Inhibition of hepatitis B virus replication in 2.2.15 cells by expressed shRNA

Hepatitis B virus: promising drug targets and therapeutic implications

Introduction: Current therapy for infection with hepatitis B virus (HBV) rarely clears the virus, and viremia commonly resurges following treatment withdrawal. To prevent serious complications of the infection, research has been aimed at identifying new viral and host targets that can be exploited to inactivate HBV replication.Areas covered: This paper reviews the use of these new molecular targets to advance anti-HBV therapy. Emphasis is on appraising data from pre-clinical and early clinical studies described in journal articles published during the past 10 years and available from PubMed.Expert opinion: The wide range of viral and host factors that can be targeted to disable HBV is impressive and improved insight into HBV molecular biology continues to provide the basis for new drug design. In addition to candidate therapies that have direct or indirect actions on HBV covalently closed circular DNA (cccDNA), compounds that inhibit HBsAg secretion, viral entry, destabilize viral RNA and effect enhanced immune responses to HBV show promise. Preclinical and clinical evaluation of drug candidates, as well as investigating use of treatment combinations, are encouraging. The field is poised at an interesting stage and indications are that reliably achieving functional cure from HBV infection is a tangible goal.

MicroRNAs Expressed during Viral Infection: Biomarker Potential and Therapeutic Considerations

MicroRNAs (miRNAs) are short sequences of noncoding single-stranded RNAs that exhibit inhibitory effects on complementary target mRNAs. Recently, it has been discovered that certain viruses express their own miRNAs, while other viruses activate the transcription of cellular miRNAs for their own benefit. This review summarizes the viral and/or cellular miRNAs that are transcribed during infection, with a focus on the biomarker and therapeutic potential of miRNAs (or their antagomirs). Several human viruses of clinical importance are discussed, namely, herpesviruses, polyomaviruses, hepatitis B virus, hepatitis C virus, human papillomavirus, and human immunodeficiency virus.

siRNA combinations mediate greater suppression of hepatitis B virus replication in mice

Hepatitis B virus (HBV) infection is a major world-wide health problem. The major obstacles for current anti-HBV therapy are the low efficacy and the occurrence of drug resistant HBV mutations. Recent studies have demonstrated that combination therapy can enhance antiviral efficacy and overcome shortcomings of established drugs. In this study, the inhibitory effect mediated by combination of siRNAs targeting different sites of HBV in transgenic mice was analyzed. HBsAg and HBeAg in the sera of the mice were analyzed by enzyme-linked immunoadsorbent assay, HBV DNA by real-time PCR and HBV mRNA by RT-PCR. Our data demonstrated that all the three siRNAs employed showed marked anti-HBV effects. The expression of HBsAg and the replication of HBV DNA could be specifically inhibited in a dose-dependent manner by siRNAs. Furthermore, combination of siRNAs compared with individual use of each siRNA, exerted a stronger inhibition on antigen expression and viral replication, even though the final concentration of siRNA used for therapy was the same. Secreted HBsAg and HBeAg in the serum of mice treated with siRNA combination were reduced by 96.7 and 96.6 %, respectively. Immunohistochemical detection of liver tissue revealed 91 % reduction of HBsAg-positive cells in the combination therapy group. The combination of siRNAs caused a greater inhibition in the levels of viral mRNA and DNA (90 and 87.7 %) relative to the control group. It was noted that the siRNA3 showed stronger inhibition of cccDNA (78.6 %). Our results revealed that combination of siRNAs mediated a stronger inhibition of viral replication and antigen expression in transgenic mice than single siRNAs.

Recent advances in use of gene therapy to treat hepatitis B virus infection

Chronic infection with hepatitis B virus (HBV) occurs in approximately 5 % of the world's human population and persistence of the virus is associated with serious complications of cirrhosis and liver cancer. Currently available treatments are modestly effective and advancing novel therapeutic strategies is a medical priority. Stability of the viral cccDNA replication intermediate is a major factor that has impeded the development of therapies that are capable of eliminating chronic infection. Recent advances that employ gene therapy strategies offer useful advantages over current therapeutics. Silencing of HBV gene expression by harnessing the RNA interference pathway has been shown to be highly effective in cell culture and in vivo. However, a potential limitation of this approach is that the post-transcriptional mechanism of gene silencing does not disable cccDNA. Early results using designer transcription activator-like effector nucleases (TALENs) and repressor TALEs (rTALEs) have shown potential as a mode of inactivating cccDNA. In this article, we review the recent advances that have been made in HBV gene therapy, with a particular emphasis on the potential anti-HBV therapeutic utility of designed sequence-specific DNA binding proteins and their derivatives.

Recent advances in developing nucleic acid-based HBV therapy

Chronic HBV infection remains an important public health problem and currently licensed therapies rarely prevent complications of viral persistence. Silencing HBV gene expression using gene therapy, particularly with exogenous activators of RNAi, holds promise for developing an HBV gene therapy. However, immune stimulation, off-targeting effects and inefficient delivery of RNAi activators remain problematic. Several new approaches have recently been employed to address these issues. Chemical modifications to anti-HBV synthetic siRNAs have been investigated and a variety of vectors are being developed for delivery of RNAi effectors. In this article, we review the potential utility of gene therapy for treating HBV infection.

Controllable inhibition of hepatitis B virus replication by a DR1-targeting short hairpin RNA (shRNA) expressed from a DOX-inducible lentiviral vector

As a highly efficient delivery system, lentiviral vectors (LVs) have become a powerful tool to assess the antiviral efficacy of RNA drugs such as short hairpin RNA (shRNA) and decoys. Furthermore, recent advanced systems allow controlled expression of the effector RNA via coexpression of a tetracycline/doxycycline (DOX) responsive repressor (tTR-KRAB). Herein, this system was utilized to assess the antiviral effects of LV-encoded shRNAs targeting three conserved regions on the pregenomic RNA of hepatitis B virus (HBV), namely the region coding for the reverse transcriptase (RT) domain of the viral polymerase (LV-HBV-shRNA1), the core promoter (CP; LV-HBV-shRNA2), and the direct repeat 1 (DR1; LV-HBV-shRNA3). Transduction of just the LV-HBV-shRNA vectors into the stably HBV expressing HepG2.2.15 cell line showed significant reductions in secreted HBsAg and HBeAg, intracellular HBcAg as well as HBV RNA and DNA replicative intermediates for all vectors, however, most pronouncedly for the DR1-targeting shRNA3. The corresponding vector was therefore applied in the DOX-controlled system. Notably, strong interference with HBV replication was found in the presence of the inducer DOX whereas the antiviral effect was essentially ablated in its absence; hence, the silencing effect of the shRNA and consequently HBV replication could be strictly regulated by DOX. This newly established system may therefore provide a valuable platform to study the antiviral efficacy of RNA drugs against HBV in a regulated manner, and even be applicable in vivo.

Knockdown of HBV surface antigen gene expression by a lentiviral microRNA-based system inhibits HBV replication and HCC growth

Current options for the treatment of hepatitis B virus (HBV) infections, a common liver cancer risk factor, are limited. While RNA interference (RNAi) technologies have been shown to inhibit HBV replication, the consequent effects on hepatocellular carcinoma (HCC) cell growth are not fully understood. The aim of this study was to evaluate the effect of RNAi-mediated decrease in the HBV surface antigen (HBsAg) gene on HBV replication and HCC growth. A lentiviral microRNA-based system expressing siRNAs targeting the HBsAg gene (LVshHBS) was developed and transfected into HepG2.2.15 cells (HBV stably expressing line). We found that LVshHBS significantly inhibited the HBsAg mRNA and protein levels in the HepG2.2.15 cells, while HBsAg secretion into the culture supernatant decreased by 70%. BALB/c (nu/nu) mice were injected with HepG2.2.15 cells transduced with LVshHBS or control vectors to investigate the effect of inhibiting the HBsAg on the development of tumour growth in a human HCC nude mice model. Compared with the control, the tumour growth in nude mice was significantly decreased after injection with LVshHBS. Microarray analysis of tumour-related genes in LVshHBS-transduced HepG2.2.15 cells showed that the expressions of genes involved in cell cycle, differentiation and oncogenesis such as ACP2, BHLHB2, CLK3, CTSC, FOS, NR1D1, PIM1 and SEPT6 genes were downregulated, while that of the E2F3 gene was upregulated. In conclusion, lentiviral microRNA-based RNAi against the HBsAg gene not only inhibits HBV replication but also inhibits the growth of HCC. Downregulation of growth-related genes is implicated in this mechanism of inhibition.

MicroRNA-like antivirals

Employing engineered DNA templates to express antiviral microRNA (miRNA) sequences has considerable therapeutic potential. The durable silencing that may be achieved with these RNAi activators is valuable to counter chronic viral infections, such as those caused by HIV-1, hepatitis B, hepatitis C and dengue viruses. Early use of expressed antiviral miRNAs entailed generation of cassettes containing Pol III promoters (e.g. U6 and H1) that transcribe virus-targeting short hairpin RNA mimics of precursor miRNAs. Virus escape from single gene silencing elements prompted later development of combinatorial antiviral miRNA expression cassettes that form multitargeting siRNAs from transcribed long hairpin RNA and polycistronic primary miRNA sequences. Weaker Pol III and Pol II promoters have also been employed to control production of antiviral miRNA mimics, improve dose regulation and address concerns about toxicity caused by saturation of the endogenous miRNA pathway. Efficient delivery of expressed antiviral sequences remains challenging and utilizing viral vectors, which include recombinant adenoviruses, adeno-associated viruses and lentiviruses, has been favored. Investigations using recombinant lentiviruses to transduce CD34+ hematological precursor cells with expressed HIV-1 gene silencers are at advanced stages and show promise in preclinical and clinical trials. Although the use of expressed antiviral miRNA sequences to treat viral infections is encouraging, eventual therapeutic application will be dependent on rigorously proving their safety, efficient delivery to target tissues and uncomplicated large scale preparation of vector formulations. This article is part of a special issue entitled: MicroRNAs in viral gene regulation.

Promotion of exon 6 inclusion in HuD pre-mRNA by Hu protein family members

The Hu RNA-binding protein family consists of four members: HuR/A, HuB, HuC and HuD. HuR expression is widespread. The other three neuron-specific Hu proteins play an important role in neuronal differentiation through modulating multiple processes of RNA metabolism. In the splicing events examined previously, Hu proteins promote skipping of the alternative exons. Here, we report the first example where Hu proteins promote inclusion of an alternative exon, exon 6 of the HuD pre-mRNA. Sequence alignment analysis indicates the presence of several conserved AU-rich sequences both upstream and downstream to this alternatively spliced exon. We generated a human HuD exon 6 mini-gene reporter construct that includes these conserved sequences. Hu protein over-expression led to significantly increased exon 6 inclusion from this reporter and endogenous HuD. Studies using truncated and mutant HuD exon 6 reporters demonstrate that two AU-rich sequences located downstream of exon 6 are important. RNAi knockdown of Hu proteins decreased exon 6 inclusion. An in vitro splicing assay indicates that Hu proteins promote HuD exon 6 inclusion directly at the level of splicing. Our studies demonstrate that Hu proteins can function as splicing enhancers and expand the functional role of Hu proteins as splicing regulators.

Involvement of mitochondrial permeability transition in hepatitis B virus replication

The HBx protein of human hepatitis B virus (HBV) activates a calcium-dependent kinase pathway which is essential for the viral replication. In this study, we found that HBx expression in the absence of other HBV proteins and in the context of HBV replication decreased the mitochondrial calcein-AM/CoCl(2) signals by 10% and 14% in HepG2 cells and by 15% and 10% in Huh7 cells, respectively. This indicates that HBx can induce mitochondrial permeability transition (MPT) and cause calcium effusion into the plasma. In addition, RNA interference of Cylophilin D decreased HBx-induced MPT and suppressed HBV DNA replication by 41% in HepG2 cells. Our results suggest that HBx expression can induce MPT and facilitate HBV DNA replication.

Drug targets in hepatitis B virus infection

Hepatitis B virus infection (HBV) is a significant global health problem. Despite the success of universal hepatitis B vaccination in many countries, more than 350 million individuals worldwide are chronically infected and 15- 40% of those will develop cirrhosis and/or hepatocellular carcinoma if left untreated. Available therapies for chronic hepatitis B (CHB) infection are effective at decreasing viremia and improving measured clinical outcomes, however, no single therapy is optimal. As such, alternative drug therapies and the investigation of their role in the management of CHB are warranted. Significant improvements in the understanding of the HBV life cycle, viral genomics, and virus-host interactions continue to lead to the development of novel viral targets and immune modulators. Currently, two major classes of agents are utilized in CHB: the interferons and the nucleos(t)ide analogues. Each agent has individual advantages and drawbacks. The development of specific antiviral therapy has led to the emergence of HBV drug-resistant strains that has limited the long-term therapeutic potential of available agents. This necessitates the development of new agents that target both wild-type and drug-resistant strains. Further understanding of the basic mechanisms and clinical nuances of drug therapy is warranted. As most novel therapies are in the earliest stages of clinical development and testing, in the near future, treatment will continue to be long-term and likely involve the use of combination therapies to prevent viral resistance. In this review, we will highlight the HBV life cycle and genome, focusing in on current and potential novel antiviral drug targets as well as the benefits and clinical challenges with these therapies.

A retrovirus-based system to stably silence GDF-8 expression and enhance myogenic differentiation in human rhabdomyosarcoma cells

BACKGROUND

Myostatin, also called GDF-8, a secreted growth and differentiating factor that belongs to the transforming growth factor-beta superfamily, is a known negative regulator of myogenesis in vivo. Overexpression of GDF-8 contributes to the lack of differentiation in human rhabdomyosarcoma (RMS) cells. We investigated whether a retrovirus-based RNA interference (RNAi) system against GDF-8 expression in human RMS cells would enhance myogenic differentiation.

METHODS

A retrovirus-based RNAi system was developed that utilized the U6-RNA polymerase III promoter to drive efficient expression and deliver the GDF8-specific short hairpin RNAs (shRNAs) in human RMS cell A204. In this system, the retrovirus vector was integrated into the host cell genome and allowed stable expression of shRNAs. GDF-8 expression was determined by real-time polymerase chain reaction and western blotting analysis. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to determine the cell proliferation. Myogenic differentiation markers were monitored by western blotting analysis. Cell cycle and apoptosis was determined by propidium iodide staining and analysed in a flow cytometer.

RESULTS

In the siGDF8 A204 cell pools, the levels of both GDF-8 mRNA and protein were dramatically reduced by this RNAi system. In differentiation conditions, inhibition of myostatin synthesis led to enhanced cell cycle withdrawal, consequently stimulated myogenic differentiation and increased the rate of tumor cell apoptosis.

CONCLUSIONS

The results demonstrate that deactivation of myostatin by using retrovirus-based RNAi thus may be useful for therapy in rhabdomyosarcomas.

Harnessing the RNA interference pathway to advance treatment and prevention of hepatocellular carcinoma

Primary liver cancer is the fifth most common malignancy in the world and is a leading cause of cancer-related mortality. Available treatment for hepatocellular carcinoma (HCC), the commonest primary liver cancer, is rarely curative and there is a need to develop therapy that is more effective. Specific and powerful gene silencing that can be achieved by activating RNA interference (RNAi) has generated enthusiasm for exploiting this pathway for HCC therapy. Many studies have been carried out with the aim of silencing HCC-related cellular oncogenes or the hepatocarcinogenic hepatitis B virus (HBV) and hepatitis C virus (HCV). Proof of principle studies have demonstrated promising results, and an early clinical trial assessing RNAi-based HBV therapy is currently in progress. Although the data augur well, there are several significant hurdles that need to be overcome before the goal of RNAi-based therapy for HCC is realized. Particularly important are the efficient and safe delivery of RNAi effecters to target malignant tissue and the limitation of unintended harmful non-specific effects.

RNA interference and antiviral therapy

RNA interference (RNAi) is an evolutionally conserved gene silencing mechanism present in a variety of eukaryotic species. RNAi uses short double-stranded RNA (dsRNA) to trigger degradation or translation repression of homologous RNA targets in a sequence-specific manner. This system can be induced effectively in vitro and in vivo by direct application of small interfering RNAs (siRNAs), or by expression of short hairpin RNA (shRNA) with non-viral and viral vectors. To date, RNAi has been extensively used as a novel and effective tool for functional genomic studies, and has displayed great potential in treating human diseases, including human genetic and acquired disorders such as cancer and viral infections. In the present review, we focus on the recent development in the use of RNAi in the prevention and treatment of viral infections. The mechanisms, strategies, hurdles and prospects of employing RNAi in the pharmaceutical industry are also discussed.

Opportunities for treating chronic hepatitis B and C virus infection using RNA interference

Activating the RNA interference (RNAi) pathway to achieve silencing of specific genes is one of the most exciting new developments of molecular biology. A particularly interesting use of this technology is inhibition of defined viral gene expression. In this review, we discuss the potential application of RNAi to treatment of chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. Globally, these hepatotropic viruses are the most important causes of cirrhosis and liver cancer. Available treatments have their limitations, which makes development of novel effective RNAi-based therapies for HBV and HCV especially significant. Several investigations carried out in vitro and in vivo are summarized, which demonstrate proof of principle that HBV and HCV can be inhibited by RNAi activators. Challenges facing further development of this technology to a stage of clinical application are discussed.

RNA interference against hepatitis B virus with endoribonuclease-prepared siRNA despite of the target sequence variations

RNA interference (RNAi) has proven to be very powerful in inhibiting hepatitis B virus (HBV) replication by cell culture and mouse model studies. We have previously reported that endoribonuclease-prepared short interfering RNAs (esiRNAs) were able to inhibit HBV replication more efficiently than synthesized siRNAs. Here we tested the hypothesis that esiRNAs are able to inhibit gene expression with limited mutations within the target region. Target sequences with different similarities to esiHBVP (esiRNA targeting the DNA polymerase and S antigen of Hepatitis B virus) were amplified and cloned into the 3' untranslated region of HBsAg, respectively. When the obtained expression vectors were co-transfected with esiHBVP into CHO cells, HBsAg expression was suppressed with same efficiency regardless of the target sequence similarities. In HepG2 cells, esiHP9 based on one of the amplified sequence that sharing 87% similarity to the target region suppressed HBsAg expression effectively and dose dependently. In vivo experiment showed that a single dose of 5 microg esiHP9 was able to reduce HBsAg and HBeAg level in the mouse sera by 88 and 77% despite of its 87% similarity to the target sequence, which was as good as esiHBVP that is 100% similar to the target sequence. All the data suggest that esiRNA can tolerate limited target sequence variations without losing its inhibitory capacity. It would be very helpful to suppress virus replication by RNAi despite of their high mutation rate.

Inhibition of hepatitis B virus replication by shRNAs in stably HBV expressed HEPG2 2.2.15 cell lines

In this study, the effect of RNAi on HBV replication was observed in a cell culture model, HepG2 2.2.15 cell line, which supports human HBV ayw replication and expression. Aim of the study was to investigate effects of shRNAs (small hairpin RNAs) targeting hepatitis B virus mRNAs on the viral replication in HepG2 2.2.15 cells. We selected three target HBV mRNA regions with different putative secondary structures to test whether the secondary structure of RNA may affect the inhibition efficacy on the target HBV RNA. Three HBV-specific siRNAs (small interfering RNA) were designed targeting X (1689-1708), Core (2229-2248) and S (765-784 nt) transcripts. HepG2 2.2.15 cells were transfected with shRNA expressing plasmids, P765, P2229 and P1689 targeting S, core and X region, respectively or a mock plasmid targeting lacZ gene. The culture media was collected throughout six days after transfection and analyzed by real-time PCR. Viral DNA production was suppressed for 7 days. The HBV DNA levels were decreased by 73, 72 and 79% with P765, P2229 and P1689 vectors, respectively. In conclusion, the shRNAs designed for X, core and S regions, specifically and significantly suppressed HBV DNA. siRNAs potentially may be used in treatment of hepatitis B.

Stable inhibition of hepatitis B virus expression and replication in HepG2.2.15 cells by RNA interference based on retrovirus delivery

RNA interference (RNAi) of virus-specific genes has emerged as a potential antiviral strategy. In order to suppress hepatitis B virus (HBV) expression and replication, a retrovirus-based RNAi system was developed, which utilized the U6-RNA polymerase III (Pol III) promoter to drive efficient expression and deliver the HBV-specific short hairpin RNAs (shRNAs) in HepG2.2.15 (2215) cells. In this system, the retrovirus vector with a puromycin selection marker was integrated into the host cell genome and allowed stable expression of shRNAs. In Puro-resistant 2215 cells, the levels of both HBV protein and mRNA were dramatically reduced by over 88% and HBV replication was suppressed. The results demonstrated that retrovirus-based RNAi technology will have foreseeable applications both in experimental biology and molecular medicine.

Therapeutic short hairpin RNA expression in the liver: viral targets and vectors

Over 500 million people worldwide are infected with one or more different and unrelated types of human hepatitis virus. Such individuals are at a high risk of developing acute or chronic hepatic disease, and ultimately dying from sequelae. Although a vaccine is available for hepatitis A and B virus, treatment options for chronically infected patients are limited, and particularly ineffective in case of hepatitis C virus (HCV) infection. A promising new avenue currently being explored is to harness the power of RNA interference for development of an antiviral therapy. The timing to pursue this particular approach is excellent, with the first in vivo animal models for HCV infection becoming available, and the technology for liver-specific expression of short hairpin RNAs advancing at a rapid pace. Here, we critically review these important current developments, and discuss the next steps to bring this novel approach into the clinics.

Establishment of a highly sensitive chemiluminescent detection system for analysis of hepatitis B virus transcription and replication level in vitro

AIM: To establish a stable and highly sensitive chemiluminescent detection system for analysis of hepatitis V virus (HBV) transcription and replication level in vitro.

METHODS: Human hepatoma cell line HepG2 and HepG2.2.15, a HepG2 cell line with HBV transcription and replication, were collected after being cultured for 3 d and then divided equally. Total RNA of the cells and HBV replication intermediates were extracted and analyzed by Northern and Southern blot hybridization, respectively, while digoxigenin labeled HBV recombinant plasmid pHBV4.1 was used as the probe of the hybridizations. The results of the hybridizations were detected by chemiluminescent detection system. Thereafter pHBV4.1 was diluted into a series of multi-stage differential log-rank concentrations, and analyzed by dot blot hybridization along with Northern and Southern blot hybridization, which were used as the internal controls.

RESULTS: High levels of HBV specific transcripts (3.5 kb and 2.4/2.1 kb mRNA) and HBV replication intermediate DNAs were detected by Northern and Southern hybridization analysis, respectively, in the HepG2.2.15 cells. No HBV specific transcripts or HBV replication intermediate DNAs were found in the HepG2 cells. Positive dot signals detected in the internal controls were weakened as the decrease of pHBV4.1 concentration. The sensitivity of the chemiluminescent detection system of the Northern and Southern hybridization analysis was 1 pg of the target nucleotides according to the internal controls, which was almost equal to that of isotope detection system. Similar results were obtained after the whole procedures were repeated for more than three times.

CONCLUSION: A stable and highly sensitive chemiluminescent detection system for analysis of HBV transcription and replication level in vitro is successfully established.

Inhibition of multiple gene expression and virus replication of HBV by stable RNA interference in 2.2.15 cells

BACKGROUND/AIMS

Hepatitis B virus (HBV) infection is a world-wide health problem. Recent studies have demonstrated the efficacy of RNA interference (RNAi) against HBV replication at cell culture and animal levels using transient transfection. The present study was to determine whether the stable transfection of short hairpin RNA (shRNA)-producing vector could achieve potent and sustained inhibition of the HBV replication in 2.2.15 cells.

METHODS

shRNA-producing vector against HBV and the empty vector were stably transfected into the 2.2.15 cells respectively. A series of experiments were performed in the producing stable lines to determine the changes of viral protein expression and replication.

RESULTS

The HBV protein expression and viral replication were suppressed dramatically and stably by the integrated shRNA-producing vectors. Most importantly, this suppression effect persists after 30 passages.

CONCLUSIONS

Our data provided the possibility of continuous and stable inhibition of HBV protein expression and replication in patients using RNAi, suggesting a potential clinical application of this novel approach. Furthermore, the established stable transfected cell lines provided a good platform for understanding the mechanism of anti-HBV by RNAi.

Genomic analysis of anti-hepatitis B virus (HBV) activity by small interfering RNA and lamivudine in stable HBV-producing cells

Hepatitis B virus (HBV) causes acute and chronic hepatitis and hepatocellular carcinoma. Small interfering RNA (siRNA) and lamivudine have been shown to have anti-HBV effects through different mechanisms. However, assessment of the genome-wide effects of siRNA and lamivudine on HBV-producing cell lines has not been reported, which may provide a clue to interrogate the HBV-cell interaction and to evaluate the siRNA's side effect as a potential drug. In the present study, we designed seven siRNAs based on the conserved HBV sequences and tested their effects on the expression of HBV genes following sorting of siRNA-positive cells. Among these seven siRNAs, siRNA-1 and siRNA-7 were found to effectively suppress HBV gene expression. We further addressed the global gene expression changes in stable HBV-producing cells induced by siRNA-1 and siRNA-7 by use of human genome-wide oligonucleotide microarrays. Data from the gene expression profiling indicated that siRNA-1 and siRNA-7 altered the expression of 54 and 499 genes, respectively, in HepG2.2.15 cells, which revealed that different siRNAs had various patterns of gene expression profiles and suggested a complicated influence of siRNAs on host cells. We further observed that 18 of these genes were suppressed by both siRNA-1 and siRNA-7. Interestingly, seven of these genes were originally activated by HBV, which suggested that these seven genes might be involved in the HBV-host cell interaction. Finally, we have compared the effects of siRNA and lamivudine on HBV and host cells, which revealed that siRNA is more effective at inhibiting HBV expression at the mRNA and protein level in vitro, and the gene expression profile of HepG2.2.15 cells treated by lamivudine is totally different from that seen with siRNA.

EsiRNAs inhibit Hepatitis B virus replication in mice model more efficiently than synthesized siRNAs

RNA interference (RNAi) has been proved to be a promising strategy to combat Hepatitis B virus (HBV) infection by way of cell culture and animal model studies. In this work, esiRNAs (endoribonuclease-prepared siRNAs) targeting all of the four open reading frames (ORFs) of HBV genome were prepared. In vitro experiment showed that esiHBVP suppressed HBsAg expression most effectively. Its capacity to suppress HBV replication in vivo was then tested. A single dose of 1 microg esiHBVP was able to reduce HBsAg and HBeAg level in the mouse serum by 90 and 89% one day after injection, while the same amount of chemically synthesized siRNA only reduced that by 33 and 45%. Immunostaining of HBcAg showed that esiHBVP inhibited HBcAg expression more potently than chemically synthesized siRNA. Quantification of HBV DNA in the mouse serum showed 1 microg eiHBVP treatment reduced serum HBV DNA copy number to 18% that of the untreated control, while 1 microg siRNA treatment only reduced that to 63%. In conclusion, the data presented here proved that esiRNA is much more efficient in suppressing HBV replication than chemically synthesized siRNA, and it might be a better therapeutic agent to fight against HBV infection.