[Hepatitis B Virus Infection: Current Management and Prevention]

Hepatitis B virus (HBV) is transmitted mainly via percutaneous or permucosal exposure to HBV- containing body fluids. Because HB vaccination is effective and safe, it is recommended for all children, ado- lescents, and all unvaccinated adults at risk of HBV infection (individuals with occupational risk, immunosup- pressed individuals, and sexually active individuals). In Japan, universal HB vaccination will be introduced for all infants in October 2016. In Japan, the prevalence of HBV genotype A, which is frequently found in North America, northwestern Europe, India, and Africa, has been increasing as a sexually transmitted infection. HBV reactivation under anticancer chemotherapy and immunosuppressive therapy is well-known as a seri- ous complication in HBV-resolved patients. Monthly monitoring of HBV-DNA is recommended for prevent- ing HBV reactivation-related hepatitis among HBV-resolved patients with non-Hodgkin B-cell lymphoma under steroid plus rituximab chemotherapy. Recently, a highly sensitive chemiluminescent enzyme immunoassay (CLEIA) for HBsAg detection by Lumipulse HBsAg-HQ was reported as the latest clinical application. Although the sensitivity of this assay (≥5 mIU/mL) is 10-fold higher than the conventional assay, it is still lower than that of the HBV-DNA assay. The useful HBsAg-HQ will be applied for detecting occult HBV infection and HBV reactivation. The aim of treatment for chronic HBV infection is to reduce the risk of complications, including cirrhosis and hepatocellular carcinoma (HCC). Pegylated interferon alfa and nucleoside/nucleotide analogues (NAs) are the current treatments for chronic HBV infection. NAs have improved the outcomes of patients with cirrhosis and HCC, and decreased the incidence of acute liver failure. [Review].

Broad Range of Hepatitis B Virus (HBV) Patterns, Dual Circulation of Quasi-Subgenotype A3 and HBV/E and Heterogeneous HBV Mutations in HIV-Positive Patients in Gabon

Integrated data on hepatitis B virus (HBV) patterns, HBV genotypes and mutations are lacking in human immunodeficiency virus type 1 (HIV-1) co-infected patients from Africa. This survey was conducted in 2010-2013 among 762 HIV-1-positive adults from Gabon who were predominantly treated with 3TC-based antiretroviral treatment. HBV patterns were identified using immunoassays detecting total antibody to hepatitis B core antigen (HBcAb), hepatitis B surface antigen (HBsAg), IgM HBcAb, hepatitis B e antigen (HBeAg), antibody to HBsAg (HBsAb) and an in-house real-time PCR test for HBV DNA quantification. Occult hepatitis B (OBI) was defined by the presence of isolated anti-HBc with detectable serum HBV DNA. HBV genotypes and HBV mutations were analyzed by PCR-direct sequencing method. Seventy-one (9.3%) patients tested positive for HBsAg, including one with acute hepatitis B (0.1%; 95% CI, 0.0%-0.2%), nine with HBeAg-positive chronic hepatitis B (CHB) (1.2%; 95% CI, 0.6%-2.2%), 16 with HBeAg-negative CHB (2.1%; 95% CI, 1.2%-3.3%) and 45 inactive HBV carriers (5.9%; 95% CI, 4.4%-7.8%). Sixty-one (8.0%; 95% CI, 6.2%-10.1%) patients showed OBI. Treated patients showed similar HBV DNA levels to those obtained in untreated patients, regardless of HBV patterns. Around 15.0% of OBI patients showed high (>1,000 UI/mL) viremia. The mutation M204V/I conferring resistance to 3TC was more common in HBV/A (47.4%) than in HBV/E isolates (0%) (P = .04). Our findings encouraged clinicians to promote HBV vaccination in patients with no exposure to HBV and to switch 3TC to universal TDF in those with CHB.

Clinical implications of hepatitis B virus mutations: Recent advances

Hepatitis B virus (HBV) infection is a major cause of acute and chronic hepatitis, and of its long-term complications. It is the most variable among DNA viruses, mostly because of its unique life cycle which includes the activity of error-prone enzyme, reverse transcriptase, and the very high virion production per day. In last two decades, numerous research studies have shown that the speed of disease progression, reliability of diagnostic methods and the success of antiviral therapy and immunization are all influenced by genetic variability of this virus. It was shown that mutations in specific regions of HBV genome could be responsible for unwanted clinical outcomes or evasion of detection by diagnostic tools, thus making the monitoring for these mutations a necessity in proper evaluation of patients. The success of the vaccination programs has now been challenged by the discovery of mutant viruses showing amino acid substitutions in hepatitis B surface antigen (HBsAg), which may lead to evasion of vaccine-induced immunity. However, the emergence of these mutations has not yet raised concern since it was shown that they develop slowly. Investigations of HBV genetic variability and clinical implications of specific mutations have resulted in significant advances over the past decade, particularly in regard to management of resistance to antiviral drugs. In the era of drugs with high genetic barrier for resistance, on-going monitoring for possible resistance is still essential since prolonged therapy is often necessary. Understanding the frequencies and clinical implications of viral mutations may contribute to improvement of diagnostic procedures, more proper planning of immunization programs and creating the most efficient therapeutic protocols.

5'-triphosphate-siRNA activates RIG-I-dependent type I interferon production and enhances inhibition of hepatitis B virus replication in HepG2.2.15 cells

Hepatitis B virus (HBV) infection often results in acute or chronic viral hepatitis and other liver diseases including cirrhosis and hepatocellular carcinoma. Current therapies for HBV usually have severe side effects and can cause development of drug-resistant mutants. An alternative and safe immunotherapeutic approach for HBV infection is urgently needed for effective anti-HBV therapy. In this study, we propose a new strategy for anti-HBV therapy that activates type-I interferon (IFN) antiviral innate immunity through stimulating pattern-recognition receptors with RNA interference (RNAi) using a 5'-end triphosphate-modified small interfering RNA (3p-siRNA). We designed and generated a 3p-siRNA targeting overlapping region of S gene and P gene of the HBV genome at the 5'-end of pregenomic HBV RNA. Our results demonstrated that 3p-siRNA induced a RIG-I-dependent antiviral type-I IFN response when transfected into HepG2.2.15 cells that support HBV replication. The 3p-siRNA significantly inhibited HBsAg and HBeAg secretion from HepG2.2.15 cells in a RIG-I-dependent manner, and the antiviral effect of 3p-siRNA was superior to that of siRNA. Furthermore, 3p-siRNA had more pronounced inhibition effects on the replication of HBV DNA and the transcription of mRNA than that of siRNA. Finally, 3p-siRNA displayed antiviral activity with long-term suppression of HBV replication. In conclusion, our findings suggest that 3p-siRNA could act as a powerful bifunctional antiviral molecule with potential for developing a promising therapeutic against chronic HBV infection.

[Construction and expression of eukaryotic expression plasmid pIRES-neo-HBAg carrying HBV fusion antigen gene]

OBJECTIVE

To construct a eukaryotic expression plasmid harboring HBV fusion antigen gene, and to express it in 293T cells.

METHODS

The HBV fusion gene fragment was amplified by PCR from the plasmid pVAX1-HBV containing HBV fusion gene. After purified, the product was cloned into pMD18-T vector. The recombinant plasmid was confirmed by endonuclease digestion and sequencing analysis, and then subcloned into eukaryotic expression vector pIRES-neo. Then the recombinant expression plasmid pIRES-neo-HBAg was transfered into 293T cells by Lipofectamine(TM); 2000. The expression of HBV fusion antigen was identified by Western blotting, flow cytometry and immunofluorescence cytochemistry.

RESULTS

The eukaryotic expression vector pIRES-neo-HBAg was constructed successfully. The expression of fusion antigen could be detected in the pIRES-neo-HBAg transfected 293T cells by Western blotting, immunofluorescence cytochemistry and flow cytometry.

CONCLUSION

The eukaryotic expression plasmid pIRES-neo-HBAg is successfully constructed and the fusion antigen is expressed in 293T cells.

[Characterization of hepatitis B virus antigen expression in vitro and in vivo transduced by different transfer plasmids carrying HBV infectious genome]

OBJECTIVE

To character HBV antigen expression in vitro and in vivo transduced by different transgenic plasmids carrying infectious genome of hepatitis B virus (HBV).

METHODS

We constructed four different lentiviral transfer plasmids (carrying 1.3 full-length genome of HBV, by replacing the EGFP express box in pCS-CG plasmid with HBV genome and with different structural element, named as pCS-HBV1.3 (pCS-HBV1.3 X, pCS-HBV1.3 P, pCS-HBV1.3 N and pCS-HBV1.3 K). We detected the expression of HBsAg and HBeAg by ELISA in different time after transfected Huh 7 cells or hydrodynamic injection into C57 BL/6 mice with transfer plasmids pCS-HBV, respectively.

RESULTS

We detected significant expression of HBsAg over 5 days after transfected Huh 7 cells (in vitro) or hydrodynamic injection into C57 BL/6 mice (in vivo) with transfer plasmids pCS-HBV1.3 X, pCS-HBV1.3 P and pCS-HBV1.3 K. The expression level and dynamics of HBsAg and HBeAg in the sera of mice is consistent with that of in the supernatant of Huh-7 cell. Furthermore, the expression of HBV antigens were modulated by the direction and position of HBV insert, also by some lentiviral vector cis-elements (cPPT and RRE).

CONCLUSION

The optimal lentiviral transfer plasmids (pCS-HBV1.3 X, pCS-HBV1.3 P and pCS-HBV1.3 K) could be further used for establishment and application of HBV transgenic cell or animal model.

[Immunosuppressant dexamethasone can significantly extend the expression of hepatitis B virus antigens in the HBV mouse model by hydrodynamic transfection method]

To develop a HBV infection mouse model by hydrodynamic-based transfection and further to optimize the method of development of HBV infection mouse model. We first developed a construct which contained inverted terminal repeat elements (ITR) of adeno-associated virus (AAV) and 1. 3 copies of HBV genome (ayw subtype). The pAAV-HBV1. 3 DNA was then injected hydrodynamically into the tail veins of C57BL/6 mice in 5 seconds. The virus load in serum and liver was assayed by ELISA and Real-time PCR. The expression of virus antigen and the pathologic changes of liver were analyzed by HE and immunohistochemical staining. Meanwhile, to develop HBV transfected immunosuppressied mouse, mice were injected intraperitoneally triple with 0.2 ml dexamethason (50 mg/kg) every two days before HBV transfection. The levels of HBsAg and HBeAg were assayed by ELISA. Our data showed: (1) HBsAg and HBeAg were positive (100%) in serum and liver of experimental normal mouse at day 10 after HBV transfection, and became negative at day 30 and day 60. Meanwhile the viral load in serum and liver in experimental group was significantly higher than that in control group at day 10, 30 and 60 after HBV transfection (P < 0.01, P < 0.05, respectively). (2) HBsAg and HBeAg in serum in immunosuppressed mouse model were positive until 60 days. In conclusion, a HBV infection mouse model was developed successfully by hydrodynamic-based transfection. By suppressing the immune status of mice injected with dexamethasone, the expression of HBV antigens was extended longer than that in normal adult mice. These models pave a way for HBV research and evaluation of HBV vaccine and drug development.

[Detection of peripheral blood HBV-LHBs transactivation function and its relationship with anti-viral efficacy]

OBJECTIVE

Explore the serum of patients with CHB of HBV large envelope protein (HBV-LHBs) trans-activation function and antiviral therapy effect relationship.

METHODS

60 cases of anti-viral treatment of patients with chronic hepatitis B to take every 3 months HBVDNA, HBV-LHBs, as well as detection of hepatitis B immune markers to observe the changes in indexes.

RESULTS

Income group 60 cases of anti-virus group HBVDNA with HBV-LHBs have a higher detection rate of the consistency of the results found no statistical significance (P > 0.05), HBV-LHBs-positive rate and positive rate of HBeAg differences (chi2 = 4.08, P < 0.05). After 24 months of antiviral therapy HBV-LHBs expression always HBVDNA in 29 cases of which occurred 24 months after the negative reaction of the 20 cases, continuous positive were seven cases of non-negative. 60 cases of patients 24 months found no HBsAg seroconversion, four cases of emergence of HBeAg seroconversion.

CONCLUSION

(1) detection of serum HBV-LHBs to reflect the hepatitis B virus replication with HBVDNA good correlation. (2) anti-viral treatment of dynamic observation of the process of HBV-LHBs expression can predict the effectiveness of anti-viral therapy.

[A construct competent to support the replication of hepatitis B virus of genotype B]

OBJECTIVE

To construct a vector that is competent to support the replication of hepatitis B virus (HBV) of genotype B.

METHODS

The HBV genome of genotype B was amplified by PCR and ligated into pBlueskript II KS(+) vector, the resulting plasmid was verified by enzyme digestion and DNA sequencing. After transfection of this plasmid into Huh7 cells, the HBsAg and HBeAg antigens in culture medium were quantified by ELISA, the transcripts and replication intermediates of HBV were detected by northern blot and southern blot respectively. On the other hand, the plasmid was hydrodynamically injected into BALB/cJ mice via tail vein. Then the HBV DNA in serum was quantified by real-time PCR, and HBcAg expression in liver tissue was detected by immunohistochemistry.

RESULTS

After transfection of the plasmid into Huh7 cells, the HBsAg and HBeAg antigens were detected in the culture medium, the transcripts and replication intermediates of HBV were detected in the cells. High titer of HBV DNA was detected in the serum of hydrodynamic-injected mice. Immunostaining indicated that HBcAg was expressed in hepatocytes of injected mice.

CONCLUSION

This construct is competent to support the replication of hepatitis B virus of genotype B.

[Expression and preliminary applications of hepatitis B surface antigen mutants]

AIM

To clone and express HBsAg mutant in the Pichia pastoris.

METHODS

The cloned wild type pGAP-S was used as the DNA template to generate mutant type pGAP-MS with a single or double nucleotide changes incorporated in complementary oligonucleotide primers. The product was linearized with BspH I and transformed into Pichia pastoris strain GS115, and stable multicopy integrants were screened in medium containing different concentrations of Zeocin.

RESULTS

The pGAP-MS expression vector was successfully constructed and stable numbers integrated strains with high copy number were obtained. The expression of HBsAg mutant protein was identified by SDS-PAGE and Western blot with specific polyclonal antibody. The molecular weight of recombinant HBsAg mutant was 38 kDa. AxSYM HBsAg V2(Abbott)assays demonstrated all 10 HBsAg mutants were reactive.

CONCLUSION

The recombinant HBsAg mutant with immunoreactivity was successfully expressed in Pichia pastoris, and it was of practical value on the quality control and clinical applications of commercial assays.

Construction and identification of a human liver specific microRNA eukaryotic expression vector

MiR-122 is one of the non-coding RNAs which showed its effects on the lipo-metablism, virus infection and HCC forming through regulation of liver gene expression. Its eukaryotic expression vector was constructed by using pSuper which was widely applied in the siRNA expression. The precursor of human miR-122 gene was amplified by polymerase chain reaction (PCR) from the human genomic DNA. The positive clones were screened by PCR and restriction enzyme digestion. The new expression vector of miR-122 was named pHsa-m122. PHsa-m122 and its controls were transfected to HepG2 cells. The miR-122 expression activity was evaluated by GFP122i sensor reporter plasmid through fluorescence detection and Western blot. It was shown that the fluorescence intensity of GFP122si and pHsa-m122 co-transfection group was weaker than that of the controls, so the functional activity of expressed miR-122 was detected. When HepG2 cells were co-transfected with HBV1.3 and pHsa-m122 plasmids, the results showed miR-122 may down-regulate the gene expression of HBV. The human liver specific microRNA eukaryotic expression vector of miR-122 was constructed successfully, which may facilitate further study of its function in the development of liver virus infection diseases and HCC.

Association of human APOBEC3 cytidine deaminases with the generation of hepatitis virus B x antigen mutants and hepatocellular carcinoma

Human APOBEC3 (apolipoprotein B mRNA editing enzyme, catalytic polypeptide 3) cytidine deaminases have been shown to be potent inhibitors of diverse retroviruses including Vif-deficient human immunodeficiency virus 1 (HIV-1), hepatitis virus B (HBV), adeno-associated virus, and endogenous retroelements. Despite the fact that these enzymes are known to be potential DNA mutators and to target retroviral DNA for cytidine deamination, the pathological effects of their deregulated expression in human diseases are not yet clear. Mutants of the viral HBx protein have been implicated in the carcinogenesis of hepatocellular carcinoma (HCC); however, little is known about how or why such mutants are generated in the human liver. Here, we report that a number of APOBEC3 deaminases preferentially edit the HBx region of HBV DNA and generate C-terminally truncated HBx mutants. Our functional studies indicated that APOBEC3-mediated HBx mutants, especially the C-terminally truncated mutants, cause a gain of function that enhances the colony-forming ability and proliferative capacity of neoplastic cells. Furthermore, we detected G-to-A hypermutation-mediated HBx mutants in preneoplastic liver tissues of selected patients with active chronic HBV infections. We also observed that the APOBEC3B (A3B) cytidine deaminase was widely up-regulated in HCC tumor tissues; it also promoted the growth of neoplastic human HepG2 liver cells and up-regulated heat shock transcription factor1 (HSF1) expression.

CONCLUSION

These findings suggest that some of the APOBEC3 deaminases play a role in the carcinogenesis of HCC through the generation of HBx mutants, providing preneoplastic and neoplastic hepatocytes with a selective clonal growth advantage. Deregulated expression of A3B in liver tissues may also have the potential to promote genetic instability and tumorigenesis.

Enhancing the potency of HBV DNA vaccines using fusion genes of HBV-specific antigens and the N-terminal fragment of gp96

BACKGROUND

Many clinical trials show that DNA vaccine potency needs to be greatly enhanced. We have reported that the N-terminal fragment of glycoprotein 96 (gp96) is able to produce an adjuvant effect for production of cytotoxic T-lymphocytes (CTLs) with hepatitis B virus (HBV)-specific peptides. Here, we report a new strategy for HBV DNA vaccine design using a partial gp96 sequence.

MATERIALS AND METHODS

We linked the N-terminal 1-355aa (N355) of gp96 to HBV genes encoding for structural proteins, the major S and middle S2S envelope proteins and the truncated core HBcAg (1-149aa). ELISPOT, tetramer staining and intracellular IFN-gamma assay were performed to analyze the induced cellular immune responses of our DNA constructs in BALB/c mice and HLA-A2 transgenic mice. The relative humoral immune responses were analyzed in different IgG isotypes.

RESULTS

The fusion genes induced 2- to 6-fold higher HBV-specific CD8(+) T cells as compared to the antigens alone. There was an approximate 10-fold decrease in the humoral immune responses with fusion genes based on HBV envelope proteins. Interestingly, the decreased humoral immune responses were not observed when antigens and plasmid encoding N355 were co-delivered. However, an approximate 20-fold higher antibody level was induced when linking N355 to a truncated HBcAg. Immunization by intramuscular injection resulted in predominantly IgG2a antibodies, which indicated that these vaccines preferentially prime Th1 responses.

CONCLUSIONS

We constructed highly immunogenic fusions by linking the N-terminal fragment of gp96 to HBV antigens. Our results imply that the N-terminal fragment of gp96 may be used as a molecular adjuvant to enhance the potency of DNA vaccines.

[Establishing a L02 cell model with whole HBV gene transfection and analyzing its expressions of HLA-A, B, C and MICA/B]

OBJECTIVE

To establish a cell model with HBV secretion by plasmid transfection with whole HBV genes into hepatic L02 cells, and to analyze the effect of HBV on the expression of HLA-A, B, C and MICA/B in L02 cells.

METHODS

The mock control plasmid was built by digesting pEcob6 plasmid with EcoR I at the HBV DNA site and ligating the fragment without HBV DNA. The L02 cells were transfected with pEcob6 or mock plasmid and pcDNA3 1-neo by liposome. The expressions of HBsAg, HBcAg/HBeAg and HBV DNA were detected by immunofluorescence assay, Abbott enzymoimmunoassay, or FQ-PCR. The expressions of HLA-A, B, C and MICA/B were determined by FACS and the differences in the two molecules were analyzed.

RESULTS

After the transfected cells were selected by G418, the HBsAg and HBeAg in the supernatant of L02-HBV cells were 24.78(S/N) and 4.117(S/N). The quantity of HBV DNA was 9.67 x 10(4) copies/ml, but in L02-mock and in L02 cells they were all negative. Under a confocal microscope HBsAg was brightly shown in the cytoplasm while HBcAg showed dimly in the cytoplasm or in the nuclei. By using FACS, the L02 and L02-mock cells showed some low expressions of HLA-A, B, C and a little expression of MICA/B, while the expression of the two molecules was higher in L02-HBV and the differences were significant (P < 0.05).

CONCLUSION

A cell model with the expression of HBV antigens and the secretion of HBV DNA was established by pEcob6 transfection into L02 cells, the transcription or replication of HBV gene might induce stronger expressions of HLA-A, B, C and MICA/B on hepatic cells. They might be related to the immune injuries of hepatic cells.

Inhibition of hepatitis B virus expression and replication by RNA interference in HepG2.2.15

AIM: To observe the inhibition of hepatitis B virus replication and expression by transfecting vector-based small interference RNA (siRNA) pGenesil-HBV X targeting HBV X gene region into HepG2.2.15 cells.

METHODS: pGenesil-HBV X was constructed and transfected into HepG2.2.15 cells via lipofection. HBV antigen secretion was determined 24, 48, and 72 h after transfection by time-resolved immunofluorometric assays (TRFIA). HBV replication was examined by fluorescence quantitative PCR, and the expression of cytoplasmic viral proteins was determined by immunohistochemistry.

RESULTS: The secretion of HBsAg and HBeAg into the supernatant was found to be inhibited by 28.5% and 32.2% (P < 0.01), and by 38.67% (P < 0.05) and 42.86% (P < 0.01) at 48 h and 72 h after pGenesil-HBV X transfection, respectively. Immunohistochemical staining for cytoplasmic HBsAg showed a similar decline in HepG2.2.15 cells 48 h after transfection. The number of HBV genomes within culture supernatants was also significantly decreased 48 h and 72 h post-transfection as quantified by fluorescence PCR (P < 0.05).

CONCLUSION: In HepG2.2.15 cells, HBV replication and expression is inhibited by vector-based siRNA pGenesil-HBV X targeting the HBV X coding region.

Expression, purification and characterization of the Hepatitis B virus entire envelope large protein in Pichia pastoris

The current HBsAg vaccine has performed a vital role in preventing the transmission of HBV during the past 20 years. However, a number of individuals still show no response or a low response to the vaccine. In the present study, the HBV envelope large protein gene was cloned into the eukaryotic expression vector pPIC9k and was subsequently expressed in the yeast Pichia pastoris. The HBV large protein (L protein) was produced and secreted into the medium, where some of the L protein formed particles. The soluble L protein and particles were purified by column chromatography and sucrose density gradient centrifugation. Western blot analysis demonstrated that the particle was composed of both HBV L and S protein. To compare the antigenicity of the L protein and HBsAg, rabbits were immunized with the soluble L protein and the commercially available HBV vaccine and the increasing level of antibodies was determined by ELISA. The results showed that the anti-HBsAg antibody, from rabbits injected with the L protein at a dose of 2 and 10microg, was detected on day 14, whereas rabbits vaccinated with 10 and 2microg HBsAg did not develop antibodies until day 21 and 28, respectively. The antibody level in groups inoculated with the L protein was approximately 50% higher than in the group injected with HBsAg using the same dose. Furthermore, 2microg L protein induced a significant and rapid anti-HBsAg antibody response than 10microg HBsAg. Therefore, we suggest that the L protein is an ideal candidate for a new generation HB vaccine to protect people from HBV infection.

RNAi-Based Knockdown of HBx mRNA in HBx-Transformed and HBV-Producing Human Liver Cells

RNA interference (RNAi) is the process of sequence-specific gene silencing induced by 21-23-nt RNA of small interfering RNA (siRNA). The HBx of hepatitis B virus (HBV) causing human liver diseases has been known as a multifunctional protein which affects transcription, cell growth, and apoptotic cell death. Here, we demonstrate that the HBx-specific siRNA (siRNAx) and short hairpin RNA (shRNAx) effectively induce the degradation of HBx mRNA in HBx-transformed and HBV-producing human liver cells by up to 80-90%. Also, the HBx expression in HBx-transformed cells was continuously silenced by retransformation with the shRNAx expression vector. These results imply that HBx-driven RNAi, either delivery of siRNAx or expression of shRNAx, provides a promising anti-HBV approach to suppress the HBx expression in human hepatoma cells.

Hepatitis B virus is inhibited by RNA interference in cell culture and in mice

BACKGROUND AND AIMS

For chronic hepatitis B virus (HBV) infection the effects of current therapies are limited. Recently, RNA interference (RNAi) of virus-specific genes has emerged as a potential antiviral mechanism. Here we studied the effects of HBV-specific 21-bp short hairpin RNAs (shRNAs) targeted to the surface antigen (HBsAg) region and the core antigen (HBcAg) region both in a cell culture system and in a mouse model for HBV replication.

METHODS

HBsAg and hepatitis B e antigen (HBeAg) in the media of the cells and in the sera of the mice were analyzed by time-resolved immunofluorometric assay, intracellular HBcAg by immunofluorescence assay, HBsAg and HBcAg in the livers of the mice by immunohistochemical assay, HBV DNA by fluorogenic quantitative polymerase chain reaction (FQ-PCR) and HBV mRNA by semi-quantitative reverse transcriptase PCR (RT-PCR).

RESULTS

Transfection with the shRNAs induced an RNAi response. Secreted HBsAg was reduced by >80% in cell culture and >90% in mouse serum, and HBeAg was also significantly inhibited. Immunofluorescence detection of intracellular HBcAg revealed 76% reduction. In the liver tissues by immunohistochemical detection, there were no HBsAg-positive cells and >70% reduction of HBcAg-positive cells for shRNA-1. And for shRNA-2 the detection of HBsAg and HBcAg also revealed substantial reduction. The shRNAs caused a significant inhibition in the levels of viral mRNA relative to the controls. HBV DNA was reduced by >40% for shRNA-1 and >60% for shRNA-2.

CONCLUSIONS

RNAi is capable of inhibiting HBV replication and expression in vitro and in vivo and thus may constitute a new therapeutic strategy for HBV infection.

Clinical Significance of the Genotype and Core Promoter/Pre-Core Mutations in Hepatitis B Virus Carriers

It has been shown that clinical and virological characteristics vary among hepatitis B virus (HBV) genotypes. In this study, we measured the virus level, disease severity, and presence or absence of core promoter (CP)/pre-core (PC) mutations in 241 HBV carriers, and investigated the clinical significance of measuring the HBV genotype. In genotype C HBV carriers, the proportion of hepatitis B e antigen (HBeAg)-positive patients was significantly higher than that in genotype B HBV carriers (0 vs. 34.4%, p < 0.05), and the virus level was higher (4.9 vs. 4.05 LGE/ml). In the genotype B HBV carriers, the incidence of PC mutation was significantly higher (69 vs. 34%, p < 0.05). In the genotype C HBV carriers, the incidence of CP mutation was significantly higher (13 vs. 78%, p < 0.05). We compared patients with the wild (W)/mutant (M) pattern in the CP/PC regions to those with the M/W pattern in the CP/PC regions among the genotype C HBV carriers. Both the proportion of HBeAg-positive patients (65.8 vs. 15.4%, p < 0.05) and the alanine aminotransferase (ALT) level (48 vs. 21.5 IU, p < 0.05) were higher in the patients with the M/W pattern in the CP/PC regions, and the disease severity was deteriorated. In conclusion, genotype B HBV may more frequently induce HBe seroconversion via PC mutation compared to genotype C HBV. Among the genotype C HBV carriers, hepatitis activity and the deterioration of the disease severity were significantly inhibited in the group in which PC mutation initially occurred, in comparison to the group in which CP mutation initially occurred.

Evaluation of liver tissue by polymerase chain reaction for hepatitis B virus in patients with negative viremia

AIM: To assess the clinical significance of Hepatitis B virus (HBV) DNA localization in the liver tissue of patients with positive HBsAg and negative viremia.

METHODS: HBV virological parameters of 33 HBsAg positive chronic hepatitis patients, including seromarkers and HBV DNA amplification in both sera and liver biopsies, were evaluated.

RESULTS: Ten patients had negative viremia and positive HBV DNA in their liver biopsies. Most of them had HBeAg-negative/HBeAb-positive chronic hepatitis. Their liver biochemical and histopathological profiles were different from the viremic patients. Their disease pattern was designated as “hepatitis B in situ”.

CONCLUSION: Hepatitis B in situ is a consequential entity which can be missed in clinical practice. It is a new clinical pattern of chronic HBV infection that considers HBV in liver biopsy and adds a new indication for antiviral therapy.

Toll-like receptor 4 plays an anti-HBV role in a murine model of acute hepatitis B virus expression

AIM: Toll-like receptor 4 (TLR4) has been shown to be important for bacterial infection, especially to lipopolysaccharide signaling. Its possible role in HBV infection is studied in the present study.

MATERIALS AND METHODS: pHBV3.6 plasmid, containing full-length HBV genome was used in the murine model of acute HBV expression by hydrodynamics in vivo transfection. TLR4 normal or mutant mouse strain was compared to investigate the possible role of TLR4 in acute HBV expression.

RESULTS: After pHBV3.6 injection, the infiltrating leukocytes expressed TLR4 were observed nearby the HBsAg-expressing hepatocytes. The HBV antigenemia as well as the replication and transcription were higher in TLR4-mutant C3H/HeJ mice than in normal C3H/HeN mice. The HBV-specific immune responses were impaired in the liver or spleen of the C3H/HeJ mice. Their inducible nitric oxide synthase (iNOS) expression on the hepatic infiltrating cells was also impaired. When adoptively transferring splenocytes from C3H/HeN mice to C3H/HeJ mice, the HBV replication was inhibited to the level as that of C3H/HeN.

CONCLUSION: These results suggest that TLR4 plays an anti-HBV role in vivo through the induction of iNOS expression and HBV-specific immune responses after HBV expression.

Oral hepatitis B vaccine candidates produced and delivered in plant material

Hepatitis B is a major global health problem; approximately two billion people are infected with the virus worldwide, despite the fact that safe and efficacious vaccines have been developed and used for nearly 20 years. Prohibitive costs for vaccine purchase and administration restrict uptake in many developing nations. Agencies such as the Global Alliance for Vaccination and Immunization are helping to make current vaccines more available, but reduced costs would greatly aid this effort. Oral delivery is an option to reduce the expense of administering hepatitis B vaccines. It may also improve compliance, and orally delivered vaccines may be more efficacious among poor responders to current vaccines. However, to induce protective efficacy, oral administration may require encapsulation of antigen and delivery of large doses. Plant-based expression systems offer an oral delivery alternative with low production costs, and they also encapsulate the antigen. Some plant-based systems also stabilize antigen and therefore reduce storage and distribution costs. The hepatitis B major surface antigen has been expressed in several plant systems. A variety of regulatory sequences and subcellular targets have been used to achieve expression suitable for early stage clinical trials. However, further increase in expression will be necessary for practical and efficacious products. Appropriate processing can yield palatable products with uniform antigen concentration. The antigen expressed in plant systems shows extensive disulphide cross-linking and oligomerization and forms virus-like particles. Oral delivery of the antigen in plant material can induce a serum antibody response, prime the immune system for a subsequent injection of antigen and give a boosted response to a prior injection. Small scale clinical trials in which the antigen has been delivered orally in edible plant material indicate safety and immunogenicity.

A fusion product of the complete Borrelia burgdorferi outer surface protein A (OspA) and the hepatitis B virus capsid protein is highly immunogenic and induces protective immunity similar to that seen with an effective lipidated OspA vaccine formula

The immunogenicity of peptides and protein fragments can be considerably enhanced by their presentation on particulate carriers such as capsid-like particles (CLP) from hepatitis B virus (HBV). Here we tested the suitability of the HBV capsid protein as a carrier for a relevant full-length pathogen-derived protein antigen. The entire 255-amino acid ectodomain of the outer surface protein A (OspA) from Borrelia burgdorferi, the causative agent of Lyme disease, was inserted into the major B cell epitope of the HBV capsid, yielding a multimerization-competent fusion protein, termed coreOspA. CoreOspA, consisting only in part of regular CLP, induced antibodies to OspA, including the Ig isotype profile and specificity for the protective epitope LA-2, with an efficiency similar to that of recombinant lipidated OspA, the first generation vaccine against Lyme disease. Moreover, coreOspA actively and passively protected mice against subsequent challenge with B. burgdorferi. The data demonstrate the capacity of the HBV capsid protein to act as a potent immunomodulator even for full-length and structurally complex polypeptide chains and thus opens new avenues for novel vaccine designs.

Hepatitis B virus genotypes and precore mutations in Scottish blood donors

BACKGROUND AND OBJECTIVES

This study was carried out to determine the frequency of hepatitis B virus (HBV) core promoter variants (nucleotide positions 1762, 1764) and precore variants (nucleotide position 1896) in hepatitis B surface antigen (HBsAg)-positive Scottish blood donors. HBV genotypes present in this population were also identified.

MATERIALS AND METHODS

A total of 85 HBsAg-positive blood donor samples were included in the study. Of these, 79 were polymerase chain reaction (PCR) positive and had sequence and mutation information. They were divided into two groups: group 1 (23 individuals) were hepatitis B e antigen (HBeAg)-positive and negative for antibody to HBe (anti-HBe); and group 2 (56 individuals) were HBeAg negative and positive for anti-HBe. A line probe assay was used to detect mutations, and a comparison was made by using direct sequence analysis. A different line probe assay was used to identify HBV genotype.

RESULTS

The frequencies of mutations in group 1 were 22% each for mutations 1762, 1764 and 1896, increasing to 26%, 35% and 55% in group 2, respectively. By contrast, direct sequence analysis failed to identify 70% of wild-type/mutant mixes. The prevalence of viral genotypes was 41% for genotype A, 12% for genotype B, 5% for genotype C, 30% for genotype D and 12% for mixed-genotype infections. Precore mutations were seen in 10%, 88%, 25% and 74% of genotypes A, B, C and D, respectively.

CONCLUSIONS

The results indicate that core promoter and/or precore mutants may be under-reported. The combination of HBV PCR and line probe assays is useful for supplementing HBV serological tests. Non-Caucasian genotypes are present in the UK blood-donating population and will therefore affect the demographics of HBV infection.

[X protein variations of genotype B and C hepatitis B virus isolated from the patients with hepatocellular carcinoma]

BACKGROUND & OBJECTIVE

X protein was one of the most important pathogens of hepatitis B virus (HBV), and was crucial in the carcinogenesis of HBV related hepatocellular carcinoma (HCC). It was demonstrated that the infection of genotype B or C HBV would result in different clinical manifestations and pathological characteristics in HCC patients, however, it was under elucidation whether these differences related to different genotypes of HBV X protein. This study was designed to investigate the amino acid differentiations of X proteins in standard genotype B or C HBV strains and the variations in HBV isolated from the HCC patients, and elucidate preliminarily the relationship between the genotype of HBV and carcinogenesis of HCC.

METHODS

HBV X genes from the serum of twenty-two HBsAg positive HCC patients were amplified, cloned and sequenced. Genotyping of the X gene was carried out by Vector NTI6.0 software and the amino acid alignment among the standard and HCC originated X protein were done by DNAMAN software.

RESULTS

Twenty-two HBV X genes were obtained and all of them could be categorized into genotype B or C. Besides of 14 amino acid differentiations within X protein between standard B and C HBV strains, HCC originated X protein of B and C genotype showed 4 consensus amino acid variations, and genotype C X protein showed additional 6 genotype-specific variations. All these differentiated and varied amino acids were located in the B, T cell epitopes and transactive or related regulatory regions.

CONCLUSIONS

In addition to amino acid differentiations, X protein of genotype B or C HBV also showed genotype-specific variations in HCC patients. Amino acid differentiations and variations may result in the different immunocompetence and transactivation capacity between X proteins of genotype B and C.

[Effects of hepatitis B virus X gene on p21(WAF1) expression through p53-dependent and p53-independent pathways]

BACKGROUND & OBJECTIVE

It was reported that the hepatitis B virus X could inhibit the function of p53 and have contrary effects on p21(WAF1), a downstream gene of p53, but the mechanism is not clear up to now. So this study was designed to investigate HBx's effect on p21(WAF1) gene.

METHODS

After co-transfection of sense or antisense wild type p53 gene (wtp53) with HBx into SMMC-7721 and HBx alone transfection into other hepatoma cell lines with different endogenous status of p53, we evaluated the luciferase expression level under the p21(WAF1) promoter by detecting the luciferase activity and alteration of cell cycle in these transfected cell lines by flow cytometry. Expressions of p53 and p21 (WAF1) in hepatoma cells after transfected with HBx were also estimated by Western blot analysis.

RESULTS

The luciferase activity (1.007+/-0.098) in SMMC-7721 cells cotransfected with HBx and sense-wtp53 was higher than that in cells with wtp53 gene alone (0.490+/-0.012, P< 0.05), and also was depressed in the other experimental groups transfected with HBx (P< 0.05). Western blot analysis showed that after transfected with HBx, p53 expression was elevated in all hepatoma cell lines with different endogenous status of p53, and the expression of p21(WAF1) and luciferase activity under the p21(WAF1) promoter (0.053+/-0.010 vs. 0.094+/-0.013, P< 0.05) were both decreased in SMMC-7721 cells with low expression of p53, but relatively increased in HepG2 cell line with high expression of p53 (1.252+/-0.052 vs. 0.767+/-0.031, P< 0.05). Flow cytometry showed that fewer SMMC-7721 (42.31%) and Hep3B (36.96%) cells were arrested in G(0)/G(1) phase in transiently transfected HBx groups than in the control groups (47.10% and 42.90%), which was the opposite case in HepG2 cell line (63.62% vs. 57.42%). Moreover, after stably transfected with pcDNA3HBx, HepG2 cells reduced in G(0)/G(1) phase in compared with the control group (57.31% vs 61.49%).

CONCLUSION

HBx may not only increase the expression of p21(WAF1) by introducing the accumulation of p53 in cytoplasm but also inhibit the transcriptional activity of p21(WAF1) promoter in a p53-independent manner.

Human S15a expression is upregulated by hepatitis B virus X protein

The hepatitis B virus (HBV)-encoded X antigen (HBxAg) may contribute to the development of hepatocellular carcinoma (HCC) through the upregulated expression of selected cellular genes. To identify these genes, RNAs isolated from HBxAg-positive and -negative HepG2 cells were compared by PCR select cDNA subtraction. One gene overexpressed in HBxAg-positive cells by Northern and Western blotting is the ribosomal protein S15a. The S15a mRNA is 535 base pairs, encoding a protein 130 amino acids long with a molecular weight of 14.3 kDa. S15a expression was upregulated in HBV-infected livers, where it costained with HBxAg. Overexpression of S15a stimulated cell growth, colony formation in soft agar, and tumor formation in SCID mice. Hence, HBxAg upregulated the expression of S15a, the latter of which participates in the development of HCC, perhaps by altering the integrity of translation.

Enhancing cellular immune response to HBV M DNA vaccine in mice by codelivery of interleukin-18 recombinant

OBJECTIVE

To investigate the effect of interleukin-18 (IL-18) on immune response induced by plasmid encoding hepatitis B virus middle protein antigen and to explore new strategies for prophylactic and therapeutic HBV DNA vaccines.

METHODS

BALB/c mice were immunized with pCMV-M alone or co-immunized with pcDNA3-18 and pCMV-M and then their sera were collected for analysing anti-HBsAg antibody by ELISA; splenocytes were isolated for detecting specific CTL response and cytokine assay in vitro.

RESULTS

The anti-HBs antibody level of mice co-immunized with pcDNA3-18 and pCMV-M was slightly higher than that of mice immunized with pCMV-M alone, but there was not significantly different (P>0.05). Compared with mice injected with pCMV-M, the specific CTL cytotoxity activity of mice immunized with pcDNA3-18 and pCMV-M was significantly enhanced (P<0.05) and the level of IFN-Gamma in supernatant of splenocytes cul-tured with HBsAg in vitro was significantly elevated (P<0.05) while the level of IL-4 had no significant difference (P>0.05).

CONCLUSION

The plasmid encoding IL-18 together with HBV M gene DNA vaccines may enhance specific TH1 cells and CTL cellular immune response induced in mice, so that IL-18 is a promising immune adjuvant.

Occult hepatitis B virus infection

The detection of HBV DNA without HBsAg with or without the presence of HBV antibodies outside the acute phase window period defines occult HBV infection. This condition has been described in hepatocellular carcinoma (HCC), chronic hepatitis B, healthy HBV carriage and recovered infection, chronic hepatitis C and individuals without serological markers of HBV. The frequency of the diagnosis depends on the relative sensitivity of both HBsAg and HBV DNA assays. It also depends on the prevalence of HBV infection in the population. Occult HBV in blood donors has a wide range of potential origins within the natural history of the infection. It may originate from recovered infections with anti-HBs and persistent, low-level, viral replication, escape mutants undetected by the HBsAg assays or healthy chronic carriage. The last situation is mostly found with anti-HBc only. Over time, antibody markers may become undetectable leaving HBV DNA as the only marker of the infection. In all cases, the viral load is low, mostly below 10(4) IU/ml, often below 100 IU/ml. At these levels, nucleic acid testing (NAT) in pools is likely to be largely ineffective. Is occult HBV transmissible by transfusion? Carriers of anti-HBs or anti-HBc only were shown infectious in immunosuppressed organ or bone marrow transplant recipients. In immunocompetent recipients, there is no evidence that anti-HBs-containing components are infectious, even in low titre. Donations carrying anti-HBc only and HBV DNA can be infectious and this is a threat where anti-HBc is not screened. Anti-HBc screening identifies most occult HBV infection but not all. HBV NAT needs either extreme sensitivity or to be performed on individual donations to eliminate HBV DNA-containing units.

Characterization of the metabolic burden onEscherichia coli DH1 cells imposed by the presence of a plasmid containing a gene therapy sequence

The presence of a plasmid, containing gene sequences for DNA immunotherapy that are not expressed in microbial culture, imposed a degradation in bioreactor performance in cultures of the host E. coli strain. Significant decreases in growth rate (24%) and biomass yield (7%) and a corresponding increase in overflow metabolism were observed in a strain containing a therapeutic sequence (a hepatitis B antigen under the control of a CMV promotor). The observed increase in overflow metabolism was incorporated into a Metabolic Flux Analysis (MFA) model (as acetate secretion). Metabolic flux analysis revealed an increase in TCA cycle flux, consistent with an increased respiration rate observed in plasmid-containing cells. These effects are thought to result from increased ATP synthesis requirements (24%) arising from the expression of the Kanr plasmid marker gene whose product accounted for 18% of the cell protein of the plasmid-containing strain. These factors will necessitate significantly higher aeration and agitation rates or lower nutrient feed rates in high-density cultures than would be expected for plasmid-free cultures.

Overexpression of HBxAg in hepatocellular carcinoma and its relationship with Fas/FasL system

AIM: To study the expression and serum level of HBxAg, Fas and FasL in tissues of HCC patients, and to assess the relationship between HBxAg and Fas/FasL system.

METHODS: Tissues from 50 patients with HCC were tested for the expression of HBxAg, Fas and FasL by S-P immunohistochemistry. Serum levels of sFas/sFasL and HBsAg/HBeAg were measured by ELISA assay. HBV X gene was detected by PCR in serum and confirmed by automatic sequencing. Fifty cases of liver cirrhosis and 30 normal controls were involved in serum analysis.

RESULTS: The expression of HBxAg, Fas and FasL in carcinoma tissues was 96%, 84% and 98%, respectively. Staining of HBxAg, Fas and FasL was observed predominately in cytoplasms, no significant difference was found in intensity between HBxAg, Fas and FasL (P > 0.05). HBxAg, Fas and FasL might express in the same area of carcinoma tissues and this co-expression could be found in most patients with HCC. The mean levels of sFas in serum from HCC, cirrhosis and normal controls were 762.29 ± 391.56 μg·L^-1, 835.36 ± 407.33 μg·L^-1 and 238.27 ± 135.29 μg·L^-1. The mean levels of sFasL in serum from HCC, cirrhosis and normal controls were 156.36 ± 9.61 μg·L^-1, 173.63 ± 18.74 μg·L^-1 and 121.96 ± 7.83 μg·L^-1. Statistical analysis showed that both sFas and sFasL in HCC and cirrhosis patients were significantly higher than those in normal controls (P < 0.01). Serum HBV X gene was found in 32% of HCC patients and 46% of cirrhotic patients. There was no significant relationship between serum level of sFas/sFasL and serum X gene detection (P > 0.05). Eight percent of HCC patients with negative HBsAg and HBeAg in serum might have X gene in serum and HBxAg expression in carcinoma tissues.

CONCLUSION: Our data suggest that HBxAg and Fas/FasL system plays an important role in the development of human HCC. Expression of HBxAg can leads to expression of Fas/ FasL system which and reverse apoptosis of hepatocellular carcinoma induced by FasL.

[The role of hepatitis B virus X gene and p53 on hepatocellular carcinoma cell growth]

OBJECTIVE

To explore the effects of hepatitis B virus X gene and p53 on hepatocellular growth.

METHODS

Two kinds of plasmids containing sense and antisense human wild p53 gene respectively were constructed. SMMU-7721 cells were transfected with HBx, sense-wtp53 antisense-wtp53 separately or cotransfected with either HBx and sense-wtp53 or HBx and antisense-wtp53. Flow cytometry was adopted to measure the apoptosis rates and the effects of HBx on cell cycle progression. The activity of p21(Waf1) promoter-luciferase construct was detected. Growth curves for SMMU-7721 stably transfected with pcDNA3 and pcDNA3HBx were analyzed.

RESULTS

After doxorubicin administration, HBx was noticed able to initiate apoptosis of the liver cells. The apoptosis rate was 5.32% in the pcDNA3 transfected and 12.66% in the pcDNA3HBx transfected groups respectively. HBx could also abrogate p53-mediated apoptosis. The apoptosis rate in groups transfected with pcDNA3, pcDNA3wtp53 and pcDNA3HBx + pcDNA3wtp53 was 5.32%, 11.72% and 4.67% respectively. In compared with the normal group, the number of cells in transiently HBx-expressed group and HBx-transfected group decreased 4.79% and 10.25% respectively. HBx inhibited the activity of p21(Waf1) promoter-luciferase constructed (P < 0.05) and promoted cell growth. The growth rate of HBx expression cells was faster.

CONCLUSION

Under DNA damage, HBx reduced expression of p21(Waf1) by repressing the activity of p53 protein, followed by disturbing the regulation of G(0)-G(1) cell cycle checkpoint, and promoted the growth rate of hepatoma cells.

Induction of immune responses by DNA vaccines in large animals

It is generally recognized that DNA vaccines are often less effective in large animals than in mice. One possible reason for this reduced effectiveness may be transfection deficiency and the low level of expression elicited by plasmid vectors in large animals. In our attempt to enhance transfection efficiency and, thereby, enhance immune responses, we employed a variety of methods inducing gene gun delivery or suppositories as delivery vehicles to mucosal surfaces, as well as electroporation for systemic immunization. To test these different systems, we used two different antigens-a membrane antigen from bovine herpesvirus glycoprotein (BHV-1) gD and a particulate antigen from hepatitis virus B. Gene gun and suppository delivery of BHV-1 gD to the vagina resulted in the induction of mucosal immunity not only in the vagina, but also at other mucosal surfaces. These data support the contention of a common mucosal immune system. In the case of electroporation, we were able to develop significant enhancement of gene expression following electroporation with surface electrodes (non-invasive electroporation) as well as invasive electroporation using single or six-needle electrodes. Various delivery systems such as bioject or needle delivery also influenced the immune response in both the presence and absence of electroporation. These studies also demonstrated that co-administration of plasmids coding for two different antigens (BHV-1 gD and hepatitis B surface antigen (HbsAg)) did not result in significant interference between the plasmids. These studies suggest that various combinations of delivery systems can enhance immunity to DNA-based vaccines and make them practical for administration of these vaccines in large animals.

Expression of hepatitis B virus X protein in transgenic mice

AIM: To establish a mice model harboring hepatitis B virus x gene (adr subtype) for studying the function of hepatitis B virus X protein, a transactivator of viral and cellular promoter/enhancer elements.

METHODS: Expression vector pcDNA3-HBx, containing CMV promoter and hepatitis B virus x gene open reading fragment, was constructed by recombination DNA technique. Hela cells were cultured in DMEM and transfected with pcDNA3-HBx or control pcDNA3 plasmids using FuGENE6 Transfection Reagent. Expression of pcDNA3-HBx vectors in the transfected Hela cells was confirmed by Western blotting. After restriction endonuclease digestion, the coding elements were microinjected into male pronuclei of mice zygotes. The pups were evaluated by multiplex polymerase chain reaction (PCR) at genomic DNA level. The x gene transgenic mice founders were confirmed at protein level by Western blotting, immunohistochemistry and immunogold transmission electron microscopy.

RESULTS: Expression vector pcDNA3-HBx was constructed by recombination DNA technique and identified right by restriction endonuclease digestion and DNA direct sequencing. With Western blotting, hepatitis X protein was detected in Hela cells transfected with pcDNA3-HBx plasmids, suggesting pcDNA3-HBx plasmids could express in eukaryotic cells. Following microinjection of coding sequence of pcDNA3-HBx, the embryos were transferred to oviducts of psedopregnant females. Four pups were born and survived. Two of them were verified to have the HBx gene integrated in their genomic DNA by multiplex PCR assay, and named C57-TgN (HBx)S MMU1 and C57-TgN (HB x) SMMU3 respectively. They expressed 17KD X protein in liver tissue by Western blotting assay. With the immunohistochemistry, X protein was detected mainly in hepatocytes cytoplasm of transgenic mice, which was furthermore confirmed by immunogold transmission electon microscopy.

CONCLUSION: We have constructed the expression vector pcDNA3-HBx that can be used to study the function of HBx gene in eukaryotic cells in vitro. We also established HBx gene (adr subtype) transgenic mice named C57-TgN (HBx) SMMU harboring HBx gene in their genome and express X protein in hepatocytes, Which might be a valuable animal system for studying the roles of HBx gene in hepatitis B virus life cycle and development of hepatocellular carcinoma in vivo.

Mechanisms for inhibition of hepatitis B virus gene expression and replication by hepatitis C virus core protein

We have demonstrated previously that the core protein of hepatitis C virus (HCV) exhibits suppression activity on gene expression and replication of hepatitis B virus (HBV). Here we further elucidated the suppression mechanism of HCV core protein. We demonstrated that HCV core protein retained the inhibitory effect on HBV gene expression and replication when expressed as part of the full length of HCV polyprotein. Based on the substitution mutational analysis, our results suggested that mutation introduced into the bipartite nuclear localization signal of the HCV core protein resulted in the cytoplasmic localization of core protein but did not affect its suppression ability on HBV gene expression. Mutational studies also indicated that almost all dibasic residue mutations within the N-terminal 101-amino acid segment of the HCV core protein (except Arg(39)-Arg(40)) impaired the suppression activity on HBV replication but not HBV gene expression. The integrity of Arg residues at positions 101, 113, 114, and 115 was found to be essential for both suppressive effects, whereas the Arg residue at position 104 was important only in the suppression of HBV gene expression. Moreover, our results indicated that the suppression on HBV gene expression was mediated through the direct interaction of HCV core protein with the trans-activator HBx protein, whereas the suppression of HBV replication involved the complex formation between HBV polymerase (pol) and the HCV core protein, resulting in the structural incompetence for the HBV pol to bind the package signal and consequently abolished the formation of the HBV virion. Altogether, this study suggests that these two suppression effects on HBV elicited by the HCV core protein likely depend on different structural context but not on nuclear localization of the core protein, and the two effects can be decoupled as revealed by its differential targets (HBx or HBV pol) on these two processes of the HBV life cycle.

[Gene expression profile in response to hepatitis B virus X gene by using an adenoviral vector]

BACKGROUND/AIMS

Hepatitis B virus (HBV) is the etiological factor for hepatocellular carcinoma (HCC). Numerous evidence has indicated a link between chronic infection with HBV and the development of HCC. Among the four proteins encoded by HBV, Hepatitis B virus X gene(HBx), best characterized as a transcriptional transactivator, gained attention owing to its presumptive role in oncogenesis. Further, HBx has been shown to stimulate signal transduction pathways such as Ras-MAPK pathway, NF-kappa B, and Src kinase. The pleiotropic events caused by HBx may be the key to understanding the HBV-mediated oncogenicity. However, the specific roles of HBx in oncogenesis remain largely elusive. To explore the role of HBx in hepatocarcinogenesis, we examined the deregulation of host genes induced by HBx expression.

METHODS

HBx was ectopically expressed in HepG2 cells using a recombinant adenovirus to transiently express HBx. Gene expression profiling of HBx was conducted on cDNA microarrays that contained 1,028 cDNAs.

RESULTS

A number of oncogenes and genes that are involved in cell growth, DNA repair, cell cycle regulation, and cell motility were deregulated by HBx.

CONCLUSIONS

Theses results suggest that HBx regulates transcription in a way that contributes to the proliferation of hepatocytes, a probable early event of HCC.

Evaluation of new approaches to prophylactic and therapeutic vaccinations against hepatitis B viruses in the woodchuck model

The woodchuck model is most suitable for vaccine studies of prophylaxis and therapeutic treatment of hepatitis B virus infection. Recently, methodological advances allowed the examination of antigen-specific T cell responses in woodchucks during woodchuck hepatitis virus (WHV) infection and vaccinations. Similar to hepatitis B virus infection in humans, multispecific T-cell responses to WHV occur during acute self-limiting infection in woodchucks. Immunizations with WHV core antigen (WHcAg) or DNA vaccines expressing WHcAg demonstrated that priming of specific T-cell responses leads to the control of WHV infection. B-cell responses but no T-cell responses to WHV surface antigens (WHsAg) were induced in chronically WHV-infected woodchucks by the therapeutic immunizations with WHsAg. Breaking T-cell tolerance appears to be critical for immunotherapeutic approaches to chronic hepatitis B.

Recovery of known T-cell epitopes by computational scanning of a viral genome

A new computational method (EpiDock) is proposed for predicting peptide binding to class I MHC proteins, from the amino acid sequence of any protein of immunological interest. Starting from the primary structure of the target protein, individual three-dimensional structures of all possible MHC-peptide (8-, 9- and 10-mers) complexes are obtained by homology modelling. A free energy scoring function (Fresno) is then used to predict the absolute binding free energy of all possible peptides to the class I MHC restriction protein. Assuming that immunodominant epitopes are usually found among the top MHC binders, the method can thus be applied to predict the location of immunogenic peptides on the sequence of the protein target. When applied to the prediction of HLA-A*0201-restricted T-cell epitopes from the Hepatitis B virus, EpiDock was able to recover 92% of known high affinity binders and 80% of known epitopes within a filtered subset of all possible nonapeptides corresponding to about one tenth of the full theoretical list. The proposed method is fully automated and fast enough to scan a viral genome in less than an hour on a parallel computing architecture. As it requires very few starting experimental data, EpiDock can be used: (i) to predict potential T-cell epitopes from viral genomes (ii) to roughly predict still unknown peptide binding motifs for novel class I MHC alleles.

[Effects of partial deletion in the core promoter of hepatitis B virus genome on viral antigen expressions]

OBJECTIVE

To study the effects of 20/21 bp partial deletion mutation (from nt 1 748 or nt 1 747 to nt 1 767) in the core promoter (CP) region of hepatitis B virus (HBV) genome complicated by precore stop condon mutation at nt 1 896 on the expression of the viral antigens.

METHODS

Eukaryotic expression vector containing full-length HBV genome with the above mutations was constructed. After transfection of the recombinant HBV plasmids into HepG2 cells, the expression of the viral antigens was examined with enzyme-linked immunosorbent assay (ELISA) and Western blotting analysis.

RESULTS

As shown by ELISA and Western blotting analysis, the amount of extracellular secretion of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) along with intracellular hepatitis B core antigen (HBcAg) in the cells transfected with vectors containing HBV genomes with partial deletion in the CP region was markedly reduced compared with that produced by wild-type HBV.

CONCLUSION

The mutations in question causes marked reduction in viral antigen production by HBV in comparison that by wild-type HBV.

Molecular, immunological and clinical properties of mutated hepatitis B viruses

Hepatitis B virus (HBV) is at the origin of severe liver diseases like chronic active hepatitis, liver cirrhosis and hepatocellular carcinoma. There are some groups of patients with high risk of generation of HBV mutants: infected infants, immunosuppressed individuals (including hemodialysis patients), patients treated with interferon and lamivudine for chronic HBV infection. These groups are the target for molecular investigations reviewed in this paper. The emergence of lamivudine- or other antiviral-resistant variants, rises concern regarding long term use of these drugs. Infection or immunization with one HBV subtype confers immunity to all subtypes. However, reinfection or reactivation of latent HBV infection with HBV mutants have been reported in patients undergoing transplant and those infected with HIV. Mutations of the viral genome which are not replicative incompetent can be selected in further course of infection or under prolonged antiviral treatment and might maintain the liver disease. Four open reading frames (ORF) which are called S-gene, C-gene, X-gene and P-gene were identified within the HBV genome. Mutations may affect each of the ORFs. Mutated S-genes were described to be responsible for HBV-infections in successfully vaccinated persons, mutated C-genes were found to provoke severe chronic liver diseases, mutated X-genes could cause serious medical problems in blood donors by escaping the conventional test systems and mutated P-genes were considered to be the reason for chemotherapeutic drug resistance. This paper reviews molecular, immunological and clinical aspects of the HBV mutants.

Structural and functional heterogeneity of naturally occurring hepatitis B virus variants

Most organisms have developed sophisticated machineries to preserve their genomic integrity. On the contrary hepatitis B virus (HBV), like a lot of other viruses can undergo rapid and drastic sequence changes, especially if the virus has to cope with natural or therapy induced antiviral mechanisms in the host. Here, we try to summarize possible implications for the molecular pathogenesis of HBV based on the extensive research on the genetic variants of HBV.

Sequence analysis of hepatitis B virus genomes from an infant with acute severe hepatitis and a hepatitis B e antigen-positive carrier mother

It is well known that fulminant hepatitis B can occur in infants born to hepatitis B e antigen (HBeAg)-negative hepatitis B virus (HBV) carrier mothers, whereas fulminant hepatitis and severe hepatitis are uncommon in infants born to HBeAg-positive mothers. We have encountered an infant with severe acute hepatitis B born to a HBeAg-positive mother. The aim of this study was to determine whether HBV variants contribute to the pathogenesis of fulminant hepatitis and severe hepatitis in an infant born to an HBeAg-positive mother. The nucleotide sequence of HBV genomes from the infant and his HBeAg-positive carrier mother was analyzed. All HBV isolated from the infant and his mother were subtype adr. The sequences of the cloned HBV genomes, each including a part of the X and precore/core regions, isolated from the infant were almost identical (homology of 99.1-99.9%) to those from his mother. There was no mutation in any of the 17 clones examined at nucleotides 1762 and 1764 in the core promoter, which is reported to be associated with fulminant hepatitis. A point mutation at nucleotide 1758 in the second AT-rich region of the basic core promoter was present in all clones. None of the clones had a point mutation at nucleotide 1896 of the precore region. In this study, no specific HBV variants contributing to the development of neonatal severe hepatitis were found. There is a possibility that host factors rather than viral factors play an important role in some cases of severe neonatal hepatitis B.

A novel cytotoxic T-cell epitope presented by HLA-A24 molecule in hepatitis C virus infection

BACKGROUND/AIMS

It has been suggested that cytotoxic T lymphocytes (CTL) have crucial roles for the hepatocellular damage in hepatitis C virus (HCV) infection. A series of CTL epitopes located in the HCV protein have been identified. However, no CTL epitopes restricted by HLA-A24, a common HLA allele in humans, has been identified.

METHODS

Peripheral blood and liver infiltrating mononuclear cells from the patients with hepatitis C virus infection and healthy controls were stimulated with a series of peptides containing HLA-A24 binding motifs located in HCV protein.

RESULTS

An immunodominant HLA-A24 restricted CTL epitope (A24-4; AYSQQTRGL, amino acids 1031-1039) presented by HLA-A24 molecule was identified using a series of synthetic peptides containing the HLA-A24 binding motifs. The CTL activity against this peptide was induced both in peripheral blood and liver infiltrating mononuclear cells from HLA-A24-positive chronic hepatitis C patients, not from HLA-A24-negative patients and HLA-A24-positive healthy controls. CTL activity was blocked by anti-HLA-A24 and anti-CD8 antibodies, not by anti-CD4 antibody. Furthermore, the A24-4-specific CTL recognized the HCV gene transfected target cells.

CONCLUSIONS

Because this peptide is presented by a common HLA class I molecule, it might be useful for protection against hepatocellular damage and vaccine development in large population of the HCV-infected patients.

Activation of the IGF-II gene by HBV-X protein requires PKC and p44/p42 map kinase signalings

We have recently shown that HBx protein, one of the causative agents of hepatocellular carcinomas, regulates Sp1 mediated transcription of insulin-like growth factor II promoter 4 (Lee et al. (1998) Oncogene 16, 2367-2380). Here we show that PKC and p44/p42MAPK signalings are required for the HBx-induced Sp1-mediated IGF-II P4 transcriptional activity since (i) PKC activation by PMA or PKC expression vector increases Sp1 phosphorylation and P4 activity in HBx-transfected HepG2 cells; (ii) PKC inhibition by PKC inhibitor Gö6976 reduces Sp1 phosphorylation, P4 activity, and IGF-II mRNA in HBx-transfected HepG2 cells; and (iii) the inhibition of MEK activation by U0126 reduces Sp1 phosphorylation, P4 activity and IGF-II mRNA in HBx-transfected HepG2 cells. These results demonstrate that PKC and p44/p42 MAPK cascades are the essential signaling pathways in Sp1-mediated IGF-II gene activation by HBx.

Expression of deletion mutants of the hepatitis B virus protein HBx in E. coli and characterization of their RNA binding activities

The hepatitis B virus protein HBx has been implicated in the development of liver cancer. It has been shown that the HBx protein is able to bind to single-stranded DNA in a specific manner. This DNA binding activity might be relevant for HBx oncogene character. To study the HBx interaction with nucleic acids in more detail we expressed full-length HBx as well as several N- and C-terminally truncated HBx proteins as 6xHis and GST-fusions in E. coli. Using a gel shift assay, we were able to demonstrate that all of the truncated HBx proteins have the ability to bind to an AU-rich RNA. The affinity of GST-HBx #3 (residues 80-142) was an order of magnitude higher than that of GST-HBx #2 (residues 5-79), indicating that a high affinity RNA binding site is located in HBx C-terminal half. AUF1 is the protein ligand that binds to AU-rich RNA regions present in certain proto-oncogene mRNAs and causes their rapid degradation. By a competitive binding experiment of AUF1 and HBx to the AU-rich RNA oligonucleotide, we show that HBx is able to displace AUF1 from its binding site on the RNA oligonucleotide. This new aspect of HBx function is discussed in the context of cellular transformation.

A vestigial X open reading frame in duck hepatitis B virus

Duck hepatitis B virus (DHBV) appears to lack a homologue of the X protein found in mammalian hepadnaviruses. By replacing stop codons in the corresponding region of the DHBV genome, a hypothetical protein which closely matches the hydrophilicity profile of X proteins can be predicted, despite limited sequence homology. We conclude that a full-length X protein was once a common feature of the hepadnaviruses, conserved in structure but not sequence.

Chemotherapeutic drug, adriamycin, restores the function of p53 protein in hepatitis B virus X (HBx) protein-expressing liver cells

Hepatitis B virus X (HBx) protein implicated in the development of liver cancer may inhibit the function of p53 tumor suppressor protein through cytoplasmic retention of p53 protein. Here, we attempt to investigate whether the functional inhibition of p53 protein by HBx protein is reversible. First, we provide the evidence for the association of endogenous p53 protein with HBx by co-immunoprecipitation in stable Chang cells that express HBx protein in an inducible manner (ChangX-34). By immunofluorescence microscopy, the major location of p53 protein of ChangX-34 cells was confirmed at the nuclear periphery as well as in the cytoplasm where HBx protein is mainly expressed. Surprisingly, anticancer drug, adriamycin induces the nuclear translocation of p53 protein sequestered in the cytoplasm. This change is accompanied by the restoration of p53 activity, which results in increased transcriptional activity at the p53-responsive DNA elements as well as increase of p21WAF1 mRNA expression. Further, we observed the induction of cell death and G1 arrest in these cells upon adriamycin treatment regardless of HBx expression. Together, we demonstrate that functional inhibition of p53 protein through its cytoplasmic retention by HBx protein is reversible. These results may be extended into other tumors of which p53 activity is modulated by viral oncoproteins.