Cloning and structural analyses of hepatitis B virus DNAs, subtype adr

Analysis of the Physicochemical Properties, Replication and Pathophysiology of a Massively Glycosylated Hepatitis B Virus HBsAg Escape Mutant

Mutations in HBsAg, the surface antigen of the hepatitis B virus (HBV), might affect the serum HBV DNA level of HBV-infected patients, since the reverse transcriptase (RT) domain of HBV polymerase overlaps with the HBsAg-coding region. We previously identified a diagnostic escape mutant (W3S) HBV that produces massively glycosylated HBsAg. In this study, we constructed an HBV-producing vector that expresses W3S HBs (pHB-W3S) along with a wild-type HBV-producing plasmid (pHB-WT) in order to analyze the physicochemical properties, replication, and antiviral drug response of the mutant. Transfection of either pHB-WT or W3S into HepG2 cells yielded similar CsCl density profiles and eAg expression, as did transfection of a glycosylation defective mutant, pHB-W3S (N146G), in which a glycosylation site at the 146aa asparagine (N) site of HBs was mutated to glycine (G). Virion secretion, however, seemed to be severely impaired in cases of pHB-W3S and pHB-W3S (N146G), compared with pHB-WT, as determined by qPCR and Southern blot analysis. Furthermore, inhibition of glycosylation using tunicamycin^TM on wild-type HBV production also reduced the virion secretion. These results suggested that the HBV core and Dane particle could be formed either by massively glycosylated or glycosylation-defective HBsAg, but reduced and/or almost completely blocked the virion secretion efficiency, indicating that balanced glycosylation of HBsAg is required for efficient release of HBV, and mutations inducing an imbalanced glycosylation of HBs would cause the virion to become stuck in the cells, which might be associated with various pathogeneses due to HBV infection.

A Traditional Chinese Medicine, Maoto, Suppresses Hepatitis B Virus Production

Worldwide, millions of people suffer from hepatitis B virus (HBV) infection, putting them at a high risk of death from liver cirrhosis and cancer. Although effective anti-HBV drugs have been developed, current drugs have some limitations, as most of them have a risk of significant side effects. Therefore, the discovery of safe and effective anti-HBV drugs is still needed. Natural compounds are considered sources of novel, safe and effective therapeutics. In this study, we screened a library of Kampos, traditional herbal medicines, for suppression of HBV production. Among them, we found that maoto reduced extracellular HBV DNA but not extracellular HBsAg during HBV infection, suggesting that it suppressed HBV production by interfering with HBV nucleocapsid incorporation into viral particles. Furthermore, we revealed that maoto reduced the expression of a host gene, Tropomyosin β chain (TPM2), whose downregulation also suppressed HBV production, similarly to maoto. Since the safety of maoto has been already confirmed, maoto can be considered a candidate anti-HBV agent if the effect is confirmed in vivo. In addition, our findings also suggest TPM2 as a novel molecular target for the development of anti-HBV agents.

TIMM29 interacts with hepatitis B virus preS1 to modulate the HBV life cycle

Hepatitis B virus (HBV), a major global health problem, can cause chronic hepatitis, liver cirrhosis, and hepatocellular carcinomas in chronically infected patients. However, before HBV infection can be adequately controlled, many mysteries about the HBV life cycle must be solved. In this study, TIMM29, an inner mitochondrial membrane protein, was identified as an interaction partner of the preS1 region of the HBV large S protein. The interaction was verified by both an immunoprecipitation with preS1 peptides and a GST-pulldown assay. Immunofluorescence studies also showed colocalization of preS1 and TIMM29. Moreover, it was determined that the preS1 bound with amino acids 92-189 of the TIMM29 protein. Infection of HBV in TIMM29-overexpressing NTCP/G2 cells resulted in a significant decrease of HBeAg and both extracellular particle-associated and core particle-associated HBV DNA without affecting cccDNA formation. Comparable results were obtained with TIMM29-overexpressing HB611 cells, which constitutively produce HBV. In contrast, knockout of TIMM29 in NTCP/G2 cells led to a higher production of HBV including HBeAg expression, as did knockout of TIMM29 in HB611. Collectively, these results suggested that TIMM29 interacts with the preS1 region of the HBV large S protein and modulates HBV amplification.

Molecular, Evolutionary, and Structural Analysis of the Terminal Protein Domain of Hepatitis B Virus Polymerase, a Potential Drug Target

Approximately 250 million people are living with chronic hepatitis B virus (HBV) infections, which claim nearly a million lives annually. The target of all current HBV drug therapies (except interferon) is the viral polymerase; specifically, the reverse transcriptase domain. Although no high-resolution structure exists for the HBV polymerase, several recent advances have helped to map its functions to specific domains. The terminal protein (TP) domain, unique to hepadnaviruses such as HBV, has been implicated in the binding and packaging of the viral RNA, as well as the initial priming of and downstream synthesis of viral DNA—all of which make the TP domain an attractive novel drug target. This review encompasses three types of analysis: sequence conservation analysis, secondary structure prediction, and the results from mutational studies. It is concluded that the TP domain of HBV polymerase is comprised of seven subdomains (three unstructured loops and four helical regions) and that all three loop subdomains and Helix 5 are the major determinants of HBV function within the TP domain. Further studies, such as modeling inhibitors of these critical TP subdomains, will advance the TP domain of HBV polymerase as a therapeutic drug target in the progression towards a cure.

HBV Drug Resistance Substitutions Existed before the Clinical Approval of Nucleos(t)ide Analogues: A Bioinformatic Analysis by GenBank Data Mining

Naturally occurring nucleos(t)ide analogue resistance (NUCr) substitution frequencies in the reverse transcriptase (RT) of the hepatitis B virus (HBV) were studied extensively after the clinical approval of nucleos(t)ide analogues (NUCs; year of approval 1998). We aimed to study NUCr substitutions in HBV RT sequences obtained before 1998 and better understand the evolution of RT sequences without NUC pressures. Our strategy was to retrieve HBV sequences from GenBank deposited before 1998. The initial search used the keywords "hepatitis B virus" or "HBV" and 1139 sequences were found. Data analyses included information extraction: sequence quality control and amino acid substitution analysis on 8 primary NUCr and 3 secondary substitution codons. Three hundred and ninety-four RT-containing sequences of 8 genotypes from 25 countries in 4 continents were selected. Twenty-seven (6.9%) sequences were found to harbor substitutions at NUCr-related codons. Secondary substitutions (rtL80V and rtV173G/A/L) occurred more frequently than primary NUCr substitutions (rtI169L; rtA181G; T184A/S; rtS202T/R; rtM204L and rtM250K). Typical amino acid substitutions associated with NUCr were of rtL80V, rtV173L and rtT184A/S. We confirm the presence of naturally occurring typical HBV NUCr substitutions with very low frequencies, and secondary substitutions are more likely to occur than primary NUCr substitutions without the selective pressure of NUCs.

The Hepatitis B Virus Genotype Affects the Persistence of Viral Replication in Immunodeficient NOG Mice

Background & Aims

At least eight genotypes of Hepatitis B virus (HBV) have been identified. HBV genotype C is the most common genotype in Japan, although the incidence of HBV genotype A is increasing. The reason underlying the differences in viral multiplication of the HBV genotypes is unclear, especially in vivo. The purpose of this study was to elucidate the differences in HBV load and the persistence of viremia in vivo between genotypes A and C.

Methods

Immunodeficient NOG mice were transfected by hydrodynamic injection with the HBV expression plasmids pHBA1.2 or pHBC1.2, which contain overlength (1.2-mer) copies of the genomes of HBV genotype A or C, respectively.

Results

One day after transfection, the number of HBcAg-positive hepatocytes and serum HBV DNA levels were similar between mice transfected with pHBA1.2 and pHBC1.2. Serum levels of HBV DNA, HBsAg and HBeAg in mice transfected with pHBA1.2 were maintained over 5 months. In contrast, those in mice with pHBC1.2 gradually decreased over time and reached undetectable levels within 3 months after transfection. HBcAg-stained hepatocytes were detected in mice transfected with pHBA1.2, but not pHBC1.2, 5 months post-transfection. Double-staining immunohistochemistry revealed that the number of cleaved caspase3-stained, HBcAg-positive hepatocytes in the pHBC1.2-transfected mice was higher than in the pHBA1.2-transfected mice 3 days post-transfection. Moreover, the plasmid DNA and covalently closed circular DNA levels were decreased in the livers of pHBC1.2-transfected mice. These results suggested that hepatocytes expressing HBV genotype C were eliminated by apoptosis in the absence of immune cells more often than in hepatocytes expressing HBV genotype A.

Conclusions

Immunodeficient mice transfected with HBV genotype A develop persistent viremia, whereas those transfected with HBV genotype C exhibit transient viremia accompanied by apoptosis of HBV-expressing hepatocytes. This differences may affect the clinical courses of patients infected with HBV genotypes A and C.

Prospective long-term study of hepatitis B virus reactivation in patients with hematologic malignancy

BACKGROUND AND AIM

To elucidate the clinical characteristics of hepatitis B virus reactivation (HBV-R), we performed a prospective long-term study of patients with hematologic malignancy, including both hepatitis B virus (HBV) carriers and those with resolved HBV infection.

METHODS

Twenty-one patients with hematopoietic stem-cell transplants (HSCT) and 36 patients given rituximab-based chemotherapy were enrolled. Entecavir was administered prophylactically to eight patients with HBV surface antigen (HBsAg). HBV-DNA was measured every month in 49 patients with resolved HBV infection, and preemptive therapy was given to eight patients with HBV-R.

RESULTS

HBV-R developed in five (26%) of 19 patients with HSCT and three (10%) of 30 patients given rituximab-based chemotherapy. HBV-R occurred a median of 3 months (range: 2-10) after the end of rituximab-based chemotherapy and 22 months (range: 9-36) after HSCT. HBV-R did not develop in patients with an antibodies against HBsAg (anti-HBs) titer exceeding 200 mIU/mL at baseline. Mutations in the "a" determinant region with amino acid replacement were detected in four of the eight patients with HBV-R. Preemptive therapy prevented severe hepatitis related to HBV-R. Entecavir treatment was stopped in four patients with HBV-R. Since the withdrawal of entecavir, HBV-DNA has not been detected in two patients persistently positive for anti-HBs. No patient had fatal hepatitis.

CONCLUSIONS

Proper management of patients with HBsAg or resolved HBV infection prevented fatal hepatitis related to HBV-R in patients who received immunosuppressive or cytotoxic therapy. Entecavir could be safely discontinued in patients with HBV-R who had acquired anti-HBs.

A rational study for identification of highly effective siRNAs against hepatitis B virus

RNA interference (RNAi) is a powerful gene knockdown technique used for study gene function. It also potentially provides effective agents for inhibiting infectious and genetic diseases. Most of RNAi studies employ a single siRNA designing program and then require large-scale screening experiments to identify functional siRNAs. In this study, we demonstrate that an assembly of results generated from different siRNA designing programs could provide clusters of predicting sites that aided selection of potent siRNAs. Based on the clusters, three siRNA target sites were selected on a conserved RNA region of hepatitis B virus (HBV), known as HBV post-transcriptional regulatory element (HBV PRE) at nucleotide positions 1317-1337, 1357-1377 and 1644-1664. All three chosen siRNAs driven by H1 promoter were highly effective and could drastically decrease expression of HBV transcripts (core, surface and X) and surface protein without induction of interferon response and cell cytotoxicity in liver cancer cell line (HepG2). Based on prediction of secondary structures, the silencing effects of siRNAs were less effective against a loop sequence of the mRNA target with hairpin structure. In summary, we demonstrate an effectual approach for identification of functional siRNAs. Moreover, highly potent siRNAs identified here may serve as novel agents for development of nucleic acid-based HBV therapy.

Effect of occult hepatitis B virus infection on the early-onset of hepatocellular carcinoma in patients with hepatitis C virus infection

Although overt hepatitis B virus (HBV) infection promotes the onset of hepatocellular carcinoma (HCC) in hepatitis C virus (HCV)-infected patients, the effect of occult HBV infection remains unclear. The aim of this study was to investigate the effect of occult HBV infection on the early-onset of HCC in HCV-infected patients. A total of 173 HCC patients with HCV infection were enrolled and classified into 2 groups according to the median age of HCC onset: the early-onset group (n=91; 61.1±5.6 years) and the late-onset group (n=82; 73.8±3.7 years). Independent factors associated with the early-onset of HCC were assessed by multivariate analysis. In the overall analysis, independent risk factors for the early-onset of HCC were the white blood cell count and alanine aminotransferase level, but not the presence of HBV DNA. In a stratification analysis according to albumin levels of ≥3.5 g/dl, the presence of HBV DNA was a significant independent risk factor for the early-onset of HCC (OR 145.18, 95% CI 1.38-15296.61, P=0.036), whereas the presence of antibodies against hepatitis B core antigen was not found to be a risk factor. The presence of HBV DNA was not a risk factor for the early-onset of HCC in the overall analysis. However, its presence was an independent factor for the early-onset of HCC in HCV-infected patients with an albumin level of ≥3.5 g/dl. Thus, occult HBV infection may accelerate hepatocarcino-genesis in HCV-infected patients with relatively low carcinogenic potential.

Structure and expression of integrated hepatitis B virus genes in an HBs antigen producing human cell line (huGK-14)

A human continuous cell line (huGK-14) within a lineage of passaged cultures was investigated in the mode of integration and expression of hepatitis B virus (HBV) genes. HBV DNA was integrated in eight different sites of the cellular DNA, in each of which HBV genome was rearranged, fragmented, and/or partly deleted. Complete HBV genome that may lead to production of infectious virus particles was not detected in the cells nor in the culture medium. Clones of cDNA containing a complete coding frame for small HBs antigen protein (type adr) were obtained from mRNA of the cells. The cells were stable over the period of six months of cultivation and more than 60 population doublings in the mode of HBV integration and HBs mRNA expression.These results provide substantial evidence for the absence of an ability for the integrated DNA to create an infectious product in the cell; for the stable production of HBs mRNA from the cells, and suggest the usefulness of this cell line as a substrate for HBV vaccine production.

Functional Characterization of Interferon Regulation Element of Hepatitis B virus Genome In Vivo

The roles of interferon regulatory element (IRE) in Hepatitis B virus (HBV) genome on inhibitory effect of interferon against HBV are controversial in vitro. This study aimed to determine the functional characterization of HBV-IRE sequence in vivo. Wild-type or IRE-mutant HBV replication-competent mice were firstly established, and mice were subquently treated with polyinosinic-polytidylin acid (polyI.C) or phosphate-buffered saline via intraperitoneal. Results showed that PolyI.C inhibited viral replication, and increased the level of 2',5'-oligoadenylate synthase mRNA transcripts, a marker of INF-α/β induction. Between wild-type and IRE-mutant HBV replication-competent mice, the levels of HBV-RNA and HBV-DNA replication intermediates were similar. After PolyI.C treatment, the decreasing of HBV-RNA was similar between two groups, but HBV-DNA replication intermediates decreased significantly less in IRE-mutant than wild-type HBV replication-competent mice. These findings suggested that IRE mutant reduced the inhibitory effect of interferon on HBV replication, which played a role in antiviral effect of interferon against HBV.

Fatal exacerbation of type B chronic hepatitis triggered by changes in relaxed circular viral DNA synthesis and virion secretion

Virological features of fulminant liver disease-causing hepatitis B virus (HBV) have not been fully elucidated. We studied longitudinally the viruses obtained before and after fulminant liver disease in a patient with chronic HBV infection showing fatal exacerbation. HBV strains were obtained before and after exacerbation (designated as FEP1 and FEP2). Their virological features were investigated by in vitro transfection. FEP1 and FEP2 possessed higher activity of overall HBV DNA synthesis than the wild-type. FEP1 lacked competence for relaxed circular (RC) HBV DNA synthesis and RC HBV DNA-containing virion secretion, but FEP2 maintained it. Chimeric analysis revealed that the preS/S gene, where FEP1 had a considerable number of mutations and deletions but FEP2 did not, was responsible for impaired RC HBV DNA synthesis and virion secretion. Furthermore, incompetence of FEP1 strain was transcomplemented by the preS/S protein of wild-type strain. In conclusion, the viral strain after exacerbation showed resurgent RC HBV DNA synthesis and virion secretion, which was caused by conversion of the preS/S gene from a hypermutated to hypomutated state. This may have been responsible for disease deterioration in the patient. This is a novel type of HBV genomic variation associated with the development of fulminant liver disease.

Lamivudine-to-entecavir switching treatment in type B chronic hepatitis patients without evidence of lamivudine resistance

PURPOSE

A considerable number of chronic hepatitis B (CH-B) patients remain under continuous lamivudine treatment, although switching treatment to entecavir could be beneficial. We investigated the antiviral efficacy of switching treatment to entecavir in CH-B patients without apparent evidence of lamivudine resistance during the preceding lamivudine treatment.

METHODS

Forty-four CH-B patients, who underwent lamivudine treatment for more than 6 months and showed no evidence of lamivudine resistance, switched to entecavir. Serial changes in hepatitis B virus (HBV) DNA were correlated with the patients' baseline HBV DNA at the commencement of entecavir administration. The entecavir-resistant substitution was examined by PCR-direct sequencing. The median follow-up period of entecavir treatment was 20 (10-23) months.

RESULTS

All 31 patients with baseline HBV DNA <2.6 logcopies/ml maintained HBV DNA-negative status during entecavir treatment. Of seven patients having HBV DNA of 2.6-<4.0 logcopies/ml, all achieved undetectable HBV DNA at the end of follow-up. As for six patients having HBV DNA >or=4.0 logcopies/ml, three patients achieved undetectable HBV DNA, whereas virological breakthrough was observed in one patient at month 15. An entecavir-resistant virus having rtM204V, rtL180M and rtS202G substitutions was detected in this patient.

CONCLUSIONS

The lamivudine-to-entecavir switching treatment may be generally recommendable in CH-B patients without evidence of lamivudine resistance during the preceding lamivudine treatment. However, great care should be taken with respect to the emergence of entecavir-resistance, especially in patients who do not respond well to the preceding lamivudine treatment.

Supportive role played by precore and preS2 genomic changes in the establishment of lamivudine-resistant hepatitis B virus

BACKGROUND

Hepatitis B virus (HBV) establishes lamivudine resistance via the resistance-causative rtM204V/I mutation and the replication-compensatory rtL180M mutation. However, both lamivudine-resistant viruses with and those without rtL180M can exist in clinical settings. To elucidate the differences between viruses with and those without rtL180M, we conducted full-length sequencing analysis of HBV derived from patients with type B chronic hepatitis showing lamivudine resistance.

METHODS

The full-length HBV DNA sequences derived from 44 patients showing lamivudine resistance were determined by polymerase chain reaction direct sequencing. Viral replicative competence was examined by in vitro transfection analysis using various HBV-expressing plasmids.

RESULTS

Throughout the HBV genome, a precore-defective A1896 mutation and a short deletion in the preS2 gene were detected more frequently in viruses without rtL180M than in those with it (64% vs. 17% [P < .005] and 50% vs. 10% [P < .01], respectively). In vitro transfection analysis revealed that the level of reduction in intracellular viral replication caused by the introduction of lamivudine resistance-associated mutations was lower in precore-defective and preS2-deleted viruses than in wild-type virus.

CONCLUSIONS

Both the precore-defective mutation and the preS2 deletion may play a supportive role in the replication of lamivudine-resistant HBV, which may be a reason for there being no need for the compensatory rtL180M mutation in lamivudine-resistant HBV possessing the precore and preS2 genomic changes.

Human oncogenic viruses: hepatitis B and hepatitis C viruses and their role in hepatocarcinogenesis

Chronic infections caused by hepatitis B virus (HBV) and/or hepatitis C virus (HCV) are the main risk factors for the development of hepatocellular carcinoma (HCC) in humans. Both viruses cause a wide spectrum of clinical manifestations ranging from healthy carrier state to acute and chronic hepatitis, liver cirrhosis, and HCC. HBV and HCV belong to different viral families (Hepadnoviridae and Flaviviridae, respectively); they are characterized by different genetic structures. Clinical manifestations of these viral infections result from the interaction between these viruses and host hepatocytes (i.e. between viral and cell genomes). Proteins encoded by both viruses play an important role in processes responsible for immortalization and transformation of these cells. Chronic inflammation determined by host immune response to the viral infection, hepatocyte death and their compensatory proliferation, as well as modulation of expression of some regulatory proteins of the cell (growth factors, cytokines, etc.) are the processes that play the major role in liver cancer induced by HBV and HCV.

Advances of candidate binding protein to envelope protein of hepatitis B virus

There are at least 4 initial coding positions in S gene of hepatitis B virus (HBV), encoding pre-pre-S, pre-S1, pre-S2 as well as major protein. There are no definite evidences to prove that envelope protein will interact with human cellular protein. This review focused on research approaches to the existing protein - protein interaction and summarized proteins of liver cells that may interact with current HBV envelope protein. However, most of currently available results need further verification.

Overexpression and purification of PreS region of hepatitis B virus antigenic surface protein adr subtype in Escherichia coli

PreS domain of Hepatitis B virus (HBV) surface antigen is a good candidate for an effective vaccine as it activates both B and T cells besides binding to hepatocytes. This report deals with overexpression and purification of adr subtype of surface antigen that is more prevalent in Pakistan. PreS region, comprising 119 aa preS1 region plus a 55 aa preS2 region plus 11 aa from the N-terminal S region, was inserted in pET21a+ vector, cloned in E. coli DH5alpha cells and expressed in E. coli BL21 codon+ cells. The conditions for over expression were optimized using different concentrations of IPTG (0.01-5 mM), and incubating the cells at different temperatures (23-41 degrees C) for different durations (0-6 h). The cells were grown under the given optimized conditions (0.5 mM IPTG concentration at 37 degrees C for 4 h), lysed by sonication and the protein was purified by ion exchange chromatography. On the average, 24.5 mg of recombinant protein was purified per liter of culture. The purified protein was later lyophilized and stored at -80 degrees.

Type B fulminant hepatitis is closely associated with a highly mutated hepatitis B virus strain

OBJECTIVE

Genome-wide sequences of hepatitis B virus strain associated with type B fulminant hepatitis have not been compared with those of acute self-limited hepatitis. We carried out full-length sequencing analysis of viral strains derived from patients with type B acute liver injury.

METHODS

Nine acute self-limited hepatitis and 6 fulminant hepatitis patients were the subjects of this study. Full-length sequencing analysis of viral DNA was done by PCR-direct sequencing.

RESULTS

Higher frequencies in fulminant hepatitis strains compared with acute hepatitis ones were observed in the T1762/A1764 (p < 0.05), A1896 (p = 0.09) and M1753 (M = C or A) (p = 0.09) mutations. Viruses related to fulminant hepatitis possessed the higher number of nucleotide substitutions than those related to acute hepatitis in the whole virus genome (p < 0.01) and various regions including preS/S gene (p < 0.05), precore/core gene (p < 0.01), polymerase gene (p < 0.05) and basic core promoter/core upstream regulatory sequence (p < 0.01). The high number of nucleotide substitutions in viruses related to fulminant hepatitis was predominantly non-synonymous in the preS/S and precore/core genes.

CONCLUSION

Development of type B fulminant hepatitis may be associated with a highly mutated hepatitis B virus strain.

Association between lamivudine sensitivity and the number of substitutions in the reverse transcriptase region of the hepatitis B virus polymerase

This study aimed to identify the viral factors responsible for poor sensitivity to lamivudine (LAM). We analyzed 49 LAM-treated chronic hepatitis B patients infected with hepatitis B virus (HBV) genotype C. Serum HBV DNA reached a level below the detection limit of the sensitive PCR assay in 31 (63.3%) within the first 24 weeks of LAM therapy (good responder group). Of the patients who did not achieve undetectable levels of HBV DNA within 24 weeks (poor responder group), 15 (83.3%) experienced virological breakthrough, whilst only four patients in the good responder group (12.9%) experienced virological breakthrough. Multivariate analysis revealed that failure to achieve a reduction in viral load to undetectable levels within 24 weeks was independently associated with the occurrence of virological breakthrough. Sequence analysis of the HBV genome revealed that point mutations in the precore region (G1896A) and enhancer I (A1287G/C) were observed more frequently in the good responder group than in the poor responder group (P = 0.002 and 0.019 respectively), and the number of substitutions in the reverse transcriptase domain of the polymerase was significantly higher in the good responders than in the poor responders (P = 0.026). In conclusion, determining the sequence of preexisting HBV, especially for enhancer I, the precore region, and the RT domain of the polymerase region, may be useful in predicting sensitivity to LAM therapy.

High level of genetic heterogeneity in S and P genes of genotype D hepatitis B virus

The genetic heterogeneity of hepatitis B virus (HBV) genotypes and subgenotypes was investigated by directly sequencing amplified PreS, S and P genes of HBV isolates obtained from the plasma of 99 subjects with chronic HBV infection. Genotype D showed the greatest intragenotypic and intrasubgenotypic divergence: in particular, the a determinant was mutated in 58.2% of the genotype D patients, two of whom showed prototypic vaccine-induced escape mutants at codon 145. Moreover, five sites under significant positive selection were found in the S protein of the D isolates: one in the a determinant and four in the highly hydrophobic C terminal. Our results suggest that careful surveillance of vaccine-induced escape mutants should be considered in populations with highly frequent genotype D infections, and raise questions concerning the possible relationship between the genetic heterogeneity, host immunity and pathogenicity of this HBV genotype.

Efficient inhibition of hepatitis B virus replication by small interfering RNAs targeted to the viral X gene in mice

The hepatitis B virus (HBV), as a major cause of acute and chronic hepatitis in humans, contains a partial double-stranded circular DNA genome of 3.2kb that is transcribed into the 3.5-, 2.4-, 2.1-, and 0.7-kb viral transcripts by the host RNA polymerase II. The HBV X (HBx) gene is consistently expressed in all four HBV viral mRNAs and thus an ideal target for developing viral inhibitors via a gene therapeutic approach. In this study, we show that two HBx-specific small interfering RNAs (siRNA), HBx1 and HBx3, significantly decrease both viral RNA and protein levels, and completely block replication in cultured cells co-transfected with a siRNA expression plasmid and an HBV replication-competent vector. To further confirm these antiviral activities of selected siRNAs in small animals, we established acute and chronic HBV mouse models by hydrodynamic injection of this plasmid containing the full-length HBV genome. Selected HBx-specific siRNAs also induced a significant anti-viral effect in living animals. Our findings should facilitate the development of an alternative therapeutic agent against HBV infection, particularly HBV-derived hepatocellular carcinoma (HCC) in which HBx has been known as one of the major pathological factors.

Alteration of gene expression in human hepatocellular carcinoma with integrated hepatitis B virus DNA

PURPOSE

Integration of hepatitis B virus (HBV) DNA into the human genome is one of the most important steps in HBV-related carcinogenesis. This study attempted to find the link between HBV DNA, the adjoining cellular sequence, and altered gene expression in hepatocellular carcinoma (HCC) with integrated HBV DNA.

EXPERIMENTAL DESIGN

We examined 15 cases of HCC infected with HBV by cassette ligation-mediated PCR. The human DNA adjacent to the integrated HBV DNA was sequenced. Protein coding sequences were searched for in the human sequence. In five cases with HBV DNA integration, from which good quality RNA was extracted, gene expression was examined by cDNA microarray analysis.

RESULTS

The human DNA sequence successive to integrated HBV DNA was determined in the 15 HCCs. Eight protein-coding regions were involved: ras-responsive element binding protein 1, calmodulin 1, mixed lineage leukemia 2 (MLL2), FLJ333655, LOC220272, LOC255345, LOC220220, and LOC168991. The MLL2 gene was expressed in three cases with HBV DNA integrated into exon 3 of MLL2 and in one case with HBV DNA integrated into intron 3 of MLL2. Gene expression analysis suggested that two HCCs with HBV integrated into MLL2 had similar patterns of gene expression compared with three HCCs with HBV integrated into other loci of human chromosomes.

CONCLUSIONS

HBV DNA was integrated at random sites of human DNA, and the MLL2 gene was one of the targets for integration. Our results suggest that HBV DNA might modulate human genes near integration sites, followed by integration site-specific expression of such genes during hepatocarcinogenesis.

Alternative peptide-fusion proteins generated by out-of-frame mutations, just upstream ORFs or elongations in mutants of human hepatitis B viruses

By various means including out-of-frame mutations, just upstream ORFs and elongations, additional peptide fusions could be generated by mutants of Human Hepatitis B Virus (HBV). Numerous frameshift mutations inducing long alternative open reading frames have been evidenced in all HBV genes. Interestingly, these mutants are frequently detected in severe liver diseases, but seldom in asymptomatic carriers. The high level of conservation of some of these sequences in spite of the fact that they could be generated by different types of mutations, as their presence in mutants found on various continents, suggest that these mutations could play a role. These mutants could combine two advantages, that related to the loss of a part of a wild-type protein and that related to the putative advantage conferred by the additional sequences. In addition, in numerous Asian genomes (more than 300 to date) pre-X or pre-pre-S regions were found just upstream to, respectively, the X and the pre-S1 genes. These two regions are translated with their respective genes in frame and recent studies have evidenced the transactivating role of the corresponding proteins. With some exceptions, these regions are genotype- and serotype-specific (C/adr). In addition, these mutants have been found principally in patients with severe hepatitis diseases, for example, hepatocarcinoma in more than one third of the cases. As additional sequences generated by HBV variants may be relevant for viral life cycle, persistence and pathogenesis, further investigations are necessary to give a clearer picture of the subject.

Expression of HBcAg mutant with long internal deletion in Saccharomyces cerevisiae and observation of its self-assembly particles by atomic force microscopy (AFM)

An internally truncated C gene of adr hepatitis B virus core antigen with long internal deletion (aa81-aa116) (DeltaHBcAg with 36aa truncation) was expressed in Saccharomyces cerevisiae and the products (DeltarHBcAg) were purified from a crude lysate of the yeast by three steps: Sephrose CL-4B chromatography, sucrose step-gradient ultracentrifugation and CsCl-isopycnic ultracentrifugation. Results of ELISA test and density analysis of CsCl-isopycnic ultracentrifugation indicated that the purified products (DeltarHBcAg protein) with HBeAg antigenicity mainly located at the densities of 1.23 g ml-1. Observation and analysis of the purified DeltarHBcAg products by AFM indicated that the DeltarHBcAg (core) protein produced in S. cerevisiae could self-assemble into three or more size classes of core particles which exhibited a polymorphous distribution of DeltarHBcAg (core) particles. These different size classes of core particles mainly centred on the range whose mean diameter was from 10 nm to 48 nm, especially on the position of 11 nm, 15.6 nm and the range from 27 nm to 41 nm, respectively. Furthermore, the most number of core particles mainly centred on the range whose mean diameter was from 27 nm to 41 nm. These results above indicated that the truncated internal long fragment (aa81-aa116) probably had no effect on self-assembly of the HBcAg core particles which implied the internal length fragment (aa81-aa116) was not the sole domain for self-assembly of HBcAg dimer or the truncated HBcAg protein subunit formed the fresh interactive domain with each other. These initial results above by AFM analysis were very important for further research on the self-assembly, ultrastructure, subunit interaction and core internal deletion mutant (CIDM) function of HBcAg core particles.

Formation of vesicular stomatitis virus pseudotypes bearing surface proteins of hepatitis B virus

It has been difficult to propagate and titrate hepatitis B virus (HBV) in tissue culture. We examined whether vesicular stomatitis virus (VSV) pseudotypes bearing HBV surface (HBs) proteins infectious for human cell lines could be prepared. For this, expression plasmids for three surface proteins, L, M, and S, of HBV were made. 293T cells were then transfected with these plasmids either individually or in different combinations. 293T cells expressing HBs proteins were infected with VSVdeltaG*-G, a recombinant VSV expressing green fluorescent protein (GFP), to make VSV pseudotypes. Culture supernatants together with cells were harvested and sonicated for a short time. The infectivities of freshly harvested supernatants were determined by quantifying the number of cells expressing GFP after neutralization with anti-VSV serum and mouse monoclonal antibodies (MAbs) against HBs protein. Among 14 cell lines tested for susceptibility to HBV pseudotype samples, HepG2, JHH-7, and 293T cells were judged to be the most susceptible. Namely, the infectious units (IU) of the culture supernatant samples neutralized with anti-VSV in the absence and presence of anti-HBs S MAbs and titrated on HepG2 cells ranged from 1,000 to 4,000 IU/ml and 200 to 400 IU/ml, respectively, suggesting the presence of VSVdeltaG*(HBV) pseudotypes. This infectivity was inhibited by treatment with lactoferrin or dextran sulfate. Pretreatment of the cells with trypsin or tunicamycin inhibited plating of the pseudotype samples. The HBV pseudotypes can be used to analyze early steps of HBV infection, including the entry mechanism of HBV.

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HBV core sequence: definition of genotype-specific variability and correlation with geographical origin

There are eight genotypes and nine subtypes of HBV. Small differences in geographical origin are associated with sequence changes in the surface gene. Here, we compared core gene sequences from different genotypes and geographical regions. Specific combinations of 24 amino acid substitutions at nine residues allowed allocation of a sequence to a subtype. Six of these nine residues were located in different T cell epitopes depending on HBV geographical area and/or genotype. Thirty-seven nucleotide changes were associated uniquely with specific genotypes and subtypes. Unique amino acid and nucleotide variants were found in a majority of sequences from specific countries as well as within subtype ayw2 and adr. Specific nucleotide motifs were defined for Korean, Indian, Chinese, Italian and Pacific region isolates. Finally, we observed amino acid motifs that were common to either South-east Asian or Western populations, irrespective of subtype. We believe that HBV strains spread within constrained ethnic groups, result in selection pressures that define sequence variability within each subtype. It suggests that particular T cell epitopes are specific for geographical regions, and thus ethnic groups; this may affect the design of immunomodulatory therapies.

Purification of the recombinant hepatitis B virus core antigen (rHBcAg) produced in the yeast Saccharomyces cerevisiae and comparative observation of its particles by transmission electron microscopy (TEM) and atomic force microscopy (AFM)

Hepatitis B virus core antigen (HBcAg) gene (C gene) was expressed in Saccharomyces cerevisiae and the products (rHBcAg or core particles) were purified from a crude lysate of the yeast by three steps: Sephrose CL-4B chromatography, Sucrose step-gradient ultracentrifugation and CsCl-isopycnic ultracentrifugation. It has been observed that HBcAg was synthesized in yeast cells as a particle consisting of polypeptides with a molecular weight of 21.5 kDa (p21.5). Results of ELISA test and density analysis of CsCl-isopycnic ultracentrifugation indicated that the purified products (rHBcAg particles) with HBcAg antigenicity mainly located at the densities of 1.27 and 1.40 g ml(-1), respectively. Observation and analysis of the purified rHBcAg products by TEM indicated that rHBcAg peptides could mainly self-assemble into two size classes of core particles. The larger particles were approximately 30.1 nm and the smaller were approximately 21.5 nm in mean diameter. Further observation and analysis of the same rHBcAg (core) particles by AFM also indicated that rHBcAg (core) particles were similar to the native HBcAg (core) particles from infected human hepatocytes and mainly composed of two size classes of partides core. The larger particles were approximately 31.3 nm and the smaller were approximately 22.5 nm in mean diameter which was similar to the results obtained by TEM. All results from both TEM and AFM suggested that core particles (capsids) produced in S. cerevisiae possessed dimorphism.

Molecular epidemiology of hepatitis B, C, D and E viruses among children in Moscow, Russia

BACKGROUND

It is known that the prevalence of HBV and HCV infections vary according to geographical areas. However, in Russia, an adequate level of information on the molecular epidemiology of hepatitis viruses has not been available so far.

OBJECTIVES

To investigate the characterization of various hepatitis viruses in Russia, we conducted molecular-based epidemiological survey of hepatitis viruses including hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV) and hepatitis E virus (HEV) among children in Moscow, Russia.

STUDY DESIGN

The study population of 374 subjects (ranging in age from 1 to 14 years old) consisted of 195 patients with liver diseases and 179 patients without liver diseases. Viral DNA/RNA was determined by nested PCR. Genotyping of HBV and HCV were examined by PCR using type-specific primers. Anti-HEV antibody was assayed by ELISA.

RESULTS

The infection rate of each virus among patients with liver diseases including acute hepatitis, chronic hepatitis or cirrhosis was 65.6% for HBV and 15.9% for HCV. In contrast, among non-liver disease patients, the infection rates were 14.4% for HBV and 0.6% for HCV, respectively. The most common viral genotypes were type D (85%) of HBV and type 1b (79.3%) of HCV. HDV RNA was detected in 7 of 149 (4.7%) HBV DNA-positive children tested. Moreover, testing for HEV among 341 subjects resulted in the detection of anti-HEV IgG in 62 cases (18.2%).

CONCLUSIONS

Our results suggest that HBV infection is widespread in Moscow and have led to a high incidence of acute and chronic liver diseases among children in this region.

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Study on definition of pre-pre-S region in hepatitis B virus genome

AIM

To investigate the new open reading frame (ORF) in hepatitis B virus (HBV) genome.

METHODS

The whole HBV genome was amplified by long-distance and accurate polymerase chain reaction (LA-PCR) method from the serum of 2 patients with chronic HBV infection, and then the PCR products were ligased into pGEM Teasy vectors. Five clones of HBV genome were sequenced. Sequences of our finding were compared with other HBV genome sequence deposited in GenBank.

RESULTS

A new ORF was found in HBV genome, just before Pre-S1 region. It was defined as pre-pre-S region. The pre-pre-S ORF was deduced to be translated with Pre-S1, Pre-S2 and S gene in frame. Its amino acids sequence was as the following: MQLIITSKLGIIYILCGRLVFYIREKLHAV PHFVGHHILGNKSYS. There was a TA-rich region before the ATG of pre-pre-S ORF, indicating a possible promoter for its transcription.

CONCLUSION

There is a new ORF pre-pre-S located upstream to pre-S1 region.

The effects of hepatitis B virus core promoter mutations on hepatitis B core antigen distribution in hepatocytes as detected by laser-assisted microdissection

BACKGROUND/AIMS

The severity of liver damage in patients with chronic hepatitis B is dependent on several factors such as subcellular localization of hepatitis B core antigen (HBcAg) and mutation of hepatitis B virus (HBV) DNA. Here we studied the interrelationship between these two factors both in situ and in vitro.

METHODS

Hepatocytes from liver biopsies showing expression of HBcAg only in the cytoplasm (n=6), only in the nucleus (n=4) and in both cytoplasms or nucleus of different hepatocytes (n=5) were picked up by laser-assisted microdissection and were checked for nucleotide sequences of core promoter region of HBV DNA. HepG2 and Huh7 cell lines transfected with wild and mutant HBV DNA were checked for localization of HBcAg.

RESULTS

The frequencies of core promoter mutations at nucleotide (nt) 1762 and nt 1764 was significantly higher in hepatocytes with cytoplasmic expression of HBcAg compared to that of nuclear expression of HBcAg (P<0.05). Cytoplasmic expression of HBcAg was observed more frequently in HepG2 and Huh7 cells transfected with HBV mutant type (nt 1762 and 1764) than HBV wild type (P<0.05).

CONCLUSIONS

Cytoplasmic localization of HBcAg was associated with HBV DNA mutations at nt 1762 and 1764.

Sequencing of human-viral DNA junctions in hepatocellular carcinoma from patients with HCV and occult HBV infection

DNA of free hepatitis B viruses (HBV) has been detected in the liver of patients infected with hepatitis C virus (HCV). It is unknown whether HBV DNA is integrated into such livers; if so, it may affect hepatocarcinogenesis. Hepatocellular carcinomas (HCCs) from 34 patients without HBV surface antigen (HBsAg) and with anti-HCV, and from 7 patients with HBsAg and without anti-HCV as controls, were examined, using the cassette-ligation-mediated polymerase chain reaction and primers based on HBV DNA sequence. In the controls, HBV DNA had been integrated into human DNA of all HCCs. On the basis of HBV DNA in tumor tissue, 23 of the 34 patients with anti-HCV had occult infection. Junctions between human DNA and HBV DNA were detected in 10 of the 34 patients without HBsAg and with anti-HCV. HBV DNA was integrated into chromosome 11q in 4 of the 10 HCCs with junctions. The DNA to either side of the human-viral junctions was sequenced. Clinically, the mean tumor size of these 10 HCCs was 39 mm; that of the 24 HCCs without integrated HBV was 25 mm. The surrounding tissue was cirrhotic in 2 of the 10 former HCCs and in 16 of the latter 24 HCCs. In conclusion, integrated HBV was detected in some patients with HCV infection; in these patients, the integrated DNA was associated with accelerated hepatocarcinogenesis.

Detection of hepatitis B virus DNA in sera from patients with chronic hepatitis B virus infection by DNA microarray method

We have developed a sensitive and quantitative assay using a DNA microarray for the detection of hepatitis B virus (HBV) DNA in serum. Fluorescently labeled target cDNA prepared from cloned HBV DNA or serum HBV DNA was hybridized to capture DNA on a slide. A linear relationship was obtained between the intensities of the array spot and the amount of the cloned or serum HBV DNA, indicating the quantitative accuracy of this assay system. In addition, there was a significant correlation between the number of molecules of serum HBV DNA determined by the DNA microarray and that determined by a branched-DNA assay (n = 21, r = 0.89). Given these results, we conclude that the DNA microarray assay system may be useful as a diagnostic technique in the clinical laboratory.

Effects of quasi-species heterogeneity of HBV on response to IFN-a therapy

AIM: To study effects of quasi-species heterogeneity of hepatitis B virus (HBV) on response to interferon(IFN)-α therapy.

METHODS: Serum quasi-species heterogeneity of HBV in 20 patients (10 responders and 10 non-responders) with chronic hepatitis B before administration of IFN-α was detected with conformation-sensitive gel electrophoresis (CSGE), and the relationship between response to IFN-α and quasi-species heterogeneity of HBV was analyzed.

RESULTS: No significant difference in levels of HBV DNA between responders (7.27×10¹⁰±8.79×10¹⁰) and non-responders (5.16×10¹⁰±5.13×10¹⁰) before IFN-α therapy was found (P > 0.05). But the quasi-species complexity and genetic diversity in non-responders were significantly higher than those in responders (8.30±1.89 vs 18.5±2.68, P < 0.001 and 0.926±0.008 vs 0.869±0.016, P < 0.001).

CONCLUSION: The level of quasi-species heterogeneity of HBV was reversely associated with the probability of response to IFN-α therapy.

Intramuscular co-injection of naked DNA encoding HBV core antigen and Flt3 ligand suppresses anti-HBc antibody response

Flt3 ligand, a recently described growth factor affecting early hematopoietic progenitor cells, can also support the expansion of dendritic cells secreting IL-12. Its potential use in a clinical setting has been suggested. Here, we studied the effect of in situ delivery of Flt3 ligand plasmid (FL) on the antibody response induced by DNA vaccine encoding wild-type hepatitis B virus core antigen (HBc/w). Intramuscular injection of FL increased the expression of DEC205 and the size of splenocytes, and immunization with HBc/w or HBc/w-transfected EL-4 cells induced strong anti-HBc antibody responses in mice. However, intramuscular injection of FL with HBc/w significantly suppressed HBc/w-induced antibody response in a dose-dependent manner. Suppression of immune response by FL injection was the most prominent when FL and HBc/w were co-injected at the same time and the same site. These results suggest that FL may inhibit humoral response induced by DNA-type vaccination, and DC locally expanded by FL may not have proper functions for induction of humoral response.

Previous or occult hepatitis B virus infection in hepatitis C virus-associated hepatocellular carcinoma without hepatic fibrosis

We investigated the role of hepatitis B virus infection in development of hepatocellular carcinoma in hepatitis C virus-infected patients without hepatic fibrosis. Of 253 patients, 8 lacked hepatic fibrosis (group 1); group 2 included the remaining 245 patients. Clinicopathologic findings were compared between the groups. Hepatitis B x gene was sought in cancers and adjoining noncancerous liver. Group 1 showed better liver function parameters and milder active hepatitis than group 2. The proportion of patients with anti-hepatitis B virus antibody tended to be higher in group 1 than in group 2. The proportion of patients with hepatitis B x RNA in cancers was significantly higher in group 1 than in group 2. All group 1 patients had previous or occult hepatitis B virus infection. Previous or occult hepatitis B virus infection may be critical in development of hepatocellular carcinomas in hepatitis C virus-infected patients without hepatic fibrosis.

Stercorarial shedding and transtadial transmission of hepatitis B virus by common bed bugs (Hemiptera: Cimicidae)

Transtadial persistence and stercorarial shedding of hepatitis B virus (HBV) in common bed bugs, Cimex lectularius L., was studied by using experimental infectious blood feedings, infectious intrathoracic inoculations, and virus detection by polymerase chain reaction and Southern hybridization. Results showed that HBV persisted after an infectious blood meal in bed bug bodies for up to 35 d after the infectious blood meal. It was passed transtadially through one molt regardless of instar, was shed in fecal droplets for up to 35 d after the infectious blood meal, but was not passed transovarially. In bugs inoculated intrathoracically, HBV was detected for 21 d postinoculation. Previous studies detected the hepatitis B surface antigen found on both infectious and noninfectious particles in bed bugs. In this study, the presence of nucleic acids amplified from a conserved core region of the viral genome in bodies and feces of C. lectularius suggests that the HBV virus may be mechanically transmitted in feces or when bugs are crushed, during feeding.

Immune response induced by immunization with Hepatitis B virus core DNA isolated from chronic active hepatitis patients

There are many mutations in the gene encoding Hepatitis B virus (HBV) core antigen of chronic active hepatitis patients, and such mutations are most likely to be related to the severity of disease. Here, we constructed plasmids containing wild-type and deletion type of HBV core gene (HBc) to develop an experimental DNA vaccine and to compare immunogenicity of two types of HBc vaccine. Twenty-nine wild-types and seven deletion types of HBc were detected in sera of 32 Korean patients with chronic active hepatitis. Four wild-types (W1, W2, W4, W6) and two deletion types (D3, D4) of HBc were cloned into the pcDNA3 vector. Intramuscular immunization with wild-type HBc efficiently increased serum anti-HBc antibody response in a dose-dependent manner. Anti-HBc antibody response in mice injected with W6 increased 14 days after immunization, and peaked after 30 days and was maintained at least up to 50 days. W6 immunization induced a specific cytotoxic T lymphocyte response to W6-transfected 3LL (3LL-W6), and reduced the sizes of tumor mass of mice challenged with 3LL-W6 or 3LL transfected with D4. However, intramuscular immunization with D3 and D4 did not show antibody response at all. D3 and D4 have 157 bp (from 331 to 491 bp) and 122 bp (from 327 to 448 bp) gene deletion, respectively, and these encode class II MHC-restricted T-cell epitope. Altogether, these results suggest that mutant virus that has deleted HBc gene may evade immune systems due to loss of T-cell epitope.

Predominance of genotype A HBV in an HBV-HIV-1 dually positive population compared with an HIV-1-negative counterpart in Japan

Hepatitis B virus (HBV) has seven genotypes, A to G. Previous studies have shown that genotype C is the most prevalent strain in chronic HBV carriers in East Asia. This study was undertaken to investigate the epidemiology of HBV genotypes among Japanese patients who are coinfected with human immunodeficiency virus type 1 (HIV-1). The sequences of the complete hepatitis B surface antifen (HBsAg) genes were obtained from 18 coinfected Japanese patients. Among the 18 patients, 12 of 13 men who had sex with men (MSM) had genotype A (92%), whereas only one of five heterosexual or hemophiliac patients had genotype A. The predominance of genotype A HBV in MSM showed a striking contrast to the current genotype prevalence in the Japanese population. Owing to the recent decrease in the rate of vertical transmission in Japan, the role of sexual behavior in the transmission of HBV cannot be overestimated. Thus, the relative proportion of genotype A may gradually increase in Japan.

Anti-HBs after hepatitis B immunization with plasma-derived and recombinant DNA-derived vaccines: binding to mutant HBsAg

The G145R mutant of the small S-protein is a major escape mutant of hepatitis B virus observed in natural infection, after immunization and HBIG therapy. In a previous study we found that plasma-derived and recombinant DNA-derived vaccine HBsAg reacted differently with monoclonal antibodies sensitive for the G145R change. In the present study we investigated the binding of polyclonal anti-HBs obtained after immunization with plasma vaccine and recombinant DNA vaccine to synthetic peptides (adw(2), adr) and rHBsAg (HepG2) (ayw(3); wild type and a 145R mutant). Anti-HBs binding to synthetic peptids (25-mers, 7aa overlap) from the "a"-loop was significantly reduced by the G145R substitution and by changing the amino acid sequence from adw(2) into adr. With mutant G145R rHBsAg the inhibitory activity of vaccine anti-HBs was decreased compared to rHBsAg wild type. In general only minor differences were observed between plasma vaccine and recombinant DNA vaccine related antibody responses. However, the individual heterogeneity in epitope specific reactivity with its possible consequences for protection (against escape mutants) is not reflected in an anti-HBs titer by standard anti-HBs assays. The presented differentiation in anti-HBs response after immunization may deliver new tools for evaluation of future vaccines.

Molecular characteristic-based epidemiology of hepatitis B, C, and E viruses and GB virus C/hepatitis G virus in Myanmar

We carried out a molecular characteristic-based epidemiological survey of various hepatitis viruses, including hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis E virus (HEV), and GB virus C (GBV-C)/hepatitis G virus (HGV), in Myanmar. The study population of 403 subjects consisted of 213 healthy individuals residing in the city of Yangon, Myanmar, and the surrounding suburbs and 190 liver disease patients (155 virus-related liver disease patients and 35 nonviral disease patients). The infection rates of the viruses among the 213 healthy subjects were as follows: 8% for HBV (16 patients), 2% for HCV (4 patients), and 8% for GBV-C/HGV (17 patients). In contrast, for 155 patients with acute hepatitis, chronic hepatitis, liver cirrhosis, or hepatocellular carcinoma, the infection rates were 30% for HBV (46 patients), 27% for HCV (41 patients), and 11% for GBV-C/HGV (17 patients). In the nonviral liver disease group of 35 patients with alcoholic liver disease, fatty liver, liver abscess, and biliary disease, the infection rates were 6% for HBV (2 patients), 20% for HCV (7 patients), and 26% for GBV-C/HGV (9 patients). The most common viral genotypes were type C of HBV (77%), type 3b of HCV (67%), and type 2 of GBV-C/HGV (67%). Moreover, testing for HEV among 371 subjects resulted in the detection of anti-HEV immunoglobulin G (IgG) in 117 patients (32%). The age prevalence of anti-HEV IgG was 3% for patients younger than 20 years and 30% or more for patients 20 years of age or older. Furthermore, a high prevalence of anti-HEV IgG (24%) was also found in swine living together with humans in Yangon. These results suggest that these hepatitis virus infections are widespread in Myanmar and have led to a high incidence of acute and chronic liver disease patients in the region.

Isolation, characterization and biological significance of hepatitis B virus mutants from serum of a patient with immunologically negative HBV infection

BACKGROUND/AIM

A low-titered hepatitis B virus infection without immunological markers was identified in a prospective study in the serum of a kidney transplant recipient by PCR. The aim of this study was to analyze HBV genomes and their biological significance.

METHODS

The genome was amplified in two overlapping fragments A and B. Sequencing of 22 clones of the A- and 12 clones of the B-fragment revealed a heterogeneous virus population. A consensus and a mutant sequence were computed, representing the complete sequence of the virus population. The two sequences were compared with 41 published genomes of the different HBV geno- and serotypes.

RESULTS

Ninety-five point mutations and two deletions were identified. Two mutations were observed in all clones and 17 other mutations in three or more clones. The deletions were found in ten and seven of 22 clones. They were located in the C-gene and led to stop codons yielding truncated e- and/or core proteins. In vitro transfection of DNA constructs containing these deletions demonstrated a stop of HBV replication and of HBeAg expression. Cotransfection experiments demonstrated a dominant negative effect of the mutants containing the deletions. In addition, we describe new variants of naturally occurring HBsAg mutants that may cause HBV infection less detectable by standard HBsAg measurement assays. They were characterized by two point mutations which were observed in 9 of 12 and 13 of 22 clones of the S-gene. They significantly reduced the HBsAg expression in in vitro transfection experiments.

CONCLUSION

We found a patient with low-titered HBV infection, with mutations of the 'a' epitope of the Santigen as well as with mutations leading to truncated core proteins which may cause a dominant negative effect.

Detection of mutations in hepatitis B virus enhancer 2/core promoter and X protein regions in patients with fatal hepatitis B virus infection

The enhancer 2/core promoter and the X protein regions located upstream of the precore and core regions in hepatitis B virus regulate expression of core/e antigen peptides. Mutations in the precore and core regions have been reported to be associated closely with the severity of type B hepatitis, and regions regulating expression of these peptides may also be involved in severe liver damage. Mutations were examined in regions that may be related to fatal liver diseases. Nucleotide sequences and deduced amino acid sequences from 20 patients with fatal type B hepatitis (12 with fulminant hepatitis and 8 with severe exacerbation) and 10 patients with self-limited acute hepatitis were analyzed. There were 50 nucleotide alterations in the enhancer 2/core promoter region of virus from 12 patients with fulminant hepatitis (average 4.1/case), 37 alterations in 8 patients with severe exacerbation (4.6/case), and 10 mutations in 10 cases of acute hepatitis (1.0/case). The numbers of amino acid mutations in X protein were 53 in 12 cases of fulminant hepatitis (4.4/case), 27 in 8 cases of severe exacerbation (3.3/case), and 9 in 10 cases of acute hepatitis (0.9/case). In fatal cases, approximately 50% of the nucleotide mutations were located within the region spanning nucleotides 1741-1777 (14.2% of the enhancer 2/core promoter region) and 30% of the amino acid mutations in X protein were located within the region containing codons 122-132 (7.1% of X protein). In addition to mutations in the precore and core regions, mutations in the enhancer 2/core promoter and the X protein regions may be associated with the pathogenesis of fatal B hepatitis infection.

Occult hepatitis B virus infection in HBs antigen-negative hepatocellular carcinoma in a Japanese population: involvement of HBx and p53

Hepatitis B virus (HBV) genome was reported to be detected in serum or liver tissues in hepatocellular carcinoma (HCC) patients negative for hepatitis B surface antigen (HBsAg). Hepatitis B x (HBx) and p53 protein were reported to play an important role in HBV-related hepatocarcinogenesis. To clarify latent HBV infection in HBsAg- and anti-hepatitis C virus (anti-HCV)-negative HCC in a Japanese population and involvement of HBx and p53 protein in these patients, we performed the sensitive and specific nested polymerase chain reaction (PCR) and immunohistochemical analysis. Of 1,024 HCC patients we saw between 1974 and 1998, 66 (6.4%) were negative for HBsAg and anti-HCV. Serum DNA was amplified by nested PCR by using specific primers of surface (S), core (C) and X regions in 26 patients negative for HBsAg and anti-HCV. Eighteen (69%) patients were positive for either S, C, or X region and the results of PCR were confirmed by Southern blotting. Of 18 PCR-positive patients, 3 were positive for anti-HBs and 9 were positive for anti-HBc, however, one was negative for any HBV markers. In HBsAg-negative and PCR-positive patients, the positive rates of expression of HBx and p53 were 8/13 (62%) and 7/13 (54%), being comparable to those in HBsAg-positive HCC patients. The results of the present study suggest that high prevalence of HBV infection is observed in HBsAg-negative HCC in a Japanese population and expression of HBx and p53 is consistent with a role, in these patients, for the transforming ability of these proteins.

Reduced transcription and progeny virus production of hepatitis B virus containing an 8-bp deletion in basic core promoter

We have demonstrated previously the presence of an 8-bp deletion mutant, spanning from nt. 1768 to nt. 1775 in the basic core promoter region of hepatitis B virus (HBV) in patients with anti-HBe positive asymptomatic phase before developing acute exacerbation after immunosuppressive treatment. The transcription and progeny virus production activities of the mutant were examined by transfection of the recombinant plasmid [pUC Del(2)] containing the head-to-tail dimer DNA of the mutant into HepG2 cells. The amounts of hepatitis B surface antigen (HBsAg) and HBe antigens secreted into the culture medium were markedly reduced. Southern blotting of DNAs extracted from the culture medium also showed reduced mutant activity to produce progeny virus. Northern blotting and RNase protection assay of RNAs extracted from transfected cells demonstrated that the transcription of both precore mRNA and pregenome RNA was reduced significantly compared to that of wild-type HBV. The promoter activity examined by transfection of the CAT plasmid containing deletion mutant DNA was much lower than that of wild type. Co-transfection experiments, however, of the CAT plasmid containing wild-type DNA with pUC Del(2) reduced CAT activity induced by wild-type, suggesting that truncated X protein produced by the mutant does not possess a sufficient transactivating activity. Gel shift assay using HepG2 nuclear extract and a probe containing four TA-rich regions in CP and various competitors suggested that the lack of the third TA-rich region was responsible for the transcription reduction of precore mRNA and pregenome RNA. The possible mechanisms are discussed.