Management and prevention of drug resistance in chronic hepatitis B

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

BACKGROUND

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

METHODS

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

RESULTS

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

Highly sensitive and specific detection of hepatitis B virus DNA and drug resistance mutations utilizing the PCR-based CRISPR-Cas13a system

OBJECTIVES

Undetectable or low-level hepatitis B virus (HBV) DNA and drug resistance mutations in patients may increase the risk of HBV transmission or cause active viral replication and other clinical problems. Here, we established a highly sensitive and practical method for HBV and drug resistance detection using a polymerase chain reaction (PCR) -based CRISPR-Cas13a detection system (referred to as PCR-CRISPR) and evaluated its detection capability using clinical samples.

METHODS

Specific CRISPR RNAs (crRNAs) are designed for HBV DNA detection and YMDD (tyrosine-methionine-aspartate-aspartate) variant identification. The HBV DNA was detected in 312 serum samples for HBV diagnosis using quantification PCR (qPCR) and PCR-CRISPR. Additionally, 424 serum samples for YMDD testing were detected by qPCR, direct sequencing, and our assay.

RESULTS

Using PCR-CRISPR, one copy per test of HBV DNA was detected with HBV-1 crRNA in 15 min after PCR amplification. Consistent results with qPCR were observed for 302 samples, while the remaining 10 samples with low-level HBV DNA were detectable by PCR-CRISPR and droplet digital PCR but not by qPCR. PCR-CRISPR diagnosed all 412 drug-resistant samples detected by the YMDD detection qPCR kit and direct sequencing, as well as the other 12 drug-resistant samples with low-level HBV DNA undetectable by qPCR and direct sequencing.

CONCLUSIONS

We developed a novel PCR-CRISPR method for highly sensitive and specific detection of HBV DNA and drug resistance mutations. One copy per test for HBV DNA and YMDD drug resistance mutations could be detected. This method has wide application prospects for the early detection of HBV infection, drug resistance monitoring and treatment guidance.

Predictors of Therapeutic Outcome to Nucleotide Reverse Transcriptase Inhibitor in Hepatitis B Patients

Hepatitis B is a clinically important public health issue. Infection leads to hepatocellular carcinoma. Therefore, patients need antiviral therapy for prolonged period to prevent the complication of the disease. Data concerning chronic hepatitis B (CHB) patients with high hepatitis B virus (HBV) DNA are limited. The aim of the study was to check the efficacy of the nucleoside reverse transcriptase inhibitors (tenofovir) in terms of suppression of HBV DNA. The secondary end point in the study is to evaluate trends of predictive variables that predict outcome of treatment. In this specific study, we evaluated 140 CHB male and female patients, of these 110 completed 48 weeks of treatment. On the basis of hepatitis B e antigen (HBeAg), patients were stratified; HBV DNA and hepatitis B surface antigen (HBsAg) levels were measured along with liver function tests. All enrolled patients were given tenofovir disoproxil fumarate 300 mg daily before breakfast. Overall, 69.1% of patients showed virologic response. HBeAg-negative patient group showed 68% viral suppression and HBeAg-positive patient group showed 45.9% over 24 months of treatment, while at 48 months it was shown to be 76.7% and 54.1%, respectively. None of the patients suffered HBsAg loss during the 48 months. Baseline high HBV DNA level was found as a significant predictor of response (OR, 1.9; 95% CI = 1.23-3.9, p = 0.005). None of the patients observed had serious adverse events. Mutations in the RT region of polymerase gene are shown to be associated with resistance to antiviral drugs. Among patients suffering with chronic HBV infection, HBeAg-negative patient group have better virologic response as compared with HBeAg-positive group. Higher concentration of HBV DNA at baseline has negative prediction for sustained viral suppression. The A-B motif interdomain rtL122F mutation was found in nonresponder patients in our study. Another mutation rtN248H observed in E motif considered to have effect on DNA primer grip, which forms part of binding pocket.

Tenofovir versus tenofovir plus entecavir for chronic hepatitis B with lamivudine resistance and entecavir resistance

We compared the viral suppressive efficacy of tenofovir disoproxil fumarate (TDF) mono-rescue therapy (TDF group) and TDF plus entecavir (ETV) combination-rescue therapy (TDF + ETV group) in chronic hepatitis B (CHB) patients with lamivudine resistance and entecavir resistance. One hundred and thirty-three CHB patients with lamivudine and entecavir resistance were investigated. Ninety-six patients were treated with TDF and 37 with TDF + ETV for at least 6 months. We compared the virologic response rate (HBV DNA level <20 IU/mL) between the two groups and identified the predictive factors of treatment outcome. There were no significant differences between the two groups in demographic characteristics. Up to 24 months [median: 18 (range 6-24) months], 85.4% and 89.2% of the TDF group and TDF + ETV group, respectively, achieved a virologic response (P=.068). Only the HBV DNA level at baseline was significantly associated with a virologic response in the multivariate analysis. In a subanalysis of patients with HBV DNA levels ≥4 log (IU/mL) at baseline, a higher proportion of patients in the TDF + ETV group than the TDF group achieved a virologic response (92.9% vs 68.3%; P<.001), while 90% of patients with HBV DNA (IU/mL) levels <4 log in all both TDF and TDF + ETV groups achieved a virologic response. TDF mono-rescue therapy is a reasonable option in patients with lamivudine resistance and entecavir resistance. However, the combination strategy should be considered in patients with high baseline HBV DNA levels.

Characterization of novel hepadnaviral RNA species accumulated in hepatoma cells treated with viral DNA polymerase inhibitors

Inhibitors of hepadnaviral DNA polymerases are predicted to inhibit both minus and plus strand of viral DNA synthesis and arrest viral DNA replication at the stage of pregenomic (pg) RNA-containing nucleocapsids. However, analyses of the RNA species of human and duck hepatitis B viruses (HBV and DHBV, respectively) in hepatoma cells treated with viral DNA polymerase inhibitors revealed the genesis of novel RNA species migrating slightly faster than the full-length pgRNA. The DNA polymerase inhibitor-induced accumulation of these RNA species were abolished in the presence of alpha-interferon or HBV nucleocapsid assembly inhibitors. Moreover, they were protected from microccocal nuclease digestion and devoid of a poly-A tail. These characteristics suggest that the novel RNA species are most likely generated from RNase H cleavage of encapsidated pgRNA, after primer translocation and synthesis of the 5' terminal portion of minus strand DNA. In support of this hypothesis, DNA polymerase inhibitor treatment of chicken hepatoma cells transfected with a DHBV genome encoding an RNase H inactive DNA polymerase (E696H) failed to produce such RNA species. Our results thus suggest that the currently available DNA polymerase inhibitors do not efficiently arrest minus strand DNA synthesis at the early stage in hepatocytes. Hence, development of novel antiviral agents that more potently suppress viral DNA synthesis or viral nucleocapsid assembly inhibitors that are mechanistically complementary to the currently available DNA polymerase inhibitors are warranted.

Present and future therapies of hepatitis B: From discovery to cure

Hepatitis B virus (HBV) is a significant global pathogen, infecting more than 240 million people worldwide. While treatment for HBV has improved, HBV patients often require lifelong therapies and cure is still a challenging goal. Recent advances in technologies and pharmaceutical sciences have heralded a new horizon of innovative therapeutic approaches that are bringing us closer to the possibility of a functional cure of chronic HBV infection. In this article, we review the current state of science in HBV therapy and highlight new and exciting therapeutic strategies spurred by recent scientific advances. Some of these therapies have already entered into clinical phase, and we will likely see more of them moving along the development pipeline.

CONCLUSION

With growing interest in developing and efforts to develop more effective therapies for HBV, the challenging goal of a cure may be well within reach in the near future.

Prediction of virologic response to tenofovir mono-rescue therapy for multidrug resistant chronic hepatitis B

Most guidelines suggest combination therapy including nucleoside and nucleotide analogues for the treatment of chronic hepatitis B (CHB) with multidrug resistance (MD-R). However, long-term combination treatment can evoke high costs and safety problems. Therefore, we investigated the efficacy of tenofovir disoproxil fumarate (TDF) mono-rescue therapy for viral suppression in patients with CHB exhibiting MD-R. We reviewed patients with CHB exhibiting antiviral drug resistance treated by TDF mono-rescue therapy from December 2012 to June 2014. The patients were categorized into three groups: lamivudine-resistance (LAM-R) group (n = 290), and LAM-R + adefovir-resistance (ADV-R) group (n = 43), and LAM-R + entecavir-resistance (ETV-R) group (n = 113). We compared the virologic response rate according to the multiplicity of resistance and investigated the predictive factors of a virologic response. For a median of 15 months (range, 6-24 months) of TDF mono-rescue therapy, the cumulative virologic response rates were 82.8, 81.4, and 84.1% in the LAM-R, LAM-R + ADV-R, and LAM-R + ETV-R groups, respectively (P = 0.239). Multivariate analysis revealed that multiplicity of resistance did not influence the achievement of a virologic response (P = 0.218). However, the baseline HBV DNA level significantly influenced the achievement of a virologic response for the treatment of CHB with MD-R (P < 0.001). TDF mono-rescue therapy is an appropriate treatment for CHB with MD-R, and the baseline HBV DNA level is a significant predictive factor for a virologic response. These factors should be considered before treating CHB with MD-R.

Synthesis and Anti-Hepatitis B Virus Evaluation of 7-Methoxy-3-heterocyclic quinolin-6-ols

A series of novel 7-methoxy-3-heterocyclic quinolin-6-ol derivatives were synthesized and evaluated for their anti-hepatitis B virus (HBV) activities and cytotoxicities in the HepG2.2.15 cell line. Five compounds, 14a, 15c, 15e, 16b, and 16f, displayed excellent potency and selectivity toward the HBV, with IC₅₀ values of less than 5.0 µM and selectivity index values of 11.0-71.5. Structure-activity relationship studies indicated that the 1,3,4-thiadiazole and sulfinylmethyl derivatives showed the most potent activities against the HBV.

Therapeutic strategies for a functional cure of chronic hepatitis B virus infection

Treatment of chronic hepatitis B virus (HBV) infection with the viral DNA polymerase inhibitors or pegylated alpha-interferon has led to a significant retardation in HBV-related disease progression and reduction in mortality related to chronic hepatitis B associated liver decompensation and hepatocellular carcinoma. However, chronic HBV infection remains not cured. The reasons for the failure to eradicate HBV infection by long-term antiviral therapy are not completely understood. However, clinical studies suggest that the intrinsic stability of the nuclear form of viral genome, the covalently closed circular (ccc) DNA, sustained low level viral replication under antiviral therapy and homeostatic proliferation of hepatocytes are the critical virological and pathophysiological factors that affect the persistence and therapeutic outcomes of HBV infection. More importantly, despite potent suppression of HBV replication in livers of the treated patients, the dysfunction of HBV-specific antiviral immunity persists. The inability of the immune system to recognize cells harboring HBV infection and to cure or eliminate cells actively producing virus is the biggest challenge to finding a cure. Unraveling the complex virus–host interactions that lead to persistent infection should facilitate the rational design of antivirals and immunotherapeutics to cure chronic HBV infection.

Molecular diagnosis and treatment of drug-resistant hepatitis B virus

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

Incidence and risk factors for incomplete HBV DNA suppression in HIV/HBV-co-infected patients initiating tenofovir-based therapy

Suppression of hepatitis B virus (HBV)-DNA to undetectable levels is an important goal for HIV/HBV-co-infected patients receiving anti-HBV-active antiretroviral therapy (ART), and current guidelines recommend that this outcome should be reached by 1 year of treatment. However, the proportion of patients that fail to achieve an undetectable HBV DNA at this time point and its determinants remain unknown in clinical practice. The objective of this study was to determine the incidence and risk factors for incomplete HBV suppression following 1 year of tenofovir-based ART. We performed a cohort study among tenofovir-treated HIV/HBV-co-infected patients. Patients had HBV viraemia, initiated tenofovir-based ART and had HBV DNA measured at 1 year of therapy. The primary outcome was incomplete HBV suppression (HBV DNA ≥2.6 log IU/mL) at 1 year. Logistic regression determined odds ratio (ORs) of incomplete HBV suppression for risk factors of interest. Among 133 patients, 54% (95% CI, 46-63%) had incomplete HBV suppression at 1 year. Incomplete suppression was associated with higher baseline HBV DNA (OR, 1.46 per log IU/mL increase; 95% CI, 1.1-1.94) and detectable HIV viraemia at 1 year (OR, 2.52; 95% CI, 1.19-5.32). Among 66 patients with suppressed HIV RNA at 1 year, 28 (42%) failed to achieve an undetectable HBV DNA. Failure to suppress HBV DNA by 1 year occurred in a sizeable proportion of tenofovir-treated HIV/HBV-co-infected patients. Higher HBV DNA and detectable HIV viraemia were risk factors for incomplete HBV suppression.

Comparing the efficacy and clinical outcome of telbivudine and entecavir naïve patients with hepatitis B virus-related compensated cirrhosis

BACKGROUND AND AIM

There is limited data on the efficacy and outcome of telbivudine (LdT) therapy in patients with chronic hepatitis B and compensated cirrhosis. We evaluated LdT as first-line therapy in these patients and compared with those treated with entecavir (ETV).

METHODS

We consecutively enrolled 88 chronic hepatitis B patients with compensated cirrhosis primarily treated with LdT at least for 2 years or less than 2 years but developed resistance, and evaluated the efficacy and clinical outcomes. Meanwhile, we matched a control group who treated with ETV for comparison.

RESULTS

In LdT group, alanine aminotransferase normalization (65.8%), hepatitis B e antigen seroconversion (39.8%), hepatitis B virus (HBV) DNA undetectablility (71.6%), and virologic resistance (23.9%) were noted after 2 years treatment. Compared with ETV group, there were significant difference in HBV DNA undetectablility (P < 0.001) and virologic resistance (P < 0.001). In addition, the decline of serum hepatitis B surface antigen levels, hepatocellular carcinoma development, mortality, disease progression, and the change of renal function were similar. Cox regression analysis showed that pretreatment low albumin level and high model for end-stage liver disease scores were risk factors for disease progression.

CONCLUSIONS

These results indicated that although LdT and ETV are similar in clinical outcomes for patients with HBV-related compensated cirrhosis, LdT still had lower HBV undetectablility and higher resistant rate after 2 years treatment, which was a challenge for being as first-line therapy in these patients who need lifelong therapy.

A review of non-nucleoside anti-hepatitis B virus agents

Hepatitis B Virus is the most common cause of chronic liver disease worldwide. Currently approved agents of chronic HBV infection treatment include interferon and nucleoside analogues. However, the side effects of interferon and the viral resistance of nucleoside analogues make the current treatment far from satisfactory. Therefore, new drugs with novel structures and mechanisms are needed. Recently, a number of non-nucleoside HBV inhibitors have been obtained from natural sources or prepared by synthesis/semi-synthesis. Some of them exhibited potent anti-HBV activity with novel mechanisms. These compounds provide useful information for the medicinal chemist to develop novel non-nucleoside compounds as anti-HBV agents.

Inferring short-range linkage information from sequencing chromatograms

Direct Sanger sequencing of viral genome populations yields multiple ambiguous sequence positions. It is not straightforward to derive linkage information from sequencing chromatograms, which in turn hampers the correct interpretation of the sequence data. We present a method for determining the variants existing in a viral quasispecies in the case of two nearby ambiguous sequence positions by exploiting the effect of sequence context-dependent incorporation of dideoxynucleotides. The computational model was trained on data from sequencing chromatograms of clonal variants and was evaluated on two test sets of in vitro mixtures. The approach achieved high accuracies in identifying the mixture components of 97.4% on a test set in which the positions to be analyzed are only one base apart from each other, and of 84.5% on a test set in which the ambiguous positions are separated by three bases. In silico experiments suggest two major limitations of our approach in terms of accuracy. First, due to a basic limitation of Sanger sequencing, it is not possible to reliably detect minor variants with a relative frequency of no more than 10%. Second, the model cannot distinguish between mixtures of two or four clonal variants, if one of two sets of linear constraints is fulfilled. Furthermore, the approach requires repetitive sequencing of all variants that might be present in the mixture to be analyzed. Nevertheless, the effectiveness of our method on the two in vitro test sets shows that short-range linkage information of two ambiguous sequence positions can be inferred from Sanger sequencing chromatograms without any further assumptions on the mixture composition. Additionally, our model provides new insights into the established and widely used Sanger sequencing technology. The source code of our method is made available at http://bioinf.mpi-inf.mpg.de/publications/beggel/linkageinformation.zip.

Truncated active human matrix metalloproteinase-8 delivered by a chimeric adenovirus-hepatitis B virus vector ameliorates rat liver cirrhosis

BACKGROUND

Liver cirrhosis is a potentially life-threatening disease caused by progressive displacement of functional hepatocytes by fibrous tissue. The underlying fibrosis is often driven by chronic infection with hepatitis B virus (HBV). Matrix metalloproteinases including MMP-8 are crucial for excess collagen degradation. In a rat model of liver cirrhosis, MMP-8 delivery by an adenovirus (Ad) vector achieved significant amelioration of fibrosis but application of Ad vectors in humans is subject to various issues, including a lack of intrinsic liver specificity.

METHODS

HBV is highly liver-specific and its principal suitability as liver-specific gene transfer vector is established. HBV vectors have a limited insertion capacity and are replication-defective. Conversely, in an HBV infected cell vector replication may be rescued in trans by the resident virus, allowing conditional vector amplification and spreading. Capitalizing on a resident pathogen to help in its elimination and/or in treating its pathogenic consequences would provide a novel strategy. However, resident HBV may also reduce susceptibility to HBV vector superinfection. Thus a size-compatible truncated MMP-8 (tMMP8) gene was cloned into an HBV vector which was then used to generate a chimeric Ad-HBV shuttle vector that is not subject to superinfection exclusion. Rats with thioacetamide-induced liver cirrhosis were injected with the chimera to evaluate therapeutic efficacy.

RESULTS

Our data demonstrate that infectious HBV vector particles can be obtained via trans-complementation by wild-type virus, and that the tMMP8 HBV vector can efficiently be shuttled by an Ad vector into cirrhotic rat livers. There it exerted a comparable beneficial effect on fibrosis and hepatocyte proliferation markers as a conventional full-length MMP-8Ad vector.

CONCLUSIONS

Though the rat cirrhosis model does not allow assessing in vivo HBV vector amplification these results advocate the further development of Ad-HBV vectors for liver-specific gene therapy, including and perhaps particularly for HBV-related disease.

Discrepancy of potential antiviral resistance mutation profiles within the HBV reverse transcriptase between nucleos(t)ide analogue-untreated and -treated patients with chronic hepatitis B in a hospital in China

Little is known about the discrepancy of the potential antiviral resistance mutation profiles within the hepatitis B virus (HBV) reverse transcriptase (RT) between nucleos(t)ide analogue (NA)-untreated and -treated patients with chronic hepatitis B. Full-length HBV RT sequences from 59 NA-treated and 105 NA-untreated Chinese patients were amplified and sequenced. Forty-two potential NA resistance (NAr) mutation sites were screened within these 164 RT sequences. The NAr mutation prevalence and frequency in the NA-treated group were significantly higher than those in the NA-untreated one (P < 0.001, respectively). The classical primary drug resistance and secondary/compensatory mutations were only detected at seven sites (rtL80, rtI169, rtL180, rtA181, rtT184, rtM204, and rtN236) in NA-treated patients. The non-classical putative NAr and pre-treatment mutations were observed at 22 sites (rtT38, rtN/S53, rtL82, rtL/I91, rtN/Y124, rtH126, rtT128, rtN/D134, rtN139, rtR153, rtV191, rtV207, rtS213, rtV214, rtE218, rtY/F221, rtV/I224, rtL229, rtI233, rtN/H238, rtR242, and rtS/C256) in both groups. Substitutions at seven non-classical mutation sites were of interest due to either detection only in patients with virologic breakthrough (rtL82 and rtV214), or potential ties with HBV genotypes (rtV191 and rtL229), or coexistence with rtM204I/V (rtL229), or increased mutation trends after NA-treatment (rtT128, rtV207, and rtN/H238). In conclusion, NA treatment not only constitutes a major selection factor for the primary and secondary/compensatory NAr mutations but also drives the changes of some of the putative NAr mutation sites, most of which are the genotype-independent RT sites (rtL82, rtT128, rtV191, rtV207, rtV214, rtL229, and rtN/H238). Their antiviral resistance potential calls for further investigations.

KASL Clinical Practice Guidelines: Management of chronic hepatitis B

The guideline on the management of chronic hepatitis B (CHB) was first developed in 2004 and revised in 2007 by the Korean Association for the Study of the Liver (KASL). Since then there have been many developments, including the introduction of new antiviral agents and the publications of many novel research results from both Korea and other countries. In particular, a large amount of knowledge on antiviral resistance--which is a serious issue in Korea--has accumulated, which has led to new strategies being suggested. This prompted the new guideline discussed herein to be developed based on recent evidence and expert opinion.

TARGET POPULATION

The main targets of this guideline comprise patients who are newly diagnosed with CHB and those who are followed or treated for known CHB. This guideline is also intended to provide guidance for the management of patients under the following special circumstances: malignancy, transplantation, dialysis, coinfection with other viruses, pregnancy, and children.

Hepatitis B: modern end points of treatment and the specter of viral resistance

The goal of antiviral treatment of chronic hepatitis B is to prevent the complications of cirrhosis, hepatic decompensation, HCC, and death. Because these clinical outcomes may take a long period of time to develop, it is important to use intermediate or surrogate end points to evaluate the efficacy and response to antiviral treatment, and to determine whether treatment can be safely stopped, especially given concern for the development of antiviral resistance with NUC therapy. Although normalization of ALT and suppression of HBV DNA viral replication are associated with favorable outcomes, the durability of their response is low, and these end points are insufficient markers for stopping treatment. HBeAg seroconversion is currently used to discontinue NUC treatment in patients with HBeAg-positive chronic hepatitis B, whereas the stopping rule for HBeAg-negative disease relies on HBsAg loss. However, HBsAg loss occurs very infrequently and is not a practical end point for clinical use, although quantitative HBsAg levels may be useful in identifying patients who could achieve a sustained virologic response to treatment.

Profile of HBV antiviral resistance mutations with distinct evolutionary pathways against nucleoside/nucleotide analogue treatment among Chinese chronic hepatitis B patients

BACKGROUND

Antiviral drug-resistant HBV mutants under a variety of treatment protocols are complex and only partly understood. Here, a population-based cross-sectional study was performed to analyse the profile of resistance mutations in distinct evolutionary pathways refractory to different nucleoside/nucleotide analogues (NAs).

METHODS

Serum samples of 199 chronic hepatitis B patients undergoing NA treatment from five hospitals in four northern cities of China were obtained between January 2007 and July 2009. The genotypic resistance of HBV in these samples was characterized. The full-length HBV reverse transcriptase region was amplified, sequenced and analysed with particular focus on the following NA-resistant changes: rtL80, rtI169, rtV173, rtL180, rtA181, rtT184, rtA194, rtS202, rtM204, rtN236 and rtM250.

RESULTS

Among 199 HBV isolates, 30 (15.08%) and 169 (84.92%) were genotypes B and C, respectively, and 65 (32.66%) harboured NA-resistant mutations. The prevalence of mutations at rtM204 was 34.33% in 134 patients who had received or who had been exposed to lamivudine-based therapy. Five cases of rtN236 mutations were detected exclusively among 75 patients receiving adefovir-dipivoxil-based therapies. A total of 19 cases of multidrug resistance rtA181 mutations were observed in those with lamivudine-, adefovir-dipivoxil- or telbivudine-based treatment (186 cases), but not in those undergoing entecavir treatment (13 cases). Mutations were not found at rtI169, rtT184, rtA194 or rtS202. rtM204 mutations (27 rtM204I, 15 rtM204V and 5 rtM204I/V cases) were detected at the highest frequency among 65 mutants (72.30% [47/65]) and found to display 16 combination mutation patterns, in which rtM204I and rtM204V were significantly associated with rtL80I/V and rtL180M, respectively (P<0.01).

CONCLUSIONS

One-third of the studied population harboured NA-resistant HBV with complicated mutation patterns. Monitoring HBV genotypic resistance mutation markers and patterns is therefore shown to be beneficial for optimizing antiviral therapies and for avoiding clinical deterioration.

Oxymatrine inhibits hepatitis B infection with an advantage of overcoming drug-resistance

Oxymatrine (OMTR) is an anti-hepatitis drug used in China. Its mechanism of action is unknown. Recently, we found that OMTR inhibits hepatitis B virus (HBV) via down-regulating the expression of heat-stress cognate 70 (Hsc70), a host protein required for HBV DNA replication. Goal of this study was to assess the effect of OMTR on clinical HBV drug-resistance. OMTR monotherapy (oral, 12 months) reduced blood HBV DNA by 96% and HBeAg by 70% in the chronic hepatitis B (CHB) patients resistant to lamivudine (n = 17), equal to its efficacy in the naïve CHB cohort (n = 20). Liver biopsy study showed that OMTR treatment caused a decrease of Hcs70 mRNA in liver cells, parallel with a reduction of intracellular HBV DNA. Combination of lamivudine with OMTR (n = 15) (oral, 12 months) showed an enhanced anti-HBV effect as compared to lamivudine monotherapy (n = 25). The incidence of drug resistance against lamivudine in the combination group was significantly lower than that in the lamivudine group (1/15 vs 7/25; p<0.01). The results were further confirmed in vitro. Treatment of HBV(+) HepH2215 cells with sub-optimal dose of OMTR for 8 months suppressed HBV replication without inducing drug resistance, whereas lamivudine monotherapy caused drug-resistant mutation in 3 months. Combination of OMTR with lamivudine prevented HBV from developing drug resistance.

Synthesis and in-vitro anti-hepatitis B virus activity of ethyl 6-bromo-8-hydroxyimidazo[1,2-a]pyridine-3-carboxylates

A series of ethyl 6-bromo-8-hydroxyimidazo[1,2-a]pyridine-3-carboxylate derivatives were synthesized and evaluated for their anti-hepatitis B virus (HBV) activity and cytotoxicity in HepG2.2.15 cells. Nearly half of the tested compounds were proved to be highly effective in inhibiting the replication of HBV DNA with IC(50) values ranging from 1.3 to 9.1 µM. Among them, 10o and 10s were identified as the most promising compounds.

Fitness and infectivity of drug-resistant and cross-resistant hepatitis B virus mutants: why and how is it studied?

The emergence of hepatitis B virus (HBV) drug-resistant (and multidrug-resistant) strains during long-term therapy with nucleoside/nucleotide analogues is associated with treatment failure and, therefore, represents a clinical challenge. For clinicians, the close monitoring and management of resistance has become a key issue in clinical practice. For HBV virologists, the understanding of the mechanism of emergence of specific mutant strains in the viral quasispecies during treatment is also an important issue. If a particular viral strain can emerge in the quasispecies within a particular environment, it is probably because its fitness is superior to other strains. The present review focuses on viral fitness as well as viral infectivity, and in particular on technical means that are available to study this viral fitness in vitro and in animal models.

Quantitative assessment of the antiviral potencies of 21 shRNA vectors targeting conserved, including structured, hepatitis B virus sites

BACKGROUND & AIMS

RNA interference (RNAi) may offer new treatment options for chronic hepatitis B. Replicating via an RNA intermediate, hepatitis B virus (HBV) is known to be principally vulnerable to RNAi. However, beyond delivery, the relevant issues of potential off-target effects, target site conservation in circulating HBV strains, and efficacy of RNAi itself have not systematically been addressed, nor can the different existing data be quantitatively compared. The aim of this study was to provide such information.

METHODS

To focus on the intracellular RNAi process itself and minimise other variables affecting overall RNAi efficacy, we used a robust co-transfection system to quantitatively assess the relative potencies of 21 small-hairpin (sh) RNA vectors, targeting conserved sites throughout the HBV genome, against viral RNAs, proteins, nucleocapsids, and secreted virions under standardised conditions.

RESULTS

The approach enabled a distinct efficacy ranking, with the six most potent shRNAs achieving 95% reductions in virion formation, sequence-specifically and without detectable interferon induction, yet by differentially affecting different steps. Efficacy correlated poorly with predictions and was not principally abolished by target structure. Sequence comparisons suggest that truly conserved, RNAi-targetable sequences comprise less than 500 nucleotides of the circulating HBV genomes.

CONCLUSIONS

The HBV genome can harbour only a finite number of optimal target sites, but current predictions are poorly suited to constrain the number of possible candidates. However, the small size of the highly conserved sequence space suggests experimental identification as a viable option.

Heat stress cognate 70 host protein as a potential drug target against drug resistance in hepatitis B virus

Heat stress cognate 70 (Hsc70) is a host protein associated with hepatitis B virus (HBV) replication. The goal of this study was to investigate whether Hsc70 could be an anti-HBV drug target. Our results showed that introducing Hsc70 increased HBV replication in HBV(+) human hepatocytes (HepG2.2.15 cells). The coiled-coil region on Hsc70 (nucleotides 1533 to 1608; amino acids 511 to 536) was the key sequence for HBV replication. Knockdown of Hsc70 expression by RNA interference (RNAi) largely inhibited HBV replication with no cytotoxicity to the host. Using an Hsc70 mRNA screening assay, the natural compound oxymatrine (OMTR) was found to be a selective inhibitor for Hsc70 expression. Then, OMTR was used to investigate the potential of Hsc70 as an anti-HBV drug target. OMTR inhibited Hsc70 mRNA expression by 80% and HBV DNA replication by over 60% without causing cytotoxicity. The anti-HBV effect of OMTR appeared to be mediated by destabilizing Hsc70 mRNA. The half-life (T(1/2)) of Hsc70 mRNA decreased by 50% in OMTR-treated hepatocytes. The Hsc70 mRNA 3'-untranslated-region (UTR) sequence was the element responsible for OMTR's destabilization activity. OMTR suppressed HBV de novo synthesis at the reverse transcription stage from pregenomic RNA (pgRNA) to DNA and was active against either wild-type HBV or strains resistant to lamivudine, adefovir, and entecavir. Therefore, host Hsc70 could be a novel drug target against HBV, and OMTR appears to inhibit HBV replication by destabilizing Hsc70 mRNA. As the target is not a viral protein, OMTR is active for either wild-type HBV or strains resistant to reverse transcriptase (RT) inhibitors.

Characterization of potential antiviral resistance mutations in hepatitis B virus reverse transcriptase sequences in treatment-naïve Chinese patients

Full-length hepatitis B virus (HBV) reverse transcriptase (RT) sequences were amplified and sequenced among 192 nucleos(t)ide analogue (NA)-naïve Chinese patients with chronic hepatitis B. Deduced amino acids (AAs) at 42 previously reported potential NA resistance (NAr) mutation positions in RT region were analyzed. Patients were found with either B-genotype (28.65%) or C-genotype (71.35%) infections. Rt53, rt91, rt124, rt134, rt221, rt224, rt238 and rt256 were identified as B- and C-genotype-dependent polymorphic AA positions. AA substitutions at 11 classical NAr mutation positions, i.e. rt80, rt169, rt173, rt180, rt181, rt184, rt194, rt202, rt204, rt236 and rt250, were not detected. However, potential NAr mutations were found in 30.73% (59/192) isolates, which involved 18 positions including rt53, rt207, rt229, rt238 and rt256, etc. The concomitant AA changes of HBsAg occurred in 16.67% (32/192) isolates including sG145R mutation. One-third of mutation positions were located in functional RT domains (e.g. rt207 and rt233), A-B interdomains (overlapping HBsAg 'a' determinant and showing most concomitant immune-associated mutations) and non-A-B interdomains (e.g. rt191 and rt213), respectively. Genotypes B and C each showed several preferred positions to mutate. These results might provide insights into understanding the evolution and selection basis of NAr HBV strains under antiviral therapy.