Molecular epidemiology of hepatitis B among Indigenous Australians in Queensland and the Torres Strait Islands

BACKGROUND

Chronic hepatitis B virus (HBV) infection is a major health problem for all Indigenous Australians. Post-2000, Hepatitis B surface antigen prevalence has decreased, although remaining four times higher among Indigenous compared with non-Indigenous people.

AIMS

This study aimed to characterise the HBV from Indigenous populations in Queensland and the Torres Strait Islands.

METHODS

Serum samples were collected, with consent, from people within Queensland Indigenous communities prior to 1990 as part of the Queensland Health vaccination programme. Ethics approval was subsequently obtained to further characterise the HBV from 93 of these stored samples. HBV DNA was extracted and genotype was obtained from 82 samples. HBV full genome sequencing was carried out for a subset of 14 samples.

RESULTS

Seventy-eight samples were identified as genotype C (2 × C12, 3 × C13 and 73 × C14), one sample as genotype A (A2) and three samples as genotype D (1 × D2, 1 × D3 and 1 × D4). The HBV/C sequences identified were most closely related to sequences isolated from Papua New Guinea and Indonesia (Papua Province).

CONCLUSIONS

The HBV isolated from the Torres Strait Islanders was notably different to the HBV/C4 strain isolated from Indigenous people of mainland northern Australia, with no evidence of recombination. This reflects the differences in culture and origin between Torres Strait Islanders and mainland Indigenous people.

A phase 2, open-label, randomized, multiple-dose study evaluating Inarigivir in treatment-naïve patients with chronic hepatitis B

BACKGROUND/AIMS

Novel agents acting against hepatitis B virus (HBV) are needed to improve HBsAg seroclearance or termed as 'functional cure'. Inarigivir (retinoic acid-inducible gene I agonist) has immunomodulatory and direct antiviral actions against HBV. We aimed to determine the safety and efficacy of Inarigivir for the treatment of HBV infection.

PATIENTS/METHODS

80 treatment-naïve patients were randomized in 4 ascending dose cohorts to receive 12 weeks of Inarigivir 25, 50, 100, 200 mg or placebo in a ratio of 4:1. All patients were then given tenofovir for another 12 weeks.

RESULTS

Least squares (LS) mean reductions in HBV DNA from baseline increased with higher doses of Inarigivir (0.6116 in 25 mg and 1.5774 in 200 mg groups vs. 0.0352 in placebo group) (95% CI 0.9518-0.2011 and 1.921-1.1634 respectively). LS mean changes in HBV RNA and HBsAg from baseline ranged from -0.3856 to -0.5794 versus -0.1474 and -0.0956 to -0.1818 versus +0.0026 in Inarigivir-treated versus placebo groups respectively. During the tenofovir-treated period, LS mean reductions in HBsAg in the Inarigivir-treated groups ranged from 0.1709 to 0.3529 versus 0.1984 in the placebo group. Inarigivir-treated groups showed mean reductions in ALT from baseline between 23.3 and 33.8 versus 0.7 U/L in the placebo group. Treatment-emergent adverse events related to Inarigivir and placebo occurred in 4.7% and 6.3% patients respectively.

CONCLUSIONS

Twelve-week Inarigivir up to 200 mg dose was associated with a reduction of HBV DNA, HBV RNA and antigen levels. A trend for greater HBsAg reduction was observed in Inarigivir pre-treated patients after switching to tenofovir.

Hepatitis B Virus Flares After Nucleot(s)ide Analogue Cessation Are Associated With Activation of Toll-Like Receptor Signaling Pathways

BACKGROUND

We evaluated the patterns of peripheral Toll-like receptor (TLR) signaling activity and the expression of TLRs and natural killer (NK) cell activation in a cohort of patients experiencing severe hepatitis flares after stopping nucleot(s)ide analogues (NAs) therapy.

METHODS

Samples were collected longitudinally from patients with chronic hepatitis B who were enrolled in a prospective study of NA discontinuation. Patients experiencing hepatitis flares were compared with patients with normal alanine aminotransferase. Peripheral blood mononuclear cells (PBMCs) were stimulated with TLR ligands and cytokine secretion in the cell culture supernatant measured. Expression of TLR2/4, NKG2D, NKp46, and triggering receptor expressed on myeloid cells 1 (TREM-1) on monocytes, NK, and NK-T cells was measured.

RESULTS

Seventeen patients with severe reactivation hepatitis flares were compared to 12 nonflare patients. Hepatitis flares were associated with increased activity of TLR2-8 and TLR9 signaling in PBMCs at the time of peak flare compared to baseline. Hepatitis flares were also associated with (1) upregulation of TLR2 and (2) TREM-1 receptor expression on NK. There were no differences at baseline between flare patients and nonflare patients.

CONCLUSIONS

Hepatitis flares off NA therapy have a significant innate inflammatory response with upregulation of TLR signaling on peripheral monocytes and TLR2 and TREM-1 expression on NK cells. This implicates the innate immune system in the immunopathogenesis of hepatitis B flares.

Stopping nucleot(s)ide analogues in non-cirrhotic HBeAg-negative chronic hepatitis B patients: HBsAg loss at 96 weeks is associated with low baseline HBsAg levels

BACKGROUND AND AIMS

Current guidelines recommend long-term nucleot(s)ide analogue (NA) therapy for patients with HBeAg-negative chronic hepatitis B (CHB). However, disease remission has been described after stopping NA therapy, as well as HBsAg loss.

METHODS

We performed a prospective multi-centre cohort study of stopping NA therapy. Inclusion criteria were HBeAg-negative CHB, the absence of cirrhosis and HBVDNA<lower limit of quantification for ≥18 months. We assessed virological and biochemical outcomes including HBsAg loss, as well as NA restart rates, over 96 weeks.

RESULTS

In total, 110 patients [62% entecavir (ETV); 28% tenofovir (TDF), 10% other] were enrolled. Median age was 56 years, 57% were male, 85% were Asian, median baseline HBsAg level was 705 (214-2325) IU/ml. Virological reactivation occurred in 109/110 patients, median time to detection was 8 (4-12) weeks, and occurred earlier after stopping TDF versus ETV (median 4 vs. 12 weeks p < 0.001). At week 96, 77 (70%) remained off-treatment, 65 (59%) had ALT <2× ULN, 31 (28%) patients were in disease remission with HBVDNA <2000 IU/ml plus ALT <2× ULN and 7 (6%) patients had lost HBsAg. Baseline HBsAg ≤10 IU/ml was associated with HBsAg loss (6/9 vs. 1/101 p < 0.001). ALT >5× ULN occurred in 35 (32%); ALT flares were not associated with HBsAg loss. There were no unexpected safety issues.

CONCLUSION

Virological reactivation was very common after stopping NA therapy and occurred earlier after stopping TDF versus ETV. The majority of patients had ALT <2× ULN at week 96, but only one-third achieved disease remission and HBsAg loss was rare. Very low HBsAg levels at baseline were uncommon but predicted for HBsAg loss and disease remission.

Origins and Evolution of the Primate Hepatitis B Virus

Recent interest in the origins and subsequent evolution of the hepatitis B virus (HBV) has strengthened with the discovery of ancient HBV sequences in fossilized remains of humans dating back to the Neolithic period around 7,000 years ago. Metagenomic analysis identified a number of African non-human primate HBV sequences in the oldest samples collected, indicating that human HBV may have at some stage, evolved in Africa following zoonotic transmissions from higher primates. Ancestral genotype A and D isolates were also discovered from the Bronze Age, not in Africa but rather Eurasia, implying a more complex evolutionary and migratory history for HBV than previously recognized. Most full-length ancient HBV sequences exhibited features of inter genotypic recombination, confirming the importance of recombination and the mutation rate of the error-prone viral replicase as drivers for successful HBV evolution. A model for the origin and evolution of HBV is proposed, which includes multiple cross-species transmissions and favors subsequent recombination events that result in a pathogen and can successfully transmit and cause persistent infection in the primate host.

Analysis of Hepatitis B Virus Haplotype Diversity Detects Striking Sequence Conservation Across Genotypes and Chronic Disease Phase

BACKGROUND AND AIMS

We conducted haplotype analysis of complete hepatitis B virus (HBV) genomes following deep sequencing from 368 patients across multiple phases of chronic hepatitis B (CHB) infection from four major genotypes (A-D), analyzing 4,110 haplotypes to identify viral variants associated with treatment outcome and disease progression.

APPROACH AND RESULTS

Between 18.2% and 41.8% of nucleotides and between 5.9% and 34.3% of amino acids were 100% conserved in all genotypes and phases examined, depending on the region analyzed. Hepatitis B e antigen (HBeAg) loss by week 192 was associated with different haplotype populations at baseline. Haplotype populations differed across the HBV genome and CHB history, this being most pronounced in the precore/core gene. Mean number of haplotypes (frequency) per patient was higher in immune-active, HBeAg-positive chronic hepatitis phase 2 (11.8) and HBeAg-negative chronic hepatitis phase 4 (16.2) compared to subjects in the "immune-tolerant," HBeAg-positive chronic infection phase 1 (4.3, P< 0.0001). Haplotype frequency was lowest in genotype B (6.2, P< 0.0001) compared to the other genotypes (A = 11.8, C = 11.8, D = 13.6). Haplotype genetic diversity increased over the course of CHB history, being lowest in phase 1, increasing in phase 2, and highest in phase 4 in all genotypes except genotype C. HBeAg loss by week 192 of tenofovir therapy was associated with different haplotype populations at baseline.

CONCLUSIONS

Despite a degree of HBV haplotype diversity and heterogeneity across the phases of CHB natural history, highly conserved sequences in key genes and regulatory regions were identified in multiple HBV genotypes that should be further investigated as targets for antiviral therapies and predictors of treatment response.

RNA Interference Therapy With ARC-520 Results in Prolonged Hepatitis B Surface Antigen Response in Patients With Chronic Hepatitis B Infection

BACKGROUND AND AIMS

ARC-520, the first an RNA interference (RNAi) therapeutic, was designed to reduce all RNA transcripts derived from covalently closed circular DNA, leading to a reduction in viral antigens and hepatitis B virus (HBV) DNA.

APPROACH AND RESULTS

We aimed to evaluate the depth of hepatitis B surface antigen (HBsAg) decline in response to multiple doses of ARC-520 compared to placebo (PBO) in two randomized, multicenter studies in nucleoside/nucleotide analogue reverse-transcriptase inhibitor (NUC)-experienced patients with hepatitis B early antigen (HBeAg)-negative (E-neg) or HBeAg-positive (E-pos) disease. A total of 58 E-neg and 32 E-pos patients were enrolled and received four monthly doses of PBO (n = 20 E-neg, 11 E-pos), 1 mg/kg ARC-520 (n = 17 E-neg, 10 E-pos), or 2 mg/kg ARC-520 (n = 21 E-neg, 11 E-pos) concomitantly with NUC. HBsAg change from baseline to 30 days after the last ARC-520 dose were compared to PBO. Both E-neg and E-pos high-dose groups significantly reduced HBsAg compared to PBO, with mean reductions of 0.38 and 0.54 log IU/mL, respectively. HBsAg reductions persisted for approximately 85 days and >85 days after the last dose in E-neg and E-pos patients, respectively. The low-dose groups did not reach statistical significance in either study. E-pos patients showed a dose-dependent reduction in HBeAg from baseline. Mean maximum reduction was 0.23 and 0.69 log Paul Ehrlich IUs/mL in the low-dose and high dose ARC-520 groups respectively. ARC-520 was well tolerated, with only two serious adverse events of pyrexia possibly related to study drug observed.

CONCLUSIONS

ARC-520 was active in both E-neg and E-pos, NUC-experienced HBV patients; but absolute HBsAg reductions were moderate, possibly due to expression of HBsAg from integrated HBV DNA, indicating the need for RNAi therapeutics that can target viral transcripts regardless of origin.

Glycoengineered hepatitis B virus-like particles with enhanced immunogenicity

Virus-like particles (VLP) represent biological platforms for the development of novel products such as vaccines and delivery platforms for foreign antigenic sequences. VLPs composed of the small surface antigen (HBsAgS) derived from the hepatitis B virus (HBV) are the immunogenic components of a licensed, preventative vaccine, which contains aluminum hydroxide as adjuvant. Herein, we report that glycoengineering of N-glycosylated HBsAgS to generate hyper-glycosylated VLPs display an enhanced immunogenicity relative to the wild type (WT) HBsAgS VLPs when expressed in FreeStyle HEK 293F cells. Comparative mass spectrometry-based N-glycan profiling, gel electrophoresis, and immunoassays demonstrated that WT and hyper-glycosylated HBsAgS VLPs contain the same type and distribution of N-glycan structures, but the latter shows a higher glycan abundance per protein mass. The antigenic integrity of the modified VLPs was also shown to be retained. To assess whether hyper-glycosylated VLPs induce an enhanced immune response in the presence of the adjuvant aluminum hydroxide, the anti-HBV surface antigen (anti-HBsAgS) antibody response was monitored in BALB/c mice, subcutaneously injected with different VLP derivatives. In the absence and presence of adjuvant, hyper-glycosylated VLPs showed an enhanced immunogenicity compared to WT VLPs. The ability of hyper-glycosylated VLPs to promote potent anti-HBsAgS immune responses compared to VLPs with a native N-glycan level as well as non-glycosylated, yeast-derived HBsAgS VLPs opens exciting avenues for generating more efficacious VLP-based vaccines against hepatitis B and improved HBsAgS VLP carrier platforms using glycoengineering.

Mother-to-child transmission of hepatitis B: Examining viral cut-offs, maternal HBsAg serology and infant testing

BACKGROUND & AIMS

Antipartum antiviral therapy in the setting of high viral load is recommended to prevent mother-to-child transmission of hepatitis B although recommended viral load cut-offs vary. Quantitative HBsAg has been proposed as an alternative screening strategy to identify high viral load in this setting. Guidelines suggest testing all infants for vaccine response and infection. We set out to re-examine viral load cut-offs; the predictive value of quantitative HBsAg and the need for follow-up infant testing in our cohort.

METHODS

A retrospective cohort study of 469 HBsAg positive mother-baby pairs from 2 tertiary hospitals in Sydney was performed. Antiviral therapy (lamivudine or tenofovir disoproxil fumarate) was offered to women with viral load ≥6 log₁₀  IU/mL (high) from 32 weeks gestation. Transmission and vaccine response was analysed according to viral load. The utility of quantitative HBsAg in identifying high viral load was examined.

RESULTS

Mother-to-child transmission only occurred in setting of high viral load, in 0.85% (1/117) of those who received antiviral therapy and in 8.66% (2/23) of those who chose not to. Quantitative HBsAg did not accurately identify high-risk mothers HBV DNA ≥6 log₁₀  IU/mL. Successful infant vaccine response was 98.7% overall, and 99.4% when viral load was <6 log₁₀  IU/mL.

CONCLUSION

Antiviral therapy initiated at 32 weeks when maternal viral load is ≥6 log₁₀  IU/mL almost completely abrogates transmission. Quantitative HBsAg does not reliably predict high viral load. When maternal viral load is <6 log₁₀  IU/mL, high vaccine efficacy and zero transmission suggests testing infants is of little value.

RNAi-based treatment of chronically infected patients and chimpanzees reveals that integrated hepatitis B virus DNA is a source of HBsAg

Chronic hepatitis B virus (HBV) infection is a major health concern worldwide, frequently leading to liver cirrhosis, liver failure, and hepatocellular carcinoma. Evidence suggests that high viral antigen load may play a role in chronicity. Production of viral proteins is thought to depend on transcription of viral covalently closed circular DNA (cccDNA). In a human clinical trial with an RNA interference (RNAi)-based therapeutic targeting HBV transcripts, ARC-520, HBV S antigen (HBsAg) was strongly reduced in treatment-naïve patients positive for HBV e antigen (HBeAg) but was reduced significantly less in patients who were HBeAg-negative or had received long-term therapy with nucleos(t)ide viral replication inhibitors (NUCs). HBeAg positivity is associated with greater disease risk that may be moderately reduced upon HBeAg loss. The molecular basis for this unexpected differential response was investigated in chimpanzees chronically infected with HBV. Several lines of evidence demonstrated that HBsAg was expressed not only from the episomal cccDNA minichromosome but also from transcripts arising from HBV DNA integrated into the host genome, which was the dominant source in HBeAg-negative chimpanzees. Many of the integrants detected in chimpanzees lacked target sites for the small interfering RNAs in ARC-520, explaining the reduced response in HBeAg-negative chimpanzees and, by extension, in HBeAg-negative patients. Our results uncover a heretofore underrecognized source of HBsAg that may represent a strategy adopted by HBV to maintain chronicity in the presence of host immunosurveillance. These results could alter trial design and endpoint expectations of new therapies for chronic HBV.

The virological aspects of hepatitis B

Human hepatitis B virus (HBV) is a hepatotropic virus that is responsible for a significant burden of disease, causing liver disease and hepatocellular carcinoma. It is a small DNA virus with a replication strategy that is similar to that of a retrovirus. HBV is prone to mutagenesis and under the influence of diverse selection pressures, has evolved into a pool of quasispecies, genotypes and mutants, which confers a significant survival advantage. The genome is small, circular, and compact but has a complex replication strategy. The viral life cycle involves the formation of a covalently closed circular DNA (cccDNA), which is organized into a minichromosome that is the template for the synthesis of viral mRNA. HBV DNA (double-stranded linear form) can also integrate into the host genome, ensuring lifelong persistence of the virus. To date, despite great advances in therapeutics, once HBV is chronically established, it is incurable. This is by virtue of many aspects of its virological structure and viral life cycle. In this review, we aim to discuss important aspects of the virology of HBV with a focus on clinical implications.

Safety, Tolerability, and Pharmacokinetics of ARC-520 Injection, an RNA Interference-Based Therapeutic for the Treatment of Chronic Hepatitis B Virus Infection, in Healthy Volunteers

ARC‐520 Injection, an RNA interference drug for the treatment of hepatitis B that targets cccDNA‐derived viral mRNA transcripts with high specificity, effectively reduces the production of viral proteins and HBV DNA. In this phase 1 randomized, double‐blind, placebo‐controlled study, 54 healthy volunteers (half male, half female) received a single, intravenous dose of 0.01–4.0 mg/kg ARC‐520 Injection (n = 36) or placebo (n = 18). Assessments included safety, tolerability, pharmacokinetics, and pharmacodynamics (cytokines and complement). Pharmacokinetics of the siRNA and peptide excipient components contained in ARC‐520 Injection showed a relatively short half‐life of 3–5 and 8–10 hours, respectively. Dose exposure linearity was demonstrated within the dose range. ARC‐520 Injection was well tolerated, with adverse‐event frequency the same as placebo and no serious adverse events. ARC‐520 Injection was initially found to induce histamine release through mast cell degranulation, resulting in 2 moderate hypersensitivity reactions. However, after initiation of pretreatment with oral antihistamine, no further hypersensitivity reactions occurred. Low‐level, transient complement induction and sporadic, mild, and transient elevations of several cytokines were observed but not associated with any symptoms. ARC‐520 Injection showed a favorable tolerability profile in this single‐dose study in healthy volunteers. Oral antihistamine pretreatment is recommended in the future to offset mast cell degranulation stimulation.

New perspectives on the hepatitis B virus life cycle in the human liver

The central role of the transcriptional template of the hepatitis B virus (HBV), covalently closed circular DNA (cccDNA), has been difficult to study in patients with chronic hepatitis B (CHB) infection. In this issue of the JCI, Zhang and colleagues reveal a mosaic distribution of viral antigens and nucleic acids and a mismatch between HBV cccDNA, RNA, and expression of the hepatitis B surface antigen (HBsAg). These unusual patterns varied over the natural history of CHB, prompting the authors to propose a new three-stage model of the HBV life cycle at the single-cell level.

Synthetic RNAi triggers and their use in chronic hepatitis B therapies with curative intent

Current therapies for chronic hepatitis B virus infection (CHB) - nucleos(t)ide analogue reverse transcriptase inhibitors and interferons - result in low rates of functional cure defined as sustained off-therapy seroclearance of hepatitis B surface antigen (HBsAg). One likely reason is the inability of these therapies to consistently and substantially reduce the levels of viral antigen production. Accumulated evidence suggests that high serum levels of HBsAg result in exhaustion of the host immune system, rendering it unable to mount the effective antiviral response required for HBsAg clearance. New mechanistic approaches are required to produce high rates of HBsAg seroclearance in order to greatly reduce off-treatment disease progression. Already shown to be a clinically viable means of reducing gene expression in a number of other diseases, therapies based on RNA interference (RNAi) can directly target hepatitis B virus transcripts with high specificity, profoundly reducing the production of viral proteins. The fact that the viral RNA transcripts contain overlapping sequences means that a single RNAi trigger can result in the degradation of all viral transcripts, including all messenger RNAs and pregenomic RNA. Advances in the design of RNAi triggers have increased resistance to degradation and reduced nonspecific innate immune stimulation. Additionally, new methods to effectively deliver the trigger to liver hepatocytes, and specifically to the cytoplasmic compartment, have resulted in increased efficacy and tolerability. An RNAi-based drug currently in clinical trials is ARC-520, a dynamic polyconjugate in which the RNAi trigger is conjugated to cholesterol, which is coinjected with a hepatocyte-targeted, membrane-active peptide. Phase 2a clinical trial results indicate that ARC-520 was well tolerated and resulted in significant, dose-dependent reduction in HBsAg for up to 57days in CHB patients. RNAi-based therapies may play an important role in future therapeutic regimes aimed at improving HBsAg seroclearance and eliminating the need for lifelong therapy. This paper 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 B."

Chronic hepatitis B: Virology, natural history, current management and a glimpse at future opportunities

The host immune system plays an important role in chronic hepatitis B (CHB), both in viral clearance and hepatocellular damage. Advances in our understanding of the natural history of the disease have led to redefining the major phases of infection, with the "high replicative, low inflammatory" phase now replacing what was formerly termed the "immune tolerant" phase, and the "nonreplicative phase" replacing what was formerly termed the "inactive carrier" phase. As opposed to the earlier view that HBV establishes chronic infection by exploiting the immaturity of the neonate's immune system, new findings on trained immunity show that the host is already somewhat "matured" following birth, and is actually very capable of responding immunologically, potentially altering future hepatitis B treatment strategies. While existing therapies are effective in reducing viral load and necroinflammation, often restoring the patient to near-normal health, they do not lead to a cure except in very rare cases and, in many patients, viremia rebounds after cessation of treatment. Researchers are now challenged to devise therapies that will eliminate infection, with a particular focus on eliminating the persistence of viral cccDNA in the nuclei of hepatocytes. In the context of chronic hepatitis B, new definitions of 'cure' are emerging, such as 'functional' and 'virological' cure, defined by stable off-therapy suppression of viremia and antigenemia, and the normalization of serum ALT and other liver-related laboratory tests. Continued advances in the understanding of the complex biology of chronic hepatitis B have resulted in the development of new, experimental therapies targeting viral and host factors and pathways previously not accessible to therapy, approaches which may lead to virological cures in the near term and functional cures upon long term follow-up. 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 B."

Elucidating the role of the HBV e antigen in manipulating the innate immune response

ABSTRACT 

HBV causes persistent infection in approximately 300 million people and is associated with up to 2 million deaths annually. While the mechanisms by which HBV establishes and maintains infection are yet to be fully elucidated, there is mounting evidence that HBV infection in humans upregulates a range of innate immune responses and HBV has in turn has evolved mechanisms to suppress these responses. One such mechanism may be the hepatitis B e antigen (HBeAg), a soluble secreted protein which is also a major driver of adaptive immune responses. In this review, we review the literature on HBeAg-mediated regulation of innate immune responses and show that this regulation may extend beyond hepatocytes to other cell types such as NK cells which play an important role in viral clearance. Although further studies using new infection models are required, taken together these findings suggest that the HBeAg is an important regulator of the host response to infection and should not be overlooked in efforts to identify novel therapeutic targets against HBV.

Short duration of lamivudine for the prevention of hepatitis B virus transmission in pregnancy: lack of potency and selection of resistance mutations

This study sought to assess the antiviral efficacy of lamivudine (LMV) administered during third trimester to reduce maternal viraemia and to identify the emergence of LMV resistance. A prospective observational analysis was performed on 26 mothers with high viral load (>10⁷ IU/mL). Twenty-one women received LMV (treated group) for an average of 53 days (range 22-88 days), and the remaining five formed the untreated control group. Serum samples from two time points were used to measure HBV DNA levels and antiviral drug resistance. The LMV-treated women achieved a median HBV DNA reduction of 2.6-log10 IU/mL. Although end-of-treatment (EOT) HBV DNA in four (18%) LMV-treated women remained at >10(7) IU/mL (± 0.5 log IU/mL), no mother-to-baby transmission was observed. In contrast, a baby from the untreated mother was HBsAg positive at 9 months postpartum. Four technologies were used for drug resistance testing. Only ultra-deep pyrosequencing (UDPS) was sufficiently sensitive to detect minor viral variants down to <1%. UDPS showed that LMV therapy resulted in increased viral quasispecies diversity and positive selection of HBV variants with reverse transcriptase amino acid substitutions at sites associated with primary LMV resistance (rtM204I/V and rtA181T) in four (19%) women. These viral variants were detected mostly at low frequencies (0.63-5.92%) at EOT, but one LMV-treated mother had an rtA181T variant that increased from 2.2% pretherapy to 25.59% at EOT. This mother was also infected with the vaccine escape variant (sG145R), which was inhibited by LMV treatment. LMV therapy during late pregnancy only reduced maternal viraemia moderately, and drug-resistant viral variants emerged.

Hepatocyte produced matrix metalloproteinases are regulated by CD147 in liver fibrogenesis

BACKGROUND

The classical paradigm of liver injury asserts that hepatic stellate cells (HSC) produce, remodel and turnover the abnormal extracellular matrix (ECM) of fibrosis via matrix metalloproteinases (MMPs). In extrahepatic tissues MMP production is regulated by a number of mechanisms including expression of the glycoprotein CD147. Previously, we have shown that CD147 is expressed on hepatocytes but not within the fibrotic septa in cirrhosis [1]. Therefore, we investigated if hepatocytes produce MMPs, regulated by CD147, which are capable of remodelling fibrotic ECM independent of the HSC.

METHODS

Non-diseased, fibrotic and cirrhotic livers were examined for MMP activity and markers of fibrosis in humans and mice. CD147 expression and MMP activity were co-localised by in-situ zymography. The role of CD147 was studied in-vitro with siRNA to CD147 in hepatocytes and in-vivo in mice with CCl4 induced liver injury using ãCD147 antibody intervention.

RESULTS

In liver fibrosis in both human and mouse tissue MMP expression and activity (MMP-2, -9, -13 and -14) increased with progressive injury and localised to hepatocytes. Additionally, as expected, MMPs were abundantly expressed by activated HSC. Further, with progressive fibrosis there was expression of CD147, which localised to hepatocytes but not to HSC. Functionally significant in-vitro regulation of hepatocyte MMP production by CD147 was demonstrated using siRNA to CD147 that decreased hepatocyte MMP-2 and -9 expression/activity. Further, in-vivo α-CD147 antibody intervention decreased liver MMP-2, -9, -13, -14, TGF-β and α-SMA expression in CCl4 treated mice compared to controls.

CONCLUSION

We have shown that hepatocytes produce active MMPs and that the glycoprotein CD147 regulates hepatocyte MMP expression. Targeting CD147 regulates hepatocyte MMP production both in-vitro and in-vivo, with the net result being reduced fibrotic matrix turnover in-vivo. Therefore, CD147 regulation of hepatocyte MMP is a novel pathway that could be targeted by future anti-fibrogenic agents.

Anti-viral therapy for prevention of perinatal HBV transmission: extending therapy beyond birth does not protect against post-partum flare

BACKGROUND

Antepartum anti-viral therapy (AVT) is often administered to prevent perinatal transmission of hepatitis B virus (HBV) infection. Little is known about the effect of AVT on post-partum flare rates and severity.

AIM

To examine whether extending AVT beyond birth influences the post-partum course.

METHODS

One hundred and one pregnancies in 91 women with HBV DNA levels ≥log 7 IU/mL were included. AVT (initially lamivudine, later tenofovir disoproxil fumarate) was commenced from 32 weeks gestation and stopped soon after birth and at 12 weeks post-partum. Outcomes according to post-partum treatment duration were examined: Group 1 = AVT ≤4 weeks (n = 44), Group 2 = AVT >4 weeks (n = 43), Group 3 = no AVT (n = 14).

RESULTS

The majority of women were HBeAg+ (97%), median age 29 years, baseline HBV DNA log 8.0 IU/mL and follow-up 48 weeks post-partum. Post-partum treatment duration was 2 weeks for Group 1 and 12 weeks for Group 2, P < 0.01. Flare rates were not significantly different: Group 1 = 22/44 (50%), Group 2 = 17/43 (40%) and Group 3 = 4/14 (29%), P = 0.32. Onset of flare was similar at 8/10/9 weeks post-partum for Groups 1/2/3 respectively, P = 0.34. The majority of flares spontaneously resolved. HBeAg seroconversion (n = 1/5/1 in Groups 1/2/3, P = 0.27) was not associated with treatment duration or the occurrence of a post-partum flare.

CONCLUSIONS

Post-partum flares are common and usually arise early after delivery. They are often mild in severity and most spontaneously resolve. Extending anti-viral therapy does not protect against post-partum flares or affect HBeAg seroconversion rates.

Molecular epidemiology of hepatitis B in the Indigenous people of northern Australia

BACKGROUND AND AIM

The hepatitis B surface antigen was first described in the blood of an Indigenous Australian man, yet little is known about its molecular epidemiology in this population, in which it is endemic. The study aimed to determine the clinical and molecular epidemiology of hepatitis B virus (HBV) in Indigenous people from northern Australia.

METHODS

Following ethics approval and informed consent, blood specimens and clinical details from Indigenous adults known to be infected with HBV and who were born and raised in Indigenous communities in northern Australia were obtained. HBV genotypes were determined in isolates with sufficient HBV DNA by polymerase chain reaction by sequencing of the polymerase/surface gene.

RESULTS

Between June 2010 and June 2012, 65 patients were recruited from six different regions of northern Australia. Thirty-two patients (49%) were hepatitis B e-antigen-positive, and 48% were hepatitis B e-antibody-positive. No patients were found to be coinfected with hepatitis C virus or human immunodeficiency virus. Of the 49 samples with sufficient viral load for genotyping, 100% were infected with genotype C4, previously only reported from two Indigenous Australians. All isolates had wild-type polymerase gene sequences despite 14 currently or previously receiving antiviral treatment. The canonical sG145R vaccine-escape variant was detected in the surface antigen of virus from two patients.

CONCLUSIONS

The exclusive HBV genotype in this ancient population is genotype C4. Whole genome sequencing and clinical follow-up of this cohort are in progress, with the aim of exploring the clinical significance of these findings.

In vitro replication phenotype of a novel (-1G) hepatitis B virus variant associated with HIV co-infection

The -1G mutant HBV is more prevalent in individuals co-infected with HIV/HBV than in individuals infected with HBV alone and in some cases is the dominant virus in circulation. This mutant is created by the deletion of a dGMP (-1G) from the guanine rich homopolymer sequence located at nts 2,085-2,090 (numbering from EcoRI site as position 1) in the HBV core gene. This deletion causes a frameshift generating a premature stop codon at (64) Asn in the HBV core gene (codon 93 in the precore gene), that truncates the precore protein, precursor of the secreted hepatitis B "e" antigen (HBeAg), and the core protein which forms the viral nucleocapsid. However, the replication phenotype of the -1G mutant HBV is unknown. An in vitro cell culture model in which hepatoma cells were transiently transfected with infectious cDNAs was used to show that the -1G mutant HBV is incapable of autonomous replication and, as expected, replication was restored to wild-type (wt) levels by supplying HBV core protein in trans. Although the -1G mutation had no deleterious effect on intracellular HBV-DNA levels, high levels of -1G mutant HBV relative to wt HBV reduced virus secretion and HBeAg secretion relative to empty vector controls. Importantly, the -1G mutant HBV also caused intracellular retention of truncated precore protein in the endoplasmic reticulum (ER) and Golgi apparatus. Together, these effects may be contributing to the increased pathology observed in the setting of HIV/HBV co-infection.

Molecular genesis of drug-resistant and vaccine-escape HBV mutants

A high rate of viral turnover, combined with an error-prone polymerase, results in a very high frequency of mutational events during HBV replication. Not surprisingly, particular selection pressures, both endogenous (host immune clearance) and exogenous (vaccines and antivirals), readily select out new 'escape' mutants. The introduction of nucleoside/nucleotide analogue (NA) therapy for chronic hepatitis B has witnessed the emergence of antiviral drug resistance as the major factor limiting drug efficacy. Furthermore, because of the overlap of the viral polymerase and envelope reading frames in the HBV DNA genome, NA resistance-associated mutations selected in the catalytic domains of the polymerase frequently result in important changes to the neutralizing antibody-binding domains of the hepatitis B surface antigen, including the emergence of antiviral drug-associated potential vaccine escape mutants (ADAPVEMs). The public health significance of ADAPVEMs is considerable in terms of the global programme for control of hepatitis B via universal infant immunization. Thus, prevention of resistance requires the adoption of strategies that not only effectively control HBV replication, but also prevent the emergence of ADAPVEMs.

Potential threat of drug-resistant and vaccine-escape HBV mutants to public health

Immune pressure exerted on HBV by anti-HBV antibodies and long-term therapy with drugs that mutagenize the viral P gene can select for mutations in its S gene, leading to vaccine escape and evasion from serological detection. Although transmissibility of these mutants is poor and their evolution towards heightened virulence appears slow, the situation could change as vaccination coverage increases, and treatment of patients with chronic hepatitis B and those coinfected by HIV and HBV becomes widespread. Enhanced surveillance programmes to track changes in the genotype and phenotype of the mutants are needed.

HBV mutations in untreated HIV-HBV co-infection using genomic length sequencing

HIV infection has a significant impact on the natural progression of hepatitis B virus (HBV) related liver disease. In HIV-HBV co-infected patients, little is known about mutations in the HBV genome, which can influence severity of liver disease. The aim of this study was to characterize and to determine the frequency of known clinically significant mutations in the HBV genomes from HIV-HBV co-infected patients and from HBV mono-infected patients. To accomplish this, genomic length HBV sequencing was performed in highly-active anti-retroviral therapy (HAART)-naïve HIV-HBV co-infected patients (n=74) and in anti-HBV therapy-naïve HBV mono-infected patients (n=55). The frequency of HBV mutations differed between the co-infected and mono-infected patients when comparing patients with the same genotype. BCP mutations A1762T and G1764A were significantly more frequent in HBV genotype C mono-infection and the -1G frameshift was significantly more frequent in co-infection and was only observed in HBV genotype A co-infection. PreS2 deletions were observed more frequently in the setting of co-infection. Further work is needed to determine if these mutational patterns influence the differences in liver disease progression in HIV-HBV co-infected and HBV mono-infected patients.

Serum hepatitis B surface antigen and hepatitis B e antigen titers: disease phase influences correlation with viral load and intrahepatic hepatitis B virus markers

Although threshold levels for hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) titers have recently been proposed to guide therapy for chronic hepatitis B (CHB), their relationship to circulating hepatitis B virus (HBV) DNA and intrahepatic HBV replicative intermediates, and the significance of emerging viral variants, remains unclear. We therefore tested the hypothesis that HBsAg and HBeAg titers may vary independently of viral replication in vivo. In all, 149 treatment-naïve CHB patients were recruited (HBeAg-positive, n = 71; HBeAg-negative, n = 78). Quantification of HBeAg and HBsAg was performed by enzyme immunoassay. Virological characterization included serum HBV DNA load, HBV genotype, basal core promoter (BCP)/precore (PC) sequence, and, in a subset (n = 44), measurement of intrahepatic covalently closed circular DNA (cccDNA) and total HBV DNA, as well as quantitative immunohistochemical (IHC) staining for HBsAg. In HBeAg-positive CHB, HBsAg was positively correlated with serum HBV DNA and intrahepatic cccDNA and total HBV DNA (r = 0.69, 0.71, 0.76, P < 0.01). HBeAg correlated with serum HBV DNA (r = 0.60, P < 0.0001), although emerging BCP/PC variants reduced HBeAg titer independent of viral replication. In HBeAg-negative CHB, HBsAg correlated poorly with serum HBV DNA (r = 0.28, P = 0.01) and did not correlate with intrahepatic cccDNA nor total HBV DNA. Quantitative IHC for hepatocyte HBsAg confirmed a relationship with viral replication only in HBeAg-positive patients.

CONCLUSION

The correlation between quantitative HBsAg titer and serum and intrahepatic markers of HBV replication differs between patients with HBeAg-positive and HBeAg-negative CHB. HBeAg titers may fall independent of viral replication as HBeAg-defective variants emerge prior to HBeAg seroconversion. These findings provide new insights into viral pathogenesis and have practical implications for the use of quantitative serology as a clinical biomarker.

Hepatitis B surface antigen levels during the natural history of chronic hepatitis B: a perspective on Asia

BACKGROUND & AIMS

Data from clinical trials suggest a potential role for on-treatment monitoring of serum HBsAg titres during interferon-alpha (pegIFN) therapy in predicting virological responses. However, baseline HBsAg titres during the natural history of chronic hepatitis B (CHB) have not been well-characterized. We aimed to define the serum HBsAg titres during the different phases of CHB in a cohort of Asian patients infected with either genotype B or C HBV.

METHODS

Two-hundred and twenty patients were classified into immune-tolerant (IT), immune-clearance (IC), non/low-replicative (LR) or hepatitis B e antigen negative hepatitis (ENH) phases. Serum HBsAg was quantified using the ARCHITECT platform (Abbott Laboratories, Chicago, USA). Correlation of HBsAg titre with HBV DNA and serum ALT within each phase of infection was performed.

RESULTS

Median HBsAg titres were different between each phase of CHB (p=0.001): IT (4.53 log(10)IU/ml), IC (4.03 log(10)IU/ml), LR (2.86 log(10)IU/ml), and ENH (3.35 log(10)IU/ml). HBsAg titres were highest in the IT phase, and lowest in the LR phase. In general, median HBsAg titres were similar between genotypes B and C HBV. Serum HBsAg titres only correlated with HBV viral load in the IC phase. No correlation between the serum HBsAg level and ALT was observed.

CONCLUSIONS

This study demonstrated significant differences in median baseline serum HBsAg titres across the different phases of CHB. These results provide further insight into the HBV viral life cycle in the setting of the various phases of CHB. Baseline HBsAg quantification may help refine future treatment algorithms for both immune-modulator therapy and oral nucleos(t)ide analogue therapy.

Hepatitis B virus and hepatitis C virus interaction in Huh-7 cells

BACKGROUND/AIMS

Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) increases the risk of development and the severity of chronic liver disease. Although dominant and suppressive effects of each virus over the other have been reported in vivo, in vitro studies of HBV/HCV co-infection have been limited to analysis of the effects of over-expression of HCV proteins on HBV replication.

METHODS

We have re-examined HBV/HCV interactions in Huh-7 cells following co-infection with cell culture-propagated HCV (HCVcc; genotype 2a) and a recombinant adenovirus vector capable of delivering a replication-competent HBV genome (AdHBV; genotype A).

RESULTS

While intracellular HCV RNA levels were significantly increased when cells were pre-infected with AdHBV, HCV replication and virion secretion were not altered by simultaneous infection with AdHBV or AdHBV superinfection of HCV-infected cells. Likewise intracellular and secreted HBV DNA levels and HBV promoter activities were either unchanged or modestly increased by HCVcc infection. Despite this, HCV E2 and HBsAg proteins colocalized extensively in co-infected cells suggesting shared stages in viral egress.

CONCLUSIONS

These studies indicate that there is little direct interaction of HBV and HCV in co-infected hepatocytes and imply that indirect effects of host-viral interactions dictate viral dominance in HBV/HCV co-infected individuals.

Perinatal transmission of hepatitis B virus: an Australian experience

OBJECTIVE

To determine the rate of perinatal hepatitis B virus (HBV) transmission in an Australian setting and to identify maternal virological factors associated with highest risk of transmission.

DESIGN, PARTICIPANTS AND SETTING

A prospective, observational study of perinatal transmission of HBV. Participants were pregnant women attending Sydney South West Area Health Service antenatal clinics who tested positive for hepatitis B surface antigen (HBsAg), and their babies. All babies were routinely offered hepatitis B immunoglobulin (HBIG) and HBV vaccination. Babies positive for HBsAg at 9-month follow-up underwent further virological testing, including HBV DNA sequencing. The study was conducted between August 2002 and May 2008.

MAIN OUTCOME MEASURES

HBV DNA levels and demographic characteristics of HBsAg-positive pregnant women; proportion of their infants with active HBV infection at 9-month follow-up; maternal characteristics affecting transmission rate; HBV DNA sequencing of infected infants and their mothers.

RESULTS

Of 313 HBsAg-positive pregnant women, 213 (68%) were HBV DNA-positive and 92 (29%) were positive for hepatitis B "e" antigen (HBeAg); 138 babies born to HBV DNA-positive mothers were tested for HBV infection (HBsAg positivity) at about 9 months of age. Four cases of transmission were identified. All four mothers had very high HBV DNA levels (> 10(8) copies/mL) and were HBeAg-positive. Three of the four infants were infected with wild-type HBV strains, with identical maternal/infant isolates. The fourth mother-infant pair had an S gene variant, HBV D144E, which has been previously reported in association with vaccine/HBIG escape. (Unfortunately, HBIG was inadvertently omitted from the immunisation schedule of this infant.) Transmission rates were 4/138 (3%) from HBV DNA-positive mothers overall, 4/61 (7%) from HBeAg-positive mothers, and 4/47 (9%) from mothers with very high HBV DNA levels. No transmission was seen in 91 babies of mothers with HBV DNA levels < 10(8) copies/mL.

CONCLUSION

In this cohort, HBV perinatal transmission was restricted to HBeAg-positive mothers with very high viral loads.

Hepatitis B virus and hepatitis C virus interaction in Huh-7 cells

BACKGROUND/AIMS

Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) increases the risk of development and the severity of chronic liver disease. Although dominant and suppressive effects of each virus over the other have been reported in vivo, in vitro studies of HBV/HCV co-infection have been limited to analysis of the effects of over-expression of HCV proteins on HBV replication.

METHODS

We have re-examined HBV/HCV interactions in Huh-7 cells following co-infection with cell culture-propagated HCV (HCVcc; genotype 2a) and a recombinant adenovirus vector capable of delivering a replication-competent HBV genome (AdHBV; genotype A).

RESULTS

While intracellular HCV RNA levels were significantly increased when cells were pre-infected with AdHBV, HCV replication and virion secretion were not altered by simultaneous infection with AdHBV or AdHBV superinfection of HCV-infected cells. Likewise intracellular and secreted HBV DNA levels and HBV promoter activities were either unchanged or modestly increased by HCVcc infection. Despite this, HCV E2 and HBsAg proteins colocalized extensively in co-infected cells suggesting shared stages in viral egress.

CONCLUSIONS

These studies indicate that there is little direct interaction of HBV and HCV in co-infected hepatocytes and imply that indirect effects of host-viral interactions dictate viral dominance in HBV/HCV co-infected individuals.

Viral dynamics of hepatitis B virus DNA in human immunodeficiency virus-1-hepatitis B virus coinfected individuals: similar effectiveness of lamivudine, tenofovir, or combination therapy

Following treatment of hepatitis B virus (HBV) infection with nucleos(t)ide reverse transcriptase inhibitors (NRTIs), there is a biphasic clearance of HBV, similar to that seen following treatment of human immunodeficiency virus-1 (HIV-1) and hepatitis C virus. Little is known about the impact of combination NRTIs and HIV-1 coinfection on HBV viral kinetic parameters following the initiation of HBV-active highly active antiretroviral therapy (HAART). HIV-1-HBV coinfected patients (n = 21) were enrolled in a viral kinetics substudy of the Tenofovir in HIV-1-HBV Coinfection study (TICO). TICO was a randomized (1:1:1) trial of tenofovir disoproxil fumarate (TDF, 300 mg) versus lamivudine (LMV, 300 mg) versus TDF/LMV within an efavirenz based HAART regimen initiated in HIV-1-HBV coinfected antiretroviral naïve individuals in Thailand. HBV DNA was measured frequently over the first 56 days. To fit the viral load data, we used a model of HBV kinetics that allows the estimation of treatment effectiveness, viral clearance and infected cell loss. We observed a biphasic decline in HBV DNA in almost all patients. We did not observe any significant differences in HBV viral dynamic parameters between the three treatments groups. Overall, median (interquartile range) HBV treatment effectiveness was 98% (95%-99%), median HBV virion half-life was 1.2 days (0.5-1.4 days), and median infected cell half-life was 7.9 days (6.3-11.0 days). When we compared hepatitis B e antigen (HBeAg)-positive and HBeAg-negative individuals, we found a significantly longer infected cell half-life in HBeAg-positive individuals (6.2 versus 9.0 days, P = 0.02).

CONCLUSION

HBV viral dynamic parameters are similar following anti-HBV NRTI monotherapy and dual combination therapy in the setting of HIV-1-HBV coinfection. HIV-1 coinfection has minimal effect on HBV viral dynamics, even in the setting of advanced HIV-1-related immunosuppression.

Prolonged use of tenofovir in HIV/hepatitis B virus (HBV)-coinfected individuals does not lead to HBV polymerase mutations and is associated with persistence of lamivudine HBV polymerase mutations

OBJECTIVES

The aim of the study was to identify and characterize hepatitis B virus (HBV) polymerase gene mutations associated with ongoing HBV replication in HIV/HBV-coinfected individuals receiving tenofovir (TDF).

METHODS

This retrospective cross-sectional study identified 28 HIV/HBV-coinfected individuals who had received TDF for at least 3 months. All patients had samples available while receiving TDF (on-TDF), and 24 also had samples available prior to treatment (pre-TDF). Case records were reviewed to obtain clinical and virological data at the times of sampling (+/-3 months). The HBV DNA of all samples was amplified using polymerase chain reaction (PCR), and the polymerase region of PCR-positive samples was sequenced and compared with reference HBV data.

RESULTS

Of the pre-TDF samples, 15 of 24 (63%) were HBV PCR positive. Of the on-TDF samples, four of 28 (14%) were HBV PCR positive (mean time on TDF 13.5 months; range 3-23 months). Lamivudine (3TC)-resistance mutations were detected in three of four (75%) of these viraemic samples. The previously identified putative TDF-resistance mutations, rtA194T+rtL180M+rtM204V, were not detected in any individual.

CONCLUSIONS

Unique mutations in the HBV polymerase gene associated with TDF resistance are rare in HIV/HBV coinfection. 3TC-resistance mutations persist and a significant proportion of patients are HBV PCR positive despite the addition of TDF.

The phenotype of hepatitis B virus-specific T cells differ in the liver and blood in chronic hepatitis B virus infection

Hepatitis B virus (HBV)-specific T cells play a key role in clearance of the virus and in the pathogenesis of liver disease. Peripheral blood (n = 25) and liver biopsies (n = 19) were collected from individuals with chronic untreated HBV infection. Whole blood, cultured peripheral blood mononuclear cells (PBMCs), and cultured liver-infiltrating lymphocytes (LILs) were each stimulated with an overlapping peptide library to the whole HBV genome. The expression of T helper 1 (Th1) cytokines [interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin 2 (IL-2)] and interleukin 10 (IL-10) was analyzed by intracellular cytokine staining and flow cytometry. In ex vivo whole blood, more lymphocytes produced Th1 cytokines than IL-10. When comparing cultured LILs with cultured PBMCs, we found a significantly higher magnitude of CD8(+) T cells from the liver producing IL-10 (P = 0.044), primarily in hepatitis B e antigen positive (HBeAg(+)) individuals. A positive correlation resulted between the magnitude of HBV-specific TNF-alpha(+) CD4(+) T cells in the liver and the degree of liver inflammation and fibrosis (P = 0.002 and P = 0.006, respectively).

CONCLUSION

The differences in cytokine production from HBV-specific T cells in blood and liver may explain the capacity for HBV to persist in the absence of significant hepatic destruction and highlights the balance between cytokine-mediated viral control and liver damage.

Identification of a novel hepatitis B virus precore/core deletion mutant in HIV/hepatitis B virus co-infected individuals

OBJECTIVES

Although HAART has resulted in improved health outcomes for most HIV-infected individuals, liver failure has emerged as a major cause of morbidity and mortality in people co-infected with hepatitis B virus (HBV). In HBV mono-infected individuals, core deletion mutants are associated with more aggressive liver disease. As HIV accelerates HBV liver disease progression, we hypothesized that HIV-HBV co-infected individuals have increased frequency of core mutations including deletions. To test this hypothesis, we have analysed genome-length sequences of HBV DNA from patients both prior to and during antiviral therapy.

SETTING

Prospective HIV/HBV co-infected cohort study.

METHODS

Genomic length HBV DNA was amplified by PCR from the serum samples of ten HIV/HBV co-infected individuals and five HBV mono-infected individuals prior to the commencement of lamivudine therapy and again after nine to 74 months of treatment. The complete genomes were sequenced and in order to further analyse some mutations, their frequency was determined in additional HIV/HBV co-infected and HBV mono-infected individuals.

RESULTS

A novel -1G mutation was identified in the HBV precore and overlapping core genes that truncated the deduced precore/core proteins. The mutant genome was the dominant species in some HIV/HBV co-infected individuals and was more prevalent in HIV/HBV co-infected individuals than HBV mono-infected individuals. The mutation was also associated with high HBV DNA concentrations in HIV/HBV co-infected individuals. Additional mutations were identified in the core/precore and polymerase genes and regulatory regions.

CONCLUSION

Mutations in the HBV core and precore genes may be contributing to disease pathogenesis in HIV/HBV co-infected individuals.

Toll-like receptors, RIG-I-like RNA helicases and the antiviral innate immune response

The antiviral innate immune response follows the detection of viral components by host pattern recognition receptors (PRRs). Two families of PRRs have emerged as key sensors of viral infection: Toll-like receptors (TLRs) and retinoic acid inducible gene-I like RNA helicases (RLHs). TLRs patrol the extracellular and endosomal compartments; signalling results in a type-1 interferon response and/or the production of pro-inflammatory cytokines. In contrast, RLHs survey the cytoplasm for the presence of viral double-stranded RNA. In the face of such host defence, viruses have developed strategies to evade TLR/RLH signalling. Such host-virus interactions provide the opportunity for manipulation of PRR signalling as a novel therapeutic approach.

The phenylpropenamide derivative AT-130 blocks HBV replication at the level of viral RNA packaging

Nucleos(t)ide analogue antiviral therapy for chronic hepatitis B has proven to be effective in the short term but the frequent development of resistance limits its clinical utility. Agents targeting other stages of viral replication are needed in order to develop improved combination therapies. The phenylpropenamide derivatives AT-61 and AT-130 have been shown to inhibit HBV replication in vitro, but the mechanism of action of these compounds remains undefined. The aim of this study was to determine the mechanism of action of AT-130, a non-nucleoside inhibitor of HBV in several in vitro models of replication. These studies found that AT-130 inhibited HBV DNA replication in hepatoma cells but had no effect on viral DNA polymerase activity or core protein translation. Total HBV RNA production was also unaffected in the presence of the drug whilst the amount of encapsidated RNA was significantly reduced, thereby inhibiting subsequent viral reverse transcription. These studies have established that the inhibition of HBV genome replication by a non-nucleoside analogue acting at the level of viral encapsidation and packaging is a potentially useful strategy for future therapeutic drug development in the management of chronic hepatitis B.

Lamivudine resistance in patients with chronic hepatitis B: role of clinical and virological factors

BACKGROUND

Lamivudine resistance is associated with long-term monotherapy for chronic hepatitis B and can lead to potentially serious clinical consequences. Scant information exists regarding the influence of hepatitis B virus variants in the development of resistance. The present study was designed to identify factors predictive of lamivudine resistance, with a particular focus on the role of precore and basal core promoter variants in the setting of hepatitis B e antigen-negative disease.

METHODS

Eighty-five patients, representing four major genotypes, were followed prospectively on lamivudine therapy. Resistance was defined as an increase in viral load, with polymerase gene sequencing confirming a lamivudine resistance mutation. Median follow up was 19 months (6-54 months). The Cox proportional hazards model was used to determine variables independently predicting for the early onset of lamivudine resistance.

RESULTS

The rate of lamivudine resistance was 6%, 31% and 51% at 12, 24 and 48 months, respectively. Multivariate analysis identified the precore variant, high baseline alanine aminotransferase (ALT), and persistent viremia (at 6 months) as independent predictors of the early development of lamivudine resistance, with rate ratios of 4.93 (95% confidence interval [CI]: 1.32-18.5), 1.22 (95%CI: 1.08-1.49), and 4.73 (95%CI: 1.49-15.0), respectively (P < 0.05). Female sex predicted early resistance (rate ratio 5.27 [95%CI: 1.23-22.5, P < 0.05]) although numbers were small (n = 12). Genotype did not influence treatment response nor time to onset of resistance.

CONCLUSION

Patients with precore variant hepatitis B virus are likely to develop lamivudine resistance early and should be considered for alternate first-line monotherapy. In the future, combination antiviral therapy may limit the development of resistance.

SeqHepB: a sequence analysis program and relational database system for chronic hepatitis B

SeqHepB is a combination of a HBV genome sequence analysis program and a relational database that houses data collected from multiple data sources. Registered users can access the sequence analysis component of SeqHepB online for rapid and detailed interrogation of HBV genomic sequences. Its main function is to determine the HBV genotype, identify key mutations associated with antiviral resistance, and identify clinically important HBV mutants. All information generated is uploaded into a database and integrated with patient medical records, pathology laboratory tests, and supplemental virology results such as in vitro drug cross-resistance values. Combined with structured query language (SQL) queries developed in the database, it is possible to extract and correlate clinical, virological, and in vitro phenotypic data rapidly and efficiently. An important component of SeqHepB is its ability to integrate mutations detected within the reverse transcriptase (RT) and locate them onto a three-dimensional (3D) model of the HBV RT that can be viewed at any angle with known antiviral drug molecules in the catalytic pocket of the enzyme. SeqHepB will enable virologists and physicians to individualise patient management, cope with the explosion of antiviral associated HBV mutations, and to conduct cross-sectional retrospective or prospective studies on HBV-infected individuals during therapy.

In vitro study of the effects of precore and lamivudine-resistant mutations on hepatitis B virus replication

Understanding the consequences of mutation in the hepatitis B virus (HBV) genome on HBV replication is critical for treating chronic HBV infection. In this study, HBV replication in HepG2 cells initiated by transduction with precore (PC), rtM204I, and wild-type (wt) HBV recombinant baculoviruses was compared. The pattern and magnitude of HBV replication initiated by the PC HBV recombinant baculovirus were similar to those observed for wt HBV throughout the time course examined. In contrast, when the rtM204I mutation was introduced into wt HBV, by day 10 postinfection the levels of intra- and extracellular HBV DNA were markedly reduced compared to those for wt HBV. Although the rtM204I mutation reduced the production of HBV replicative intermediates, no effect on the level of covalently closed circular DNA or HBV transcripts was observed at late time points. Coinfection studies with different ratios of wt and rtM204I baculoviruses showed that the rtM204I variant did not produce a product that inhibited HBV replication. However, the combination of the wt and rtM204I baculoviruses yielded HBV DNA levels at late time points that were greater than those for the wt alone, suggesting that wt polymerase may function in trans to boost rtM204I replication. We concluded that the rtM204I mutation generates a polymerase that is not only resistant to lamivudine but also replicates nucleic acids to lower levels in vitro.

Chronic hepatitis B: current testing strategies

The worldwide burden of hepatitis B mandates accurate and timely diagnosis of patients infected with the hepatitis B virus (HBV) and the use of treatment strategies derived from evidence-based guidelines. HBV is a DNA virus that produces a series of viral protein products circulating HBV DNA. Serologic and nucleic acid testing are critical to disease prevention and treatment objectives. Information from such testing helps determine patients' infectivity and immune status, appropriate monitoring strategies, and the efficacy of treatment, as well as providing data that contributes to a better understanding of the natural history and epidemiology of the disease. This article reviews the clinical use of state-of-the-art serologic and nucleic acid tests, including the relevance of hepatitis B e antigen and antibody and HBV DNA measurements as markers of disease activity. Viral load can be used to distinguish between active and inactive disease, define response to therapy, and detect the development of antiviral resistance. Some recent reports have suggested that high viral load is associated with poorer patient outcomes (eg, more rapid progression to cirrhosis and a higher incidence of hepatocellular carcinoma). Durable suppression of HBV DNA is evolving to become the primary goal of therapy, although all currently licensed medications have used histology as the primary end point of therapy. Suggested frequencies for HBV DNA monitoring are presented.

Antiviral drug resistance: clinical consequences and molecular aspects

Antiviral drug resistance now poses a major problem for the management of patients with chronic hepatitis B. In theory, resistance may be prevented if a sufficiently potent antiviral drug, or combination of antiviral agents, is used that prevents viral replication and thereby the ongoing selection of hepatitis B virus quasispecies. Emergence of drug resistance in patients with hepatitis B generally results in progression of liver disease and in some cases, significant clinical deterioration if hepatic reserve is compromised. Currently, there are two major patterns of resistance mutations found in the viral reverse transcriptase (rt) that can be selected during monotherapy: (1) those that include the codon rtM204, which is part of the catalytic domain (YMDD) of the enzyme; (2) and those that do not include the codon. The rtM204I/V is selected by lamivudine and L-nucleosides. It is also part of the entecavir resistance profile and the tenofovir-lamivudine combination resistance profile. In contrast, resistance to adefovir is associated with mutations at rtN236T +/- rtA181V. A reasonable clinical goal is to develop an overall strategy that prevents the selection of resistance. These strategies have yet to be optimized for hepatitis B, but may include multiple therapies such as immune-based therapies in combination with one or more nucleoside analogue treatments. Future treatment protocols can be modeled on the use of multiple agents comprising highly active anti-retroviral therapy regimens that have been developed for the successful management of patients infected with human immunodeficiency virus.

Chronic hepatitis B: recommendations for therapy based on the natural history of disease in Australian patients

BACKGROUND

Chronic hepatitis B infection (CHB) is a major health problem in Australia and worldwide. CHB is associated with significant long-term morbidity and mortality. Well tolerated treatment is now available, however the development of resistance is common and the optimal timing of treatment is yet to be determined. Identifying the factors that influence the natural history of CHB may help determine which patients need treatment and when to start it.

OBJECTIVE

To determine the demographics, clinical features and virological profile of Australian patients infected with CHB and the influence of these factors on disease activity and severity.

STUDY DESIGN

Review of prospectively collected demographic, clinical and virological features of all patients positive for hepatitis B surface antigen (HBsAg) for more than 6 months who were referred to St. Vincent's Hospital liver clinics. Age, sex and ethnicity were correlated with hepatitis B e antigen status (HBeAg), HBV replication status (ALT and HBV DNA), genotype and liver histology.

RESULTS

703 chronic hepatitis B surface antigen positive patients were identified. The patients were predominantly male with an average age of 44. Eighty two percent of patients were born overseas, primarily from Asian (65%) and Mediterranean countries (14%). Two thirds (426) had an elevated ALT (median 79) at presentation. HBeAg was positive in 37%. Active viral replication, defined as abnormal ALT or positive HBVDNA, was present in 74%, 48% of whom were HBeAg negative. In a subset of 103 patients genotyped, 8% had genotype A, 29% B, 41% C and 22% D. Genotype correlated with ethnicity; patients infected with genotypes A were predominantly Caucasian, B and C were Asian, and D were Mediterranean. Of 296 (42%) patients who underwent liver biopsy, 76 (27%) had advanced fibrosis. Advanced fibrosis was associated with increasing age and Mediterranean ethnicity.

CONCLUSION AND RECOMMENDATIONS

Perinatal or early childhood transmission is predominant mode of infection in Australia. Two thirds of this cohort had active replication and were at increased risk of developing cirrhosis and/or hepatoma. Advanced disease was associated with age and ethnicity. HBeAg negative CHB accounts for almost half of all those with active viral replication. This parallels the rise in this form of CHB in Asia and the Mediterranean basin. Screening should be offered to people born in, or with parents born in areas of high endemnicity. To detect the development of active disease, patients with positive HBsAg but normal ALT should have liver function tests done 6 monthly and those with elevated ALT should be referred for consideration of therapy, irrespective of HBeAg status.

New therapeutic strategies in the treatment of hepatitis B virus infection

Principally, because of the association of the chronic carrier state with the development of cirrhotic liver disease and hepatocellular carcinoma, chronic hepatitis B infection is a public health problem of global significance. In the main, therapy for chronic hepatitis B is limited to the use of alpha interferon for a limited number of chronic hepatitis B virus (HBV) carriers who have chronic hepatitis with active viral replication. The development of antiviral nucleoside analogues for the herpes viruses and human immunodeficiency virus (HIV) has resulted in the identification of several compounds which also have activity against HBV. Unfortunately, these agents have not been associated with the clearance of hepatitis B infection, but rather only the suppression of active infection while the patient is receiving medication. In addition, the development of drug-resistance to these agents by the virus will most likely limit their long-term efficacy. Gene therapy has recently been applied to HBV both in vitro and in vivo. This has included the use of antisense oligodeoxynucleotides and RNA, ribozymes, dominant negative mutants and therapeutic HBV vaccines. These newer therapeutic modalities may hold promise as effective treatments for chronic hepatitis B, but to date, have been limited by the problem of delivery to the target cell population or infected organ in vivo. Combination nucleoside analogue therapy may also provide an important treatment modality for chronic hepatitis B, although this will require further investigation.

Hepatic failure due to fibrosing cholestatic hepatitis in a patient with pre-surface mutant hepatitis B virus and mixed connective tissue disease treated with prednisolone and chloroquine

Fibrosing cholestatic hepatitis (FCH) is a severe variant of hepatitis B infection that has until recently been described almost exclusively in the setting of organ transplantation and HIV infection. This case report describes a patient with pre-surface (pre-S) mutant hepatitis B virus (HBV) infection who developed a fatal form of FCH after high dose prednisolone for mixed connective tissue disease (MCTD). The role of corticosteroids and pre-S viral mutation in the pathogenesis of the disease is discussed, and the importance of early diagnosis is emphasised. This report alerts the physician to the need for close monitoring of LFTs and HBV DNA of hepatitis B carriers during immunosuppressive therapy regardless of the indication. As in the transplantation setting, viral DNA levels should be kept to undetectable if viral replication or recurrence is to be prevented.

Hepatic failure due to fibrosing cholestatic hepatitis in a patient with pre-surface mutant hepatitis B virus and mixed connective tissue disease treated with prednisolone and chloroquine

Fibrosing cholestatic hepatitis (FCH) is a severe variant of hepatitis B infection that has until recently been described almost exclusively in the setting of organ transplantation and HIV infection. This case report describes a patient with pre-surface (pre-S) mutant hepatitis B virus (HBV) infection who developed a fatal form of FCH after high dose prednisolone for mixed connective tissue disease (MCTD). The role of corticosteroids and pre-S viral mutation in the pathogenesis of the disease is discussed, and the importance of early diagnosis is emphasised. This report alerts the physician to the need for close monitoring of LFTs and HBV DNA of hepatitis B carriers during immunosuppressive therapy regardless of the indication. As in the transplantation setting, viral DNA levels should be kept to undetectable if viral replication or recurrence is to be prevented.

Effects of interferon alpha therapy on the catalytic domains of the polymerase gene and basal core promoter, precore and core regions of hepatitis B virus

AIMS

The aim of the present study was to examine the catalytic domains of the polymerase gene, the basal core promoter and the precore and core regions of the hepatitis B virus (HBV) genome for specific mutations. These may account for the response to interferon alpha (IFN-alpha) treatment, which may have prognostic value.

METHODS

Multiple serum samples were collected prospectively from 30 patients with chronic active hepatitis B who were treated with IFN-alpha. Patients were assigned to one of three groups: group A (n = 11) and group B (n = 10) individuals were hepatitis B e antigen (HBeAg)-positive prior to treatment. Group A patients underwent HBeAg seroconversion after treatment while group B patients did not. Group C (n = 9) patients were HBeAg-negative prior to treatment. The HBV DNA was extracted from the sera collected before, during and after treatment and the various genomic regions were amplified, sequenced and examined for mutations.

RESULTS

During IFN-alpha therapy, multiple changes were found in the catalytic domains of the HBV polymerase gene in all groups. The frequency of mutations and associated amino acid changes were highest in virus from group C patients and lowest in group A patients. The interdomain regions of the viral polymerase were the most affected. Multiple mutations were also found in the precore, core and core promoter regions. However, no specific mutations were associated with clinical response or outcome.

CONCLUSIONS

During IFN-alpha treatment, multiple mutations occurred in the HBV genome, including the catalytic domains of the polymerase gene. Changes that did occur could not be correlated to the clinical response or treatment outcome. However, no mutations were found that have been linked to lamivudine escape, indicating that lamivudine therapy would be effective in IFN-alpha non-responder patients.

Evidence of patient-to-patient transmission of hepatitis C virus through contaminated intravenous anaesthetic ampoules

Two separate cases of acute hepatitis C virus (HCV) infection following medical procedures, arthroscopy and colonoscopy, are reported. In both episodes, patient risk factors were reviewed, and staff and other patients' sera were tested for HCV antibodies and RNA. HCV RNA positive samples were genotyped, sequenced, and subjected to phylogenetic analysis. No risk factors for HCV infection were identified for either case except for medical procedures. HCV RNA positive patients were identified preceding both cases on the respective theatre lists. HCV infection in a second low risk patient was also identified. Nucleic acid sequencing and phylogenetic analysis of HCV from the two putative source patients and the three recipient patients demonstrated a high degree of relatedness respectively. The results suggest that patient-to-patient transmission occurred in both episodes via contamination of intravenous anaesthetic ampoules with HCV used on multiple patients. Injectable medication ampoules should not be used for more than one patient.

Effect of the G1896A precore mutation on drug sensitivity and replication yield of lamivudine-resistant HBV in vitro

Hepatitis B e antigen (HBeAg) negative chronic hepatitis B (CHB) is frequently caused by a mutation (G1896A) in the hepatitis B virus (HBV) precore (PC) reading frame that creates a stop codon, causing premature termination of the PC protein. During lamivudine treatment, drug resistance develops at a similar rate in HBeAg positive and HBeAg negative CHB. Lamivudine-resistant HBV mutants have been shown to replicate inefficiently in vitro in the absence of PC mutations, but it is unknown whether the presence of PC mutations affects replication efficiency or antiviral sensitivity. This study utilized the recombinant HBV baculovirus system to address these issues. HBV baculoviruses encoding the G1896A PC stop codon mutation were generated in wild-type (WT) and lamivudine-resistant (rtM204I and rtL180M + rtM204V) backgrounds, resulting in a panel of 6 related recombinant baculoviruses. In vitro assays were performed to compare the sensitivities of the PC mutant viruses with lamivudine and adefovir and to compare relative replication yields. The PC mutation did not significantly affect sensitivities to either adefovir or lamivudine. WT HBV and PC mutant HBV showed similar replication yields, whereas the replication yields of the lamivudine-resistant mutants were greatly reduced in HBeAg positive HBVs, confirming previous observations. However, the presence of the PC mutation was found to compensate for the replication deficiency in each of the lamivudine-resistant mutants, increasing the replication yields of each virus. In conclusion, the PC stop codon mutation appears to increase the replication efficacy of lamivudine-resistant virus but does not affect in vitro drug sensitivity.

Mechanisms of drug resistance and novel approaches to therapy for chronic hepatitis C

Hepatitis C virus (HCV) is now the major cause of transfusion-associated and parenterally transmitted viral hepatitis and accounts for a significant proportion of hepatitis cases worldwide. The majority of infections become persistent and approximately 20% of chronically infected individuals develop cirrhosis, which is strongly associated with progression to hepatocellular carcinoma. Molecular biological investigations into the structure and function of HCV and its genes has led to the identification of a number of potential targets for selective antiviral intervention. The present review summarizes current research activity into these novel drug targets and addresses the basis for clinical non-response in the current interferon-alpha-based therapies. Future therapeutic strategies that utilize HCV-specific antiviral agents should prove effective in controlling active viral replication, but the risk of emergence of drug-resistance will need to be addressed due to the quasispecies feature of HCV replication.

Clinical relevance of viral dynamics and genotypes in hepatitis B virus

Advances in molecular diagnostic technology make it possible to accurately measure viral loads and this has allowed the detailed study of viral dynamics of HIV, hepatitis C virus (HCV) and hepatitis B virus (HBV). Following antiviral therapy, there are at least two phases of viral load decay: one corresponding to clearance of free virions and a second, slower phase corresponding to eradication of infected cells. Application of mathematical models allows for the assessment of antiviral efficacy and improved design of therapeutic regimens. The clinical application of these tools should help optimize patient outcome. Another advantage of molecular diagnostics is characterization of the heterogeneity of viruses in particular patient populations under selective pressure situations. The HBV can be classified into seven major genotypes (A-G) that have mainly a geographic distribution. Recent genotypic studies have revealed the clinical and therapeutic relevance of viral genotyping in HBV infections.