Targeted inhibition of HBV gene expression by single-chain antibody mediated small interfering RNA delivery

PreS/2-21-Guided siRNA Nanoparticles Target to Inhibit Hepatitis B Virus Infection and Replication

A viable therapy is needed to overcome the deadlock of the incurable chronic hepatitis B (CHB). The prolonged existence of covalently closed circular DNA (cccDNA) and integrated HBV DNA in the nucleus of hepatocytes is the root cause of CHB. As a result, it is critical to successfully suppress HBV DNA replication and eliminate cccDNA. RNA interference has been proven in recent research to silence the expression of target genes and thereby decrease HBV replication. However, siRNA is susceptible to be degraded by RNA enzymes in vivo, making it difficult to deliver successfully and lacking of tissue targeting. To exploit the advantages of siRNA technology while also overcoming its limitations, we designed a new strategy and prepared biomimetic nanoparticles that were directed by PreS/2-21 peptides and precisely loaded HBV siRNA. Experiments on these nanoparticles in vitro and in vivo revealed that they are tiny, stable, safe and highly targetable, with high inhibitory effects on HBV DNA, pgRNA, cccDNA, HBeAg and HBsAg. PreS/2-21-directed nanoparticles loaded with HBV gene therapy drugs are expected to be promising for the treatment of CHB.

Efficient delivery of HBV NLS siRNAs into HepG2.2.15 cells for HBV inhibition through novel recombinant preS1‑tP proteins

Hepatitis B virus (HBV) infection and related liver complications remain severe public health problems worldwide. Previous investigations have shown that small interfering (si)RNAs can offer an effective strategy for the treatment of chronic hepatitis B. The present study aimed to develop a novel siRNA‑delivering system of therapeutic HBV nuclear localization sequence (NLS) siRNAs using the recombinant preS1‑truncated protamine (tP) proteins. The preS1 region of the LHB was used in place of scFv to construct the recombinant preS1‑tP proteins, which were applied to deliver siRNAs targeting the HBV NLS to inhibit HBV replication and infection in HepG2.2.15 cells overexpressing sodium taurocholate cotransporting polypeptide (NTCP). The results revealed that HepG2.2.15 cells with stable NTCP expression (HepG2.2.15‑NTCP cells) transfected with the recombinant lentivirus showed increased expression of NTCP genes. The HBV NLS siRNAs significantly suppressed HBV mRNA content and levels of HBsAg and HBeAg in the HepG2.2.15‑NTCP cells. Recombinant preS1‑tP proteins tagged with His and glutathione S‑transferase were found to enter into HepG2.2.15‑NTCP cells and bind with DNA. The HBV NLS siRNAs were delivered into HepG2.2.15‑NTCP cells by recombinant preS1‑tP proteins, which resulted in decreased expression of HBV mRNA, HBsAg and HBeAg, HBV DNA and covalently closed circular DNA in the HepG2.2.15‑NTCP cells. Therefore, the recombinant preS1‑tP proteins successfully delivered NLS siRNAs into HepG2.2.15 cells and repressed HBV infection and replication.

Inhibition of HBV replication by delivering the dual-gene expression vector pHsa-miR16-siRNA in HepG2.2.15 cells

This study aimed to construct the dual-gene expression vector pHsa-miR16-siRNA which can express human miR-16 and HBV X siRNA, and examine its regulatory effect on HBV gene expression in the HepG2.2.15 cell line. The expression vectors siR-1583 and pHsa-miR16-siRNA were designed and constructed. HepG2.2.15 cells were transfected with the empty vector, siR-1583, pmiR-16 and pHsa-miR16-siRNA, respectively. ELISA was performed to measure the expression of HBsAg and HBeAg in the culture supernatant 48 and72 h post transfection. Fluorescence quantitative PCR was used to measure the HBV mRNA degradation efficiency and HBV DNA copy number. The results showed that the expression of HBV genes was significantly inhibited in HepG2.2.15 cells transfected with siR-1583, pmiR-16 and pHsa-miR16-siRNA, respectively, when compared with that in cells transfected with the empty vectors, with the inhibitory effect of pHsa-miR16-siRNA being the most significant. ELISA showed that the inhibitory rates of HBsAg and HBeAg in pHsa-miR16-siRNA transfected cells were correspondingly 87.3% and 85.0% at 48 h, and 88.6% and 86.5% at 72 h post transfection (P<0.01 vs. control group). RT-PCR showed that the level of HBV mRNA decreased by 80.2% (t=-99.22, P<0.01), the genomic HBV DNA by 92.8% (t=-73.06, P<0.01), and the supernatant of HBV DNA copy number by 89.8% (t=-47.13, P<0.01) in pHsa-miR16-siRNA transfected group. It was suggested that the dual-gene expression vector pHsa-miR16-siRNA can inhibit the replication of HBV more efficiently than a single-gene expression vector.

Single-chain antibody–delivered Livin siRNA inhibits human malignant melanoma growth in vitro and in vivo

Although gene therapy has brought new insights into the treatment of malignant melanoma, targeting delivery of nucleic acid which targets critical oncogene/anti-oncogene in vivo is still a bottleneck in the therapeutic application. Our previous in vitro studies have found that the oncogene Livin could serve as a potential molecular target by small interfering RNA for gene therapy of malignant melanoma. However, how to transport Livin small interfering RNA into malignant melanoma cells specifically and efficiently in vivo needs further investigation. Cumulative evidence has suggested that single-chain antibody–mediated small interfering RNA targeted delivery is an effective way to silence specific genes in human cancer cells. Indeed, this study designed a protamine–single-chain antibody fusion protein, anti-MM scFv-tP, to deliver Livin small interfering RNA into LiBr cells. Further experiments confirmed the induction of cell apoptosis and suppression of cell proliferation by anti-MM scFv-tP in LiBr cells, along with efficient silence of Livin gene both in vitro and in vivo. Altogether, our findings provide a feasible approach to transport Livin small interfering RNA to malignant melanoma cells which would be a new therapeutic strategy for combating malignant melanoma.

Human CD64-targeted non-viral siRNA delivery system for blood monocyte gene modulation

A subset of phagocytes including inflammatory monocytes in blood migrate and give rise to macrophages in inflammatory tissues which generated the idea that blood monocytes are the therapeutic targets for drug delivery. Fc gamma receptor I (CD64) is a membrane receptor for the Fc region of immunoglobulin G, primarily expressed on monocyte-lineage, and H22 a monoclonal antibody for human CD64 had shown rapid blood monocyte binding and occupation in clinical studies. Small interfering RNA-mediated gene silencing as a therapeutic has been proposed and is a promising strategy in terms of its "knock-down" ability on the target gene prior to translation. However, its instability and off-targeting effect must be overcome for success in clinical studies. In this study, we developed a non-viral delivery system composed of oligo-nona-arginine (9R) and anti-human CD64 single chain antibodies (H22) for human monocyte-specific siRNA delivery. A targeted and efficient siRNA delivery mediated by anti-CD64 scFv-9R was observed in CD64 positive human leukemia cells, THP-1. With primary human blood cells, anti-CD64 scFv-9R mediated gene silencing was quantitatively confirmed representing blood monocyte selective gene delivery. These results demonstrate the potential of anti-CD64 scFv-9R mediated siRNA delivery for the treatment of human inflammatory diseases via blood monocytes gene delivery.

HER2-siRNA delivered by EGFR-specific single chain antibody inhibits NSCLC cell proliferation and tumor growth

Overexpression of human epidermal growth factor receptor type2 (HER2) is closely associated with aggressive progression and poor prognosis in non-small cell lung cancer (NSCLC). Here, we generated an EGFR-scFv-arginine nonamer peptide fusion protein (scFv-9R) as a cargo to deliver HER2 specific siRNA into HER2-positive NSCLC cells both in vitro and in vivo. HER2-siRNAs delivered by scFv-9R effeciently silenced HER2 expression in EGFR-positive NSCLC cells, and consequently resulted in G1 arrest and cell growth inhibition. Importantly, intravenous injection of scFv-9R/HER2-siRNA complex markedly suppressed growth of EGFR-positive NSCLC xenograft in nude mice, resulting from downregulated HER2 expression, reduced cell proliferation and enhanced cell apoptosis. Collectively, our study provides a novel therapeutic strategy for the treatment of EGFR-positive, HER2-overexpressed NSCLC.

siRNA Targeting the 2Apro Genomic Region Prevents Enterovirus 71 Replication In Vitro

Enterovirus 71 (EV71) is the most important etiological agent of hand, foot, and mouth disease (HFMD) in young children, which is associated with severe neurological complications and has caused significant mortalities in recent HFMD outbreaks in Asia. However, there is no effective antiviral therapy against EV71. In this study, RNA interference (RNAi) was used as an antiviral strategy to inhibit EV71 replication. Three small interfering RNAs (siRNAs) targeting the 2A^pro region of the EV71 genome were designed and synthesized. All the siRNAs were transfected individually into rhabdomyosarcoma (RD) cells, which were then infected with strain EV71-2006-52-9. The cytopathic effects (CPEs) in the infected RD cells, cell viability, viral titer, and viral RNA and protein expression were examined to evaluate the specific viral inhibition by the siRNAs. The results of cytopathogenicity and MTT tests indicated that the RD cells transfected with the three siRNAs showed slight CPEs and significantly high viability. The 50% tissue culture infective dose (TCID₅₀) values demonstrated that the viral titer of the groups treated with three siRNAs were lower than those of the control groups. qRT–PCR and western blotting revealed that the levels of viral RNA and protein in the RD cells treated with the three siRNAs were lower than those in the controls. When RD cells transfected with siRNAs were also infected with strain EV71-2008-43-16, the expression of the VP1 protein was significantly inhibited. The levels of interferon α (IFN-α) and IFN-β did not differ significantly in any group. These results suggest that siRNAs targeting the 2A^pro region of the EV71 genome exerted antiviral effects in vitro.

Design and Generation of Humanized Single-chain Fv Derived from Mouse Hybridoma for Potential Targeting Application

Single-chain variable antibody fragments (scFvs) are attractive candidates for targeted immunotherapy in several human diseases. In this study, a concise humanization strategy combined with an optimized production method for humanizing scFvs was successfully employed. Two antibody clones, one directed against the hemagglutinin of H5N1 influenza virus, the other against EpCAM, a cancer biomarker, were used to demonstrate the validity of the method. Heavy chain (VH) and light chain (VL) variable regions of immunoglobulin genes from mouse hybridoma cells were sequenced and subjected to the construction of mouse scFv 3-D structure. Based on in silico modeling, the humanized version of the scFv was designed via complementarity-determining region (CDR) grafting with the retention of mouse framework region (FR) residues identified by primary sequence analysis. Root-mean-square deviation (RMSD) value between mouse and humanized scFv structures was calculated to evaluate the preservation of CDR conformation. Mouse and humanized scFv genes were then constructed and expressed in Escherichia coli. Using this method, we successfully generated humanized scFvs that retained the targeting activity of their respective mouse scFv counterparts. In addition, the humanized scFvs were engineered with a C-terminal cysteine residue (hscFv-C) for site-directed conjugation for use in future targeting applications. The hscFv-C expression was extensively optimized to improve protein production yield. The protocol yielded a 20-fold increase in production of hscFv-Cs in E. coli periplasm. The strategy described in this study may be applicable in the humanization of other antibodies derived from mouse hybridoma.

siRNA delivered by EGFR-specific scFv sensitizes EGFR-TKI-resistant human lung cancer cells

The overexpression of epidermal growth factor receptor (EGFR) is closely associated with a poor outcome in non-small cell lung cancer (NSCLC), and EGFR is an ideal biomarker for the targeted therapy of NSCLC. Although patients with EGFR-activating mutations respond to EGFR tyrosine kinase inhibitors (EGFR-TKIs), they eventually acquire resistance, which typically results from a secondary EGFR mutation or the activation of other signaling pathways. Novel approaches to overcome or prevent EGFR-TKI resistance are clinically important. In this study, we developed an EGFR-scFv-arginine nonamer peptide fusion protein, s-9R, as an siRNA carrier. Here, we show that s-9R effectively and specifically delivers EGFR-siRNAs, KRAS-siRNA and MET-siRNA into NSCLC cells and silences the expression of target genes. The sensitivity of NSCLC cells to gefitinib was restored after treatment with the s-9R/siRNA complex, and the apoptosis rates of the treated cells were significantly higher than those of the control groups. Furthermore, the co-administration of s-9R/siRNA and gefitinib successfully suppressed the progression of H1975 xenograft tumors and extended the life span of tumor-bearing nude mice. Collectively, the results of this study provide not only a new scFv derivative for delivering siRNA into EGFR-overexpressing, TKI-resistant NSCLC cells but also a novel method for overcoming TKI resistance.

Design and characterization of novel recombinant listeriolysin O-protamine fusion proteins for enhanced gene delivery

To improve the efficiency of gene delivery for effective gene therapy, it is essential that the vector carries functional components that can promote overcoming barriers in various steps leading to the transport of DNA from extracellular to ultimately nuclear compartment. In this study, we designed genetically engineered fusion proteins as a platform to incorporate multiple functionalities in one chimeric protein. Prototypes of such a chimera tested here contain two domains: one that binds to DNA; the other that can facilitate endosomal escape of DNA. The fusion proteins are composed of listeriolysin O (LLO), the endosomolytic pore-forming protein from Listeria monocytogenes, and a 22 amino acid sequence of the DNA-condensing polypeptide protamine (PN), singly or as a pair: LLO-PN and LLO-PNPN. We demonstrate dramatic enhancement of the gene delivery efficiency of protamine-condensed DNA upon incorporation of a small amount of LLO-PN fusion protein and further improvement with LLO-PNPN in vitro using cultured cells. Additionally, the association of anionic liposomes with cationic LLO-PNPN/protamine/DNA complexes, yielding a net negative surface charge, resulted in better in vitro transfection efficiency in the presence of serum. An initial, small set of data in mice indicated that the observed enhancement in gene expression could also be applicable to in vivo gene delivery. This study suggests that incorporation of a recombinant fusion protein with multiple functional components, such as LLO-protamine fusion protein, in a nonviral vector is a promising strategy for various nonviral gene delivery systems.

Oncomodulin/truncated protamine-mediated Nogo-66 receptor small interference RNA delivery promotes axon regeneration in retinal ganglion cells

The optic nerve often suffers regenerative failure after injury, leading to serious visual impairment such as glaucoma. The main inhibitory factors, including Nogo-A, oligodendrocyte myelin glycoprotein, and myelin-associated glycoprotein, exert their inhibitory effects on axonal growth through the same receptor, the Nogo-66 receptor (NgR). Oncomodulin (OM), a calcium-binding protein with a molecular weight of an ∼12 kDa, which is secreted from activated macrophages, has been demonstrated to have high and specific affinity for retinal ganglion cells (RGC) and promote greater axonal regeneration than other known polypeptide growth factors. Protamine has been reported to effectively deliver small interference RNA (siRNA) into cells. Accordingly, a fusion protein of OM and truncated protamine (tp) may be used as a vehicle for the delivery of NgR siRNA into RGC for gene therapy. To test this hypothesis, we constructed OM and tp fusion protein (OM/tp) expression vectors. Using the indirect immunofluorescence labeling method, OM/tp fusion proteins were found to have a high affinity for RGC. The gel shift assay showed that the OM/tp fusion proteins retained the capacity to bind to DNA. Using OM/tp fusion proteins as a delivery tool, the siRNA of NgR was effectively transfected into cells and significantly down-regulated NgR expression levels. More importantly, OM/tp-NgR siRNA dramatically promoted axonal growth of RGC compared with the application of OM/tp recombinant protein or NgR siRNA alone in vitro. In addition, OM/tp-NgR siRNA highly elevated intracellular cyclic adenosine monophosphate (cAMP) levels and inhibited activation of the Ras homolog gene family, member A (RhoA). Taken together, our data demonstrated that the recombinant OM/tp fusion proteins retained the functions of both OM and tp, and that OM/tp-NgR siRNA might potentially be used for the treatment of optic nerve injury.

Therapeutic targeting of microRNAs: current status and future challenges

MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNAs that have crucial roles in regulating gene expression. Increasing evidence supports a role for miRNAs in many human diseases, including cancer and autoimmune disorders. The function of miRNAs can be efficiently and specifically inhibited by chemically modified antisense oligonucleotides, supporting their potential as targets for the development of novel therapies for several diseases. In this Review we summarize our current knowledge of the design and performance of chemically modified miRNA-targeting antisense oligonucleotides, discuss various in vivo delivery strategies and analyse ongoing challenges to ensure the specificity and efficacy of therapeutic oligonucleotides in vivo. Finally, we review current progress on the clinical development of miRNA-targeting therapeutics.

Advances in targeted delivery of small interfering RNA using simple bioconjugates

INTRODUCTION

Development of drugs based on RNA interference by small interfering RNA (siRNA) has been progressing slowly due to a number of challenges associated with the in vivo behavior of siRNA. A central problem is controlling siRNA delivery to specific cell types. Here, we review existing literature on one type of strategy for solving the issue of cell-specific delivery of siRNA, namely delivering the siRNA as part of simple bioconjugate constructs.

AREAS COVERED

This review presents current experience from strategies aimed at targeting siRNA to specific cell types, by associating the siRNA with a targeting moiety, in a simple bioconjugate construct. We discuss the use of different types of targeting moieties, as well as the different conjugation strategies employed for preparing these bioconjugate constructs that deliver the siRNA to target cells. We focus especially on the in-built or passive functionalities associated with each strategy, in order to identify key elements of successful siRNA delivery strategies with potential for further exploration.

EXPERT OPINION

By evaluating the current literature on this subject, we identify strategies and concepts that are suitable for future studies, to enable the development of highly efficient simple bioconjugates for targeted siRNA delivery with therapeutic application.

Targeted small interfering RNA-immunoliposomes as a promising therapeutic agent against highly pathogenic Avian Influenza A (H5N1) virus infection

This study describes a proof-of-concept study on the use of small interfering RNA (siRNA)-immunoliposomes as a therapeutic agent against H5N1 influenza virus infection. siRNA specific for influenza virus nucleoprotein (NP) mRNA was employed as the key antiviral agent to inhibit viral replication in this study. A humanized single-chain Fv antibody (huscFv) against the hemagglutinin (HA) of H5N1 highly pathogenic avian influenza virus (HPAI) was used as the targeting molecule to HA of H5N1 virus, which is abundantly expressed on the surface of infected cells (the HA target cells). The huscFv was applied to cationic polyethylene glycol-conjugated 3β-[N-(N',N'-dimethylaminoethane) carbamoyl] cholesterol-dioleoylphosphatidyl ethanolamine (PEGylated DC-Chol-DOPE) liposomes to generate immunoliposomes for siRNA delivery. The immunoliposomes were shown to specifically bind HA-expressing Sf9 cells and demonstrated enhanced siRNA transfection efficiency. The siRNA transfection efficiency was significantly reduced after preincubation of the HA target cells with an excess amount of free huscFv. These results therefore demonstrated that the enhanced siRNA delivery by use of immunoliposomes was mediated via targeting by huscFv. Furthermore, the siRNA silencing effect was more pronounced when the immunoliposomes were administered 6 to 12 h post-H5N1 infection in MDCK cells compared with the nontargeted liposomes. This proof-of-concept study may contribute to the future design and development of an siRNA delivery system for combating viral infectious diseases in humans.

High-level expression, purification, and characterization of bifunctional ScFv-9R fusion protein

Fibroblast growth factor receptor 3 (FGFR3) is a noted proto-oncogene involved in the pathogenesis of many tumors, so more and more studies focus on the potential use of receptor kinase inhibitor and therapeutic antibodies against FGFR3. In this study, we designed a novel fusion protein containing the single-chain Fv (ScFv) against FGFR3 and 9-arginine, denoted as ScFv-9R. To achieve the high-level production and soluble expression, ScFv and ScFv-9R were fused with small ubiquitin-related modifier (Sumo) by polymerase chain reaction and expressed in Escherichia coli BL21 (DE3). The recombinant bacteria was induced by 0.5 mM isopropyl-β-D-thiogalactopyranoside for 20 h at 20 °C; supernatants of Sumo-ScFv was harvested and purified by DEAE Sepharose FF and Ni-NTA orderly, and supernatants of Sumo-ScFv-9R was harvested and purified by Ni-NTA. After cleaved by the Sumo protease, the recombinant ScFv or ScFv-9R was released from the fusion protein, respectively. The purity of ScFv or ScFV-9R was shown to be higher than 90 %, and their yield reached 3-5 mg per liter of bacterial culture. In vitro data showed that ScFV-9R can attenuate the phosphorylation of FGFR3 and ERK in the absence or presence of FGF9. Gel retardation assay showed that 1 μg of ScFv-9R could efficiently bind to about 4 pmol siRNA. Fluorescent microscope analysis showed that ScFv-9R can efficiently bind and deliver siRNA into RT112 cells. In conclusion, we use Sumo fusion system to acquire high-level production, soluble expression, and bifunctional activity of ScFv-9R in E. coli. Our results also revealed that ScFv-9R, as a novel carrier, may have potential applications in antitumor studies and pharmaceutical development.

Changes in innate and permissive immune responses after hbv transgenic mouse vaccination and long-term-siRNA treatment [corrected]

Background

Currently, no licensed therapy can thoroughly eradicate hepatitis B virus (HBV) from the body, including interferon α and inhibitors of HBV reverse-transcription. Small interfering RNA (siRNA) seem to be a promising tool for treating HBV, but had no effect on the pre-existing HBV covalently closed circular DNA. Because it is very difficult to thoroughly eradicate HBV with unique siRNAs, upgrading the immune response is the best method for fighting HBV infection. Here, we aim to explore the immune response of transgenic mice to HBV vaccination after long-term treatment with siRNAs and develop a therapeutic approach that combines siRNAs with immunopotentiators.

Methodology/Principal Findings

To explore the response of transgenic mice to hepatitis B vaccine, innate and acquired immunity were detected after long-term treatment with siRNAs and vaccination. Antiviral cytokines and level of anti-hepatitis B surface antigen antibody (HBsAg-Ab) were measured after three injections of hepatitis B vaccine.

Results

Functional analyses indicated that toll-like receptor-mediated innate immune responses were reinforced, and antiviral cytokines were significantly increased, especially in the pSilencer4.1/HBV groups. Analysis of CD80+/CD86+ dendritic cells in the mouse liver indicated that dendritic cell antigen presentation was strengthened. Furthermore, the siRNA-treated transgenic mice could produce detectable HBsAg-Ab after vaccination, especially in the CpG oligonucleotide vaccine group.

Conclusions/Significance

For the first time, our studies demonstrate that siRNAs with CpG HBV vaccine could strengthen the immune response and break the immune tolerance status of transgenic mice to HBV. Thus, siRNAs and HBV vaccine could provide a sharp double-edged sword against chronic HBV infection.

Nanomedicines based on recombinant fusion proteins for targeting therapeutic siRNA oligonucleotides

The enormous promise of siRNA technology for rational and targeted therapy can only be realized if the inherent problems in terms of pharmaceutical development are overcome. Besides liposomal and polymeric nanoparticles, fusion proteins hold great potential for cell-type specific delivery of siRNA. Consisting of a protein binder and an oligonucleotide complexing domain, fusion proteins are designed for targeted delivery to a certain tissue or organ and subsequent release of the siRNA after cellular uptake. This article focuses on the possibilities and importance of targeting and complexing domains, including polymers and dendrimers. In vitro and in vivo evaluations are discussed with an in-depth view on pharmacokinetic properties. Remaining challenges concerning specificity on the tissue and molecular levels are highlighted.

Anti-Her2 single-chain antibody mediated DNMTs-siRNA delivery for targeted breast cancer therapy

The targeted delivery of small interfering RNA (siRNA) to specific tumor tissues and tumor cells remains as one of the key challenges in the development of RNA interference as a therapeutic application. To target breast cancer, we developed a therapeutic delivery system using a fusion protein of an anti-Her2 single-chain antibody fragment with a positively charged protamine, namely F5-P, as the carrier to specifically deliver siRNA-targeting DNA methyltransferases 1 and/or 3b genes (siDNMTs) into Her2-expressing breast tumor cells. The carrier F5-P, expressed by the Escherichia coli system, was able to bind siRNA molecules and specifically deliver the siRNA to Her2-expressing BT474 breast cancer cells but not Her2-nonexpressing MDA-MB-231 breast cancer cells, while delivery of siDNMTs to BT474 cells successfully silenced the expression of targeted DNA methyltransferases (DNMTs) and facilitated the de-methylation of the RASSF1A tumor suppressor gene promoter, leading to the suppression of tumor cell proliferation. Moreover, as demonstrated in the BT474 xenograft murine model, F5-P successfully delivered siRNA into a Her2-expressing breast tumor, and tumor growth inhibition was mediated by an intravenous injection of F5-P/siDNMTs complex by down-regulating the expression of DNMTs and restoring tumor suppressor gene expression. These data suggest that the delivery of siDNMTs by F5-P could be used to treat Her2-expressing breast cancer.

Inhibition of hepatitis B Virus replication by hepatocyte nuclear factor 4-alpha specific short hairpin RNA

BACKGROUND

Previous studies showed that hepatocyte nuclear factor 4α (HNF4α) may play a critical role in hepatitis B virus (HBV) replication.

AIMS

This study aimed to investigate the effect of knocking down of HNF4α with RNA interference technique on HBV replication in a HBV replication mouse model.

METHODS

Four HNF4α, specific short hairpin RNA (shRNA)-producing plasmids were constructed. HBV mRNA and DNA replication intermediates were analysed using Northern and Southern blot respectively. The expression of HNF4α and HBV core antigen (HBcAg) was detected using immunohistochemistry technique.

RESULTS

One of the HNF4α shRNAs, HNF4α shRNA1, efficiently inhibited the expression of HNF4α in HepG2 cells and mice liver. HBV RNA transcripts and DNA replication intermediates in HNF4α shRNA1 group were decreased 67.3 and 76%, respectively, in HepG2 cells, and 68.1 and 70.6% in mice liver respectively. The expression level of HBcAg in the liver was also decreased with the inhibition of HNF4α expression.

CONCLUSIONS

These results suggested that decreasing of HNF4α expression was associated with the reduced level of HBV replication in HepG2 cells and mice liver. These data indicated that HNF4α played a critical role in HBV replication in vivo, and HNF4α shRNA could inhibit HBV replication in vivo.

Targeted delivery of PLK1-siRNA by ScFv suppresses Her2+ breast cancer growth and metastasis

A major obstacle to developing small interfering RNAs (siRNAs) as cancer drugs is their intracellular delivery to disseminated cancer cells. Fusion proteins of single-chain fragmented antibodies (ScFvs) and positively charged peptides deliver siRNAs into specific target cells. However, the therapeutic potential of ScFv-mediated siRNA delivery has not been evaluated in cancer. Here, we tested whether Polo-like kinase 1 (PLK1) siRNAs complexed with a Her2-ScFv-protamine peptide fusion protein (F5-P) could suppress Her2(+) breast cancer cell lines and primary human cancers in orthotopic breast cancer models. PLK1-siRNAs transferred by F5-P inhibited target gene expression, reduced proliferation, and induced apoptosis of Her2(+) breast cancer cell lines and primary human cancer cells in vitro without triggering an interferon response. Intravenously injected F5-P/PLK1-siRNA complexes concentrated in orthotopic Her2(+) breast cancer xenografts and persisted for at least 72 hours, leading to suppressed PLK1 gene expression and tumor cell apoptosis. The intravenously injected siRNA complexes retarded Her2(+) breast tumor growth, reduced metastasis, and prolonged survival without evident toxicity. F5-P-mediated delivery of a cocktail of PLK1, CCND1, and AKT siRNAs was more effective than an equivalent dose of PLK1-siRNAs alone. These data suggest that F5-P could be used to deliver siRNAs to treat Her2(+) breast cancer.

Antibodies to cell surface proteins redirect intracellular trafficking pathways

Antibody-mediated intracellular delivery of therapeutic agents has been considered for treatment of a variety of diseases. These approaches involve targeting cell-surface receptor proteins expressed by tumors or viral proteins expressed on infected cells. We examined the intracellular trafficking of a viral cell-surface-expressed protein, rabies G, with or without binding a specific antibody, ARG1. We found that antibody binding shifts the native intracellular trafficking pathway of rabies G in an Fc-independent manner. Kinetic studies indicate that the ARG1/rabies G complex progressively co-localized with clathrin, early endosomes, late endosomes, and lysosomes after addition to cells. This pathway was different from that taken by rabies G without addition of antibody, which localized with recycling endosomes. Findings were recapitulated using a cellular receptor with a well-defined endogenous recycling pathway. We conclude that antibody binding to cell-surface proteins induces redirection of intracellular trafficking of unbound or ligand bound receptors to a specific degradation pathway. These findings have broad implications for future developments of antibody-based therapeutics.

Inhibition of hepatitis B virus (HBV) by LNA-mediated nuclear interference with HBV DNA transcription

Silencing target genes with small regulatory RNAs is widely used to investigate gene function and therapeutic drug development. Recently, triplex-based approaches have provided another attractive means to achieve targeted gene regulation and gene manipulation at the molecular and cellular levels. Nuclear entry of oligonucleotides and enhancement of their affinity to the DNA targets are key points of such approaches. In this study, we developed lipid-based transport of a locked-nucleic-acid (LNA)-modified oligonucleotide for hepatitis B virus (HBV) DNA interference in human hepatocytes expressing HBV genomic DNA. In these cells, the LNA-modified oligonucleotides passed efficiently across the cell membrane, and lipid-coating facilitated translocation from the cytoplasm to the nucleus. The oligonucleotide specifically targeting HBV DNA clearly interfered with HBV DNA transcription as shown by a block in pregenomic RNA (pgRNA) production. The HBV DNA-targeted oligonucleotide suppressed HBV DNA replication and HBV protein production more efficiently than small interfering RNAs directed to the pgRNA. These results demonstrate that fusion with lipid can carry LNA-modified oligonucleotides to the nucleus where they regulate gene expression. Interfering with HBV DNA transcription by LNA-modified oligonucleotides has strong potential as a new strategy for HBV inhibition.

Antisense oligonucleotide inhibits avian influenza virus H5N1 replication by single chain antibody delivery system

H5N1 avian influenza virus (AIV) causes widespread infections in poultry and wild birds, and has the potential to emerge as a pandemic threat to human. Antisense oligonucleotides (AS ODNs) are highly effective at inhibiting gene replication. Antibody-mediated delivery is a novel approach to target specific cells and tissues. In this study, we designed and synthesized three AS ODNs (PA4, PA492 and PA1203) specific for conserved region of AIV PA protein, and all the three AS ODNs could inhibit viral replication. The PA492 ODN showed the best antiviral effect by viral titers and quantitative RT-PCR in MDCK cells. The fusion protein scFv-tP was constructed as a single chain variable fragment (scFv) against AIV hemaglutinin antigen with a truncated protamine (tP). The results showed that scFv-tP fusion improved the antiviral effectiveness of PA492 in MDCK cells as measured by viral titers, quantitative RT-PCR and indirect immunofluorescence (IFA) assays. In addition, scFv-tP-delivered PA492 was also found to partially protect mice from lethal H5N1 influenza virus challenge. Using scFv-tP delivery, fluorescein isothiocyanate labeled-PA492 was found to be significantly localized in the lungs, compared to liposome-delivered PA492. Moreover, the fusion protein mediated PA492 had a lower lung index and viral titers in the infected mice as compared with the liposome method. These results provided a potential method for using anti-HA fusion protein for the targeted delivery of AS ODNs against AIV H5N1.

Inhibition of human breast cancer cell invasion by siRNA against urokinase-type plasminogen activator

Urokinase plasminogen activator (uPA) correlates closely with breast cancer metastasis via triggering the degradation of divergent matrix proteins. Here, uPA was selectively knocked down in breast carcinoma MDA-MB-231 cells by siRNAs. The in vitro migration of MDA-MB-231 cells was effectively suppressed accompanied by a decrease in extracellular MMP-9 activities. The colony formation ability of MDA-MB-231 cells was inhibited following uPA knockdown, while the proliferation was not affected. The uPA knockdown in MDA-MB-231 cells caused significantly suppressed tumor metastasis in nude mice. Thus, siRNAs targeted to uPA have implications in the development of novel approaches to preventing breast cancer metastasis.

Generation and characterization of a fusion protein of single-chain fragment variable antibody against hemagglutinin antigen of avian influenza virus and truncated protamine

The hemagglutinin antigen (HA) of avian influenza virus (AIV) is an immunogen abundant on the surfaces of infected cells, and can be used as a target for specific antibodies to clear viral infection. Protamine has been demonstrated to deliver DNA into cells effectively. Accordingly, a fusion protein of anti-HA single-chain fragment variable (scFv) and truncated protamine (tP) may be used as a vehicle for delivering the anti-AIV siRNA into the AIV-infected cells for gene therapy. To test this hypothesis, we constructed a novel recombinant plasmid, pET28-scFv-tP, by connecting the genes for anti-H5N1 AIV HA-specific scFv with synthesized oligonucleotides encoding the 22 amino acids of human tP and a linker. Furthermore, the recombinant scFV-tP was expressed and purified, with a yield of 7-8mg of scFv-tP and a purity of >92% from 1L of bacterial culture. Characterization of its bioactivity revealed that scFv-tP recognized HA, similar to its scFv control, in a dose-dependent manner and that the scFv-tP, but not its scFv control, bound to DNA and delivered plasmid and oligonucleotide DNA into the AIV-infected MDCK cells effectively. More importantly, transfection with the mixture of the scFv-tP and plasmid for the NP-specific siRNA significantly inhibited the replication of AIV in MDCK cells, as compared with that transfection with the scFv-plasmid mixture, even with the plasmid in liposome. Our data demonstrated that the recombinant scFv-tP retained the functions of both scFv and tP, and might be potentially used for delivering genetic materials for targeting therapy of AIV infection in vivo.

Does RNA interference provide new hope for control of chronic hepatitis B infection?

Hepatitis B virus (HBV) infection is a global human health problem, with an estimated 350 million people having chronic hepatitis B (CHB) infection worldwide. The majority of infections acquired during adulthood are resolved without intervention; however, infections acquired at birth or during early childhood have a 90% chance of progressing to CHB, leading to a host of adverse effects on the liver, including cirrhosis and cancer. CHB is currently treated with a combination of cytokines and/or nucleoside/nucleotide analogues; however, adverse side effects to cytokine therapy and the selection of resistance mutations to nucleoside analogues often abrogate the efficacy of treatment. The recent discovery that small interfering RNA and microRNA are active in mammalian cells suggests it might be possible to supplement existing HBV therapies with small RNA-based therapeutic(s).

Production and characterization of a recombinant single-chain antibody against Hantaan virus envelop glycoprotein

Hantaan virus (HTNV) is the type of Hantavirus causing hemorrhagic fever with renal syndrome, for which no specific therapeutics are available so far. Cell type-specific internalizing antibodies can be used to deliver therapeutics intracellularly to target cell and thus, have potential application in anti-HTNV infection. To achieve intracellular delivery of therapeutics, it is necessary to obtain antibodies that demonstrate sufficient cell type-specific binding, internalizing, and desired cellular trafficking. Here, we describe the prokaryotic expression, affinity purification, and functional testing of a single-chain Fv antibody fragment (scFv) against HTNV envelop glycoprotein (GP), an HTNV-specific antigen normally located on the membranes of HTNV-infected cells. This HTNV GP-targeting antibody, scFv3G1, was produced in the cytoplasm of Escherichia coli cells as a soluble protein and was purified by immobilized metal affinity chromatography. The purified scFv possessed a high specific antigen-binding activity to HTNV GP and HTNV-infected Vero E6 cells and could be internalized into HTNV-infected cells probably through the clathrin-dependent endocytosis pathways similar to that observed with transferrin. Our results showed that the E. coli-produced scFv had potential applications in targeted and intracellular delivery of therapeutics against HTNV infections.

Lipidic systems for in vivo siRNA delivery

The ability of small-interfering RNA (siRNA) to silence specific target genes not only offers a tool to study gene function but also represents a novel approach for the treatment of various human diseases. Its clinical use, however, has been severely hampered by the lack of delivery of these molecules to target cell populations in vivo due to their instability, inefficient cell entry, and poor pharmacokinetic profile. Various delivery vectors including liposomes, polymers, and nanoparticles have thus been developed in order to circumvent these problems. This review presents a comprehensive overview of the barriers and recent progress for both local and systemic delivery of therapeutic siRNA using lipidic vectors. Different strategies for formulating these siRNA-loaded lipid particles as well as the general concern about their safe use in vivo will also be discussed. Finally, current advances in the targeted delivery of siRNA and their impacts on the field of RNA interference (RNAi)-based therapy will be presented.

Long-term RNA interference and its application to hepatitis B virus

RNA interference (RNAi) is an ancient defensive mechanism in eukaryotes to control gene expressing and defend their genomes from foreign invaders. It refers to the phenomenon that double-stranded RNA results in the sequence-specific silencing of target gene expression. Although it was documented in a relatively short time ago, intensive research has facilitated making its mechanism clear. Researchers have found that it was a powerful tool for analyzing the functions of genes and treating tumors, infectious diseases and genetic abnormalities that are associated with a dominant gene defect. However, delivery in vivo, low blood stability and poor intracellular uptake present significant challenges for the development of RNAi reagents in clinical use. Thus, long-term inducible RNAi was designed. There are hundreds of millions of hepatitis B virus (HBV) carriers in the world at present, a portion of whom will lose their lives after several years due to chronic complications such as cirrhosis, hepatocellular carcinomas or both. Although a preventive vaccine is now available, the present therapeutic options for chronically infected patients are limited and of low efficiency. Admittedly, to date most RNAi experiments have been done in vitro, but it is hoped that they may be developed into a therapeutic strategy for HBV in the near future. In this article the principles and construction of long-term RNA are discussed. Its therapeutic potentiality and attention to the potential hazards will also outlined. We conclude that this ancient defensive mechanism can be recruited as a powerful weapon in the fight against HBV.

[In vivo delivery of siRNA]

RNA interference (RNAi) is a mechanism of posttranscriptional gene silencing mediated by small interfering RNA (siRNA). The ability of synthetic siRNA to silence genes in vivo has made it well suited as therapeutic drug, but the instability and polarity of siRNA and the complexity of in vivo circumstances retarded rapid development of RNAi-based therapies. In this review, a summary of the advances on in vivo siRNA delivery is presented and discussed.

Research progress of RNA interference in anti-infection of hepatitis B virus

RNA interference (RNAi) can specifically suppress the expression of genes, and it is the most effective gene-silencing technique. Both in vivo and in vitro researches have approved the effect of RNAi on hepatitis B virus (HBV) infection. In recent years, multiple researches have been launched on selection of target sequences of small interfering RNA (siRNA), application of chemical modification, and selection of transduction method, short hairpin RNA (shRNA) vector and combination strategies. In this paper, we briefly review the advances of RNAi in anti-HBV infection.

Targeted delivery of siRNA against hepatitis C virus by apolipoprotein A-I-bound cationic liposomes

BACKGROUND/AIMS

Hepatitis C virus (HCV) is one of the major human hepatic RNA viruses. Recently, we developed a liver-specific siRNA delivery technology using DTC-Apo composed of cationic liposomes (DTC) and apolipoprotein A-I (apo A-I). Here, we investigated whether DTC-Apo nanoparticles can systemically deliver siRNA into mouse hepatocytes expressing HCV proteins and inhibit their expression efficiently.

METHODS

A transient HCV model was constructed by hydrodynamic injection of plasmid DNA expressing viral structural proteins under hepatic control region and alpha1-antitrypsin promoter elements. Using this model, DTC-Apo containing HCV-core-specific siRNA was intravenously injected to assess antiviral activity as well as the duration of silencing.

RESULTS

Post-administration of DTC-Apo/HCV-specific siRNA at a dose of 2mg siRNA/kg inhibited viral gene expression by 65-75% in the liver on day 2. Improved activity (95% knockdown on day 2) without immunotoxicity was obtained by 2'-OMe-modification at two U sequences on its sense strand. Notably, the gene silencing effect of the modified siRNA was still maintained at day 6, while the unmodified one lost RNAi activity after day 4.

CONCLUSIONS

Our results suggest that DTC-Apo liposome is a highly potential delivery vehicle to transfer therapeutic siRNA especially targeting HCV to the liver.

Not miR-ly small RNAs: big potential for microRNAs in therapy

RNA interference (RNAi) describes a set of natural processes in which genes are silenced by small RNAs. RNAi has been widely used as an experimental tool that has recently become the focus of drug development efforts to treat a variety of diseases and disorders. Like all molecular therapies, in vivo delivery is the major hurdle to realizing therapeutic RNAi. Several strategies have been developed that increase small RNA half-life in the blood, facilitate transduction across biological membranes, and mediate cell-specific delivery. Importantly, these strategies permit targeting of mRNAs as well as microRNAs (miRNAs), a class of small RNAs encoded in the genome. miRNAs are required for multiple developmental and cellular processes. Dysfunction of miRNAs can result in a host of pathologies, suggesting that miRNAs are potential targets of therapy. Recent studies of miRNA function in immune-specific pathways indicate that specific miRNAs might be exploited as therapeutic targets to treat immune disorders, including autoimmunity, allergy, and hematopoietic cancers.

RNAi for treating hepatitis B viral infection

Chronic hepatitis B virus (HBV) infection is one of the leading causes of liver cirrhosis and hepatocellular carcinoma (HCC). Current treatment strategies of HBV infection including the use of interferon (IFN)-α and nucleotide analogues such as lamivudine and adefovir have met with only partial success. Therefore, it is necessary to develop more effective antiviral therapies that can clear HBV infection with fewer side effects. RNA interference (RNAi), by which a small interfering RNA (siRNA) induces the gene silence at a post-transcriptional level, has the potential of treating HBV infection. The successful use of chemically synthesized siRNA, endogenous expression of small hairpin RNA (shRNA) or microRNA (miRNA) to silence the target gene make this technology towards a potentially rational therapeutics for HBV infection. However, several challenges including poor siRNA stability, inefficient cellular uptake, widespread biodistribution and non-specific effects need to be overcome. In this review, we discuss several strategies for improving the anti-HBV therapeutic efficacy of siRNAs, while avoiding their off-target effects and immunostimulation. There is an in-depth discussion on the (1) mechanisms of RNAi, (2) methods for siRNA/shRNA production, (3) barriers to RNAi-based therapies, and (4) delivery strategies of siRNA for treating HBV infection.

Potential role of RNAi in the treatment of HCV infection

Chronic HCV infection is a leading cause of chronic hepatitis and its sequelae, liver cirrhosis and hepatocellular carcinoma. Current therapeutic options are limited, associated with significant adverse effects and costly. Accordingly, there is strong impetus to develop novel therapeutic strategies that act through alternate mechanisms. RNAi has been widely used for the analysis of gene function and represents a potentially promising approach for the treatment of HCV infection. siRNAs are short RNA duplexes approximately 21 nts long. When introduced into mammalian cells, siRNA can silence specific gene expression. Although efficient suppression of HCV replicon RNA in cell culture has been demonstrated with siRNAs, there is much work to be done to improve delivery, limit off-target effects and minimize development of virus resistance. Here, we review the use of RNAi as a tool to inhibit HCV gene expression and discuss the potential advantages and obstacles for this new potential therapeutic approach against HCV infection.