Inhibition of HBV replication by siRNA in a stable HBV-producing cell line

Potent inhibition of endogenous gene expression by RNA interference has been achieved by using sequence-specific posttranscriptional gene silencing through the action of small interfering RNA molecules (siRNA). In these reports, the natural function of genes could be deduced through the ensuing loss of function. Based on the extraordinary effectiveness in silencing endogenous genes, we wondered whether siRNA could be applied against viral replication in a hepatitis B virus (HBV) model using HBV-specific siRNA. To test this idea, HepG2 2.2.15, a human hepatoblastoma cell line that constitutively produces infectious HBV particles, was transfected with HBV-specific siRNAs and controls. HBV surface antigen (HBsAg) secretion into culture media was inhibited by 78%, 67%, and 42% with siRNA against the polyadenylation (PA), precore (PreC), and surface (S) regions, respectively, compared with controls as detected by enzyme-linked immunosorbent assay. After exposure to HBVPA siRNA, Northern blot analysis showed that HBV pregenomic RNA levels were decreased by 72%, and levels of HBV RNA containing the polyadenylation signal sequence were suppressed by 86%, as detected by RNase protection assay. Levels of HBV core-associated DNA, a replication intermediate, also decreased by 71%. Immunocytochemistry revealed that 30% to 40% of the cells transfected with HBVPA siRNA were completely negative for detectable HBsAg levels. Controls consisting of treatment with HBV-specific siRNA alone, lipofection reagent alone, or random double-stranded RNA (dsRNA) lipofection complex failed to decrease HBV surface antigen, HBV messenger RNA (mRNA), or core-associated HBV-DNA levels. In conclusion, siRNA inhibits hepatitis B viral replication in a cell culture system. Future studies are needed to explore the specific delivery of siRNA to liver cells in vivo and the applicability of this approach.

Hepatitis B virus infection of transplanted human hepatocytes causes a biochemical and histological hepatitis in immunocompetent rats

AIM: To characterize the host response to hepatitis B virus (HBV) infection in human hepatocytes transplanted into immunocompetent rodent rats tolerized by, and transplanted with primary human hepatocytes.

METHODS: One week after the transplantation, rats were inoculated with HBV, and viral gene expression, replication, and host response was monitored.

RESULTS: HBV DNA was detectable in serum for at least 60 days. HBsAg levels rose steadily for 3 weeks post-inoculation and then plateaued at a level of about 0.6 pg/ml. HBV RNA was also found in liver at levels that remained constant through the time course. Immunofluorescence revealed clusters of hepatocytes that stained positive for HBcAg. The presence of HBV covalently closed circular DNA (cccDNA) in liver was demonstrated using nuclease digestion of single-stranded DNA followed by PCR. Serum ALT levels rose and reached a peak level of 180 IU/L on day 18, but remained elevated for 60 days. Histology revealed a progressive predominantly mononuclear lobular hepatitis.

CONCLUSION: These data indicate that human hepatocytes transplanted into rats rendered tolerant to these cells, when infected by HBV, results in biochemical as well as histological evidence of hepatitis that accompanies viral gene expression, and DNA replication.

Conjugation of an antisense oligodeoxynucleotide to ribonuclease h results in sequence-specific cleavage and intracellular inhibition of HCV gene expression

A recombinant E. coli ribonuclease H (RNase H) was chemically coupled to an antisense oligodeoxynucleotide (ODN) against the 5'-noncoding region (5'-NCR) of the hepatitis C virus. Purity of the conjugates was confirmed by sodium deodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as a band corresponding to approximately 23 kDa. Conjugate function was tested by the cleavage of a HCV RNA transcript including the 5'-NCR and core region and showed HCV sequence-specific cleavage by the appearance of an expected approximately 1000 nt fragment of RNA. Cleavage was not seen by RNase H alone, or ODN alone. Delivery studies using (32)P- and (125)I-labeling showed that while RNAse H failed to enter cells, the conjugate was efficiently taken into the cells. To assess intracellular effects, a cell line, Huh-7/CMV-NCRCDeltaluc, which expresses HCV mRNA (nt 1-585) fused to a marker gene, was transfected with the conjugate. Reporter gene expression was suppressed by 51.2% with the conjugate compared to only 39.7% by ODN alone, 35.8% by a mixture of RNase H plus ODN, and not at all by RNase H alone. In conclusion, the RNase H-ODN conjugate effectively cleaved an HCV transcript in vitro and inhibited expression of an HCV-marker fusion construct in a liver-derived cell line.

Secondary structure and hybridization accessibility of hepatitis C virus 3'-terminal sequences

The 3'-terminal sequences of hepatitis C virus (HCV) positive- and negative-strand RNAs contribute cis-acting functions essential for viral replication. The secondary structure and protein-binding properties of these highly conserved regions are of interest not only for the further elucidation of HCV molecular biology, but also for the design of antisense therapeutic constructs. The RNA structure of the positive-strand 3' untranslated region has been shown previously to influence binding by various host and viral proteins and is thus thought to promote HCV RNA synthesis and genome stability. Recent studies have attributed analogous functions to the negative-strand 3' terminus. We evaluated the HCV negative-strand secondary structure by enzymatic probing with single-strand-specific RNases and thermodynamic modeling of RNA folding. The accessibility of both 3'-terminal sequences to hybridization by antisense constructs was evaluated by RNase H cleavage mapping in the presence of combinatorial oligodeoxynucleotide libraries. The mapping results facilitated identification of antisense oligodeoxynucleotides and a 10-23 deoxyribozyme active against the positive-strand 3'-X region RNA in vitro.

Hepatitis C and HIV co-infection: A review

Co-infection with hepatitis C virus and human immunodeficiency virus is common in certain populations. Among HCV (+) persons, 10% are also HIV (+), and among HIV (+) persons, 25% are also HCV (+). Many studies have shown that in intravenous drug users, co-infection prevalence can be as high as 90%-95%. There is increasing evidence supporting the concept that people infected with HIV have a much more rapid course of their hepatitis C infection. Treatment of co-infection is often challenging because highly active anti-retroviral therapy (HAART) therapy is frequently hepatotoxic, especially in the presence of HCV. The purpose of this review is to describe the effects that HIV has on hepatitis C, the effects that hepatitis C has on HIV, and the treatment options in this challenging population.

Evaluation of multicomponent non-viral vectors for liver directed gene delivery

Multicomponent, non-viral gene delivery vehicles are designed to have as a minimum, a DNA binding component, and a cell recognition component for specific delivery to target cells. The DNA binding component cannot only bind, but also protect DNA from serum degradation, and tends to condense DNA to sizes that can be taken up by receptor-mediated processes of target cells. Generally, cationic peptides, single chained, e.g. poly-L-lysine or branched polymers or synthetic peptides with DNA binding properties are used for DNA binding components. Ligands for binding to receptors on cell surfaces can be covalently linked to the DNA binding component. Multicomponent, non-viral vectors have been successfully used to deliver genes into cells in vitro and in vivo. Improvements have been made to the non-viral carriers resulting in increased solubility of DNA/carrier complexes and longer survival in serum. Improvements have also been made by incorporating fusogenic/lysosomolytic components that enable DNA/carrier complexes to escape intracellular degradation and enhance the levels and duration of expression of genes in vitro and in vivo.

[Fragile X mental retardation protein interacts with human NDK/Nm23-H2]

OBJECTIVE

To investigate the physiological role of fragile X mental retardation protein (FMRP) and screen the proteins interacting with FMRP in human fetal hippocampus cDNA library.

METHODS

Human fetal hippocampus cDNA library was constructed in yeast two-hybrid DAD vector pGAD10. Quality of the library was measured by picking up random colonies as templates for PCR testing. Proteins interacting with FMRP were screened by yeast two-hybrid system. Furthermore, the interaction site of FMRP was mapped in yeast.

RESULTS

The average length of inserts of the two-hybrid library was 1.5 kb, and the ratio of recombinant colonies was about 90%. Human NDK/Nm23-H2 was found interacting with FMRP. NDK/Nm23-H2 interacted with FMRP exon 1-12, as well as FMRP isoforms without exon 12, and exons 14-17. NDK/Nm23-H2 couldn't interact with FMRP exon 1-6 and exon 2-7 fragments.

CONCLUSIONS

Human NDK/Nm23-H2 can bind FMRP directly. The interaction site of FMRP is located at its exon 1-11. This interaction in vitro might alter the intracellular distribution of NDK/Nm23-H2, and even regulates the transcription and expression of FMRP.

A double-blind, placebo-controlled trial of extract of Ginkgo biloba added to haloperidol in treatment-resistant patients with schizophrenia

BACKGROUND

Many studies have indicated that excess free radical formation may be involved in the pathogenesis of patients with schizophrenia. Some investigators suggested that the use of free radical scavengers might provide improvement in schizophrenia. The aim of this study was to determine the effectiveness and to evaluate the side effects of extract of Ginkgo biloba (EGb) plus haloperidol in chronic, treatment-resistant inpatients with schizophrenia.

METHOD

One hundred nine patients meeting DSM-III-R criteria for schizophrenia completed a double-blind, placebo-controlled, parallel-group study of EGb plus haloperidol. Fifty-six of the patients were randomly assigned to receive a fixed dose of 360 mg/day of EGb plus a stable dose of haloperidol, 0.25 mg/kg/day, and 53 were assigned to receive placebo plus the same dose of haloperidol for 12 weeks. Patients were assessed using the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Negative Symptoms (SANS), and the Scale for the Assessment of Positive Symptoms (SAPS) at baseline, week 6, and week 12 and the Treatment Emergent Symptom Scale (TESS) for side effects at week 12.

RESULTS

There was a significant reduction in both groups in BPRS total score after 12 weeks of treatment (p < .05). However, a significant reduction in total SAPS and SANS scores was noted in the EGb group (p < .05), but not in the placebo group. There was a lower SAPS total score in the EGb group than in the placebo group at the end of 12 weeks of treatment (p < .05). Of those treated with EGb plus haloperidol, 57.1% were rated as responders as compared with only 37.7% of those receiving placebo plus haloperidol when assessed by the SAPS (chi2 = 4. 111, p = .043). After 12 weeks of treatment, TESS subscore 1 (behavioral toxicity) and subscore 3 (symptoms of nerve system) were significantly decreased in the EGb group compared with the placebo group (p < .05).

CONCLUSION

EGb treatment may enhance the effectiveness of antipsychotic drugs and reduce their extrapyramidal side effects.

Risperidone versus haloperidol in the treatment of acute exacerbations of chronic inpatients with schizophrenia: a randomized double-blind study

The purpose of this study was to compare the efficacy and safety of risperidone and haloperidol in treatment-resistant chronic schizophrenic patients. Subjects (n = 78) who met DSM-III criteria for schizophrenia were randomly assigned to receive 6 mg/day of risperidone or 20 mg/day of haloperidol for 12 weeks. Clinical efficacy was determined using the Positive and Negative Syndrome Scale (PANSS), and side-effects with the Treatment Emergent Symptom Scale (TESS). Risperidone produced a mean 39.8 +/- 24.1% reduction in total PANSS score compared to a mean 28.3 + 19.4% reduction in the haloperidol group (P < 0.05). Analysis of changes for the three subscores of the PANSS revealed that the general psychopathology and negative subscores were significantly improved in the risperidone group compared to the haloperidol group. As for the side-effects, the risperidone group showed a significantly lower TESS total score, as well as nervous system symptoms subscore and cardiovascular symptoms subscore, compared to the haloperidol group. Risperidone appears to be a more effective and better tolerated antipsychotic drug in treatment-refractory Chinese schizophrenia than haloperidol.

A ribonuclease H-oligo DNA conjugate that specifically cleaves hepatitis B viral messenger RNA

Ribonuclease H (RNaseH) recognizes and efficiently cleaves the RNA strand of DNA-RNA hybrids, but has no inherent sequence selectivity. However, the formation of DNA-RNA hybrids does require specific sequence recognition. On the basis of this concept, we wondered whether antisense oligonucleotides complementary to target RNA covalently linked to RNase H could be used to direct specific cleavage events mediated by RNase H. The aim of this research was to couple a DNA oligonucleotide to RNase H to confer specificity of ribonuclease activity toward hepatitis B viral (HBV) mRNA. A modified 13-base oligonucleotide that is specific for the DR1 region of HBV mRNA was conjugated to modified E. coli RNase H using a water soluble cross-linker. A 1200 base fragment of HBV RNA including the DR1 region was synthesized as a substrate using T7 RNA polymerase. Incubation of the RNase H-oligonucleotide conjugate with the RNA transcript resulted in cleavage of the HBV mRNA transcript in a concentration dependent manner. Eighty-five percent of substrate was cleaved under optimal conditions. Controls consisting of RNase H alone, oligonucleotide alone, and incubation of the conjugate with an unrelated mRNA substrate resulted in no cleavage activity. RNase H coupled to an HBV antisense oligonucleotide can specifically cleave target HBV transcripts.

Targeted polynucleotides for inhibition of hepatitis B and C viruses

AIM

To determine whether a combination of cell targeting and sequence recognition of nucleic acids can provide specificity for the inhibition of viral gene expression.

METHODS

Antisense oligonucleotides complexed to a protein-based DNA carrier system were used to target hepatocytes for the inhibition of human hepatitis viral gene expression. The DNA carrier system contained an asialoglycoprotein as a cell-targeting component, which could direct the uptake of complexed DNA specifically to asialoglycoprotein receptors present selectively on the surface of mammalian hepatocytes.

RESULTS

HBV and HCV viral gene expression were substantially and specifically inhibited by use of antisense oligonucleotides complexed to a protein-based DNA carrier system.

CONCLUSION

Targeted delivery of nucleic acids by use of receptor-mediated endocytosis can result in inhibition of viral gene expression without host toxicity.

Liver cell transplantation -- novel animal model for human hepatic viral infections

AIM

To generate a model of human hepatitis B infection (HBV) in immunocompetent rats with chimeric human liver.

METHODS AND RESULTS

Normal rats were tolerized to human hepatocytes by exposure to human hepatocytes at day 17 of gestation. We transplanted human hepatocytes and inoculated HBV into the rats after birth. Mixed lymphocytes assay, a measure for tolerance, indicated that animals fetally exposed to human hepatocytes developed tolerance to human hepatocytes. Spleen lymphocytes from tolerized animals did not proliferate when challenged with donor human hepatocytes. In contrast, control animals given saline fetally developed no tolerance to human hepatocytes. Tolerant animals with transplanted human hepatocytes were susceptible to HBV infection. Western blot analysis and immuno-histochemistry of liver sections from tolerized, HBV infected animals with transplanted human hepatocytes showed the presence of functioning human hepatocytes that synthesized human albumin, of which 30% were also positive for HB surface antigen and HBV DNA. The presence of covalent closed circular HBV DNA in the liver indicated active HBV viral replication.

CONCLUSION

Tolerized rats with chimeric human livers can be infected with HBV and used as an animal model for HBV infection. Tolerized rats with chimeric human livers can also be used for generating models of other human hepatic viral diseases.

Transplantation of human hepatocytes into tolerized genetically immunocompetent rats

AIM: To determine whether normal genetically immunocompetent rodent hosts could be manipulated to accept human hepatocyte transplants with long term survival without immunosuppression.

METHODS: Tolerance towards human hepatocytes was established by injection of primary human hepatocytes or Huh7 human hepatoma cells into the peritoneal cavities of fetal rats. Corresponding cells were subsequently transplanted into newborn rats via intrasplenic injection within 24 h after birth.

RESULTS: Mixed lymphocyte assays showed that spleen cells from non-tolerized rats were stimulated to proliferate when exposed to human hepatocytes, while cells from tolerized rats were not. Injections made between 15 d and 17 d of gestation produced optimal tolerizaton. Transplanted human hepatocytes in rat livers were visualized by immunohistochemical staining of human albumin. By dot blotting of genomic DNA in livers of tolerized rats 16 weeks after hepatocyte transplantation, it was found that approximately 2.5 × 10⁵ human hepatocytes survived per rat liver. Human albumin mRNA was detected in rat livers by RT-PCR for 15 wk, and human albumin protein was also detectable in rat serum.

CONCLUSION: Tolerization of an immunocompetent rat can permit transplantation, and survival of functional human hepatocytes.

The scaffold protein, Homer1b/c, regulates axon pathfinding in the central nervous system in vivo

Homer proteins are a family of multidomain cytosolic proteins that have been postulated to serve as scaffold proteins that affect responses to extracellular signals by regulating protein-protein interactions. We tested whether Homer proteins are involved in axon pathfinding in vivo, by expressing both wild-type and mutant isoforms of Homer in Xenopus optic tectal neurons. Time-lapse imaging demonstrated that interfering with the ability of endogenous Homer to form protein-protein interactions resulted in axon pathfinding errors at stereotypical choice points. These data demonstrate a function for scaffold proteins such as Homer in axon guidance. Homer may facilitate signal transduction from cell-surface receptors to intracellular proteins that govern the establishment of axon trajectories.

Crystallographic structures of the ligand-binding domains of the androgen receptor and its T877A mutant complexed with the natural agonist dihydrotestosterone

The structures of the ligand-binding domains (LBD) of the wild-type androgen receptor (AR) and the T877A mutant corresponding to that in LNCaP cells, both bound to dihydrotestosterone, have been refined at 2.0 A resolution. In contrast to the homodimer seen in the retinoid-X receptor and estrogen receptor LBD structures, the AR LBD is monomeric, possibly because of the extended C terminus of AR, which lies in a groove at the dimerization interface. Binding of the natural ligand dihydrotestosterone by the mutant LBD involves interactions with the same residues as in the wild-type receptor, with the exception of the side chain of threonine 877, which is an alanine residue in the mutant. This structural difference in the binding pocket can explain the ability of the mutant AR found in LNCaP cells (T877A) to accommodate progesterone and other ligands that the wild-type receptor cannot.

AACR/NHRI Joint Conference: hepatitis and hepatocellular carcinoma: novel approaches

This international meeting, co-sponsored by the National Health Research Institutes of Taiwan (NHRI) and the AmericanAssociation for Cancer Research (AACR), was dedicated to two pioneering scientists, Juei-Low Sung (Koo Foundation, Sun Yat-Sen Cancer Center, Taipei, Taiwan) and Kwang-Juei Lo (Taipei Veterans General Hospital, Taipei, Taiwan). The meeting focused on various aspects of viral hepatitis and hepatocellular carcinoma (HCC), and the relation between the two. Topics ranged from epidemiological studies, identification of environmental and genetic risk factors, mechanisms of pathogenesis, and research presentations on standard and novel treatment modalities. Highlights included discussions on adefovir dipivoxil (Gilead Sciences), emtricitabine (FTC; Triangle Pharmaceuticals), clevudine (L-FMAU; Triangle Pharmaceuticals/Abbott/Bukwang Pharmaceutical Industries), entecavir (Bristol-Myers Squibb), and especially L-isomer nucleoside analogs, for use in hepatitis B virus (HBV) therapy. Mention was also made of the potential roles of histamine and mycophenolic acid in the treatment of hepatitis C virus (HCV) infections, and of polyphenols and thalidomide for HCC.

Human hepatocytes transplanted into genetically immunocompetent rats are susceptible to infection by hepatitis B virus in situ

Immune tolerance of human cells without generalized immunosuppression was created in groups of normal fetal rats at 17 days of gestation by inoculation ip with primary human hepatocytes in utero. One day after birth, suspensions of human hepatocytes were transplanted via intrasplenic injection and one week later groups of rats were inoculated with hepatitis B virus (HBV). Tolerized rats that were transplanted with human hepatocytes and subsequently infected with HBV produced hepatitis B surface antigen (HBsAg) in serum beginning on day 3. Levels rose fivefold and remained stable at 0.75 pg/ml through at least 60 days. Of cells that stained positive for human serum albumin, approximately 30% were found to be also positive for HBsAg by immunohistochemistry. Serum HBV DNA was detectable from 1 to 15 weeks postinfection. Finally, covalently closed circular DNA, reflecting HBV replication, was found in liver and serum. Controls that were tolerized and not transplanted, but inoculated with HBV, as well as untreated controls, had no evidence of HBV gene expression or replication under identical conditions. The data support the conclusion that primary human hepatocytes transplanted into genetically immunocompetent rodent hosts, survive and maintain sufficient differentiation to produce human serum albumin and be infected by HBV.

Activity-dependent CREB phosphorylation: convergence of a fast, sensitive calmodulin kinase pathway and a slow, less sensitive mitogen-activated protein kinase pathway

The cAMP-responsive element binding protein (CREB), a key regulator of gene expression, is activated by phosphorylation on Ser-133. Several different protein kinases possess the capability of driving this phosphorylation, making it a point of potential convergence for multiple intracellular signaling cascades. Previous work in neurons has indicated that physiologic synaptic stimulation recruits a fast calmodulin kinase IV (CaMKIV)-dependent pathway that dominates early signaling to CREB. Here we show in hippocampal neurons that the fast, CaMK-dependent pathway can be followed by a slower pathway that depends on Ras/mitogen-activated protein kinase (MAPK), along with CaMK. This pathway was blocked by dominant-negative Ras and was specifically recruited by depolarizations that produced strong intracellular Ca(2+) transients. When both pathways were recruited, phosphorylated CREB (pCREB) formation was overwhelmingly dominated by the CaMK pathway between 0 and 10 min, and by the MAPK pathway at 60 min, whereas the two pathways acted in concert at 30 min. The Ca(2+) signals that produced only rapid CaMK signaling to pCREB or both rapid CaMK and slow MAPK signaling deviated significantly for only approximately 1 min, yet their differential impact on pCREB extended over a much longer period, between 20 and 60 min and beyond, which is of likely significance for gene expression. The CaMK-dependent MAPK pathway may inform the nucleus about stimulus amplitude. In contrast, the CaMKIV pathway may be well suited to conveying information on the precise timing of localized synaptic stimuli, befitting its greater speed and sensitivity, whereas the previously described calcineurin pathway may carry information about stimulus duration.

Spaced stimuli stabilize MAPK pathway activation and its effects on dendritic morphology

Memory storage in mammalian neurons probably depends on both biochemical events and morphological alterations in dendrites. Here we report an activity-dependent stabilization of the MAP kinase (MAPK) pathway, prominent in hippocampal dendrites. The longevity of the signal in these dendrites was increased to hours when multiple spaced stimuli were used. Likewise, spaced stimuli and MAPK activation were critical for protrusion of new dendritic filopodia that also remained stable for hours. Our experiments define a new role for stimulus-specific responses of MAPK signaling in activity-dependent neuronal plasticity. The local biochemical signaling in dendrites complements MAPK signaling in gene expression. Together, these processes may support long-lasting behavioral changes.

Progress toward a synthetic virus : a multicomponent system for liver-directed DNA delivery

Vectors for gene transfer can be categorized as viral and nonviral. The advantages of nonviral carriers are their ease of preparation and scale-up, flexibility regarding the size of DNA to be transferred, and safety in vivo. Despite these advantages, nonviral vectors need to be further optimized for their efficiency is generally low. Thus, the future of non-viral vectors will be dependent on the possibility of creating synthetic efficient systems. A possible and reasonable approach is to develop artificial nucleic acid carriers that incorporate functional elements mimicking viruses.

Transfection and expression of HCV-NS5B gene in Huh-7 cells

OBJECTIVE

To study the mechanism of hepatitis C virus (HCV) replication and to test gene therapy for hepatitis C, a human liver cell line expressed HCV RNA polymerase has been established.

METHODS

NS5B gene has been transfected into Huh-7 cells by lipofectamine. The results of transfection were confirmed by PCR and Southern blot analysis, and the level of the non-structural protein 5B (NS5B) in Huh-7 cells was detected by Western blot analysis.

RESULTS

There were NS5B gene fragments and the expression of NS5B protein in Huh-7c cells transfected with pTeT-NS5B or pcDNA-NS5B plasmid.

CONCLUSIONS

We have established a HCV RNA polymerase expression system in Huh-7 cells which can be further used to analyze the mechanism of HCV replication and provide a cell model for gene therapy in vitro.