consistently, inhibiting or reducing LSD1 levels led to repression of viral gene expression. This correlates with the transcriptionally repressive mark H3K9 methylation and reduction on the activating marks H3 acetylation and H3K4 methylation on viral promoters. Investigating the importance of viral proteins we found that LSD1 recruitment to viral promoters was dependent on the viral transactivator protein HBx. Moreover, the histone methyltransferase Set1A and HBx are simultaneously bound to the core promoter, and Set1A expression correlates with cccDNA H3K4 methylation. Our results shed light on the mechanisms of HBV regulation mediated by the cccDNA chromatin structure, offering new therapeutic targets to develop drugs for the treatment of chronically infected HBV patients.

HBV genotypes and drug resistance mutations in antiretroviral treatment-naive and treatment-experienced HBV-HIV-coinfected patients

BACKGROUND

The presence of HBV resistance mutations upon initiation or during antiretroviral therapy (ART) in HIV-coinfected patients is an important determinant of treatment response. The main objective of the study was to determine the prevalence of HBV resistance mutations in antiretroviral treatment-naive and treatment-experienced HBV-HIV-coinfected Ghanaian patients with detectable HBV viraemia.

METHODS

HBV-HIV-coinfected patients who were ART-naive or had received at least 9 months of lamivudine (3TC)-containing ART were enrolled in a cross-sectional study. Demographic and clinical data were collected and HBV DNA quantified. Partial HBV sequences were amplified by PCR and sequenced bi-directionally to obtain a 2.1-2.2 kb fragment for phylogenetic analysis of HBV genotypes and evaluation of drug resistance mutations.

RESULTS

Of the 100 HBV-HIV-coinfected study patients, 75 were successfully PCR-amplified, and 63 were successfully sequenced. Of these 63 patients, 27 (42.9%) were ART-experienced and 58 (92.1%) had HBV genotype E. No resistance mutations were observed in the 36 ART-naive patients, while 21 (77.8%) of 27 treatment-experienced patients had resistance mutations. All patients with resistance mutations had no tenofovir in their regimens, and 80% of them had HIV RNA <40 copies/ml. The 3TC resistance mutations rtL180M and rtM204V were observed in 10 (47.6%) of the 21 patients, while 5 patients (23.8%) had rtV173L, rtL180M and rtM204V mutations.

CONCLUSIONS

A high proportion of HBV-HIV-coinfected patients with detectable viraemia on 3TC-containing ART had resistance mutations despite good ART adherence as determined by HIV RNA suppression. This study emphasizes the need for dual therapy as part of a fully suppressive ART in all HBV-HIV-coinfected patients in Ghana.

The Woodchuck, a Nonprimate Model for Immunopathogenesis and Therapeutic Immunomodulation in Chronic Hepatitis B Virus Infection

The woodchuck hepatitis virus (WHV) and its host, the eastern woodchuck, is a very valuable model system for hepatitis B virus infection. Many aspects of WHV replication and pathogenesis resemble acute and chronic hepatitis B infection in patients. Since the establishment of immunological tools, woodchucks were used to develop new therapeutic vaccines and immunomodulatory approaches to treat chronic hepadnaviral infections. Combination therapy of nucleos(t)ide analogs, with prime-boost vaccination and triple therapy, including immunomodulatory strategies by blocking the interaction of the programmed death-1 (PD-1) receptor with its ligand inducing a potent T-cell response in chronic WHV carrier woodchucks, suppression of viral replication, and complete elimination of the virus in 30% of the animals. Both strategies may be used for future therapies in patients with chronic hepatitis B.

Current status of immunomodulatory therapy in chronic hepatitis B, fifty years after discovery of the virus: Search for the "magic bullet" to kill cccDNA

Chronic hepatitis B (CHB) is currently treated with IFN-α and nucleos(t)ide analogues, which have many clinical benefits, but there is no ultimate cure. The major problem consists in the persistence of cccDNA in infected hepatocytes. Because no antiviral drug has been evaluated which significantly reduces copies of cccDNA, cytolytic and noncytolytic approaches are needed. Effective virus-specific T- and B-cell responses remain crucial in eliminating cccDNA-carrying hepatocytes and for the long-term control of HBV infection. Reduction of viremia by antiviral drugs provides a window for reconstitution of an HBV-specific immune response. Preclinical studies in mice and woodchucks have shown that immunostimulatory strategies, such as prime-boost vaccination and PD-1 blockade, can boost a weak virus-specific T cell response and lead to effective control of HBV infection. Based on data obtained in our preclinical studies, the combination of antiviral drugs and immunomodulators may control HBV viremia during a patient's drug-off period. In this article, we review current immune-modulatory approaches for the treatment of chronic hepatitis B and the elimination of cccDNA in preclinical models. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis".

The clinical implication of single nucleotide polymorphisms in deoxycytidine kinase in chronic hepatitis B patients treated with lamivudine

Deoxycytidine kinase (dCK) is a critical enzyme involved in intracellular phosphorylation of lamivudine (LAM) to its active triphosphates. We conducted this study to determine dCK polymorphisms in Koreans and to evaluate whether the discovered single nucleotide polymorphisms (SNPs) were associated with treatment outcomes in chronic hepatitis B (CHB) patients treated with LAM. The full-length dCK gene was sequenced from 24 healthy volunteers and 24 patients with CHB. One hundred twenty-seven patients with CHB who were followed-up for at least 24 months after LAM treatment were enrolled. Virological response as determined by undetectable HBV DNA was defined as a good drug response. Primary non-response at 6 months and virological breakthrough within 12 months were defined as a poor drug response. Six novel dCK SNPs were found (-2052C/A, IVS3 - 46G/del, IVS4 + 40G/T, IVS5 + 39T/C, IVS5 - 72A/T, and 966-975T10/T11). In particular, two promoter SNPs, namely -360C/G and -201C/T, were in full linkage disequilibrium. These two SNPs had a higher allele frequency than previously reported in Caucasian, Japanese, and Chinese (26% vs. 2%, 13.1%, and 15.6%, respectively). There was no significant difference between treatment response groups in terms of the distributions of SNP genotypes or allele frequencies. However, there was significant difference in the allele frequency of -360G/-201T between HBeAg seroclearance group and HBeAg non-seroclearance group (P = 0.045). In conclusion, six novel dCK SNPs were discovered. Two promoter SNPs, namely -360C/G and -201C/T, were more frequent in Koreans than other populations. In particular, HBeAg-positive patients with the -360G/-201T haplotype may help HBeAg seroclearance in response to LAM therapy.

Characterization of novel entecavir resistance mutations

BACKGROUND & AIMS

Entecavir (ETV) is approved for the treatment of chronic hepatitis B virus (HBV) infections, but the virus can acquire resistance to the drug. This requires lamivudine resistance mutations (LAMr) and at least one additional mutation. Here, we characterized two novel mutations, rtI163V and rtA186T, associated with viral breakthrough (VBT) in an ETV-refractory patient.

METHODS

HBV from an ETV-refractory patient was sequenced, and newly identified mutations were inserted into a replication-competent clone by mutagenesis. Clones were analyzed for replication efficacy and susceptibility to ETV in vitro. Chimeric mice with human hepatocytes were inoculated with the patient's serum at VBT, and monitored for viral mutation pattern using a next-generation sequencing approach.

RESULTS

RtI163V and rtA186T mutations were detected together with LAMr (rtL180M and rtM204V) at VBT. RtA186T plus LAMr reduced susceptibility to ETV more than 111.1-fold compared with the wild-type clone, while rtI163V plus LAMr resulted in a 20.4-fold reduction. RtA186T significantly reduced viral replication efficacy, while the rtI163V mutation rescued it. Interestingly, the viral mutation pattern in the chimeric mice indicated dominant (or selective) proliferation of a clone containing rtI163V and rtA186T mutations plus LAMr under ETV treatment. Three-dimensional docking simulation indicated that rtA186T reduced the binding affinity of the HBV polymerase to ETV.

CONCLUSIONS

VBT in this ETV-refractory patient is attributable to the novel ETV resistance mutations rtI163V and rtA186T. RtA186T was apparently responsible for ETV resistance but the selection of a clone with the double mutation plus LAMr suggests that rtI163V is required to sustain viral fitness.

Substitution at rt269 in Hepatitis B Virus Polymerase Is a Compensatory Mutation Associated with Multi-Drug Resistance

The emergence of compensatory mutations in the polymerase gene of drug resistant hepatitis B virus (HBV) is associated with treatment failure. We previously identified a multi-drug resistant HBV mutant, which displayed resistance towards lamivudine (LMV), clevudine (CLV), and entecavir (ETV), along with a strong replication capacity. The aim of this study was to identify the previously unknown compensatory mutations, and to determine the clinical relevance of this mutation during antiviral therapy. In vitro mutagenesis, drug susceptibility assay, and molecular modeling studies were performed. The rtL269I substitution conferred 2- to 7-fold higher replication capacity in the wild-type (WT) or YMDD mutation backbone, regardless of drug treatment. The rtL269I substitution alone did not confer resistance to LMV, ETV, adefovir (ADV), or tenofovir (TDF). However, upon combination with YMDD mutation, the replication capacity under LMV or ETV treatment was enhanced by several folds. Molecular modeling studies suggested that the rtL269I substitution affects template binding, which may eventually lead to the enhanced activity of rtI269-HBV polymerase in both WT virus and YMDD mutant. The clinical relevance of the rtL269I substitution was validated by its emergence in association with YMDD mutation in chronic hepatitis B (CHB) patients with sub-optimal response or treatment failure to LMV or CLV. Our study suggests that substitution at rt269 in HBV polymerase is associated with multi-drug resistance, which may serve as a novel compensatory mutation for replication-defective multi-drug resistant HBV.

Current and future antiviral drug therapies of hepatitis B chronic infection

Despite significant improvement in the management of chronic hepatitis B virus (HBV) it remains a public health problem, affecting more than 350 million people worldwide. The natural course of the infection is dynamic and involves a complex interplay between the virus and the host’s immune system. Currently the approved therapeutic regimens include pegylated-interferon (IFN)-α and monotherapy with five nucleos(t)ide analogues (NAs). Both antiviral treatments are not capable to eliminate the virus and do not establish long-term control of infection after treatment withdrawal. IFN therapy is of finite duration and associates with low response rates, liver decompensating and numerous side effects. NAs are well-tolerated therapies but have a high risk of drug resistance development that limits their prolonged use. The imperative for the development of new approaches for the treatment of chronic HBV infection is a challenging issue that cannot be over-sided. Research efforts are focusing on the identification and evaluation of various viral replication inhibitors that target viral replication and a number of immunomodulators that aim to restore the HBV specific immune hyporesponsiveness without inducing liver damage. This review brings together our current knowledge on the available treatment and discusses potential therapeutic approaches in the battle against chronic HBV infection.

Recent advances in micro/nanotechnologies for global control of hepatitis B infection

The control of hepatitis B virus (HBV) infection is a challenging task, specifically in developing countries there is limited access to diagnostics and antiviral treatment mainly due to high costs and insufficient healthcare infrastructure. Although the current diagnostic technologies can reliably detect HBV, they are relatively laborious, impractical and require expensive resources that are not suitable for resource-limited settings. Advances in micro/nanotechnology are pioneering the development of new generation methodologies in diagnosis and screening of HBV. Owing to combination of nanomaterials (metal/inorganic nanoparticles, carbon nanotubes, etc.) with microfabrication technologies, utilization of miniaturized sensors detecting HBV and other viruses from ultra-low volume of blood, serum and plasma is realized. The state-of-the-art microfluidic devices with integrated nanotechnologies potentially allow for inexpensive HBV screening at low cost. This review aims to highlight recent advances in nanotechnology and microfabrication processes that are employed for developing point-of-care (POC) HBV assays.

Therapeutic vaccination and immunomodulation in the treatment of chronic hepatitis B: preclinical studies in the woodchuck

Infection with hepatitis B virus (HBV) may lead to subclinical, acute or chronic hepatitis. In the prevaccination era, HBV infections were endemic due to frequent mother to child transmission in large regions of the world. However, there are still estimated 240 million chronic HBV carriers today and ca. 620,000 patients die per year due to HBV-related liver diseases. Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to satisfactory results. Induction of HBV-specific T cells by therapeutic vaccination or immunomodulation may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients with or without therapeutic reduction of viral load did not result in effective immune control of HBV infection, suggesting that combination of antiviral treatment with new formulations of therapeutic vaccines is needed. The woodchuck (Marmota monax) and its HBV-like woodchuck hepatitis virus are a useful preclinical animal model for developing new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments using nucleos(t)ide analogues, with prime-boost vaccination using DNA vaccines, new hepadnaviral antigens or recombinant adenoviral vectors were tested in the woodchuck model. In this review, we summarize these encouraging results obtained with these therapeutic vaccines. In addition, we present potential innovations in immunostimulatory strategies by blocking the interaction of the inhibitory programmed death receptor 1 with its ligand in this animal model.

Nucleotide analogue-resistant mutations in hepatitis B viral genomes found in hepatitis B patients

Chronic hepatitis B (CHB) is treated with nucleos(t)ide analogues (NAs). The reverse transcriptase (RT) region in the hepatitis B virus (HBV) genome mutates to resist NA treatment, yet the RT mutations have not been well characterized. Furthermore, the HBV genotype might influence RT sequence evolution, NA resistance (NAr) mutation patterns and drug resistance development. We examined 42 NAr mutation sites in 169 untreated and 131 NA-treated CHB patient samples. Patients were identified with HBV-B and HBV-C genotype infections, with a higher prevalence and mutation frequency of HBV-C than HBV-B. Seventeen reported NAr mutation sites and 13 novel mutations were detected. NAr-related mutation prevalence was significantly higher in NA-treated versus untreated patients. Primary antiviral-resistant mutants only existed in NA-treated patients. Sequencing data revealed seven HBV-C-specific mutations and three HBV-B-specific mutations. In conclusion, NA treatment and HBV genotype might constitute the selection basis and promote NA-resistant HBV strain evolution under antiviral therapy.

Hepatitis B surface antigen levels at 6 months after treatment can predict the efficacy of lamivudine-adefovir combination therapy in patients with lamivudine-resistant chronic hepatitis B

Background/Aims

Quantitation of hepatitis B surface antigen (HBsAg) is an increasingly popular method to determine the treatment response in chronic hepatitis B (CHB) patients. The clinical value of HBsAg level measurement during rescue therapy for lamivudine (LMV)-resistant CHB patients have not been evaluated to date. Therefore, this study investigated the correlation between HBsAg level and treatment response in LMV-resistant CHB patients treated with adefovir (ADV) add-on therapy.

Methods

LMV-resistant CHB patients treated with LMV-ADV combination therapy for over 2 years were included. HBsAg levels were measured at 6 month intervals until 1 year, and annually thereafter. Treatment response was assessed by determining the virological response (VR, undetectable HBV DNA levels) during treatment.

Results

Fifty patients were included, of which 40 showed a VR. HBsAg levels were not different significantly at baseline (4.0 vs. 3.6 Log10 IU/mL, P=0.072). However, the HBsAg level decreased after 6 months of treatment in patients with a VR and became different significantly between the groups thereafter (3.9 vs. 3.3 at 6 months, P=0.002; 3.8 vs. 3.2 at 1 year, P=0.004; 3.9 vs. 3.2 at 2 years, P=0.008; 3.7 vs. 3.1 at 3 years, P =0.020).

Conclusions

The HBsAg level at 6 months after treatment can help predict treatment response.

Panaxadiol and panaxatriol derivatives as anti-hepatitis B virus inhibitors

28 Derivatives of panaxadiol (PD) and panaxatriol were synthesized and evaluated for their anti-HBV activity on HepG 2.2.15 cells, of which 17 derivatives inhibited HBV DNA replication. Compounds 4, 9, 10, 14, and 15 showed moderate activity against HBV DNA replication with IC50 values ranged from 7.27 to 28.21 μM compared with PD. In particular, 3-O-2'-thenoyl panaxadiol (4) inhibited not only HBV DNA replication (IC50 = 16.5 μM, SI > 115.7) but also HBsAg (IC50 = 30.8 μM, SI > 62.0) and HBeAg (IC50 = 18.2 μM, SI > 105.14) secretions. Their structure-activity relationships were discussed for guiding future research toward the discovery of new anti-HBV agents.

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.

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

Dehydroandrographolide and andrographolide, two natural diterpenoids isolated from Andrographis paniculata possessed activity against HBV DNA replication with IC50 values of 22.58 and 54.07μM and low SI values of 8.7 and 3.7 in our random assay. Consequently, 48 derivatives of dehydroandrographolide and andrographolide were synthesized and evaluated for their anti-HBV properties to yield a series of active derivatives with lower cytotoxicity, including 14 derivatives against HBsAg secretion, 19 derivatives against HBeAg secretion and 38 derivatives against HBV DNA replication. Interestingly, compound 4e could inhibit not only HBsAg and HBeAg secretions but also HBV DNA replication with SI values of 20.3, 125.0 and 104.9. Furthermore, the most active compound 2c with SI value higher than 165.1 inhibiting HBV DNA replication was revealed with the optimal logP value of 1.78 and logD values. Structure-activity relationships (SARs) of the derivatives were disclosed for guiding the future research toward the discovery of new anti-HBV drugs.

Recent insights into hepatitis B virus-host interactions

Hepatitis B virus (HBV) poses a threat to global public health mainly because of complications of HBV-related chronic liver disease. HBV exhibits a narrow host range, replicating primarily in hepatocytes by a still poorly understood mechanism. For the generation of progeny virions, HBV depends on interactions with specific host factors through its life cycle. Revealing and characterizing these interactions are keys to identifying novel antiviral targets, and to developing specific treatment strategies for HBV patients. In this review, recent insights into the HBV-host interactions, especially on virus entry, intracellular trafficking, genome transcription and replication, budding and release, and even cellular restriction factors were reviewed.

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.

rtM204Q may serve as a novel lamivudine-resistance-associated mutation of hepatitis B virus

Background and Aims

Lamivudine (LAM) is still widely used for anti-HBV therapy in China. The study aimed to clarify whether a newly-found rtM204Q mutation from patients was associated with the drug resistance.

Methods

HBV complete reverse-transcriptase region was screened by direct sequencing and verified by clonal sequencing. Replication-competent plasmids containing patient-derived 1.1mer mutant or wild-type viral genome were constructed and transfected into HepG2 cells. After cultured with or without serially-diluted antiviral drugs, intracellular HBV replicative intermediates were quantitated for calculating the 50% effective concentration of drug (EC₅₀).

Results

A total of 12,000 serum samples of 9,830 patients with chronic HBV infection were screened. rtM204Q mutation was detected in seven LAM-refractory patients. By contrast, rtM204I/rtM204V mutations were detected in 2,502 patients' samples. The rtM204Q emerged either alone or in concomitance with rtM204I/rtM204V, and all were accompanied with virologic breakthrough in clinical course. Clonal sequencing verified that rtM204Q mutant was predominant in viral quasispecies of these samples. Phenotypic analysis showed that rtM204Q mutant had 89.9% of replication capacity and 76-fold increased LAM EC₅₀ of the concomitant wild-type strain. By contrast, rtM204I mutant in the sample had lower replication capacity and higher LAM resistance (46.3% and 1396-fold increased LAM EC₅₀ of the wild-type strain) compared to rtM204Q mutant. rtM204Q mutant was susceptible to adefovir dipivoxil (ADV) in vitro and ADV/ADV+LAM rescue therapy in clinic.

Conclusion

rtM204Q is suggested to be a novel LAM-resistance-associated mutation. It conferred a moderate resistance with higher competent natural replication capacity compared to rtM204I mutation.

New therapeutic vaccination strategies for the treatment of chronic hepatitis B

Chronic hepatitis B virus (CHB) is currently treated with either interferon-based or nucleot(s)ide-based antiviral therapies. However, treatment with pegylated interferon alpha results in a durable antiviral response in only about 30% patients and is associated with side effects. Most patients receiving nucleot(s)ide analogue treatment do not establish long-term, durable control of infection and have rebounding viremia after cessation of therapy. Thus, novel therapy strategies are necessary to achieve the induction of potent and durable antiviral immune responses of the patients which can maintain long-term control of viral replication. Therapeutic vaccination of HBV carriers is a promising strategy for the control of hepatitis B. Here the authors review new therapeutic vaccination strategies to treat chronic hepatitis B which may be introduced for patient treatment in the future.

Enhancing virus-specific immunity in vivo by combining therapeutic vaccination and PD-L1 blockade in chronic hepadnaviral infection

Hepatitis B virus (HBV) persistence is facilitated by exhaustion of CD8 T cells that express the inhibitory receptor programmed cell death-1 (PD-1). Improvement of the HBV-specific T cell function has been obtained in vitro by inhibiting the PD-1/PD-ligand 1 (PD-L1) interaction. In this study, we examined whether in vivo blockade of the PD-1 pathway enhances virus-specific T cell immunity and leads to the resolution of chronic hepadnaviral infection in the woodchuck model. The woodchuck PD-1 was first cloned, characterized, and its expression patterns on T cells from woodchucks with acute or chronic woodchuck hepatitis virus (WHV) infection were investigated. Woodchucks chronically infected with WHV received a combination therapy with nucleoside analogue entecavir (ETV), therapeutic DNA vaccination and woodchuck PD-L1 antibody treatment. The gain of T cell function and the suppression of WHV replication by this therapy were evaluated. We could show that PD-1 expression on CD8 T cells was correlated with WHV viral loads during WHV infection. ETV treatment significantly decreased PD-1 expression on CD8 T cells in chronic carriers. In vivo blockade of PD-1/PD-L1 pathway on CD8 T cells, in combination with ETV treatment and DNA vaccination, potently enhanced the function of virus-specific T cells. Moreover, the combination therapy potently suppressed WHV replication, leading to sustained immunological control of viral infection, anti-WHs antibody development and complete viral clearance in some woodchucks. Our results provide a new approach to improve T cell function in chronic hepatitis B infection, which may be used to design new immunotherapeutic strategies in patients.

Chronic hepatitis B virus (HBV) infection is still one of the major public health problems. Two billion people worldwide have been infected with HBV, of whom more than 360 million developed chronic infection. Every year, approximately one million of these individuals will die from HBV-associated liver diseases such as cirrhosis and hepatocellular carcinoma (HCC). Treatment of chronic hepatitis B remains a clinical challenge, and alternative strategies to treat chronic HBV infection are urgently needed. Here, we designed a new combination strategy to enhance the patient's own antiviral immune response and to achieve long-term viral suppression. The therapeutic effect of our combination therapy strategy for chronic hepadnaviral infection was tested in the woodchuck model. We demonstrated that our novel combination therapy could elicit potent antiviral immune response and achieved a strong antiviral effect, leading to sustained immunological control of chronic hepadnaviral infection and complete viral clearance in treated woodchucks. The results of this study may have an impact on clinical trials of the immunotherapy in chronically HBV-infected patients.

Baseline prognostic factors and statistic model to predict early virological response in telbivudine-treated patients with chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV) infection is still a worldwide disease, which may cause liver cirrhosis or even hepatocellular carcinoma. Telbivudine is a potent nucleoside analogue used in the treatment of chronic hepatitis B (CHB); however, drug resistance has remained a challenge. As early virological response can predict long-term efficacy of nucleotide analogue treatment, numerous studies have been conducted in this area.

OBJECTIVES

The aim of this study was to establish baseline prognostic factors and a statistical model to predict early virological response in telbivudine-treated CHB patients.

PATIENTS AND METHODS

One hundred and eight CHB patients without any experience of nucleotide analogue therapy were assigned to receive telbivudine (600 mg, once daily) for at least 24 weeks, and then were followed up every two weeks. Cox proportional hazard regression model analyses were employed to evaluate baseline variables, and further developing a statistical model to predict early virological response.

RESULTS

Negative family history of HBV infection (P = 0.000235), baseline higher serum TBIL (P = 0.038714) and AST (P = 0.020684) concentrations, and lower level of HBV-DNA (P = 0.0034784) were identified to be associated with higher possibility of early virological response. A model was established based on these variables to calculate the risk scores (R) for CHB patients. R > -0.38 suggested early virological response to telbivudine. The model was validated among an independent set of 20 patients.

CONCLUSIONS

Family history as well as baseline bilirubin, AST and HBV DNA levels can predict early virological response. The model provides a better tool for response prediction based on the four prognostic factors.

Novel Woodchuck Hepatitis Virus (WHV) transgene mouse models show sex-dependent WHV replicative activity and development of spontaneous immune responses to WHV proteins

The woodchuck model is an informative model for studies on hepadnaviral infection. In this study, woodchuck hepatitis virus (WHV) transgenic (Tg) mouse models based on C57BL/6 mice were established to study the pathogenesis associated with hepadnaviral infection. Two lineages of WHV Tg mice, harboring the WHV wild-type genome (lineage 1217) and a mutated WHV genome lacking surface antigen (lineage 1281), were generated. WHV replication intermediates were detected by Southern blotting. DNA vaccines against WHV proteins were applied by intramuscular injection. WHV-specific immune responses were analyzed by flow cytometry and enzyme-linked immunosorbent assays (ELISAs). The presence of WHV transgenes resulted in liver-specific but sex- and age-dependent WHV replication in Tg mice. Pathological changes in the liver, including hepatocellular dysplasia, were observed in aged Tg mice, suggesting that the presence of WHV transgenes may lead to liver diseases. Interestingly, Tg mice of lineage 1281 spontaneously developed T- and B-cell responses to WHV core protein (WHcAg). DNA vaccination induced specific immune responses to WHV proteins in WHV Tg mice, indicating a tolerance break. The magnitude of the induced WHcAg-specific immune responses was dependent on the effectiveness of different DNA vaccines and was associated with a decrease in WHV loads in mice. In conclusion, sex- and age-dependent viral replication, development of autoimmune responses to viral antigens, pathological changes in the liver in WHV Tg mice, and the possibility of breaking immune tolerance to WHV transgenes will allow future studies on pathogenesis related to hepadnaviral infection and therapeutic vaccines.

Comparison of the efficacy of Lamivudine plus adefovir versus entecavir in the treatment of Lamivudine-resistant chronic hepatitis B: a systematic review and meta-analysis

BACKGROUND

Hepatitis B virus infection remains 1 of the major health threats worldwide. Currently, lamivudine plus adefovir combination therapy or entecavir monotherapy is usually used for the treatment of patients with lamivudine-resistant chronic hepatitis B (CHB). However, there are few systematic comparisons between the efficacy of lamivudine plus adefovir and the efficacy of entecavir in the treatment of these patients.

OBJECTIVE

The goal of this systematic study and meta-analysis was to assess the efficacy of lamivudine plus adefovir compared with entecavir for the treatment of patients with lamivudine-resistant CHB.

METHODS

A comprehensive literature search of PUBMED, Web of Science, WANFANG database, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Review, were screened to obtain citations from January 1990 to January 2012 in this study. Data analysis was done by using the Review Manager Software 5.1.

RESULTS

Eight studies were suitable for analysis. A total of 696 patients with lamivudine-resistant CHB were studied and grouped according to treatment: 341 patients in the entecavir group and 355 patients in the lamivudine plus adefovir group. The results found that the rates of undetectable hepatitis B virus DNA levels, alanine aminotransferase normalization, hepatitis B e antigen loss, and hepatitis B e antigen seroconversion were not significantly different between the lamivudine plus adefovir group and the entecavir group. Moreover, the rate of adverse reactions was also not significantly different between the 2 groups. However, virologic breakthrough for the patients with lamivudine resistance was higher in the entecavir group than in the lamivudine plus adefovir group.

CONCLUSIONS

For these CHB patients with lamivudine resistance, lamivudine plus adefovir was a better treatment option than entecavir alone.

Reversal of multidrug resistance by the inhibition of ATP-binding cassette pumps employing "Generally Recognized As Safe" (GRAS) nanopharmaceuticals: A review

Pumps of the ATP-binding cassette superfamily (ABCs) regulate the access of drugs to the intracellular space. In this context, the overexpression of ABCs is a well-known mechanism of multidrug resistance (MDR) in cancer and infectious diseases (e.g., viral hepatitis and the human immunodeficiency virus) and is associated with therapeutic failure. Since their discovery, ABCs have emerged as attractive therapeutic targets and the search of compounds that inhibit their genetic expression and/or their functional activity has gained growing interest. Different generations of pharmacological ABC inhibitors have been explored over the last four decades to address resistance in cancer, though clinical results have been somehow disappointing. "Generally Recognized As Safe" (GRAS) is a U.S. Food and Drug Administration designation for substances that are accepted as safe for addition in food. Far from being "inert", some amphiphilic excipients used in the production of pharmaceutical products have been shown to inhibit the activity of ABCs in MDR tumors, emerging as a clinically translatable approach to overcome resistance. The present article initially overviews the classification, structure and function of the different ABCs, with emphasis on those pumps related to drug resistance. Then, the different attempts to capitalize on the activity of GRAS nanopharmaceuticals as ABC inhibitors are discussed.

Ultradeep pyrosequencing and molecular modeling identify key structural features of hepatitis B virus RNase H, a putative target for antiviral intervention

Last-generation nucleoside/nucleotide analogues are potent against hepatitis B virus (HBV) and have a high barrier to resistance. However, delayed responses have been observed in patients previously exposed to other drugs of the same class, long-term resistance is possible, and cure of infection cannot be achieved with these therapies, emphasizing the need for alternative therapeutic approaches. The HBV RNase H represents an interesting target because its enzyme activity is essential to the HBV life cycle. The goal of our study was to characterize the structure of the HBV RNase H by computing a 3-dimensional molecular model derived from E. coli RNase H and analyzing 2,326 sequences of all HBV genotypes available in public databases and 958,000 sequences generated by means of ultradeep pyrosequencing of sequences from a homogenous population of 73 treatment-naive patients infected with HBV genotype D. Our data revealed that (i) the putative 4th catalytic residue displays unexpected variability that could be explained by the overlap of the HBx gene and has no apparent impact on HBV replicative capacity and that (ii) the C-helix-containing basic protrusion, which is required to guide the RNA/DNA heteroduplex into the catalytic site, is highly conserved and bears unique structural properties that can be used to target HBV-specific RNase H inhibitors without cross-species activity. The model shows substantial differences from other known RNases H and paves the way for functional and structural studies as a prerequisite to the development of new inhibitors of the HBV cell cycle specifically targeting RNase H activity.

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.

Options for the management of antiviral resistance during hepatitis B therapy: reflections on battles over a decade

Although much advancement has been achieved in the treatment of chronic hepatitis B, antiviral resistance is still a challenging issue. Previous generation antiviral agents have already developed resistance in a number of patients, and it is still being used especially in resource limited countries. Once antiviral resistance occurs, it predisposes to subsequent resistance, resulting in multidrug resistance. Therefore, prevention of initial antiviral resistance is the most important strategy, and appropriate choice and modification of therapy would be the cornerstone in avoiding treatment failures. Until now, management of antiviral resistance has been evolving from sequential therapy to combination therapy. In the era of tenofovir, the paradigm shifts again, and we have to decide when to switch and when to combine on the basis of newly emerging clinical data. We expect future eradication of chronic hepatitis B virus infection by proper prevention and optimal management of antiviral resistance.

Duck HBV DNA copy numbers in isolated hepatocyte nuclei vary dramatically and decline during entecavir therapy

BACKGROUND

We aimed to develop a quantitative assay to measure duck HBV (DHBV) DNA in single hepatocyte nuclei from DHBV-infected animals and to observe intranuclear DHBV DNA kinetics undergoing entecavir (ETV) therapy.

METHODS

DHBV DNA in isolated nuclei was amplified by quantitative real-time PCR. Liver tissues from chronically-infected ducks with or without ETV treatment were assessed. Cell cycle phases were defined with flow cytometry in single nuclei.

RESULTS

We successfully established a quantitative assay to measure intranuclear DHBV DNA in single nuclei with high specificity, sensitivity and acceptable interassay variations. The intranuclear viral DNA copy numbers varied dramatically (2-204 copies/nuclei) in 11 ducks with active viral replication. Average intranuclear DHBV DNA copies from individual animals (7.57-57.67 copies/nuclei) significantly correlated with total intranuclear (rs=0.955, P<0.001) and serum (rs=0.745, P=0.008) viral DNA levels. The median intranuclear DHBV DNA copies in virus-positive nuclei were greater in gap 0/1 than those in gap 2/mitosis and synthesis phases (P<0.001). Median intranuclear viral DNA copies in virus-positive nuclei decreased from 21 to 6 (P<0.001) under 14-19 weeks of ETV therapy. However, subsequently, further reductions were not achieved in four animals after extended 16 week treatment (6 versus 11, P=0.034).

CONCLUSIONS

Intranuclear DHBV DNA levels varied significantly, which could be partially attributed to effects of cell cycle phases, and could be decreased by ETV therapy.

Characterization of antiviral resistance mutations among the Eastern Indian Hepatitis B virus infected population

Background

Antiviral therapy using nucleos(t)ide analogues (NAs) is an effective control measure of chronic hepatitis B virus (HBV) infection; however they need long term treatment. Presence of drug-resistance mutations may get in the way of the efficacy of antiviral therapy. Our study was aimed at defining the prevalence of HBV drug-resistance in HBVrt region in a population of 147 HBsAg positive patients.

Findings

HBV/D has shown multiple types of HBVrt mutations both among treatment naïve (65.0%, 13 of 20 HBV/D) and treated patients (56.2%, 9 of 16 HBV/D). In additional, several mutations, with a suggested role in drug resistance, were detected among the treatment naïve as well as the treated patients. The mutations reported to be involved in reduction of drug effectiveness, was common among non-responders to therapy as well as among the naïve patients. Notably, classical antiviral resistance mutations (rtL80I/V-rtI169T-rtV173L-rtL180M-rtA181T/V/S-rtT184A/S/G/C-rtA194T-rtS202C /G/I -rtM204V/I-rtN236T-rtM250V) were not detected.

Conclusion

The prevalence of putative NAr mutations among non responders to therapy suggests that they might have role in reduced efficacy of currently available antivirals and requires further investigations.

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.

Chronic hepatitis B: what should be the goal for new therapies?

Chronic hepatitis B can currently be medically managed with either pegylated interferon-alpha (pegIFN-α) or one of the five nucleos(t)ide analog Direct Acting Antivirals (DAAs) that inhibit the hepatitis B virus (HBV) DNA polymerase. While pegIFN-α is effective in approximately one-third of the treated patients, the polymerase inhibitors significantly reduce viral load in the vast majority of those treated. However, neither pegIFN-α nor nucleosi(t)de analogs are capable of reliably eliminating the virus and achieving a cure. Moreover, the interferons and polymerase inhibitors are recommended by US, European and Asian professional society practice guidelines for use in only a subset of those infected with HBV. This subset is the population with the greatest levels of circulating viral DNA and abnormal liver function. Although this is the population at the highest risk for cirrhosis and liver cancer, those who fall outside the treatment guidelines, with low levels of viral replication and normal serum ALTs, may also benefit from antiviral therapy. The questions are thus: are new classes of drugs needed to manage chronic hepatitis B? Is a cure possible? Is a cure even necessary? It is therefore important to define the meaning of a cure and determine what the goals of new therapies should be. In this article, we address those questions and propose two operational definitions of medically attainable cures. The first is a "functional cure" based on the clinical outcome, in which the patient's life expectancy becomes the same as that of an individual who has resolved his HBV infection without therapy. Because such an outcome cannot be measured over the short term, we also define an "apparent virological cure," based on the stable off-drug suppression of HBV viremia and antigenemia and the normalization of ALTs and other laboratory tests. We suggest that such a virological cure should be the goal of future therapeutics in all patients with chronic hepatitis B. The extent to which a virological cure predicts a functional cure will only be determined by long-term follow-up.

Optimal management of chronic hepatitis B patients with treatment failure and antiviral drug resistance

The management of treatment failure in patients with chronic hepatitis B, remains a clinical concern. Incomplete viral suppression and the emergence of drug resistance are key determinants of treatment failure. The correct choice of a potent first-line 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 have significantly lower rates of resistance compared with those with a low barrier to resistance. Management of treatment failure requires precise clinical and virological monitoring as well as early treatment intervention with appropriate noncross-resistant antivirals. Long-term surveillance of treatment efficacy and possible emergence of drug resistance is necessary in patients who have been sequentially treated with multiple antivirals. The identification of novel treatment targets remains a major research goal to improve the efficacy of current antiviral therapy through combination therapy regimens.