Hepatitis B viruses with precore region defects prevail in persistently infected hosts along with seroconversion to the antibody against e antigen

Clinical isolates of hepatitis B virus genotype C have higher in vitro transmission efficiency than genotype B isolates

Serum samples were collected from 54 hepatitis B e antigen (HBeAg)-positive Chinese patients infected with hepatitis B virus (HBV) subgenotype B2 or C2. They were compared for transmission efficiency using same volume of samples or infectivity using same genome copy number. Adding polyethylene glycol (PEG) during inoculation did not increase infectivity of fresh samples but markedly increased infectivity following prolonged sample storage. Differentiated HepaRG cells infected without PEG produced more hepatitis B surface antigen (HBsAg) and higher HBsAg/HBeAg ratio than sodium taurocholate cotransporting polypeptide (NTCP)-reconstituted HepG2 cells infected with PEG. They better supported replication of core promoter mutant in contrast to wild-type (WT) virus by HepG2/NTCP cells. Overall, subgenotype C2 samples had higher viral load than B2 samples, and in general produced more HBeAg, HBsAg, and replicative DNA following same-volume inoculation. Precore mutant was more prevalent in subgenotype B2 and had reduced transmission efficiency. When same genome copy number of viral particles was inoculated, viral signals were not necessarily higher for three WT C2 isolates than four WT B2 isolates. Using viral particles generated from cloned HBV genome, three WT C2 isolates showed slightly reduced infectivity than three B2 isolates. In conclusion, subgenotype C2 serum samples had higher transmission efficiency than B2 isolates in association with higher viral load and lower prevalence of precore mutant, but not necessarily higher infectivity. PEG-independent infection by HBV viremic serum samples is probably attributed to a labile host factor.

Hepatitis B virus genome diversity in adolescents: Tenofovir disoproxil fumarate treatment effect and HBeAg serocon version

More systematic analysis of hepatitis B virus (HBV) genome diversity, linked with tenofovir disoproxil fumarate (TDF) treatment and HBeAg seroconversion, are needed. GS-US-174-0115 was a double-blind, placebo-controlled, Phase 3, 192-week clinical trial that evaluated TDF in adolescents with chronic hepatitis B (CHB). HBV full-genome deep sequencing was performed using Illumina MiSeq at baseline (BL; n = 85), Week 8 (W8; n = 80), Week 72 (W72; PBO only, n = 42), and treatment-free follow-up (TDF only, n = 25). The viral diversity was calculated using Shannon entropy and population nucleotide diversity with a 2% variant cutoff. Our data showed (i) a higher viral diversity in the X region at baseline than the core/polymerase/surface regions, (ii) higher core/surface viral diversity at baseline for patients with seroconversion, (iii) an expected reduction in viral diversity after 8 weeks of TDF treatment, and (iv) a drop in viral diversity at W72 for patients receiving placebo with a seroconversion (n = 7). The higher viral diversity in X was associated with higher baseline alanine aminotransferase (ALT) levels (p < .001). Patients with greater reduction of diversity at W8 of TDF treatment had higher baseline ALT levels. For placebo patients who seroconverted, the drop in viral diversity at W72 (p = .04) coincided with reduction of serum HBV DNA (average change from baseline = -4.10 log10 copies/ml) and unique combinations of variants were enriched in a patient's viral population post seroconversion. The basal core promoter (BCP) variants, A1762T and G1764A, and the pC variant, G1896A, were most often enriched at or after seroconversion.

Envelope Proteins of Hepatitis B Virus: Molecular Biology and Involvement in Carcinogenesis

The envelope of hepatitis B virus (HBV), which is required for the entry to hepatocytes, consists of a lipid bilayer derived from hepatocyte and HBV envelope proteins, large/middle/small hepatitis B surface antigen (L/M/SHBs). The mechanisms and host factors for the envelope formation in the hepatocytes are being revealed. HBV-infected hepatocytes release a large amount of subviral particles (SVPs) containing L/M/SHBs that facilitate escape from the immune system. Recently, novel drugs inhibiting the functions of the viral envelope and those inhibiting the release of SVPs have been reported. LHBs that accumulate in ER is considered to promote carcinogenesis and, especially, deletion mutants in the preS1/S2 domain have been reported to be associated with the development of hepatocellular carcinoma (HCC). In this review, we summarize recent reports on the findings regarding the biological characteristics of HBV envelope proteins, their involvement in HCC development and new agents targeting the envelope.

Spontaneous reactivation of hepatitis B virus with a frameshift mutation in the precore region in an elderly hepatitis B virus carrier with lifestyle-related diseases

A 76-year-old woman with spontaneous reactivation of hepatitis B virus (HBV) without any immunosuppressants who had been successfully treated with tenofovir alafenamide fumarate (TAF) was reported. The patient was admitted to our hospital because of acute exacerbation of the liver function and jaundice. She had been found to have chronic HBV infection with a normal liver function and had been treated for lifestyle-related diseases, such as diabetes mellitus, dyslipidemia and hypertension, for over 10 years at a local clinic. At admission, her serum HBV DNA was high (7.3 log IU/mL), and anti-hepatitis B core protein immunoglobulin M was slightly elevated (1.47 S/CO). Due to the absence of known risk factors for HBV reactivation, the reactivation was regarded as "spontaneous". After the initiation of the nucleotide analog TAF, her liver function gradually improved with a decrease in the HBV DNA load. Her HBV genome was typed as subgenotype B1 and possessed a frameshift mutation due to an insertion of T after nucleotide (nt) 1817 and G to A mutations at nt 1896 and nt 1899 (G1896A/G1899A) in the precore region as well as serine to glutamine substitution of amino acid 21 in the core protein. In addition to these viral mutations, aging and complications of lifestyle-related diseases in the present case may have been responsible for the spontaneous HBV reactivation. Careful observation and management of aged HBV carriers with underlying diseases are needed even when persistent HBV infection is free from symptoms and liver dysfunction and no immunosuppressive conditions are involved.

The evolution and clinical impact of hepatitis B virus genome diversity

The global burden of hepatitis B virus (HBV) is enormous, with 257 million persons chronically infected, resulting in more than 880,000 deaths per year worldwide. HBV exists as nine different genotypes, which differ in disease progression, natural history and response to therapy. HBV is an ancient virus, with the latest reports greatly expanding the host range of the Hepadnaviridae (to include fish and reptiles) and casting new light on the origins and evolution of this viral family. Although there is an effective preventive vaccine, there is no cure for chronic hepatitis B, largely owing to the persistence of a viral minichromosome that is not targeted by current therapies. HBV persistence is also facilitated through aberrant host immune responses, possibly due to the diverse intra-host viral populations that can respond to host-mounted and therapeutic selection pressures. This Review summarizes current knowledge on the influence of HBV diversity on disease progression and treatment response and the potential effect on new HBV therapies in the pipeline. The mechanisms by which HBV diversity can occur both within the individual host and at a population level are also discussed.

High mutation prevalence of precore and basal core promoter in pregnant women who underwent spontaneous HBeAg seroconversion within one year postpartum

BACKGROUND

Seroconversion of hepatitis B e antigen (HBeAg) is a critical event in the natural course of hepatitis B virus (HBV) infection.

AIM

We herein characterize the virological factors associated with postpartum spontaneous HBeAg seroconversion.

METHODS

A total of 214 pregnant women positive for both hepatitis B surface antigen (HBsAg) and HBeAg were followed up at 7-12 months postpartum.

RESULTS

Of the subjects, 26 (12.1%) achieved spontaneous HBeAg seroconversion. Receiver operating curve analysis indicated that HBV DNA level <1.0 × 10⁷ IU/mL, HBsAg <1.0 × 10⁴ IU/mL and HBeAg <7.36 × 10² S/CO each independently predicted HBeAg seroconversion within 12 months postpartum. At delivery, 73.1% (19/26) women with postpartum HBeAg seroconversion had precore (PC) and/or basal core promoter (BCP) mutations, higher than that (5/36, 13.9%) in the women without postpartum seroconversion. Binary logistic regression analysis indicated that the presence of mutations in PC, BCP, and both PC and BCP at delivery was associated with an increased likelihood (OR = 13.286, 16. 238, and 22.143 respectively, all P < 0.05) to undergo postpartum spontaneous HBeAg seroconversion.

CONCLUSION

These results suggest that quantitative determination of virological markers and sequencing PC and BCP can predict spontaneous HBeAg seroconversion, which could be valuable in deciding antiviral therapy against HBV.

Tracing the evolutionary history of hepadnaviruses in terms of e antigen and middle envelope protein expression or processing

Hepatitis B virus (HBV) is the prototype of hepadnaviruses, which can be subgrouped into orthohepadnaviruses infecting mammals, avihehepadnaviruses of birds, metahepadnaviruses of fish, and herpetohepadnaviruses of amphibians and reptiles. The middle (M) envelope protein and e antigen are new additions in the evolution of hepadnaviruses. They are alternative translation products of the transcripts for small (S) envelope and core proteins, respectively. For HBV, e antigen is converted from precore/core protein by removal of N-terminal signal peptide followed by furin-mediated cleavage of the basic C-terminus. This study compared old and newly discovered hepadnaviruses for their envelope protein and e antigen expression or processing. The S protein of bat hepatitis B virus (BHBV) and two metahepadnaviruses is probably myristoylated, in addition to two avihepadnaviruses. While most orthohepadnaviruses express a functional M protein with N-linked glycosylation near the amino-terminus, most metahepadnaviruses and herpetohepadnaviruses probably do not. These viruses and one orthohepadnavirus, the shrew hepatitis B virus, lack an open precore region required for e antigen expression. Potential furin cleavage sites (RXXR sequence) can be found in e antigen precursors of orthohepadnaviruses and avihepadnaviruses. Despite much larger precore/core proteins of avihepadnaviruses and their limited sequence homology with those of orthohepadnaviruses, their proximal RXXR motif can be aligned with a distal RXXR motif for orthohepadnaviruses. Thus, furin or another basic endopeptidase is probably the shared enzyme for hepadnaviral e antigen maturation. A precore-derived cysteine residue is involved in forming intramolecular disulfide bond of HBV e antigen to prevent particle formation, and such a cysteine residue is conserved for both orthohepadnaviruses and avihepadnaviruses. All orthohepadnaviruses have an X gene, while all avihepadnaviruses can express the e antigen. M protein expression appears to be the most recent event in the evolution of hepadnaviruses.

Large-scale viral genome analysis identifies novel clinical associations between hepatitis B virus and chronically infected patients

Despite the high global prevalence of chronic hepatitis B (CHB) infection, datasets covering the whole hepatitis B viral genome from large patient cohorts are lacking, greatly limiting our understanding of the viral genetic factors involved in this deadly disease. We performed deep sequencing of viral samples from patients chronically infected with HBV to investigate the association between viral genome variation and patients' clinical characteristics. We discovered novel viral variants strongly associated with viral load and HBeAg status. Patients with viral variants C1817T and A1838G had viral loads nearly three orders of magnitude lower than patients without those variants. These patients consequently experienced earlier viral suppression while on treatment. Furthermore, we identified novel variants that either independently or in combination with precore mutation G1896A were associated with the transition from HBeAg positive to the negative phase of infection. These observations are consistent with the hypothesis that mutation of the HBeAg open reading frame is an important factor driving CHB patient's HBeAg status. This analysis provides a detailed picture of HBV genetic variation in the largest patient cohort to date and highlights the diversity of plausible molecular mechanisms through which viral variation affects clinical phenotype.

High Frequency of Either Altered Pre-Core StartCodon or Weakened Kozak Sequence in the CorePromoter Region in Hepatitis B Virus A1 Strainsfrom Rwanda

Hepatitis B virus (HBV) is endemic in Rwanda and is a major etiologic agent for chronic liver disease in the country. In a previous analysis of HBV strains from Rwanda, the S genes of most strains segregated into one single clade of subgenotype, A1. More than half (55%) of the anti-HBe positive individuals were viremic. In this study, 23 complete HBV genomes and the core promoter region (CP) from 18 additional strains were sequenced. Phylogenetic analysis of complete genomes confirmed that most Rwandan strain formed a single unique clade, within subgenotype A1. Strains from 17 of 22 (77%) anti-HBe positive HBV carriers had either mutated the precore start codon (9 strains with either CUG, ACG, UUG, or AAG) or mutations in the Kozak sequence preceding the pre-core start codon (8 strains). These mutually exclusive mutations were also identified in subgenotypes A1 (70/266; 26%), A2 (12/255; 5%), and A3 (26/49; 53%) sequences from the GenBank. The results showed that previous, rarely described HBV variants, expressing little or no HBeAg, are selected in anti-HBe positive subgenotype Al carriers from Rwanda and that mutations reducing HBeAg synthesis might be unique for a particular HBV clade, not just for a specific genotype or subgenotype.

Core gene insertion in hepatitis B virus genotype G functions at both the encoded amino acid sequence and RNA structure levels to stimulate core protein expression

Hepatitis B virus genotype G possesses a 36-nucleotide (nt) insertion at the 5' end of core gene, adding 12 residues to core protein. The insertion markedly increased core protein level irrespective of viral genotype, with the effect reproducible using CMV-core gene construct. Here we used such expression constructs and transient transfection experiments in Huh7 cells to identify the structural bases. The insertion is predicted to create a stem-loop structure 14nt downstream of core gene AUG. A + 1 or + 2 frameshift into the 36nt mitigated enhancement of core protein level. Point mutations to disrupt or restore the stem-loop had opposite effects on core protein expression. Shifting the translation initiation site downstream or further upstream of the stem-loop rendered it inhibitory or no longer stimulatory of core protein expression. Therefore, both the reading frame and a properly positioned stem-loop structure contribute to marked increase in core protein expression by the 36-nt insertion.

Virological and Clinical Characteristics of Hepatitis B Virus Genotype A

Hepatitis B virus (HBV) infection is one of the most prevalent chronic viral infections in humans. The overall prevalence of hepatitis B surface antigen (HBsAg) is reported to be 3.6%; however, it varies depending upon the geographic area. HBV is classified into ten genotypes (A through J) on the basis of an intergroup genomic divergence of > 8%. Specifically, HBV genotype A exhibits several unique virological and clinical characteristics and can be further classified into seven subtypes. Among them, subtype A2 or Ae (A2/[e]) is occasionally responsible for nosocomial infection and among homosexual males. Regarding virological factors, the G1896A precore mutation is rarely observed in genotype A as it would disrupt an essential stem-loop structure in the ε signal essential for pregenomic RNA packaging. HBV genotype A also harbors a 6-nucleotide C-terminal insertion in the hepatitis B-e antigen (HBeAg) precursor, resulting in a variable-length HBeAg protein product observed in serum of positive patients. These molecular traits likely contribute to the specific clinical presentation of genotype A-infected patients, such as mild acute hepatitis B (AHB), longer persistence of HBsAg positivity in AHB, and increased chronicity after AHB in adults. However, genotype A shows a better response to interferon than other genotypes in chronic hepatitis B patients. Here, we review the virological and clinical characteristics of HBV genotype A that will be useful in elucidating the association among persistent viral infection, host genetic factors, and treatment in future studies.

Prevalence and Characteristics of Precore Mutation in Iran and Its Correlation with Genotypes of Hepatitis B

Introduction

Mutation of the HBV precore gene prevents the production of HBeAg, which is an important target for immune responses. Distribution of this mutation varies along with frequency of HBV genotypes in accordance with geographic and ethnic variations. The general objective of this study was to evaluate the prevalence and characteristics of precore mutation in Iran and its correlation with genotypes of hepatitis B.

Methods

In this cross-sectional study, viral DNA of 182 Iranian hepatitis B surface antigen positive patients who were admitted to Bandar Abbas Blood Transfusion Organization in 2012 and 2013 was retrieved from their serum samples. HBeAg, anti-HBe, and anti-HBc IgM diagnostic tests were performed using ELISA kits. Precore and Pre-S regions were amplified using specific primers and PCR thereafter to determine the genotypes; precore mutation, PCR, and restriction fragment length polymorphism (RFLP) methods also were applied. SPSS version 12 was used for data analysis by Mann–Whitney U test, Fisher’s exact probability test, and t-test.

Results

A total of 62 patients (34.1%) had precore mutation (A1896G), and genotype D was the predominant genotype in these patients, which was followed by an unknown genotype that was suspected for genotype B. Interestingly, the relationships between precore mutation and HBeAg (p=0.037) and genotype D (p=0.005) were significant; however, no correlation was observed between this mutation and acute or chronic hepatitis and sex of patients.

Conclusion

This study found high prevalence of precore mutations in southern Iran, which was significantly associated with HBeAg and genotype D.

Hepatitis B Virus e Antigen Activates the Suppressor of Cytokine Signaling 2 to Repress Interferon Action

Hepatitis B virus (HBV) infection causes acute hepatitis B (AHB), chronic hepatitis B (CHB), liver cirrhosis (LC), and eventually hepatocellular carcinoma (HCC). The presence of hepatitis B e antigen (HBeAg) in the serum generally indicates ongoing viral replication and disease progression. However, the mechanism by which HBeAg regulates HBV infection remains unclear. Interferons (IFNs) are pleiotropic cytokines that participate in host innate immunity. After binding to receptors, IFNs activate the JAK/STAT pathway to stimulate expression of IFN-stimulated genes (ISGs), leading to induction of antiviral responses. Here, we revealed that HBeAg represses IFN/JAK/STAT signaling to facilitate HBV replication. Initially, HBeAg stimulates the expression of suppressor of cytokine signaling 2 (SOCS2). Subsequently, SOCS2 impairs IFN/JAK/STAT signaling through reducing the stability of tyrosine kinase 2 (TYK2), downregulating the expression of type I and III IFN receptors, attenuating the phosphorylation and nucleus translocation of STAT1. Finally, SOCS2 inhibits the expression of ISGs, which leads to the repression of IFN action and facilitation of viral replication. These results demonstrate an important role of HBeAg in the regulation of IFN action, and provide a possible molecular mechanism by which HBV resists the IFN therapy and maintains persistent infection.

Differential regulation of hepatitis B virus core protein expression and genome replication by a small upstream open reading frame and naturally occurring mutations in the precore region

Hepatitis B virus (HBV) transcribes two subsets of 3.5-kb RNAs: precore RNA for hepatitis B e antigen (HBeAg) expression, and pregenomic RNA for core and P protein translation as well as genome replication. HBeAg expression could be prevented by mutations in the precore region, while an upstream open reading frame (uORF) has been proposed as a negative regulator of core protein translation. We employed replication competent HBV DNA constructs and transient transfection experiments in Huh7 cells to verify the uORF effect and to explore the alternative function of precore RNA. Optimized Kozak sequence for the uORF or extra ATG codons as present in some HBV genotypes reduced core protein expression. G1896A nonsense mutation promoted more efficient core protein expression than mutated precore ATG, while a +1 frameshift mutation was ineffective. In conclusion, various HBeAg-negative precore mutations and mutations affecting uORF differentially regulate core protein expression and genome replication.

Enhanced pregenomic RNA levels and lowered precore mRNA transcription efficiency in a genotype A hepatitis B virus genome with C1766T and T1768A mutations obtained from a fulminant hepatitis patient

The viral factors associated with the development of fulminant hepatitis B are not fully understood. We recently found four unique mutations [G to A at nucleotide 1742 (G1742A), C1766T, T1768A and T1809C] in the basal core promoter (BCP) region of a genotype A hepatitis B virus (HBV) strain (FH) obtained from a 53-year-old man with fatal fulminant hepatitis. To elucidate the association of the mutations of the FH genome with the disease, we constructed a 1.3-fold FH genome and its five variants by replacing one or two mutated nucleotides with wild-type nucleotide(s) via site-directed mutagenesis, and transfected human hepatoma cells (HepG2/C3A) with the constructs. There were no discernible differences between FH and two variants (FH_A1742G and FH_C1809T) with regard to viral replication and protein expression. However, in comparison to three other variants (FH_T1766C, FH_A1768T and FH_T1766C/A1768T) with wild-type nucleotide(s) at 1766 and/or 1768, the FH genome exhibited a 2.5-5-fold enhancement of viral replication by heightened pregenomic RNA synthesis and a 1.5-2.5-fold reduction in the hepatitis B e antigen (HBeAg) synthesis by the downregulation of the precore mRNA level. An immunofluorescence analysis revealed the increased and predominant cytoplasmic localization of the core protein in the FH genome. The present study demonstrates that the C1766T/T1768A mutations in the BCP region of genotype A HBV enhance viral replication, downregulate HBeAg expression and are responsible for the predominant localization of the core protein in the cytoplasm, which are likely associated with the development of fulminant hepatitis.

G1896A Precore Mutation and Association With HBeAg Status, Genotype and Clinical Status in Patients With Chronic Hepatitis B

BACKGROUND

Precore stop codon (G1896A) mutation is one of the commonest mutations found in patients with chronic hepatitis B. However, over the years, this mutation was not reported much in Malaysia.

OBJECTIVES

We therefore investigated the presence of G1896A mutation in Malaysian population and its association with HBeAg status, clinical stage, hepatitis B virus (HBV) genotype and e-seroconversion rate.

PATIENTS AND METHODS

Serum samples from 93 patients confirmed as hepatitis B carriers were collected for molecular assay. The whole genome of HBV was amplified by polymerase chain reaction and directly sequenced. The precore and basal core promoter regions were analyzed for presence of mutations.

RESULTS

The most commonly observed mutation in the precore region was C1858T with 64.5% prevalence. The precore mutation of interest (G1896A) was identified in 25.8% of isolates. The basal core promoter mutations detected were A1762T-G1764A (26.9%), C1653T (8.6%), A1752G (10.8%) and C1766T (2.2%). No significant association was observed between G1896A mutation and HBeAg-negativity. Nonetheless, G1896A was highly prevalent among HBV genotype B. Clinical association revealed that subjects with G1896A mutations were mainly detected in asymptomatic chronic hepatitis B (58.3%) and liver cirrhosis (41.7%). One subject was diagnosed with fulminant hepatitis (4.2%) and 8.3% had hepatocellular carcinoma (HCC).

CONCLUSIONS

Our data suggested an intermediate prevalence of G1896A mutation among Malaysian hepatitis B carriers. The stop codon mutation has a significant association with genotype B and patients with chronic hepatitis B and liver cirrhosis.

Lower mutation frequency of BCP/precore regions in e antigen-negative chronic HBV-infected children instead of adults patients

To describe the Hepatitis B e antigen(HBeAg) seroconversion related mutation profiles of the basal core promoter(BCP)/precore regions in e antigen seroconverted child patients, a cohort of 245 child patients with CHB and a control patients group of 92 adult patients with CHB were recruited. The mutation frequencies of six nucleotides or nucleotide combinations including nucleotide (nt)1896, nt1762/1764, nt1752, nt1846, nt1899 and nt1753 showed significant differences between HBeAg positive and HBeAg-negative child patients groups. The frequencies of these HBeAg seroconversion-related mutations were significantly lower in HBeAg-negative children with CHB than in HBeAg-negative adults with CHB, especially for the mutation G1896A (41.1% vs 91.7%, P<0.001), and the average number of BCP/precore region mutations in samples from HBeAg-negative child patients was also obviously lower than in HBeAg-negative adult patients(3.62±3.03 vs 4.89±2.09, P<0.001), suggesting less impact of mutations in the BCP/precore region on HBeAg seroconversion in child patients than adult patients.

Spontaneous reactivation of hepatitis B virus (HBV) infection in patients with resolved or occult HBV infection

Reactivation of a former hepatitis B virus (HBV) infection can be triggered by immunosuppressive therapy, diseases associated with an immunocompromised state, organ transplantation or the withdrawal of antiviral drugs. Despite the absence of such risk factors, a spontaneous reactivation of HBV replication occurred in two elderly patients with resolved or occult HBV infection. A 73-year-old male underwent coronary artery bypass grafting in October 2008, and was negative for HBsAg but positive for anti-HBs. In July 2009, his serum became positive for HBsAg, HBeAg and HBV DNA (6.4 log copies/ml; genotype C), but negative for anti-HBc IgM, with abrupt elevation of the liver enzymes. The entire genomic sequence of HBV recovered from this patient revealed no mutations in the core promoter and precore regions that interfere with HBeAg production. A 76-year-old male with a history of endoscopic mucosal resection for esophageal cancer in 2002 and an initial diagnosis of diabetes mellitus in 2009, at which time he was negative for HBsAg. He was found to be positive for HBsAg in September 2012 during a laboratory examination performed prior to the resection of recurrent esophageal cancer, despite a low HBV load (2.1 log copies/ml). Three months later, without the administration of any anticancer drugs, the HBV DNA (genotype B) level increased to 5.1 log copies/ml. A precore G1896A variant with high quasispecies diversity was recovered from the patient. Aging, surgical stress and complication of disease(s) associated with compromised immunity, such as cancer, arteriosclerosis and diabetes mellitus may trigger spontaneous HBV reactivation.

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

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

Retrospective study of the prevalence and clinical significance of hepatitis B virus precore and basal core promoter variants

BACKGROUND

Hepatitis B virus (HBV) precore (PC) and basal core promoter (BCP) variants are well known; however, their prevalence in North America is unclear, especially among hepatitis B e antigen-negative patients.

OBJECTIVE

To investigate the prevalence of PC⁄BCP mutations and their clinical significance.

METHODS

One hundred twenty-eight patients positive for both hepatitis B surface antigen and hepatitis B e antibody were selected, and PC⁄BCP mutations were identified using a line probe assay. The subjects' charts were reviewed for race⁄ethnicity, HBV genotype, HBV viral load, sex, liver enzyme levels, imaging and biopsy results up to 10 years before the study.

RESULTS

The prevalence of PC and BCP variants were 47.6% and 62.5%, respectively. Older age was associated with aspartate aminotransferase-to-platelet index ratio (APRI) ≥0.7 (P=0.011) and abnormal imaging⁄biopsy results (P=0.0008). Although the presence of BCP variant(s) was associated with APRI ≥0.7 (P=0.029), it was not associated with abnormal imaging⁄biopsy results. The combination of age ≥50 years and the presence of BCP variant(s) was associated with abnormal imaging⁄biopsy results, suggestive of either cirrhosis or hepatocellular carcinoma (not observed with PC mutation). Neither sex or genotype, or median HBV viral load showed significant influence on any of these outcomes.

CONCLUSIONS

The present study suggests that the prevalence of PC and BCP mutations are higher than what has been previously reported. One potential explanation would be increased immigration in the past decade. Considering the potential public health and clinical implications of these variants, long-term multicentre and prospective studies could further unravel the uncertainty around these variants.

Natural history of chronic hepatitis B virus infection

Hepatitis B virus infection represents a major global health problem. Currently, there are more than 240 million chronically infected people worldwide. The development of chronic hepatitis B virus-mediated liver disease may lead to liver fibrosis, cirrhosis and eventually hepatocellular carcinoma. Recently, the discovery of the viral entry receptor sodium taurocholate cotransporting polypeptide has facilitated new approaches for a better understanding of viral physiopathology. Hopefully, these novel insights may give rise to the development of more effective antiviral therapy concepts during the next years. In this review, we will discuss the natural history of hepatitis B virus infection including the viral biology, the clinical course of infection and the role of the immune response.

Molecular analysis of the interspousal transmission of hepatitis B virus in two Japanese patients who acquired fulminant hepatitis B after 50 and 49 years of marriage

A 71-year-old (C1I) and 69-year-old (C2I) Japanese female contracted fulminant hepatitis B after 50 and 49 years of marriage, respectively. Both index cases exhibited high levels of anti-HBc IgM antibodies (24.2 and 31.5 S/CO, respectively), suggestive of acute hepatitis B virus (HBV) infection, although they had no discernible risk factors for HBV infection, except for chronically HBV-infected spouses with detectable HBV DNA (3.3 log copies/ml [C1S: 72-year-old] and 7.2 log copies/ml [C2S: 71-year-old]). The HBV genotype/subgenotype was identical in each couple (B/B1 or C/C2). The HBV isolates from the index cases and spouses shared a nucleotide sequence identity of 99.5% and 99.7%, respectively, over the entire genome, and these four isolates had the highest nucleotide sequence identity of only 97% to HBV isolates deposited in DNA databases. Phylogenetic trees confirmed a close relationship of the HBV isolates between C1I and C1S and between C2I and C2S, supported by a high bootstrap value of 100% within each couple, indicating the transfer of HBV infection between spouses. These four isolates shared a precore mutation of G1896A known to be associated with fulminant hepatitis B. Although the history of sexual contact within a reasonable incubation period was obscure for one stable, monogamous couple (C1I and C1S), the other couple had a monogamous sexual relationship within six months prior to disease onset. This study indicates that two elderly Japanese patients with fulminant hepatitis B acquired HBV infection via interspousal (most likely sexual) transmission during long-lasting marriages.

Genetic characterization and genotyping of hepatitis B virus (HBV) isolates from donors with an occult HBV infection

BACKGROUND AND OBJECTIVES

Screening of Thai blood donors has resulted in the detection of donors with an occult HBV infection (OBI), where HBsAg is undetectable, but hepatitis B virus (HBV) DNA is present in serum in low concentrations. This study was designed to determine whether the occurrence of OBI in donors was linked to the HBV genotype and possibly to mutations in the surface (S) and core (C) gene regions.

MATERIALS AND METHODS

Mutations in the S and C gene regions in 48 Thai donors with OBI were mapped by sequencing. Genotyping was determined with the INNO-LiPA test and by phylogenetic analysis of sequences from the S and C genes.

RESULTS

The majority of OBI samples were genotype C (81·3%) with 6·3% of samples being genotype B. In addition, two genotype I isolates were identified. Mutations in the S region (100%) were found especially in loop 1 of the major hydrophilic loop (MHL) at positions I110L, T114S, T126I and S113T, whereas mutations in the C region (65%) were within the basal core promoter region (position A1762T/G1764A) and precore region (position G1896A).

CONCLUSION

The majority of OBI samples were HBV genotype C, although genotype I, which is newly emerging in Thailand, was also detected. The study demonstrated that OBI was probably not associated with a particular HBV genotype or with certain mutations in the S and C gene regions. However, mutations in the C gene region which could potentially impair viral replication and HBsAg production and potentially lead to OBI were identified.

New perspective on the natural course of chronic HBV infection

Chronic hepatitis B virus (HBV) infection is a significant threat to public health and an enormous burden on society. Mechanisms responsible for chronic HBV infection remain poorly understood. A better understanding of the natural course of chronic HBV infection may shed new light on the mechanisms underlying this disease and help in designing new antiviral strategies. Natural course of chronic HBV infection is conventionally viewed as an uninterrupted process that is usually marked by HBV e antigen (HBeAg) seroconversion or characterized by different phases associated with assumed host responses to HBV infection. However, none of these descriptions captures or highlights the core events that determine the natural course of chronic HBV infection. In this review, we briefly present the current knowledge on this subject and explain the significance and implication of events that occur during infection. A pre-core mutant becomes predominant in the viral population following elimination of the wild-type virus in duck hepatitis B virus-chronically infected animals. The coupled events in which first there is viral clearance that clears wild-type virus and then there is the reinfection of wild-type virus cleared livers with mutant virus are highly relevant to understanding of the natural course of chronic HBV infection under both treated and untreated conditions. In our new perspective, a general natural course of chronic HBV infection comprises cycles of viral clearance and reinfection, and such cycles prolong the chronic HBV infection course. Reviewing published data on the natural course of chronic HBV infection can reduce the possibility of missing important points in the initial data interpretation.

Molecular epidemiological study of hepatitis B virus genotypes in Southwest, China

Hepatitis B virus (HBV) is highly endemic in Southwest China; an area with many ethnic minorities. Information about the genetic distribution of HBV is still limited. In 2010, a multistage cluster sampling method was carried out in the Southwest China. Five hundred forty serum samples of participants were collected. Polymerase chain reaction followed by nucleotide sequencing of parts of the HBV S and C genes was performed. HBV genotype and subgenotype were determined. Recombination analysis was carried out. HBV infectious markers, HBV DNA and mutations in the basic core promoter (BCP) A1762T/G1764A and G1896A were analyzed. The results show us that HBV genotypes C/D recombinant (38.6%), B (31.6%), and C (23.3%), were predominant in Southwest China. C/D4 (96.8%) was endemic in the Tibetan and B2 (43.5%) in Han, and C1 (66.7%) was predominant in the Yi minority. 67.5% (56/83) of genotype C/D was Hepatitis B surface antigen (HBsAg) positive/Hepatitis B e antigen (HBeAg) positive/HBV DNA≥20,000 IU/ml, BCP A1762T/G1764A double mutation was frequent in genotype C and C/D, and G1896A was frequent in B and B/C. Thus, HBV genotypes distribution differed significantly in area and minority in Southwest China. C/D recombinant is endemic in the Tibetan, while B, C genotypes are predominant in Han minority. C/D recombinant exhibits higher frequency with HBeAg positive, high level of HBV DNA and BCP A1762T/G1764A double mutation.

Variability in the precore and core promoter region of the hepatitis B virus genome

There is increasing evidence that hepatitis B virus (HBV) infections with different genotypes and subgenotypes differ in response to treatment and long-term prognosis. The differences emerge from variability within the genomes that leads to structural deviations at the pregenomic level and to changes at the translational level. Naturally occurring HBV strains covering the four major genotypes A-D were obtained from 393 patients and part of the genome was amplified using polymerase chain reaction (PCR), sequenced, and analyzed for mutational differences in the precore and core promoter regions. The study confirmed that core promoter and precore mutations occur at key positions (A1762T, G1764A, G1896A, and G1899A), and that the proportions of strains with seroconvertion in patients differ between the four HBV genotypes. A rare double mutation (C1857T together with G1897A) was observed, and C1856T was found together with the emerging G1898A mutation, which itself was found to be more widespread geographically than previously described. We found a novel mutation (T1850C), never before observed in human HBV strains but known from woodchuck hepatitis virus (WHV). A novel association of mutation C1773T with G1764T, C1766A, and G1757A was also found within a site already suggested to be a putative binding site for HNF-3. This novel association is proposed by us to be of importance for additional binding of HNH-2 to this site and is a better indicator of the emergence of the double mutation G1764T and C1766A than the G1757A mutation proposed previously.

Predominance of precore mutations and clinical significance of basal core promoter mutations in chronic hepatitis B virus infection in Indonesia

Chronic hepatitis B virus (HBV) infection is a major health problem worldwide, with a particularly high prevalence in the Asian-Pacific region. During chronic hepatitis B virus (HBV) infection, mutations commonly occur in the basal core promoter (BCP) and precore (PC) regions of HBV, affecting HBeAg expression, particularly following HBeAg serocon-version. Mutations in the B- and T-cell epitopes of the HBV core have also been observed during disease progression. The clinical significance of HBV genome variability has been demonstrated, however the results are a subject of controversy. Considering the characteristics of the virus associated with geographical location, the profiles of BCP, PC and core mutations and their clinical implications in patients with chronic HBV infection in Surabaya, Indonesia, were investigated. The BCP, PC and core mutations and HBV genotypes were detected by direct sequencing. The HBeAg/anti-HBe status and HBV DNA levels were also assessed. This study enrolled 10 patients with chronic HBV infection (UC) from Dr Soetomo General Hospital and Indonesian Red Cross, Surabaya, East Java, Indonesia, 10 patients with chronic hepatitis B and liver cirrhosis (LC) and 4 patients with chronic hepatitis B and hepatocellular carcinoma (HCC) from Dr Soetomo General Hospital. The PC mutation A1896 was predominant in all the groups (60-100%), together with the PC variant T1858, which was associated with HBV genotype B. The number of detected core mutations (Thr/Ser130) was higher in HCC patients (50%). However, the BCP mutations T1762/A1764 were predominant in LC patients (50-60%). The LC and HCC patients carried HBV isolates with additional mutations, at least at BCP or PC, mainly following HBeAg seroconversion. In the majority of anti-HBe-positive samples, the BCP T1762/A1764 mutations were associated with a high viral load, regardless of the PC 1896 status. In conclusion, the PC mutations were found to be predominant in all the groups. However, the BCP mutations were mainly detected in the LC group and may be considered as a critical indicator of a poor clinical outcome.

Distinct evolution and predictive value of hepatitis B virus precore and basal core promoter mutations in interferon-induced hepatitis B e antigen seroconversion

Precore (PC) (G1896A) and basal core promoter (BCP) (A1762T/G1764A) mutations of the hepatitis B virus (HBV) genome often emerge in chronic hepatitis B (CHB) patients. Their roles in hepatitis B e antigen (HBeAg) seroconversion induced by interferon (IFN) therapy remain controversial, partly because quantitative analysis for these mutants is lacking. This study aimed to develop a new assay to accurately quantify the PC and BCP mutant percentages and correlate their dynamic changes with IFN-induced HBeAg seroconversion in HBeAg-positive CHB patients. The PC and BCP mutant percentages were analyzed by polymerase chain reaction (PCR)-pyrosequencing. Our results showed that this quantitative assay for PC and BCP mutants achieved high accuracy (R(2) > 0.99) within a range between 10% and 90% mutants. We examined dynamic changes of the PC and BCP mutant percentages following IFN treatment in 203 HBeAg-positive CHB patients. By multiple logistic regression analysis, we found that the chance of HBeAg seroconversion increased by 2.2% (odds ratio [OR] = 1.022, 95% confidence interval [CI]: 1.009-1.034, P = 0.001) and 2.3% (OR = 1.023, 95% CI: 1.010-1.037, P = 0.001) per 1% increase of the pretreatment PC and BCP mutant percentages, respectively, after adjustment for other predictors. However, only the pretreatment PC mutation percentage was significantly associated with HBeAg seroconversion with HBV DNA < 2,000 IU/mL (OR = 1.030, 95% CI: 1.014-1.047, P < 0.001). Furthermore, the mutant percentage of PC, but not BCP, in patients achieving HBeAg seroclearance with HBV DNA < 20,000 IU/mL increased significantly during IFN treatment (P = 0.039). Interestingly, patients with HBeAg seroconversion who had a high PC mutant percentage at the end of IFN treatment tended to exhibit high viremia after seroconversion.

CONCLUSION

Quantitative analysis of PC and BCP mutants can predict IFN-induced HBeAg seroconversion and demonstrate their distinct evolution patterns during HBeAg seroconversion. (HEPATOLOGY 2013).

Hepatitis B virus genetic variants: biological properties and clinical implications

Hepatitis B virus (HBV) causes a chronic infection in 350 million people worldwide and greatly increases the risk of liver cirrhosis and hepatocellular carcinoma. The majority of chronic HBV carriers live in Asia. HBV can be divided into eight genotypes with unique geographic distributions. Mutations accumulate during chronic infection or in response to external pressure. Because HBV is an RNA-DNA virus the emergence of drug resistance and vaccine escape mutants has become an important clinical and public health concern. Here, we provide an overview of the molecular biology of the HBV life cycle and an evaluation of the changing role of hepatitis B e antigen (HBeAg) at different stages of infection. The impact of viral genotypes and mutations/deletions in the precore, core promoter, preS, and S gene on the establishment of chronic infection, development of fulminant hepatitis and liver cancer is discussed. Because HBV is prone to mutations, the biological properties of drug-resistant and vaccine escape mutants are also explored.

Synergistic effects of A1896, T1653 and T1762/A1764 mutations in genotype c2 hepatitis B virus on development of hepatocellular carcinoma

The effects of genomic changes in hepatitis B virus (HBV) on the occurrence of hepatocellular carcinoma (HCC) are still unclear, especially in relation to the genotype of HBV. In this study, we examined the effects of genomic changes in HBV of genotype C2 on the development of HCC. A total of 318 patients with HBV-associated HCC and 234 patients with chronic hepatitis B (CHB) were studied. All of HCC cases were diagnosed histologically and treated with surgical resection. The whole of the X, S, basal core promoter (BCP) and precore regions of the viral genome from sera or liver tissues were sequenced. All subjects had HBV of genotype C2. The prevalence of the T1653 mutation in the X region and the A1896 mutation in the precore region of HBV was significantly higher in the HCC group than in the control CHB group (22% vs 11%, P = 0.003; 50% vs 23%, P < 0.001, respectively). Moreover, the T1762/A1764 mutations in the BCP region in combination with either T1653 or A1896 were more common in the HCC compared with the CHB group (BCP+X1653: 18% vs 11%, P = 0.05; BCP+PC, 40% vs 15%, P < 0.001, respectively). In multivariate analysis, T1653 and A1896 were revealed to be independent risk factors for HCC development. G1896A in the precore region and C1653T mutation in the X region of genotype C2 HBV are important risk factors for HCC development. Also, the A1762T/G1764A double mutation may act in synergy with C1653T to increase the risk of HCC in patients chronically infected with HBV genotype C2.

Residual risk of transfusion-transmitted hepatitis B virus (HBV) infection caused by blood components derived from donors with occult HBV infection in Japan

BACKGROUND

Nucleic acid amplification testing (NAT) for hepatitis B virus (HBV) during blood screening has helped to prevent transfusion-transmitted HBV infection (TT-HBV) in Japan. Nevertheless, 4 to 13 TT-HBV infections arise annually.

STUDY DESIGN AND METHODS

The Japanese Red Cross (JRC) analyzed repository samples of donated blood for TT-HBV that was suspected through hemovigilance. Blood donations implicated in TT-HBV infections were categorized as either window period (WP) or occult HBV infection (OBI) related. In addition, we analyzed blood from 4742 donors with low antibody to hepatitis B core antigen (anti-HBc) and antibody to hepatitis B surface antigen (anti-HBs) titers using individual-donation NAT (ID-NAT) to investigate the relationship between anti-HBc titer and proportion of viremic donors.

RESULTS

Introduction of a more sensitive NAT method for screening minipools of 20 donations increased the OBI detection rate from 3.9 to 15.2 per million, while also the confirmed OBI transmission rate increased from 0.67 to 1.49 per million. By contrast the WP transmission rate decreased from 0.92 to 0.46 per million. Testing repository samples of donations missed by minipools of 20 donations NAT showed that 75 and 85% of TT-HBV that arose from WP and OBI donations, respectively, would have been interdicted by ID-NAT. The ID-NAT trial revealed that 1.94% of donations with low anti-HBc and anti-HBs titers were viremic and that anti-HBc titers and the frequency of viremia did not correlate.

CONCLUSIONS

The JRC has elected to achieve maximal safety by discarding all units with low anti-HBc and anti-HBs titers that account for 1.3% of the total donations.

Association between S21 substitution in the core protein of hepatitis B virus and fulminant hepatitis

BACKGROUND

The viral factors of hepatitis B virus (HBV), such as genotypes and mutations, were reported to affect the development of fulminant hepatitis B (FHB), but the mechanism is still unclear.

OBJECTIVES

To investigate HBV mutations associated with FHB, especially in the subgenotype B1/Bj HBV (HBV/B1), which are known to cause FHB frequently in Japan.

STUDY DESIGN

A total of 96 serum samples from acute self-limited hepatitis B (AHB) patients and 13 samples from FHB patients were used for full-genome/partial sequencing. A total of 107 chronic infection patients with HBV were also examined for the distribution of mutants.

RESULTS

In the analysis of full-genome sequences of HBV/B1 (FHB, n=11; non-FHB, n=35) including those from the databases, mutations at nt 1961 [T1961V (not T)] and nt 1962 [C1962D (not C)], which change S21 in the core protein, were found more frequently in FHB than in non-FHB (100% vs. 20%, 55% vs. 3%, respectively). When our FHB and AHB samples were compared, T1961V and C1962D were significantly more frequent in FHB than in AHB, both in the overall analysis (46% vs. 6%, 39% vs. 3%, respectively) and in HBV/B1 (100% vs. 29%, 100% vs. 14%, respectively). A newly developed PCR system detecting T1961V showed that HBV/B1 and low viral load were independent factors for the mutation among chronic infection patients.

CONCLUSIONS

T1961V/C1962D mutations were found frequently in FHB, especially in HBV/B1. The resulting S21 substitution in the core protein may play important roles in the development of FHB.

Hepatitis B virus gene mutations in liver diseases: a report from New Delhi

OBJECTIVES

The study was designed to characterize the surface, core promoter, precore/core region sequences for the presence of mutations in hepatitis B virus (HBV) associated with different liver diseases.

METHODS

567 HBV associated patients with different liver diseases were enrolled in this study. All samples were analyzed for HBV surface, core promoter, precore/core region mutations and genotypes using PCR and direct sequencing.

RESULTS

HBV genotype D (72.8%) was the predominant type followed by genotype A (27.2%). The serum viral load of HBV was highest in HBsAg carriers group and lowest in patients with hepatocellular carcinoma. 17.9% patients with cirrhosis and 24.6% hepatocellular carcinoma cases were ADV-resistant with rtA181T/V mutations in the S-gene. A1896T was found more frequently in fulminant hepatic failure compared to acute viral hepatitis patients (p = 0.038). T1753V mutation was significantly higher in patients with cirrhosis of liver (34.6%) than in chronic hepatitis (18.9%) and hepatocellular carcinoma patients (21.2%; p = 0.001). T1762/A1764 mutation was observed in all the groups. C1914G core gene mutation was associated with the hepatocellular carcinoma (32.2%) compared to other groups. HBV genotype D predominated in comparison to genotype A. An increased frequency of precore mutation and BCP double mutations amongst the population studied was also observed.

CONCLUSION

Mutations such as T1762/A1764, T1753V and C1914G were usually associated with advanced forms of liver disease and had an increased risk of HCC. The nucleotide variability in the basal core promoter and precore regions possibly plays a role in the progression of HBV disease. Prospective studies on the sequence variations of the preC/C region of the HBV genome and the molecular mechanisms in relation to progression of liver disease would aid in better understanding of the biological significance of HBV strains in India.

Incidence and determinants of spontaneous seroclearance of hepatitis B e antigen and DNA in patients with chronic hepatitis B

BACKGROUND & AIMS

The spontaneous seroclearance of hepatitis B e antigen (HBeAg) and hepatitis B virus (HBV) DNA are important markers of progression of chronic HBV infection. We performed a long-term cohort study to elucidate the incidence and determinants of HBeAg and HBV DNA seroclearance in patients with chronic hepatitis B.

METHODS

A total of 1289 participants with a serum HBV DNA level of 10,000 copies/mL or more and without cirrhosis when the study began (1991-1992) were followed up until June 2004. A subset of patients that tested positive for HBeAg at baseline (n = 439) was included in the analysis of HBeAg seroclearance. Cox proportional hazards models were used to estimate seroclearance rate ratios for various determinants associated with the outcomes.

RESULTS

After 3161.2 person-years of follow-up evaluation, HBeAg seroclearance occurred in 187 participants (incidence rate, 5.9 per 100 person-years). The cumulative lifetime incidence of HBeAg seroclearance among patients who were 30 to 40, or 50, 60, 70, or 74 years old was 38.8%, 69.4%, 81.9%, 89.1%, and 95.5%, respectively. Major predictors of HBeAg seroclearance included female sex, genotype B, the precore 1896 mutant, increased serum levels of alanine aminotransferase, and low baseline serum levels of HBV DNA. The median (interquartile range) serum level of HBV DNA at the time of HBeAg seroclearance was 177,801 copies/mL (4941-3,247,560 copies/mL). HBV DNA seroclearance occurred in 199 participants (15.4%) during the mean follow-up period of 7.8 years (incidence rate, 1.97 per 100 person-years). The cumulative lifetime incidence of HBV DNA seroclearance at 40, 50, 60, 70, and 77 years old was 10.0%, 25.0%, 38.8%, 54.2%, and 82.8%, respectively. Lower levels of HBV DNA at study entry and among those with the precore 1896 wild-type variant were associated with an increased rate of HBV DNA seroclearance. Among individuals who were HBeAg-seropositive at study entry and cleared serum HBV DNA during the follow-up period, 89% had cleared HBeAg by the time they had an undetectable serum level of HBV DNA.

CONCLUSIONS

Serum level of HBV DNA is the most important predictor of seroclearance of HBeAg and HBV DNA. This finding supports current clinical guidelines for antiviral treatments of chronic hepatitis B.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Two distinct subtypes of hepatitis B virus-related acute liver failure are separable by quantitative serum immunoglobulin M anti-hepatitis B core antibody and hepatitis B virus DNA levels

Hepatitis B virus (HBV)-related acute liver failure (HBV-ALF) may occur after acute HBV infection (AHBV-ALF) or during an exacerbation of chronic HBV infection (CHBV-ALF). Clinical differentiation of the two is often difficult if a previous history of HBV is not available. Quantitative measurements of immunoglobulin M (IgM) anti-hepatitis B core antibody (anti-HBc) titers and of HBV viral loads (VLs) might allow the separation of AHBV-ALF from CHBV-ALF. Of 1,602 patients with ALF, 60 met clinical criteria for AHBV-ALF and 27 for CHBV-ALF. Sera were available on 47 and 23 patients, respectively. A quantitative immunoassay was used to determine IgM anti-HBc levels, and real-time polymerase chain reaction (rtPCR) was used to determine HBV VLs. AHBV-ALFs had much higher IgM anti-HBc titers than CHBV-ALFs (signal-to-noise [S/N] ratio median: 88.5; range, 0-1,120 versus 1.3, 0-750; P < 0.001); a cut point for a S/N ratio of 5.0 correctly identified 44 of 46 (96%) AHBV-ALFs and 16 of 23 (70%) CHBV-ALFs; the area under the receiver operator characteristic curve was 0.86 (P < 0.001). AHBV-ALF median admission VL was 3.9 (0-8.1) log10 IU/mL versus 5.2 (2.0-8.7) log10 IU/mL for CHBV-ALF (P < 0.025). Twenty percent (12 of 60) of the AHBV-ALF group had no hepatitis B surface antigen (HBsAg) detectable on admission to study, wheras no CHBV-ALF patients experienced HBsAg clearance. Rates of transplant-free survival were 33% (20 of 60) for AHBV-ALF versus 11% (3 of 27) for CHBV-ALF (P = 0.030).

CONCLUSIONS

AHBV-ALF and CHBV-ALF differ markedly in IgM anti-HBc titers, in HBV VLs, and in prognosis, suggesting that the two forms are, indeed, different entities that might each have a unique pathogenesis.

Enhanced replication of hepatitis B virus with frameshift in the precore region found in fulminant hepatitis patients

BACKGROUND

The genotype B of hepatitis B virus (HBV) was reported to associate with fulminant hepatitis (FH). We aimed to clarify the characteristics of HBV obtained from FH patients in an area of Japan where genotype B HBV is prevalent.

METHODS

Using serum samples of 16 HBV-associated FH patients, partial HBV sequences were determined. The effects of HBV mutation/insertion/deletion were evaluated using an in vitro HBV replication system.

RESULTS

Of the 16 HBV isolates, 31% belonged to subgenotype B1/Bj, 38% were subgenotype B2/Ba, and 31% were subgenotype C2/Ce. Notably, the single nucleotide insertion/deletion that resulted in a frameshift of the precore protein was found exclusively in 60% of B1/Bj strains. An in vitro study showed that all of the frameshift mutants had significantly higher amounts of HBV DNA than did the wild type. One of the isolates had a novel insertion of A between nucleotides 1900 and 1901, which resulted in a 3-nucleotide change within the Kozak sequence of the core protein and enhanced the core protein expression in vitro.

CONCLUSIONS

The frameshift insertion/deletion in the precore region enhanced HBV replication and might be associated with the development of FH by the subgenotype B1/Bj HBV.

Precore/core promoter mutations and hepatitis B virus genotype in hepatitis B and C dually infected patients treated with interferon-based therapy

We studied the prevalence and distribution of precore/basal core promoter (BCP) mutations and hepatitis B virus (HBV) genotypes in HBV/hepatitis C virus (HCV) dually-infected patients, and evaluated their impact on long-term HBV response of interferon (IFN)-based therapy. The HBV genotypes and sequences of the precore/BCP regions were determined in 180 HBV/HCV dually-infected patients and were compared with 90 age, sex and hepatitis B e antigen-matched chronic hepatitis B controls. Serum HBV DNA and hepatitis B surface antigen (HBsAg) were assessed every 3-6 months after therapy with IFN or pegylated-IFN plus ribavirin in 135 dually-infected patients with active hepatitis C. Dually-infected patients had a higher prevalence of genotype C HBV (P=0.022) and a lower frequency of G1896A mutation (P=0.004) as compared with controls. Among dually-infected patients, genotype C was associated with a higher frequency of A1762T/G1764A mutation (P<0.001), but with lower HBV DNA (P<0.001) and a lower frequency of A1752T/G (P=0.008), C1799G (P<0.001) and G1896A mutation (P<0.001) than genotype B. Based on Cox proportional hazards model, young age (hazard ratio (HR)=0.952, P=0.001), sustained virological response to HCV (HR=4.638, P=0.044), C1766T mutation (HR=5.216, P=0.003) and A1846T mutation (HR=2.332, P=0.031) correlated with HBV DNA reactivation (⩾2000IU/ml) after therapy. Age (HR=1.068, P=0.020), G1896A mutation (HR=0.140, P=0.01) and A1846T mutation (HR=0.086, P=0.018) were associated with HBsAg seroclearance independently. In conclusion, specific mutations in the precore/BCP regions could be useful in predicting long-term HBV response in HBV/HCV dually-infected patients treated with IFN-based therapy.

Ultra-deep pyrosequencing analysis of the hepatitis B virus preCore region and main catalytic motif of the viral polymerase in the same viral genome

Hepatitis B virus (HBV) pregenomic RNA contains a hairpin structure (ε) located in the preCore region, essential for viral replication. ε stability is enhanced by the presence of preCore variants and ε is recognized by the HBV polymerase (Pol). Mutations in the retrotranscriptase domain (YMDD) of Pol are associated with treatment resistance. The aim of this study was to analyze the preCore region and YMDD motif by ultra-deep pyrosequencing (UDPS). To evaluate the UDPS error rate, an internal control sequence was inserted in the amplicon. A newly developed technique enabled simultaneous analysis of the preCore region and Pol in the same viral genome, as well as the conserved sequence of the internal control. Nucleotide errors in HindIII yielded a UDPS error rate <0.05%. UDPS study confirmed the possibility of simultaneous detection of preCore and YMDD mutations, and demonstrated the complexity of the HBV quasispecies and cooperation between viruses. Thermodynamic stability of the ε signal was found to be the main constraint for selecting main preCore mutations. Analysis of ε-signal variability suggested the essential nature of the ε structural motif and that certain nucleotides may be involved in ε signal functions.

Current status of antiviral therapy for hepatitis B

Chronic hepatitis B (CHB) is a major public health problem affecting up to 400 million people globally. Complications of CHB including liver failure and hepatocellular carcinoma result in 1.2 million deaths per year, making CHB the 10th leading cause of mortality worldwide. The natural history of CHB is variable and complex. The past decade witnessed important developments for the therapy of hepatitis B and marked the new era of oral therapy. The ultimate goal of CHB therapy is to arrest the progression of liver injury and to prevent the development of liver failure and hepatocellular carcinoma. Currently, six agents are approved for the treatment of CHB. Each of these agents, given as monotherapy, has been shown to produce virological, biochemical, and histological benefits for both HBeAg positive and negative CHB. There are, however, limitations in spite of their efficacy. The significant side-effect profile of interferon, for example, limits its long-term use. The approved oral agents are tolerable with prolonged use but drug resistance could limit long-term monotherapy. To date, combination therapy with nucleoside analogue and pegylated interferon or two nucleos(t)ide analogues given for one year does not show superiority in durability of response compared to monotherapy. Ongoing research effort is critical to identify the ideal hepatitis B therapy that is safe, effective, and produces durable response with a finite course of therapy. It is equally important to conduct a well designed, prospective natural history study to identify predictors of disease progression. This will accurately guide treatment strategy for this important disease.

Characterization of the basal core promoter and precore regions in anti-HBe-positive inactive carriers of hepatitis B virus

BACKGROUND

The study of hepatitis B virus (HBV) genomic heterogeneity has become a major issue in investigations aimed at understanding the relationship between HBV mutants and the wide spectrum of clinical and pathological conditions associated with HBV infection. Although most chronically infected HBV patients are inactive carriers, several virological aspects of this state remain unclear.

METHODS

In order to determine the prevalence and clinical significance of mutations in the basal core promoter (BCP) and precore (pC) regions among inactive carriers, the nucleotide sequences from 41 inactive carriers were analyzed and compared with those from 29 individuals with chronic active hepatitis.

RESULTS

Genotypes A (24.3%), D (37.1%), F1b (12.9%), and F4 (18.6%) were the most prevalent. Mutations in the BCP/pC regions were observed in most of the inactive carriers (92.7%) and in most of the patients with chronic active hepatitis (93.1%). The prevalence of mutation 1764(A) was significantly higher in patients with chronic active hepatitis (65.5%) than in inactive carriers (36.6%) (p=0.038), whereas the prevalences of mutations at the other positions analyzed were not significantly different. Older patients (>50 years) showed BCP/pC patterns with a higher number of substitutions. Mutations were found to be biased by genotype: the 1896(A) mutation was highly prevalent in genotypes D and F4, while alternative substitutions in the pC region were more prevalent in genotypes A and F1b.

CONCLUSIONS

Mutations in the BCP/pC regions are the hallmark of chronic anti-HBe-positive individuals; nevertheless, the even distribution of mutations in active and inactive carriers suggests that BCP/pC mutations may occur during HBV infection not strictly related to the HBV infection activity.

Recent advances in the research of hepatitis B virus-related hepatocellular carcinoma: epidemiologic and molecular biological aspects

Hepatocellular carcinoma (HCC) is one of the commonest cancers worldwide, and more than half of HCC patients are attributable to persistent hepatitis B virus (HBV) infections. The best and cheapest way to prevent HBV-related HCC is the implementation of universal hepatitis B vaccination program, by which the incidence rates of childhood HCC have been reduced in several countries, including Taiwan. However, there are still hundreds of millions of HBV carriers in the world that remain a global health challenge. In the past decade, several hepatitis B viral factors such as serum HBV DNA level, genotype, and naturally occurring mutants have already been identified to influence liver disease progression and HCC development in HBV carriers. Several easy-to-use scoring systems based on clinical and viral characteristics are developed to predict HCC risk in HBV carriers and may facilitate the communication between practicing physicians and patients in clinical practice. In addition, the role of nonviral factors in HBV-related HCC has also been increasingly recognized. On the basis of these emerging data, it is recommended that HBV carriers should be screened and monitored to identify those who have a higher risk of liver disease progression and require antiviral treatments. Regarding the molecular carcinogenesis of HCC development, despite some progress in the research of cell biology of HCC in the past decade, aberrant pathways involved in maintaining HCC phenotypes have not been completely elucidated yet. In the future, through comprehensive and integrated approaches to analyze the genomes of human HCC, novel target genes or pathways critically involved in hepatocarcinogenesis may hopefully be identified.

Infectivity of HBV DNA positive donations identified in look-back studies in Hyogo-Prefecture, Japan

AIMS/OBJECTIVES

To clarify transfusion incidence of hepatitis B virus (HBV) infected blood negative for mini pool-nucleic acid amplification testing (MP-NAT).

BACKGROUND

Japanese Red Cross (JRC) blood centres screen donated blood to avoid contamination with HBV. However, a low copy number of HBV may be overlooked.

METHODS/MATERIALS

In Hyogo-Prefecture, JRC blood centres screened 787 695 donations for HBV from April 2005 to March 2009. Of these, 685 844 were donations from the repeat donors. To detect the donors with HBV, serological tests, MP-NAT and/or individual donation (ID)-NAT were performed. To detect the recipients with transfusion-transmitted HBV infection (TTHBI), serological analysis and/or ID-NAT were performed.

RESULTS

In this study, 265 of the 685 844 repeat donations were serologically and/or MP-NAT positive for HBV. Their repository samples from the previous donation were examined in a look-back study; 13 of the 265 repository samples proved ID-NAT positive. Twelve recipients were transfused with HBV-infected blood components derived from 10 of the 13 HBV-infected donors. Only 1 of the 12 recipients was identified as TTHBI case. Seven of the 12 recipients escaped from our follow-up study and 4 recipients were negative for HBV during the observation period.

CONCLUSION

On the basis of the look-back study among the repeat donors in Hyogo-Prefecture, Japan, donations with HBV-infected blood negative for MP-NAT occurred with a frequency of 13 in 685 844 donations (∼1/53 000 donations). However, more than half of the recipients transfused with HBV-infected blood negative for MP-NAT could not be followed up. It is necessary to establish a more cautious follow-up system.

Establishment of an HBsAg mixed titer performance panel and HBsAg working standard for quality control of HBsAg diagnostic kits in Korea

BACKGROUND

International Standards or commercial panels used for performance validation of diagnostic kits might not reflect the viral characteristics common in Korea. Also, continuous use of these materials is difficult because of limited quantity and high cost.

OBJECTIVES

Establishment of HBsAg reference materials to be used as National Standards for validation of HBsAg diagnostic kits.

STUDY DESIGN

568 plasma units with OD less than 2.0 on HBsAg EIA were collected. HBsAg testing with 3 EIAs and 1 CIA was performed on all units. HBsAg positive units were subjected to HBV DNA quantification, genotyping and subtyping. Candidates for the mixed titer performance panel and working standard were confirmed for HBsAg by neutralization. A collaborative study was conducted for the candidates of the mixed titer performance panel and the working standard.

RESULTS

Based on the results of the collaborative study, a working standard (KFDA08/024) consisting of a series of four-fold dilutions of 2 materials, one with genotype/subtype C2/adr and the other with C1/adw, was established. A mixed titer performance panel composed of 2 negative and 16 positive samples was also established. A G1896A and a T/I126S mutant are included in the positive samples.

CONCLUSIONS

An HBsAg mixed titer performance panel and a working standard reflecting HBV genotypes/subtypes prevalent in Korea have been established as National Standards. This will enable consistent supply of validation materials, improve the validation system of HBsAg diagnostic kits in Korea and lead to quality improvement of diagnostic kits.

Clinical significance of genotypes and precore/basal core promoter mutations in HBV related chronic liver disease patients in North India

PURPOSE

Data on genotypes, basal core promoter (BCP) and precore mutants of hepatitis B virus and their association with different HBV related liver disease have been studied inadequately and are controversial. Thus, the aim of this study was to determine the incidence of BCP and precore HBV mutants and their relationship with HBV genotype and different stages of HBV related liver disease in North Indian patients.

METHODS

A total 273 patients with different stages of HBV related liver diseases were enrolled. Nested polymerase chain reaction (PCR) was used to amplify the BCP/PC regions. RFLP and direct sequencing were performed to validate the mutations identified in these regions. HBV genotyping was accomplished by multiplex PCR.

RESULTS

Genotype D was the predominant genotype found in each of the various HBV related liver diseases. The BCP mutation was found significantly more often in inactive carriers and compensated cirrhosis as compared to the other groups. The BCP mutation was present in 29.1% of patients with genotype D versus 17.1% with genotype A (P = 0.001). The precore mutation was also more frequently observed with genotype D compared with genotype A (36.9 vs. 4.8%, P = 0.0007).

CONCLUSION

Genotype D is predominant in North Indian patients. The BCP and precore mutations occur in one-third of HBV positive patients in association with the genotype D. We did not find any correlation with severity of liver disease with genotypes and mutations.

Bioinformatic analysis of the hepadnavirus e-antigen and its precursor identifies remarkable sequence conservation in all orthohepadnaviruses

The hepatitis B e-antigen (HBeAg) is a non-particulate secretory protein expressed by all viruses within the family Hepadnaviridae. It is not essential for viral assembly or replication but is important for establishment of persistent infection in vivo. Although the exact mechanism(s) by which the HBeAg manifests chronicity are unclear, the HBeAg elicits both humoral and cell-mediated immunity, down-regulates the innate immune response to infection, as well as functioning as a T cell tolerogen and regulating the immune response to the intracellular nucleocapsid. A bioinformatics approach was used to show that the HBeAg and precursory genetic codes share remarkable sequence conservation in all mammalian-infecting hepadnaviruses, irrespective of host, genotype, or geographic origin. Whilst much of this sequence conservation was within key immunomodulatory epitopes, highest conservation was observed at the unique HBeAg N-terminus, suggesting this sequence in particular may play an important role in HBeAg function.