Effects of a naturally occurring mutation in the hepatitis B virus basal core promoter on precore gene expression and viral replication

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.

Mutation Reporter Tool: an online tool to interrogate loci of interest, with its utility demonstrated using hepatitis B virus

Background

An online tool, which extracts and summarises nucleotide or amino acid sequence data at specified loci of interest, was developed and tested using the basic core promoter/precore (BCP/PC) region of the hepatitis B virus (HBV). The tool is aimed at researchers without specialist computer skills.

Methods

The tool consists of a web-based front-end, with a CGI script, which runs Python code to generate an output web-page. The Python code searches the input sequence data for a specified anchor motif, after which it generates summary tables and graphs of residue and motif distributions.

Results

After the user provides an input file in FASTA format containing aligned sequence data (nucleotides or amino acids) and specifies an anchor motif at a known coordinate, the tool summarizes the nucleotides or amino acids at the specified loci, their frequency and analyzes motif patterns of the loci.The tool can output a graph that displays the frequency of mutations relative to a reference sequence. The tool was used to analyze the BCP/PC region of HBV belonging to subgenotypes A1, A2 and subgenotype D and to serotype HBV. The “Discovery Mode” ignores conserved loci and assists in identifying potential loci of interest.

Conclusions

Although HBV was used to demonstrate the utility of the Mutation Reporter Tool, the tool has wide application as it is genome-agnostic: nucleotide or amino acid sequence data from any organism can be processed. Rapid characterisation of many sequences can be achieved easily when the loci of interest are known. The tool is available online, without charge, at http://hvdr.bioinf.wits.ac.za/tools

Hepatitis B e antigen-suppressing mutations enhance the replication efficiency of adefovir-resistant hepatitis B virus strains

Hepatitis B e antigen (HBeAg) negative hepatitis B virus (HBV) infections caused by precore (PC) or basal core promoter (BCP) mutations are associated with disease progression and complications. PC or BCP mutations may enhance the replication capacity of distinct drug-resistance-associated polymerase mutations, but their effect on adefovir-resistant HBV mutants is unclear. Importantly, BCP mutations were an independent risk factor for virological breakthrough in lamivudine-resistant patients treated with adefovir. We aimed at addressing the functional consequences of PC and BCP mutations on the replication and drug susceptibility of adefovir-resistant HBV mutants. Therefore, HBV constructs with wild type (WT) or adefovir-resistant rtN236T, rtA181V and rtA181T mutations, with or without concomitant PC or BCP mutations, were analysed in vitro using molecular assays. The adefovir-resistant polymerase mutations rtN236T, rtA181V and rtA181T showed a drastically reduced viral replication compared with WT. Interestingly, additional PC or BCP mutations enhanced the reduced replication efficacy of adefovir-resistant constructs and restored HBV replication to WT level. HBV rtA181T mutants displayed abolished hepatitis B surface antigen (HBsAg) secretion, owing to a sW172* stop codon in the overlapping envelope gene. All rtN236T- or rtA181V/T-containing constructs, regardless of concomitant PC or BCP mutations, were resistant to adefovir, but remained susceptible to telbivudine, entecavir and tenofovir. In conclusion, adefovir drug resistance mutations reduced viral replication, which can be significantly increased by additional HBeAg-suppressing PC or BCP mutations. Because increased HBV replication in HBeAg-negative patients has been associated with an unfavourable clinical course, close monitoring appears indispensable during adefovir treatment in HBeAg-negative patients.

Comparative analysis of viral genomes from acute and chronic hepatitis B reveals novel variants associated with a lower rate of chronicity

Infection with the hepatitis B virus (HBV) may lead to an acute or chronic infection. It is generally accepted that the clinical outcome of infection depends on the balance between host immunity and viral survival strategies. In order to persist, the virus needs to have a high rate of replication and some immune-escape capabilities. Hence, HBVs lacking these properties are likely to be eliminated more rapidly by the host, leading to a lower rate of chronicity. To test this hypothesis, 177 HBV genomes from acute non-fulminant cases and 1,149 from chronic cases were retrieved from GenBank for comparative analysis. Selection of candidate nucleotides associated with the disease state was done using random guess cut-off and the Bonferroni correction. Five significant nucleotides were detected using this filtering step. Their predictive values were assessed using the support vector machine classification with five-fold cross-validation. The average prediction accuracy was 61% ± 1%, with a sensitivity of 24% ± 1%, specificity of 98% ± 1%, positive predictive value of 92% ± 4% and negative predictive value of 56% ± 1%. BCP/X, enhancer I and surface/polymerase variants were found to be associated almost exclusively with acute hepatitis. These HBV variants are novel potential markers for non-progression to chronic hepatitis.

Direct acting antivirals for the treatment of chronic viral hepatitis

The development and evaluation of antiviral agents through carefully designed clinical trials over the last 25 years have heralded a new dawn in the treatment of patients chronically infected with the hepatitis B and C viruses, but not so for the D virus (HBV, HCV, and HDV). The introduction of direct acting antivirals (DDAs) for the treatment of HBV carriers has permitted the long-term use of these compounds for the continuous suppression of viral replication, whilst in the case of HCV in combination with the standard of care [SOC, pegylated interferon (PegIFN), and ribavirin] sustained virological responses (SVRs) have been achieved with increasing frequency. Progress in the case of HDV has been slow and lacking in significant breakthroughs.This paper aims to summarise the current state of play in treatment approaches for chonic viral hepatitis patients and future perspectives.

HBV Subgenotype C2 Infection, A1762T/G1764A Mutations May Contribute To Hepatocellular Carcinoma with Cirrhosis in Southeast China

BACKGROUND

To glean insights into the relationship among hepatitis B virus (HBV) genotype/subgenotypes, A1762T/G1764A mutations and advanced liver disease such as liver cirrhosis (LC) and hepatocellular carcinoma (HCC) in Southeast China.

METHODS

A case-control study was performed, consisting of chronic hepatitis B (CHB) patients (n=160), LC patients (n=150), and HCC patients (n=156). Fluorescence quantitative polymerase chain reaction (FQ-PCR) was used to detect A1762T/G1764A mutations. HBV genotypes/subgenotypes were determined by multiplex PCR. All patients' clinical data was systematically collected from the hospital records.

RESULTS

Our study revealed HBV genotypes C (63.95%) and B (33.69%) were predominant in chronically infected patients, subgenotype B2, C2 and C1 were the major subgenotypes. Both subgenotype C2 infection and A1762T/G1764A mutations were associated with LC and HCC with cirrhosis, subgenotype C2 (OR=2.033, 95%CI=1.246-3.323, P=0.003 for LC vs CHB; OR=3.247, 95%CI=1.742-6.096, P=0.001 for HCC with cirrhosis vs CHB; respectively ), and A1762T/G1764A mutations (OR=1.914, 95%CI=1.188-3.085, P=0.005 for LC vs CHB; OR=2.996, 95%CI=1.683-5.353, P=0.002 for HCC with cirrhosis vs CHB; respectively), but no differences in the frequencies of both variants between LC and HCC with cirrhosis groups were found.

CONCLUSIONS

HBV subgenotype C2 infection and A1762T/G1764A mutations are both risk factors of LC and HCC with cirrhosis development in the patients with CHB in Southeast China, but all no helpful for predicting HCC development in LC patients.

T1846 and A/G1913 are associated with acute on chronic liver failure in patients infected with hepatitis B virus genotypes B and C

The aim of this study was to determine whether mutations in the hepatitis B virus (HBV) genome are associated with the onset of acute on chronic liver failure (ACLF). For the longitudinal study, full-length HBV genomes were cloned and sequenced from four ACLF patients and compared with sequences from matching samples collected before ACLF. For the cross-sectional study, 166 serum samples were obtained, including 49 samples from patients with ACLF. The results of longitudinal study showed that C53T, A1846T, and G1896A were the most common mutations in association with ACLF. In the cross-sectional study 61.2% patients with ACLF presented with T1846, which was higher than patients with chronic hepatitis B (CHB) (11.1%), liver cirrhosis (LC) (31.1%), and hepatocellular carcinoma (HCC) (33.3%). Prevalence of A/G1913 was 42.9% in patients with ACLF, also higher than patients with CHB (2.2%), LC (17.8%), and HCC (11.1%). There were no differences in HBV genotype and patients' HBeAg status among patients with ACLF, LC, and HCC. However, prevalence of T1846 was much higher in patients infected with genotype B (57.1%) than genotype C (30.4%). A/G1913 was higher in HBeAg negative patients (28%) than HBeAg positive patients (13.2%). Results of a multivariable analysis showed that T1846 and A/G1913 were independent factors for ACLF (OR = 3.373 and 4.244, respectively). Interestingly, T1846 destroys an ATG codon of a small open reading frame in the preC region, which may increase core protein expression. We conclude that T1846 and A/G1913 in the preC/C gene are closely associated with ACLF.

Hepatitis B precore protein: pathogenic potential and therapeutic promise

Hepatitis B virus (HBV), a small and economically packaged double-stranded DNA virus, represents an enormous global health care burden. In spite of an effective vaccine, HBV is endemic in many countries. Chronic hepatitis B (CHB) results in the development of significant clinical outcomes such as liver disease and hepatocellular carcinoma (HCC), which are associated with high mortality rates. HBV is a non-cytopathic virus, with the host's immune response responsible for the associated liver damage. Indeed, HBV appears to be a master of manipulating and modulating the immune response to achieve persistent and chronic infection. The HBV precore protein or hepatitis B e antigen (HBeAg) is a key viral protein involved in these processes, for instance though the down-regulation of the innate immune response. The development of new therapies that target viral proteins, such as HBeAg, which regulates of the immune system, may offer a new wave of potential therapeutics to circumvent progression to CHB and liver disease.

Hepatitis B virus basal core promoter mutations A1762T/G1764A are associated with genotype C and a low serum HBsAg level in chronically-infected HBeAg-positive Chinese patients

The present study was aimed to obtain baseline information of basal core promoter A1762T/G1764A and precore G1896A mutations of hepatitis B virus (HBV) in 192 HBeAg-positive chronically-infected Chinese patients, who were potential candidates for antiviral treatment. The detection of these mutations (including minor mutant subpopulations) was achieved by direct sequencing, whose sensitivity for minor mutant subpopulations identification was confirmed by clone sequencing. Patients enrolled were infected with either genotype B (46.35%) or C (53.65%) HBV identified by routine tests in our laboratory. The A1762T/G1764A or G1896A mutations were detected in 125specimens (125/192, 65.10%), in which 77 (77/125, 61.60%) existed as subpopulations. The A1762T/G1764A mutations were found to be more prevalent in genotype C than that in genotype B HBV [62.14% (64/103) vs. 20.22% (18/89), P<0.0001]. There is no statistically significant link between G1896A and genotypes. The emergence of A1762T/G1764A mutations was also found to be associated with an older age, an elevated ALT/AST level, and a lower HBsAg level in serum [wild-type vs. mutant: 4.57 (3.46-5.42) vs. 3.93 (2.51-5.36), P<0.0001]. In conclusion, HBV basal core promoter mutations A1762T/G1764A are associated with genotype C and a low serum HBsAg level in chronically-infected HBeAg-positive Chinese patients.

Molecular characterization of hepatitis B virus X gene in chronic hepatitis B patients

Background

HBV-X protein is associated with the pathogenesis of HBV related diseases, specially in hepatocellular carcinomas of chronic patients. Genetic variability of the X gene includes genotypic specific variations and mutations emerging during chronic infection. Its coding sequence overlaps important regions for virus replication, including the basal core promoter. Differences in the X gene may have implications in biological functions of the protein and thus, affect the evolution of the disease. There are controversial results about the consequences of mutations in this region and their relationship with pathogenesis. The purpose of this work was to describe the diversity of HBV-X gene in chronic hepatitis patients infected with different genotypes, according to liver disease.

Methods

HBV-X gene was sequenced from chronic hepatitis B patient samples, analyzed by phylogeny and genotyped. Nucleotide and aminoacid diversity was determined calculating intragenetic distances. Mutations at 127, 130 and 131 aminoacids were considered in relation to liver disease.

Results

The most prevalent genotype detected in this cohort was F (F1 and F4), followed by D and A. Most of the samples corresponding to genotypes A and F1 were HBeAg(+) and for genotypes D and F4, HBeAg(−) samples were represented in a higher percentage. Intragenetic distance values were higher in HBeAg(−) than in positive samples for all genotypes, and lower in overlapped regions, compared to single codification ones. Nucleotide and aminoacid diversities were higher in HBeAg(−), than in HBeAg(+) samples.

Conclusions

Independently of the infecting genotypes, mutations at any of 127, 130 and/or 131 aminoacid positions and HBeAg(−) status were associated with mild liver disease in this cohort.

Quantitative dynamics of hepatitis B basal core promoter and precore mutants before and after HBeAg seroconversion

BACKGROUND & AIMS

Hepatitis B e antigen (HBeAg) seroconversion is an important clinical and virological "landmark" during chronic hepatitis B virus (HBV) infection. Mutant viruses carrying the precore G1896A and/or the basal core promoter (BCP) A1762T/G1764A mutations are associated with HBeAg seroconversion. However, the exact role of these mutants in HBeAg seroconversion remains unclear, partly because the evolution of these mutant viruses before and after seroconversion has not been well studied.

METHODS

Using our novel mutant quantification methods, the percentage of the mutant viruses was analyzed both cross-sectionally and longitudinally, before and after seroconversion.

RESULTS

Cross-sectional analysis showed that the percentage of both precore and BCP mutants gradually increased with age in the HBeAg-positive population. Follow-up of 18 HBeAg-positive patients revealed that the mutant percentage may stay low and stable for many years, followed by a steady increase in the percentage of G1896A and/or A1762T/G1764A mutants, from <10% to 50-100%, within about 3 years prior to seroconversion. In all cases, increase of mutant percentage was preceded or accompanied by elevated serum alanine aminotransferase. After the seroconversion, the mutant percentage could remain high or decrease significantly, sometimes to below 20%.

CONCLUSIONS

Levels of G1896A and A1762T/G1764A mutants (of genotypes B and C) in the HBeAg-positive patients may predict the time of HBeAg seroconversion. The dominance of these mutants in the HBeAg-positive phase is more likely the result of immune selection rather than the enhanced replication capability of the mutants. However, anti-HBe antibody may not be a major selection force for these mutants.

Mutational complex genotype of the hepatitis B virus X /precore regions as a novel predictive marker for hepatocellular carcinoma

This study explored the combined effect of number and pattern of mutations in the X/precore regions of the hepatitis B virus (HBV) genome, mutational complex genotype (MCG), on hepatocellular carcinoma (HCC) development. Sequence variations were determined by direct sequencing and multiplex restriction fragment mass polymorphism analysis in 150 age-, sex- and hepatitis B e antigen (HBeAg) status-matched patients with and without HCC. In addition, a longitudinal study and an external validation of MCG were conducted. All were HBV subgenotype C2. Eight high-frequency mutations (G1613A, C1653T, T1753V, A1762T, G1764A, A1846T, G1896A and G1899A) were significantly associated with HCC. Whereas C1653T, T1753V, G1764A and A1846T were independent mutational factors for HCC, the significance of these individual mutations was negligible when analyzed with all clinico-virological variables. The total number of mutations was the only independent viral factor for HCC, irrespective of HBeAg status. There was a significant dose-risk relationship between the number of mutations and HCC, in which high risks for HCC were associated with mutation numbers ≥ 6. Pattern analysis of the mutations revealed disparity in distribution among the top seven high-risk mutation combination patterns, which accounted for 40 and 2.7% of HCC and non-HCC cases, respectively. The predictive accuracy of the high-risk mutations for HCC was similar to that of α-fetoprotein. Longitudinal and external validation studies also supported the association of mutation number with HCC development. MCG in the HBV X/precore regions is a risk indicator for HCC, and might serve as a new guide to the HCC screening scheme for chronic HBV carriers.

Interaction of mutant hepatitis B X protein with p53 tumor suppressor protein affects both transcription and cell survival

This study examines the differential activities between wild-type Hepatitis B virus X protein (WtHBx) and a mutant HBx (MutHBx), which bears a hotspot mutation at nucleotides 1,762 and 1,764, resulting in a lysine to methionine change at codon 130 and a valine to isoleucine change at codon 131. This mutation leads to hepatocellular carcinoma, and we evaluated how WtHBx and MutHBx proteins differ in their interactions with the p53 tumor suppressor protein. This was experimentally addressed through co-immunoprecipitation assays examining the interaction between WtHBx and MutHBx proteins with p53, reporter assays determining the impact of the HBx proteins on p53-mediated gene transcription, and clonogenic survival assays evaluating the effect of HBx on cell growth in lines of varying p53-expression status. Both WtHBx and MutHBx proteins physically interact with p53 protein, but have different impacts on p53-mediated gene transcription. WtHBx did not effect p53-mediated gene transcription, whereas MutHBx inhibited it (P < 0.01). MutHBx inhibited colony formation in p53-proficient cells (P < 0.01), but not p53-deficient lines. Although both HBx proteins interact with p53, they affect p53-mediated gene transcription differently. WtHBx has no effect, whereas MutHBx inhibits it. In clonogenic survival assays, MutHBx inhibited cell growth in p53-proficient cells rather than enhanced it. This suggests that for MutHBx to behave oncogenically, the p53 pathway must be crippled or absent. This study has identified some important novel ways in which WtHBx and MutHBx differentially interact with p53 and this could begin to form the cellular explanation for the association between this particular mutant and liver cancer.

Antiviral resistance mutations potentiate HBV surface antigen-induced transcription of hfgl2 prothrombinase gene

Antiviral resistance mutations in the hepatitis B virus (HBV) polymerase (pol) gene have been demonstrated to play an important role in the progression of liver disease and the development of hepatocellular carcinoma. The HBV pol gene overlaps the S gene encoding surface antigen (HBsAg). Previous studies from our laboratory have shown that HBV core protein (HBc) and X protein (HBx), but not HBV S protein (HBs), promote hfgl2 prothrombinase transcription. To investigate whether the nucleotide (nucleoside)-induced resistant mutations of HBs potentiate transcription of hfgl2 prothrombinase gene, we generated two mutant HB expression constructs harboring rtM204V/sI195M or rtM204I/sW196L mutations. Two mutant expression plasmids were co-transfected with hfgl2 promoter luciferase-reporter plasmids and β-galactosidase plasmid in CHO cells and HepG2 cells, respectively. Luciferase assay showed that the rtM204I/V mutant HBs could activate the transcription of hfgl2 promoter compared with the wild type HBs. Site-directed mutagenesis and further experiment (co-transfection) demonstrated that transcription factor Ets translocated to its cognate cis-element in the hfgl2 promoter. The results show that mutated HBs caused by antiviral drug resistance induce transcription of the hfgl2 gene dependent on the transcription factor Ets.

Impact of hepatitis B e antigen-suppressing mutations on the replication efficiency of entecavir-resistant hepatitis B virus strains

Hepatitis B e antigen (HBeAg)-negative hepatitis B commonly requires long-term treatment with nucleos(t)ide analogues aiming at persistently suppressing hepatitis B virus (HBV) replication to halt progression of liver disease and prevent complications. Entecavir (ETV) is widely used in HBeAg-negative hepatitis B, but distinct HBV polymerase mutations can confer resistance against ETV, in conjunction with lamivudine resistance. Precore (PC) and basal core promoter (BCP) mutations that underlie HBeAg-negativity enhance replication of lamivudine-resistant mutants. To comprehensively analyse the impact of PC or BCP mutations on viral replication of ETV-resistant HBV mutants, replication-competent HBV constructs were generated harbouring lamivudine resistance (rtM204V/rtL180M, rtM204I) plus ETV resistance (rtS202G, rtS202I or rtT184G) on wild-type (WT)-, PC- and BCP-backgrounds. Functional consequences on viral fitness and susceptibility to antivirals were assessed in vitro. The presence of any ETV resistance drastically reduced viral replication when compared to WT HBV. In rtS202G mutants (plus lamivudine resistance), addition of either PC or BCP mutations moderately enhanced the reduced replication, without reaching WT HBV levels. In rtS202I or rtT184G mutants, PC and BCP mutations did not significantly improve viral fitness. All ETV-resistant constructs, independently of PC or BCP mutations, showed resistance towards ETV and lamivudine, but remained susceptible to tenofovir. Our data demonstrate that HBeAg-suppressing PC or BCP mutations cannot restore the strongly reduced replicative capacity of ETV-resistant HBV mutants to WT level, although they moderately increase replication of rtS202G combination mutants. ETV resistance thereby differs from lamivudine resistance alone, corroborating that ETV is in short term a safe option for HBeAg-negative patients.

Current status of liver transplantation for hepatitis B virus

The management of hepatitis B in liver transplantation has evolved significantly over the past 2 decades. Introduction of hepatitis B immune globulin and subsequently nucleos(t)ide analogues has revolutionized transplantation for hepatitis B virus (HBV), increasing survival for patients transplanted for this indication. With the availability of new and potent antivirals for HBV, the need for liver transplant should continue to decrease in the coming years. Moreover, the newer antivirals with high resistance barriers will allow effective long-term viral prophylaxis and therefore, prevention of recurrence.

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.

Hepatitis B virus core promoter mutations contribute to hepatocarcinogenesis by deregulating SKP2 and its target, p21

BACKGROUND & AIMS

Clinical studies have associated hepatitis B virus core promoter (CP) mutations with an increased risk of hepatocellular carcinoma. The CP region overlaps with the HBV X (HBx) gene, which has been implicated in hepatocarcinogenesis. The cyclin kinase inhibitor p21WAF1/CIP1 is an important regulator of cell cycle progression and proliferation. We determined whether HBx mutants that result from mutations in the CP deregulate p21 and these processes.

METHODS

We constructed a series of HBx mutants with changes in the CP region that correspond to A1762T/G1764A (TA), T1753A, T1768A, or a combination of these (combo) and expressed them, along with wild-type HBx under control of its endogenous promoter, in primary human hepatocytes (PHHs) and HepG2 cells. We then analyzed the effects of CP mutations on expression and degradation of p21 and the effects on cell cycle progression and proliferation.

RESULTS

The combo mutant decreased levels of p21 and increased cyclin E expression in PHHs and HepG2 cells. The combo mutant, but not HBx with single or double CP mutations, accelerated p21 degradation in HepG2 cells. The combo mutant increased expression of S-phase kinase-associated protein 2 (SKP2) in PHHs and Huh7 cells. Silencing of SKP2 abrogated the effects of CP mutations on p21 expression. The kinetics of p21 expression correlated with changes in cell cycle distribution. The combo mutant accelerated cell cycle progression; p21 overexpression restored G1 arrest.

CONCLUSIONS

HBx mutants with changes that correspond to a combination of CP mutations up-regulate SKP2, which then down-regulates p21 via ubiquitin-mediated proteasomal degradation. CP mutations might increase the risk of hepatocellular carcinoma via this pathway.

Role of hepatitis B virus base core and precore/core promoter mutations on hepatocellular carcinoma in untreated older genotype C Chinese patients

The aim of the study was to investigate the prevalence of mutations of basal core promoter (BCP) and precore (PreC) region of hepatitis B virus (HBV) and their association with hepatocellular carcinoma. A total of 341 untreated older HBV patients were divided into three groups: chronic hepatitis B (CHB, 185), cirrhotic hepatocellular carcinoma (LC-HCC, 113) and non-cirrhotic hepatocellular carcinoma (non-LC-HCC, 43). HBV BCP and PreC mutations and genotypes were determined by direct sequencing. Using univariate analysis, age (≥ 45 years), single mutations including A1896 and A1899 and multiple mutations T1762/A1764 + A1896, T1762/A1764 + A1899 and T1762/A1764 + A1896 + A1899 were more frequently detected in LC-HCC and non-LC-HCC patients than in CHB patients. BCP T1762/A1764 mutations were highly detected in LC-HCC patients than in CHB patients. Multivariate logistic regression analysis (adjusted for age and gender) revealed that among HBeAg-positive patients, BCP T1762/A1764 mutations (OR, 5.975; P = 0.05), PreC A1899 mutation (OR, 4.180; P = 0.013) and multiple mutations T1762/A1764 + A1899 (OR, 6.408; P = 0.006) were independently associated with the development of LC-HCC; PreC A1899 mutation (OR, 7.347; P = 0.034) was also independently associated with the development of non-LC-HCC. On the other hand, among HBeAg-negative patients, PreC A1896 mutation (OR, 5.176; P = 0.002) and multiple mutations T1762/A1764 + A1896 (OR, 4.149; P = 0.007) were independently associated with the development of non-LC-HCC. These results indicated that older age (≥ 45 years) was associated with LC-HCC and non-LC-HCC development. BCP T1762/A1764 mutations and PreC A1899 mutation were associated with the LC-HCC development in HBeAg-positive patients. PreC A1896 mutation was associated with the non-LC-HCC development in HBeAg-negative patients.

Effects of hepatitis B virus precore and basal core promoter mutations on the expression of viral antigens: genotype B vs C

Hepatitis B virus (HBV) genotypes/mutants are known to affect natural outcomes. The virologic differences among HBV genotype, precore and basal core promoter (BCP) mutations were investigated. HBV strains were isolated from 18 hepatitis B e antigen (HBeAg)-positive patients (nine genotype B and nine genotype C). All had precore and BCP wild-type sequences. After cloning of full-length HBV genome, the effects of viral genotype, precore and BCP mutations singly or additively on the expression of viral DNA and antigens were investigated by mutagenesis and transfection assays in Huh7 cells. Significant findings included the following: (i) expression of intracellular core protein increased when precore or BCP mutation was introduced in genotype C strains; (ii) expression of intracellular surface protein was lower in genotype C precore wild-type strain compared with genotype B; (iii) precore mutation was associated with a lower extracellular expression level of HBV DNA; (iv) secretion of hepatitis B surface antigen in genotype C was lower than that in genotype B; and (v) secretion of HBeAg in genotype B was lower than that in genotype C. No additive effect was observed by combining precore and BCP mutations. Hence, HBV genotype and precore/BCP mutations correlate with intrahepatic expression of viral antigens in vitro.

Clinical and virological characteristics of chronic hepatitis B with concurrent hepatitis B E antigen and antibody detection

The concurrent detection of hepatitis B e antigen (HBeAg) and its corresponding antibody (anti-HBe) in patients with chronic hepatitis B virus (HBV) infection is well established but the clinical features remain poorly understood. Demographic information, clinical and laboratory data were collected from 1624 consecutive inpatient records of patients with chronic hepatitis B. Viral genotype, basic core promoter and precore mutations were determined by direct sequencing. In vitro HBeAg and anti-HBe binding experiments were conducted with three pairs of HBeAg-positive and anti-HBe-positive serum samples, which were mixed at variable ratios and incubated at 37°C for 3-24h. Of the 1624 chronic patients, 169 (10.4%) had concurrent HBeAg and anti-HBe positivity, and this was associated with intermediate age and HBV-DNA load, higher alanine aminotransferase level and more pronounced liver damage compared with HBeAg-positive or anti-HBe-positive patients alone. HBeAg and anti-HBe titres (median and interquartile range, S/CO) in the concurrent positive group were 4.2 (1.8-9.6) and 0.54 (0.27-0.72), which were closer to their respective cut-off values than those of HBeAg-positive or anti-HBe-positive groups alone. For the cases successfully sequenced, 110/134 (82.1%) harboured T1762/A1764 or/and A1896 mutants. The binding experiments showed that HBeAg and anti-HBe could be concurrently observed provided an optimal ratio (HBeAg to anti-HBe) was chosen. In antiviral treatment-naive patients, concurrence of HBeAg and anti-HBe was not uncommon, and such patients had profound liver disease. An optimal ratio between HBeAg and anti-HBe led to their concurrent detection when sera were tested by sensitive assays.

Distinct mutant hepatitis B virus genomes, with alterations in all four open reading frames, in a single South African hepatocellular carcinoma patient

Sequence variation of hepatitis B virus (HBV) can influence the replication, antigen expression and pathogenicity of the virus. We report on the mutational analysis of HBV performed in a 28-year-old Black South African female diagnosed with HBV-induced hepatocellular carcinoma. Full-genome amplification and DNA sequencing of HBV was carried out. Five distinct complete genomic clones were described with extensive genomic and intragenic variation. Phylogenetic analysis revealed that all five clones belonged to subgenotype A1 and that there were at least four virus populations with genomes of different lengths ranging from 3194 to 3253 base pairs. In this particular patient, four major characteristic features, not previously reported to occur simultaneously in HBV isolated from a single patient, were observed. Firstly, all the clones harboured a 13 base pair deletion and a 45 base pair insertion in the basic core promoter (BCP). Secondly, a 37 base pair insertion in the core gene with three adjacent single nucleotide deletions were observed. Thirdly, premature S gene stop codons were observed in some clones and lastly X gene initiation codon mutations were also observed. The complex nature of the mutations in the HBV isolated from this single patient may have contributed to the early onset of hepatocarcinogenesis.

The YMDD and rtA194T mutations result in decreased replication capacity in wild-type HBV as well as in HBV with precore and basal core promoter mutations

BACKGROUND

A recent study indicated that addition of the hepatitis B e antigen (HBeAg) precore (PC) or basal core promoter (BCP) mutations to wild-type HBV offset the reduced replication of the HBV polymerase rtA194T±rtL180M+rtM204V mutations. rtA194T was reportedly associated with tenofovir resistance. We investigated these findings in genotype D HBV, where both PC and BCP naturally occur in vivo.

METHODS

A plasmid containing a wild-type 1.3 genome length genotype D HBV laboratory strain was used as a parent for PC, BCP, rtA194T±rtL180M+rtM204V, rtL180M+rtM204V and rtM204I mutants. Viral replication was evaluated by Southern blot analysis of intracellular HBV core DNA following transient transfection of HepG2 cells. Drug susceptibility was evaluated by quantitative PCR of intracellular HBV DNA.

RESULTS

PC and BCP mutations each increased HBV DNA replication by approximately 200% over wild-type. rtA194T reduced replication by <40%, whereas rtL180M+rtM204V, rtL180M+rtA194T+rtM204V or rtM204I each reduced by >75% from their respective wild-type, PC or BCP genome backbone (P<0.05). The enhanced replication by PC or BCP offset the reduction by rtA194T; however, the other reverse transcriptase (RT) mutations in PC or BCP backbones remained significantly lower than wild-type (P<0.05). Regardless of the backbone, rtA194T±rtL180M+rtM204V remained susceptible to tenofovir in vitro. rtA194T alone remained susceptible to lamivudine, while rtL180M+rtM204V and rtL180M+rtA194T+rtM204V were resistant.

CONCLUSIONS

PC or BCP mutations increased HBV DNA replication, offset the decreased replication by rtA194T alone, but they did not fully rescue the impaired replication conferred by other RT mutations as compared with wild-type. rtA194T±rtL180M+rtM204V did not confer tenofovir resistance.

Hepatitis B e Antigen Negative Chronic Hepatitis in Indian Patients : A Reality

BACKGROUND

Hepatitis B e antigen negative chronic hepatitis (e(-) CHB) with detectable levels of hepatitis B virus DNA (HBV DNA) in serum has been reported in cases from Asia. This study was undertaken to find out prevalence e(-)CHB and to correlate its presence with the clinical status and severity of the illness in cases of chronic liver disease in India.

METHODS

All patients of infective hepatitis, who were hepatitis B surface antigen (HBsAg) positive by enzyme-linked immunosorbent assay (ELISA), were evaluated with liver function tests and HBeAg and antiHBe antibody studies. Polymerase chain reaction (PCR) test was carried out to detect HBV DNA qualitatively.

RESULT

Out of 2064 samples tested by ELISA, 429 (20.78 %) were HBsAg positive. HBV DNA (qualitative) was performed on all 429 patients and 74 (17.2%) were HBV DNA positive. Of these only 42 (56.75 %) tested positive for HBeAg. Overall, 8.3 % of HBeAg negative patients (32/384) were viraemic with evidence of chronic liver disease/clinical cirrhosis and alteration of transaminase levels, while three cases (0.84 %) HBeAg positive cases did not show presence of HBV DNA.

CONCLUSION

This study shows e(-)CHB prevalence rate of 8.3% in patients with HBV infection in India. Since HBeAg negative patients had detectable levels of HBV DNA as seen in HBeAg positive patients, benefit of antiviral therapy should be given to them. Population studies on e(-) CHB cases are needed to determine its true prevalence, natural course and response to therapy.

Hepatitis B virus genotype C isolates with wild-type core promoter sequence replicate less efficiently than genotype B isolates but possess higher virion secretion capacity

Infection by hepatitis B virus (HBV) genotype C is associated with a prolonged viremic phase, delayed hepatitis B e antigen (HBeAg) seroconversion, and an increased incidence of liver cirrhosis and hepatocellular carcinoma compared with genotype B infection. Genotype C is also associated with the more frequent emergence of core promoter mutations, which increase genome replication and are independently associated with poor clinical outcomes. We amplified full-length HBV genomes from serum samples from Chinese and U. S. patients with chronic HBV infection and transfected circularized genome pools or dimeric constructs of individual clones into Huh7 cells. The two genotypes could be differentiated by Western blot analysis due to the reactivities of M and L proteins toward a monoclonal pre-S2 antibody and slightly different S-protein mobilities. Great variability in replication capacity was observed for both genotypes. The A1762T/G1764A core promoter mutations were prevalent in genotype C isolates and correlated with increased replication capacity, while the A1752G/T mutation frequently found in genotype B isolates correlated with a low replication capacity. Importantly, most genotype C isolates with wild-type core promoter sequence replicated less efficiently than the corresponding genotype B isolates due to less efficient transcription of the 3.5-kb RNA. However, genotype C isolates often displayed more efficient virion secretion. We propose that the low intracellular levels of viral DNA and core protein of wild-type genotype C delay immune clearance and trigger the subsequent emergence of A1762T/G1764A core promoter mutations to upregulate replication; efficient virion secretion compensates for the low replication capacity to ensure the establishment of persistent infection by genotype C.

Viral level is an indicator of long-term outcome of hepatitis B virus e antigen-negative carriers with persistently normal serum alanine aminotransferase levels

The association between viral level and the long-term outcomes of hepatitis B virus (HBV) carriers who test negative for hepatitis B virus e antigen (HBeAg) but have persistently normal serum alanine aminotransferase levels (PNALT) remains unclear. We examined hepatocarcinogenesis, hepatitis reactivation, predictive factors and the time course of HBV DNA levels during follow-up in 104 HBeAg-negative Japanese carriers with PNALT. During a mean follow-up period of 6.4 ± 3.4 years, 5 patients (4.8%) had hepatocarcinogenesis and 14 (13.5%) had hepatitis reactivation. At 5 and 10 years, the cumulative rates of hepatocarcinogenesis were 2.4% and 9.9%, while those of hepatitis activation were 13.7% and 15.5%, respectively. An HBV DNA level of ≥5 log10  copies/mL was the sole predictor of hepatocarcinogenesis with a univariate analysis. An HBV DNA level of ≥5 log10  copies/mL and an alanine aminotransferase (ALT) level of >20 to ≤40 IU/L were independent predictors of hepatitis reactivation in a Cox model. Because there was no association between hepatocarcinogenesis and ALT activity, the HBV DNA level was considered an essential predictor. In addition, the baseline HBV DNA level was related to the future level and was not subject to wide fluctuations. Our results showed that an HBV DNA level of ≥5 log10  copies/mL predicts subsequent hepatocarcinogenesis and hepatitis reactivation in HBeAg-negative carriers with PNALT. As the baseline HBV DNA level reflects the future level, appropriate clinical management according to the viral level is expected to decrease future risk.

A336C/A336T/T337C variations in HBV core gene and spontaneous hepatitis B e antigen loss in chronic hepatitis B patients

BACKGROUND

A336C/A336T/T337C variations in HBV core gene were demonstrated to relate to the decreases in serum HBV DNA levels and HBV replication in chronic hepatitis B patients. Usually the drastic decrease in serum HBV DNA levels correlates with spontaneous HBeAg loss during the course of chronic HBV infection. The aim of the present study was to investigate whether there was correlation between A336C/A336T/T337C variations and spontaneous HBeAg loss

METHODOLOGY/PRINCIPAL FINDINGS

A modified PCR-RFLP assay and ELISA were adopted to determine A336C/A336T/T337C variations and serum HBeAg levels in chronic hepatitis B patients without any antiviral therapy, respectively, whereas G1896A variation and HBV genotype were detected using Taqman-PCR assay. RFLP pattern C, E, G, C/G mixture and a new pattern C' were found in this study. A336C/A336T/T337C variations occurred in 40/166(24.1%) chronic hepatitis B patients. Chi-square test showed that C336/T336/C337 variants was more frequent in chronic hepatitis B patients with A1896 variants than those with the wild type G1896 (χ2 = 4.7, P = 0.03), and moreover, patients with C336/T336/C337 variants had a significantly lower HBeAg-positive percentage than those with the wild type A336/T337. Binary logistic regression identified genotype B (OR = 4.1, 95%CI = 1.8-9.2, P = 0.001), the presence of C336/T336/C337 variants (OR = 3.2, 95%CI = 1.2-8.5, P = 0.02) and A1896 variants (OR = 7.8, 95%CI = 3.3-18.5, P < 0.001) as independent factors associated with spontaneous HBeAg loss.

CONCLUSION/SIGNIFICANCE

A336C/A336T/T337C were naturally occurring polymorphisms in HBV core gene, and moreover, the presence of C336/T336/C337 variants was first demonstrated to be an independent factor associating with spontaneous HBeAg loss in chronic hepatitis B patients.

Transient occult hepatitis B virus infection in a blood donor with high viremia

BACKGROUND

Screening of blood donors for viral nucleic acids has recently been introduced in several countries. With the use of transcription-mediated amplification, a blood donor was detected who had 90,000 copies of hepatitis B virus (HBV) DNA/mL but no hepatitis B surface antigen (HBsAg) or antibody to hepatitis B core antigen (anti-HBc). One month later, anti-HBc and hepatitis B surface antibody (anti-HBs) appeared; HBV DNA disappeared after 2 months. This study asked why HBsAg was undetectable in this rare case of transient occult HBV infection.

STUDY DESIGN AND METHODS

The HBV DNA in the first sample was cloned and sequenced to identify mutations. The physical nature of the virus was examined by polyethylene glycol precipitation, DNase digestion, density gradient centrifugation, and immunoprecipitation.

RESULTS

Several mutations were found all over the genome, but the HBs antigen loop was unchanged. A stop mutation in the precore region led to loss of hepatitis B e antigen (HBeAg) expression. No HBV DNA–containing immune complexes were present. The plasma did not contain nonencapsidated HBV DNA that could explain the absence of HBsAg. The virus was immune precipitated by antibodies against HBsAg or preS1 antigen. The ratio of HBV to HBsAg subviral particles was estimated to be 1 in less than 20 whereas in overt cases the ratio is 1 in more than 1000.

CONCLUSION

The acute resolving occult HBV infection was caused by an HBeAg-negative variant, which otherwise was almost normal. The negative HBsAg result was probably due to an unusually low production of surplus HBsAg. The absence of the viral immunomodulator HBeAg and the early appearance of anti-HBs suggested a rapid noncytolytic HBsAg-specific T-cell response leading to low expression of HBsAg.

An outbreak of hepatitis B with high mortality in India: association with precore, basal core promoter mutants and improperly sterilized syringes

In 2009, an outbreak of hepatitis B with high mortality was observed in Sabarkantha district, Gujarat state, India with 456 cases and 89 deaths. Hospitalized patients with self-limiting disease (152, AVH)) and fulminant hepatic failure (39, FHF including 27 fatal and 12 survivals) were investigated. These were screened for diagnostic markers for hepatitis viruses, hepatitis B virus (HBV) genotyping and mutant analysis. Complete HBV genomes from 22 FHF and 17 AVH cases were sequenced. Serosurveys were carried out in the most and least affected blocks for the prevalence of HBV and identification of mutants. History of injection from a physician was associated with FHF and AVH cases. Co-infection with other hepatitis viruses or higher HBV DNA load was not responsible for mortality. Four blocks contributed to 85.7% (391/456) of the cases and 95.5% (85/89) mortality while two adjacent blocks had negligible mortality. Sequence analysis showed the presence of pre-core and basal core promoter mutants and 4 amino acid substitutions exclusively among FHF cases. None of the self-limiting patients exhibited these dual mutations. Genotype D was predominant, D1 being present in all FHF cases while D2 was most prevalent in AVH cases. Probably due to violation of accepted infection control procedures by the qualified medical practitioners, HBV prevalence was higher in the affected blocks before the outbreak. Gross and continued use of HBV contaminated (mutant and wild viruses) injection devices led to an explosive outbreak with high mortality with a striking association with pre-C/BCP mutants and D1 genotype.

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.

Hepatitis B virus genotype B results in better immediate, late and sustained responses to peginterferon-alfa in hepatitis-B-e-antigen-positive patients

BACKGROUND AND AIMS

This study investigated outcome predictors in hepatitis-B-e-antigen (HBeAg)-positive chronic hepatitis B patients treated with peginterferon alfa-2a.

METHODS

A total of 88 HBeAg-positive patients receiving peginterferon alfa-2a for 6 months and followed up for at least 24 weeks were prospectively analyzed. Precore and core promoter genes of hepatitis B virus (HBV) were sequenced from the serial serum samples of 88 patients.

RESULTS

After 24 weeks of follow up, 38.6% and 28.4% of patients achieved HBeAg clearance and combined response, respectively. Multivariate analysis disclosed that pretreatment HBeAg sample to cut-off (S/Co) ratio ≤ 200, alanine aminotransferase > 200 IU/mL, HBV genotype B and T1846 were independent factors for HBeAg clearance, and HBeAg S/Co ratio ≤ 200 and HBV genotype B were major determinants for combined response. HBeAg S/Co ratio ≤ 10 at week 12 of therapy was the useful factor for treatment response and had a greater power (P = 0.012) to predict HBeAg clearance than HBV DNA. Patients with HBeAg clearance had a higher frequency of A1896 mutation at baseline and during therapy than those without HBeAg clearance, and the frequency of A1896 decreased during treatment. During follow up, delayed HBeAg seroconversion and reactivation of HBV after HBeAg clearance were observed in eight non-responders and 20 patients with HBeAg clearance, respectively. HBV genotype B was a significant factor to predict both responses.

CONCLUSIONS

Pretreatment HBeAg S/Co ratio ≤ 200 and HBV genotype B were major determinants for treatment response to peginterferon. Genotype-B-infected patients had higher probability of delayed HBeAg clearance and sustained response. Rapid decrease of HBeAg titer was useful on treatment predictor.

Association of core promoter mutations of hepatitis B virus and viral load is different in HBeAg(+) and HBeAg(-) patients

AIM: To identify the prevalence of hepatitis B e antigen (HBeAg) and to assess the association of hepatitis B virus (HBV) core promoter mutations and viral load in Indonesian patients.

METHODS: Sixty-four patients with chronic hepatitis, 65 with liver cirrhosis and 50 with hepatocellular carcinoma were included in this study. HBeAg and hepatitis B e antibody (HBeAb) tests were performed using enzyme-linked immunosorbent assay and the mutations were analyzed by sequencing. Viral load was measured by real-time polymerase chain reaction.

RESULTS: Of 179 patients, 108 (60.3%) were HBeAg(-) and 86 (79.6%) of these HBeAg(-) patients had been seroconverted. The A1896 mutation was not found in HBeAg(+) patients, however, this mutation was detected in 70.7% of HBeAg(-) patients. This mutation was frequently found when HBeAg was not expressed (87.7%), compared to that found in HBeAg seroconverted patients (65.1%). The A1899 mutation was also more prevalent in HBeAg(-) than in HBeAg(+) patients (P = 0.004). The T1762/A1764 mutation was frequently found in both HBeAg(+) and HBeAg(-) patients, however, the prevalence of this mutation did not significantly differ among the two groups (P = 0.054). In HBeAg(+) patients, the T1762/A1764 mutation was correlated with lower HBV DNA (P < 0.001). The A1899 mutation did not correlate with HBV DNA (P = 0.609). In HBeAg(-) patients, the T1762/A1764 mutation alone was not correlated with HBV DNA (P = 0.095), however, the presence of either the T1762/A1764 or A1896 mutations was associated with increased HBV DNA (P < 0.001).

CONCLUSION: The percentage of HBeAg(-) patients is high in Indonesia, and most of the HBeAg(-) patients had been seroconverted. The A1896 mutation was most likely the major cause of HBeAg loss. The T1762/A1764 mutation alone was associated with lower viral loads in HBeAg(+) patients, but not in HBeAg(-) patients.

Improved method for rapid and efficient determination of genome replication and protein expression of clinical hepatitis B virus isolates

Different hepatitis B virus (HBV) genotypes and variants are associated with different clinical outcomes and/or response to antiviral therapy, yet the comparison of the in vitro replication capacity of a large number of clinical isolates remains technically challenging and time-consuming. Although the full-length HBV genome can be amplified from high-titer blood samples by PCR using High Fidelity(plus) DNA polymerase and primers targeting the conserved precore region, the HBV clones thus generated are replication deficient due to the inability to generate the terminally redundant pregenomic RNA essential for genome replication. The transfection experiment is further complicated by PCR errors and the presence of viral quasispecies. A previous study found that the precise removal of non-HBV sequence by SapI digestion led to HBV replication in transfected cells, possibly due to low-level genome circularization by a cellular enzyme. We released HBV genome from the cloning vector using BspQI, an inexpensive isoschizomer of SapI, and increased the efficiency of genome replication by an extra step of in vitro DNA ligation. The uncut plasmid DNA can be used for transfection if the sole purpose is to study envelope protein expression. We found significant PCR errors associated with the High Fidelity(plus) DNA polymerase, which could be greatly diminished using Phusion DNA polymerase or masked by the use of a clone pool. The reduced PCR error and modified enzymatic steps prior to transfection should facilitate a more widespread functional characterization of clinical HBV isolates, while the clone pool approach is useful for samples with significant sequence heterogeneity.

Genotypes, mutations, and viral load of hepatitis B virus and the risk of hepatocellular carcinoma: HBV properties and hepatocarcinogenesis

Chronic infection with hepatitis B virus (HBV) is the major risk factor for hepatocellular carcinoma (HCC) worldwide. Ten HBV genotypes (A-J) have been discovered so far. Genotypes B and C are endemic in East and Southeast Asia. Genotype C HBV is associated with increased risks of cirrhosis and HCC. Genotype B (B2) is associated with the development of HCC in non-cirrhotic patients younger than 50 years and with relapse of HCC after surgical treatment. It is also associated with earlier hepatitis B e antigen seroconversion than genotype C. High HBV load is independently associated with the occurrence and post-treatment recurrence of HCC. Different genotypes have distinct patterns of mutations. Viral mutations in the core promoter region and in the preS region are frequently found to be significantly associated with an increased risk of HCC. These mutations often occur before the onset of HCC and accumulate during the progression of chronic HBV infection. Multiple such mutations are more frequent in patients with HCC and are specific for HCC. HBV subgenotypes, viral mutations, and viral load can be used for the prediction of HCC. Early identification of HBV-infected individuals who will eventually develop HCC will help to develop active prophylactic protocols to reduce or delay the occurrence of HCC.

Management of hepatitis B: Consensus of the Japan Society of Hepatology 2009

Recently, much progress has been made in the field of hepatitis B, such as natural history of the disease in relation to the amount of hepatitis B virus (HBV) DNA, genotypes of HBV influencing the natural course and treatment effects, mutations of HBV influencing the severity of the disease and development of hepatocellular carcinoma, and antiviral treatment such as nucleos(t)ide analogues and pegylated interferon. To make the consensus for the diagnosis, management and treatment of hepatitis B, a meeting was held during 45th annual meeting of Japan Society of Hepatology (JSH) in June 2009. In the meeting, recommendations and informative statements were discussed on the following subjects: (i) natural history of HBV infection; (ii) clinical implication of HBV genotypes; (iii) HBV mutations and their potential impact on pathogenesis of HBV infection; (iv) indications for antiviral treatment of chronic hepatitis B; (v) nucleos(t)ide analogues for chronic hepatitis B; and (vi) interferon therapy for chronic hepatitis B. The presenters reviewed the data on these subjects and proposed the consensus statements and recommendations. These statements were discussed among the organizers and presenters, and were approved by the participants of the meeting. In the current report, the relevant data were reviewed and the 12 consensus statements and nine recommendations on chronic hepatitis B were described.

JGH Foundation emerging leadership lecture. Significance of hepatitis B virus genotypes and mutations in the development of hepatocellular carcinoma in Asia

Advances in molecular biology technology in the last two decades have allowed detailed study of the viral mutations and genomic heterogeneity of hepatitis B virus (HBV). The first mutant discovered was precore stop codon mutation. It was reported in HBeAg-negative patients and initially thought to associate with fulminant hepatitis. Subsequent studies have suggested that it is merely one of the mechanisms of losing HBeAg by the virus. Another mutation that can downregulate the production of HBeAg is the basal core promoter mutation, which is located in the X gene upstream of the precore region. Based on the configuration of codon 15 and the stability of the epsilon of the precore region, these two mutants will be differentially selected during the course of HBeAg seroconversion. The most common HBV genotypes in South-East Asia are genotype B and C HBV. The higher hepatocellular carcinoma (HCC) risk of genotype C HBV has been confirmed by longitudinal studies in Hong Kong and Taiwan. One possible carcinogenic mechanism is its association with basal core promoter mutation, which has also been found to be a risk factor of HCC. Within genotype C HBV, subgenotype Cs is predominant in South-East Asia and subgenotype Ce is predominant in East Asia. Subgenotype Ce HBV has been found to have the highest risk of HCC as compared with subgenotype Cs or genotype B HBV. The understanding of the carcinogenic mechanisms of these HBV strains may shed light into future therapeutics in the prevention and treatment of HBV-related HCC.

Temporal acquisition of sequential mutations in the enhancer II and basal core promoter of HBV in individuals at high risk for hepatocellular carcinoma

To investigate the roles of mutations in enhancer II (Enh II) and basal core promoter (BCP) of hepatitis B virus (HBV) in hepatocellular carcinoma (HCC), we determined the sequence of Enh II/BCP in 152 HCC and 136 non-HCC patients from a high-incidence area of East China. A longitudinal study was conducted on 21 cases in which serial plasma samples were available before HCC. In total, six point mutations, including T1653, V1753, T1762, A1764, T1766 and A1768, were found to occur more frequently in HCC patients. Multivariate analysis showed that the T1653 [odds ratio (OR), 2.07; 95% confidence interval (CI), 1.114-3.845] and V1753 (OR, 3.099; 95% CI, 1.520-6.317) were independent factors that were associated with HCC. Although a T1762/A1764 double mutation was found in 73.0% of the HCC patients and 66.9% of the non-HCC patients, if the combined pattern with other adjacent mutations was not taken into account, it alone showed a lower frequency in HCC patients compared with non-HCC patients (19.7 versus 34.6%, P = 0.005). Interestingly, while the OR of HCC patients with a double mutation was only 0.393 (95% CI, 0.234-0.660), it increased to 1.861 (95% CI, 1.161-2.984) with a triple mutation and to 4.434 (95% CI, 1.630-12.063) with a quadruple mutation. The longitudinal study demonstrated that the mutations in Enh II/BCP accumulated during the development of HCC. In conclusion, the T1653 and V1753 mutations were independent risk factors for HCC in East China. The T1762/A1764 double mutation was necessary but not sufficient to produce an association between Enh II/BCP mutations and HCC.

A population-based cohort study for the risk factors of HCC among hepatitis B virus mono-infected subjects in Japan

BACKGROUND

There have only been a few prospective studies investigating risk factors associated with the development of hepatocellular carcinoma (HCC) among chronic hepatitis B patients all over the world, and no study has been conducted in Japanese population.

METHODS

A population-based cohort consisting of 19393 subjects (middle aged or older) with over 13 years' follow-up was investigated in Japan.

RESULTS

Of 19393 subjects, 479 had hepatitis B virus (HBV) mono-infection (2.5%). During the 245923 person-years' follow-up (average follow-up period 12.7 years), 13 cases of newly diagnosed HCC were documented in the HBV mono-infected group. Several factors at baseline (male, smoking, alanine aminotransferase, the positivity of HBe antigen and HB core-related antigen, the proportion of HBV DNA ≥ 5 log copies/mL, T1753V mutation, and A1762T/G1764A double mutation) were significantly associated with HCC among HBV mono-infected subjects. Multivariate-adjusted Cox hazard model showed that A1762T/G1764A (hazard ratio 7.05 [95% confidence interval (CI) 1.03-48.12, P = 0.046]) was the only independent risk factor for the development of HCC. Kaplan-Meier method also showed that the probability of HCC occurrence-free was significantly lower in HBV mono-infected subjects with A1762T/G1764A double mutation than those without these mutations.

CONCLUSION

HBV mono-infected subjects with A1762T/G1764A double mutation could be at high risk of HCC development during the natural course of HBV infection.

A mathematical model of the intracellular replication and within host evolution of hepatitis type B virus: Understanding the long time course of chronic hepatitis

Hepatitis B virus (HBV) causes acute and chronic liver disease. Especially, chronic hepatitis is a major risk factor of liver cirrhosis and hepatocellular carcinoma. Viral kinetics of HBV observed in peripheral blood is quite different depending on the clinical course of hepatitis. But the relationship between the intracellular replication dynamics and clinical course of HBV infection is unclear. Further it is very difficult to predict the long time course of hepatitis because the nature of HBV is changed by mutation within host with high mutation rate. We investigate the intracellular replication dynamics and within host evolution of HBV by using a mathematical model. Two different intracellular replication patterns of HBV, "explosive" and "arrested", are switched depending on the viral gene expression pattern. In the explosive replication, prominent growth of HBV is observed. On the other hand, the virion production is restricted in the arrested replication. It is suggested that the arrested and explosive replication is associated with chronic hepatitis and exacerbation of hepatitis respectively. It is shown by our evolutionary simulation that the exacerbation of hepatitis is caused by the emergence of explosive genotype of HBV from arrested genotype by mutation during chronic hepatitis. It is also shown that chronic infection without exacerbation is maintained by short waiting time for virion release and superinfection with arrested genotype. It is suggested that extension of waiting time for virion release and existence of uninfected hepatocyte in the liver may become risk factors for the exacerbation of hepatitis.

Nucleotide changes related to hepatocellular carcinoma in the enhancer 1/x-promoter of hepatitis B virus subgenotype C2 in cirrhotic patients

Hepatocellular carcinoma (HCC) is widely known to develop more frequently in cirrhotic patients with a high expression of Hepatitis B virus X protein (HBx), which is controlled by the enhancer 1 (Enh1)/X-promoter. To examine the effect of the mutations in the Enh1/X-promoter region in hepatitis B virus (HBV) genomes on the development of HCC, we investigated the differences in HBV isolated from cirrhotic patients with or without HCC along with the promoter activities of certain specific mutations within the Enh1/X-promoter. We examined 160 hepatitis B surface antigen (HBsAg)-positive cirrhotic patients (80 HCC patients, 80 non-HCC patients) by evaluating the biochemical, virological, and molecular characteristics. We evaluated the functional differences in certain specific mutations within the Enh1/X-promoter. The isolated sequences included all of the subgenotypes C2. The sites that showed higher mutation rates in the HCC group were G1053A and G1229A, which were found to be independent risk factors through multiple logistic analysis (P < 0.05). Their promoter activities were elevated 2.38- and 4.68-fold, respectively, over that of the wild type in the HepG2 cells. Similarly, both the mRNA and protein levels of HBx in these two mutants were much higher than that in wild type-transfected HepG2 cells. Mutated nucleotides of the Enh1/X-promoter, especially G1053A and G1229A mutations in the HBV subgenotype C2 of patients with cirrhosis, can be risk factors for hepatocarcinogenesis, and this might be due to an increase in the HBx levels through the transactivation of the Enh1/X-promoter.

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.

Hepatitis B virus genotypes and precore and core mutants in UAE patients

Background

Knowledge of the HBV genotype with which a patient is infected is crucial information for a physician to have when planning clinical treatment for that patient. Previous studies have suggested that there are possible differences in the pathogenicity and therapeutic response of different HBV genotypes. However, the prevalence of the various HBV genotypes and Precore and Core mutations is unknown in the UAE. Therefore, we sought to determine the prevalence of the different HBV genotypes in the UAE population.

Methodology/Principal Findings

A total of 88 HBsAg-positive patients were included in the study.

A method for genotyping and subtyping HBV by partial HBsAg gene sequencing using primers that are complementary to all known genotypes was used. Precore and core region of these viruses were also sequenced in 88 patients.

HBV genotype D was the most prevalent (79.5%) genotype identified in our study population, followed by genotypes A (18.2%) and C (2.3%). The following subtypes were isolated: ayw2 (80.7%), adw2 (14.8%), and adw (2.3%). The HBV-DNA viral load was higher in HBeAg-positive patients than it was in patients who were HBeAg-negative. Precore mutants were found in 51 (58.0%) of 88 patients. Mutations in the basal core promotor were found in 22 (25.3%) of 88 patients.

Conclusion/Significance

HBV infection is a major health problem in the UAE, and while genotypes B and C are the most prevalent HBV genotypes in the Asian population, our study reveals that genotype D is the predominant genotype that is present in the UAE. More patients were HBeAg-negative than were HBeAg-positive in our study sample, which could be due to the duration of infection of the included patients. Additionally, the viral loads of the HBeAg-positive patients were higher those of the HBeAg-negative patients. Analysis of nucleotide 1858 showed presence of thymine in all patients with genotypes C, and D and in a few patients with genotypes A. This nucleotide was closely related to the presence of precore mutants. Mutations in the basal core promoter were found in 22 of 88 (25.3%) samples. These mutations were more frequent in patients infected with genotype A (37.5%) and not found in patients infected with genotype C.

Main mutations in the hepatitis B virus basic core promoter (A1762T/G1764A) before HBeAg loss are markers that identify patients who will require long-term treatment

BACKGROUND

Some patients continue to have detectable HBV-DNA levels with liver disease progression after hepatitis B e antigen (HBeAg) loss. It is important to identify these patients, candidates for long-term treatment.

AIMS

To evaluate hepatitis B virus (HBV) genotype and the main mutations in the basic core promoter (BCP, A1762T/G1764A) and precore (G1896A) sequences as markers of persistent HBV-DNA after HBeAg loss.

METHODS

We analysed 60 serum samples from 20 Caucasian, HBeAg-positive, chronic hepatitis B patients, who lost HBeAg and were followed-up longitudinally. HBV genotype and precore and BCP mutations were determined before, at the time of, and after HBeAg loss.

RESULTS

After HBeAg loss, eight (40%) patients continued to have undetectable HBV-DNA and 12 (60%) had persistent HBV-DNA (median level 4.7 log(10) copies/mL). The presence of BCP mutations prior to therapy was the only variable associated with persistently detectable viraemia (P = 0.017). Four patients with genotype A and no mutations in the BCP region experienced hepatitis B surface antigen (HBsAg) loss after a mean period of 35 months from baseline.

CONCLUSIONS

Main BCP mutations in HBeAg-positive patients are useful markers to identify patients who will not have sustained virological suppression after HBeAg loss and therapy discontinuation and could benefit from long-term treatment.