RNA interference: Antiviral weapon and beyond

A determination of pan-pathogen antimicrobials?

While antimicrobial drug development has historically mitigated infectious diseases that are known, COVID-19 revealed a dearth of ‘in-advance’ therapeutics suitable for infections by pathogens that have not yet emerged. Such drugs must exhibit a property that is antithetical to the classical paradigm of antimicrobial development: the ability to treat infections by any pathogen. Characterisation of such ‘pan-pathogen’ antimicrobials requires consolidation of drug repositioning studies, a new and growing field of drug discovery. In this review, a previously-established system for evaluating repositioning studies is used to highlight 4 therapeutics which exhibit pan-pathogen properties, namely azithromycin, ivermectin, niclosamide, and nitazoxanide. Recognition of the pan-pathogen nature of these antimicrobials is the cornerstone of a novel paradigm of antimicrobial development that is not only anticipatory of pandemics and bioterrorist attacks, but cognisant of conserved anti-infective mechanisms within the host-pathogen interactome which are only now beginning to emerge. Ultimately, the discovery of pan-pathogen antimicrobials is concomitantly the discovery of a new class of antivirals, and begets significant implications for pandemic preparedness research in a world after COVID-19.

Specific in vivo knockdown of protein function by intrabodies

Intracellular antibodies (intrabodies) are recombinant antibody fragments that bind to target proteins expressed inside of the same living cell producing the antibodies. The molecules are commonly used to study the function of the target proteins (i.e., their antigens). The intrabody technology is an attractive alternative to the generation of gene-targeted knockout animals, and complements knockdown techniques such as RNAi, miRNA and small molecule inhibitors, by-passing various limitations and disadvantages of these methods. The advantages of intrabodies include very high specificity for the target, the possibility to knock down several protein isoforms by one intrabody and targeting of specific splice variants or even post-translational modifications. Different types of intrabodies must be designed to target proteins at different locations, typically either in the cytoplasm, in the nucleus or in the endoplasmic reticulum (ER). Most straightforward is the use of intrabodies retained in the ER (ER intrabodies) to knock down the function of proteins passing the ER, which disturbs the function of members of the membrane or plasma proteomes. More effort is needed to functionally knock down cytoplasmic or nuclear proteins because in this case antibodies need to provide an inhibitory effect and must be able to fold in the reducing milieu of the cytoplasm. In this review, we present a broad overview of intrabody technology, as well as applications both of ER and cytoplasmic intrabodies, which have yielded valuable insights in the biology of many targets relevant for drug development, including α-synuclein, TAU, BCR-ABL, ErbB-2, EGFR, HIV gp120, CCR5, IL-2, IL-6, β-amyloid protein and p75NTR. Strategies for the generation of intrabodies and various designs of their applications are also reviewed.

RNAi: antiviral therapy against dengue virus

Dengue virus infection has become a global threat affecting around 100 countries in the world. Currently, there is no licensed antiviral agent available against dengue. Thus, there is a strong need to develop therapeutic strategies that can tackle this life threatening disease. RNA interference is an important and effective gene silencing process which degrades targeted RNA by a sequence specific process. Several studies have been conducted during the last decade to evaluate the efficiency of siRNA in inhibiting dengue virus replication. This review summarizes siRNAs as a therapeutic approach against dengue virus serotypes and concludes that siRNAs against virus and host genes can be next generation treatment of dengue virus infection.

Bioenergetics and gene silencing approaches for unraveling nucleotide recognition by the human EIF2C2/Ago2 PAZ domain

Gene silencing and RNA interference are major cellular processes that control gene expression via the cleavage of target mRNA. Eukaryotic translation initiation factor 2C2 (EIF2C2, Argonaute protein 2, Ago2) is considered to be the major player of RNAi as it is the core component of RISC complexes. While a considerable amount of research has focused on RNA interference and its associated mechanisms, the nature and mechanisms of nucleotide recognition by the PAZ domain of EIF2C2/Ago2 have not yet been characterized. Here, we demonstrate that the EIF2C2/Ago2 PAZ domain has an inherent lack of binding to adenine nucleotides, a feature that highlights the poor binding of 3′-adenylated RNAs with the PAZ domain as well as the selective high trimming of the 3′-ends of miRNA containing adenine nucleotides. We further show that the PAZ domain selectively binds all ribonucleotides (except adenosine), whereas it poorly recognizes deoxyribonucleotides. In this context, the modification of dTMP to its ribonucleotide analogue gave a drastic improvement of binding enthalpy and, hence, binding affinity. Additionally, higher in vivo gene silencing efficacy was correlated with the stronger PAZ domain binders. These findings provide new insights into the nature of the interactions of the EIF2C2/Ago2 PAZ domain.

RNAi-mediated double gene knockdown and gustatory perception measurement in honey bees (Apis mellifera)

This video demonstrates novel techniques of RNA interference (RNAi) which downregulate two genes simultaneously in honey bees using double-stranded RNA (dsRNA) injections. It also presents a protocol of proboscis extension response (PER) assay for measuring gustatory perception. RNAi-mediated gene knockdown is an effective technique downregulating target gene expression. This technique is usually used for single gene manipulation, but it has limitations to detect interactions and joint effects between genes. In the first part of this video, we present two strategies to simultaneously knock down two genes (called double gene knockdown). We show both strategies are able to effectively suppress two genes, vitellogenin (vg) and ultraspiracle (usp), which are in a regulatory feedback loop. This double gene knockdown approach can be used to dissect interrelationships between genes and can be readily applied in different insect species. The second part of this video is a demonstration of proboscis extension response (PER) assay in honey bees after the treatment of double gene knockdown. The PER assay is a standard test for measuring gustatory perception in honey bees, which is a key predictor for how fast a honey bee's behavioral maturation is. Greater gustatory perception of nest bees indicates increased behavioral development which is often associated with an earlier age at onset of foraging and foraging specialization in pollen. In addition, PER assay can be applied to identify metabolic states of satiation or hunger in honey bees. Finally, PER assay combined with pairing different odor stimuli for conditioning the bees is also widely used for learning and memory studies in honey bees.

Therapeutic potential of RNA interference: a new molecular approach to antiviral treatment for hepatitis C

Hepatitis C virus (HCV) infection remains a major cause of chronic liver disease with an estimated 170 million carriers worldwide. Current treatments have significant side effects and have met with only partial success. Therefore, alternative antiviral drugs that efficiently block virus production are needed. During recent decades, RNA interference (RNAi) technology has not only become a powerful tool for functional genomics but also represents a new therapeutic approach for treating human diseases including viral infections. RNAi is a sequence-specific and post-transcriptional gene silencing process mediated by double-stranded RNA (dsRNA). As the HCV genome is a single-stranded RNA that functions as both a messenger RNA (mRNA) and replication template, it is an attractive target for the study of RNAi-based viral therapies. In this review, we will give a brief overview about the history and current status of RNAi and focus on its potential application as a therapeutic option for treatment for HCV infection.

Inhibition of monkeypox virus replication by RNA interference

The Orthopoxvirus genus of Poxviridae family is comprised of several human pathogens, including cowpox (CPXV), Vaccinia (VACV), monkeypox (MPV) and Variola (VARV) viruses. Species of this virus genus cause human diseases with various severities and outcome ranging from mild conditions to death in fulminating cases. Currently, vaccination is the only protective measure against infection with these viruses and no licensed antiviral drug therapy is available. In this study, we investigated the potential of RNA interference pathway (RNAi) as a therapeutic approach for orthopox virus infections using MPV as a model. Based on genome-wide expression studies and bioinformatic analysis, we selected 12 viral genes and targeted them by small interference RNA (siRNA). Forty-eight siRNA constructs were developed and evaluated in vitro for their ability to inhibit viral replication. Two genes, each targeted with four different siRNA constructs in one pool, were limiting to viral replication. Seven siRNA constructs from these two pools, targeting either an essential gene for viral replication (A6R) or an important gene in viral entry (E8L), inhibited viral replication in cell culture by 65-95% with no apparent cytotoxicity. Further analysis with wild-type and recombinant MPV expressing green fluorescence protein demonstrated that one of these constructs, siA6-a, was the most potent and inhibited viral replication for up to 7 days at a concentration of 10 nM. These results emphasis the essential role of A6R gene in viral replication, and demonstrate the potential of RNAi as a therapeutic approach for developing oligonucleotide-based drug therapy for MPV and other orthopox viruses.

RNA interference-mediated silencing of the respiratory syncytial virus nucleocapsid defines a potent antiviral strategy

We describe the design and characterization of a potent human respiratory syncytial virus (RSV) nucleocapsid gene-specific small interfering RNA (siRNA), ALN-RSV01. In in vitro RSV plaque assays, ALN-RSV01 showed a 50% inhibitory concentration of 0.7 nM. Sequence analysis of primary isolates of RSV showed that the siRNA target site was absolutely conserved in 89/95 isolates, and ALN-RSV01 demonstrated activity against all isolates, including those with single-mismatch mutations. In vivo, intranasal dosing of ALN-RSV01 in a BALB/c mouse model resulted in potent antiviral efficacy, with 2.5- to 3.0-log-unit reductions in RSV lung concentrations being achieved when ALN-RSV01 was administered prophylactically or therapeutically in both single-dose and multidose regimens. The specificity of ALN-RSV01 was demonstrated in vivo by using mismatch controls; and the absence of an immune stimulatory mechanism was demonstrated by showing that nonspecific siRNAs that induce alpha interferon and tumor necrosis factor alpha lack antiviral efficacy, while a chemically modified form of ALN-RSV01 lacking measurable immunostimulatory capacity retained full activity in vivo. Furthermore, an RNA interference mechanism of action was demonstrated by the capture of the site-specific cleavage product of the RSV mRNA via rapid amplification of cDNA ends both in vitro and in vivo. These studies lay a solid foundation for the further investigation of ALN-RSV01 as a novel therapeutic antiviral agent for clinical use by humans.

RNA interference and its therapeutic potential against HIV infection

BACKGROUND

HIV-1 infection is the major cause of AIDS. RNA interference (RNAi) has great potential to work as a powerful tool against HIV infection. Therefore, the possibilities of use of siRNA (small-interfering RNA) as a tool to deal with HIV infection are discussed in this article.

OBJECTIVE

Highly active anti retroviral therapy (HAART) has been successful in reducing the rate of progression to AIDS, but HIV utilizes various tricks to escape from the inhibitory effect of HAART. Therefore, new tools are required to delay progression of infection or block the replication cycle of HIV.

METHODS

This article has been written on the basis of informations available in the form of published literature in various journals.

CONCLUSION

RNAi is a very promising strategy that in principle will provide many new targets against HIV infection. The mechanism of sequence complementarity utilized by siRNAs against their targets provides a new approach to fight against HIV infection. However, this technology still needs many fine refinements before its potential for HIV treatment strategies can be utilized. This review discusses the possibilities of using siRNA as a therapeutic tool for HIV treatment.

Antisense oligonucleotides-based inhibition of gene and protein expression of tissue inhibitor of metalloproteinase-2 on experimental liver fibrosis in rats

AIM: To investigate the inhibitory effect of tissue inhibitor of metalloproteinase-2 (TIMP-2) targeted antisense oligonucleotide (asON) on the progress of experimental liver fibrosis in rats.

METHODS: Twenty-two rats were divided into asON treatment (n = 6), model (n = 6), and normal control group (n = 10). The liver fibrosis model was induced by human serum albumin (HSA). During modeling, the rats were treated with antisense oligonucleotides via tail vein. The level of TIMP-2 expression was detected by reverse transcription polymerase chain reaction (RT-PCR), in situ hybridization, immunohistochemical staining and enzyme linked immunosorbent assay (ELISA). The effect of asON on liver fibrosis was analyzed by histopathological exami-nation, immunohistochemical staining of collagenⅠand Ⅳ, and special staining of collagen fiber as well as electron microscopy.

RESULTS: The pathological grading was notably im-proved in asON group than that in model group (u = 2.071, P <0.05). The serum and tissue expression of TIMP-2 were lower in asON group than those in model group (T = 55, P <0.05; t = 3.332, P <0.05), but higher than those in the control (T = 55, P <0.05; t = 5.550, P <0.05). Image quantitative analysis for immunohistochemical staining of collagen Ⅳ showed that the value was significant decreased in asON group as compared with that in model group (t = 2.310, P <0.05), but still higher than that in the control (t = 3.623, P <0.05); The value for collagenⅠwas also decreased in asON group as compared with that in model group (t = 2.845, P <0.05). Less collagen deposition was found in the hepatic sinusoid of asON group, which was not significantly different from that of model group.

CONCLUSION: TIMP-2 targeted asON can inhibit the progress of experimental liver fibrosis in rats.

Inhibition of hepatitis viral replication by siRNA

Small interfering RNA (siRNA)-mediated sequence-specific gene silencing is a powerful tool to inhibit endogenous and exogenous gene expression, and it holds great potential to prevent and eradicate viral infection, for which existing therapy is inadequate, such as HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV). A number of studies have documented the effectiveness of siRNA against HBV or HCV at various regions of the viral genome in infected human hepatoma cell lines. Selected siRNA may reduce the production of viral replicons, as well as structural or non-structural proteins by > 90%. Only a few in vivo studies that demonstrated the efficacy of siRNA in the suppression of HBV replication in mice are available. Thus, reliable models of HBV and HCV infection in small animals or non-human primates are needed to evaluate the delivery and efficacy of siRNA as a therapeutic modality for viral hepatitis.

siRNA injection induces sequence-independent protection in Penaeus monodon against white spot syndrome virus

White spot syndrome virus (WSSV) is a major disease in crustaceans, particularly shrimp, due to the current intensity of aquaculture practices. Novel strategies including vaccination to control this virus would be highly desirable. However, invertebrates lack a true adaptive immune response system and seem to rely on various innate immune responses. An alternative and more specific approach to counteract WSSV infections in shrimp could be by the exploitation of RNA interference. As long dsRNA molecules induce a general, sequence-independent anti-viral immunity in shrimp [Robalino, J., Browdy, C.L., Prior, S., Metz, A., Parnell, P., Gross, P., Warr, G., 2004. J. Virol. 78, 10442-10448], it was investigated whether shorter 21 nt siRNAs with homology to the WSSV vp15 and vp28 genes would give a sequence-specific interference response in the shrimp Penaeus monodon. Vp28 siRNAs as well as nonspecific control gfp siRNAs were able to specifically and efficiently silence their homologous genes in a heterologous baculovirus insect cell expression system. However, in shrimps no such a specific effect was observed. Shrimp injected with vp15 or vp28 siRNAs before WSSV challenge gave a significantly lower mortality rate, but not significantly different when shrimps were injected with gfp siRNA. Thus, large dsRNA molecules as well as siRNAs induce a sequence-independent anti-viral immunity when injected in shrimp.

RNA interference: from gene silencing to gene-specific therapeutics

In the past 4 years, RNA interference (RNAi) has become widely used as an experimental tool to analyse the function of mammalian genes, both in vitro and in vivo. By harnessing an evolutionary conserved endogenous biological pathway, first identified in plants and lower organisms, double-stranded RNA (dsRNA) reagents are used to bind to and promote the degradation of target RNAs, resulting in knockdown of the expression of specific genes. RNAi can be induced in mammalian cells by the introduction of synthetic double-stranded small interfering RNAs (siRNAs) 21–23 base pairs (bp) in length or by plasmid and viral vector systems that express double-stranded short hairpin RNAs (shRNAs) that are subsequently processed to siRNAs by the cellular machinery. RNAi has been widely used in mammalian cells to define the functional roles of individual genes, particularly in disease. In addition, siRNA and shRNA libraries have been developed to allow the systematic analysis of genes required for disease processes such as cancer using high throughput RNAi screens. RNAi has been used for the knockdown of gene expression in experimental animals, with the development of shRNA systems that allow tissue-specific and inducible knockdown of genes promising to provide a quicker and cheaper way to generate transgenic animals than conventional approaches. Finally, because of the ability of RNAi to silence disease-associated genes in tissue culture and animal models, the development of RNAi-based reagents for clinical applications is gathering pace, as technological enhancements that improve siRNA stability and delivery in vivo, while minimising off-target and nonspecific effects, are developed.

A small interfering RNA targeting coxsackievirus B3 protects permissive HeLa cells from viral challenge

We examined the ability of small interfering RNAs (siRNAs) to disrupt infection by coxsackievirus B3 (CVB3). The incorporation of siRNAs dramatically decreased cell death in permissive HeLa cells in parallel with a reduction in viral replication. Three of four siRNAs had potent anti-CVB3 activity. The present study thus demonstrates that the antiviral effect is due to the downregulation of viral replication. In addition, an effective CVB3-specific siRNA had similar antiviral effects in other related enteroviruses possessing sequence homology in the targeted region. Because the CVB3-specific siRNA is effective against other enteroviruses, siRNAs have potential for a universal anti-enterovirus strategy.

Molecular strategies to inhibit HIV-1 replication

The human immunodeficiency virus type 1 (HIV-1) is the primary cause of the acquired immunodeficiency syndrome (AIDS), which is a slow, progressive and degenerative disease of the human immune system. The pathogenesis of HIV-1 is complex and characterized by the interplay of both viral and host factors. An intense global research effort into understanding the individual steps of the viral replication cycle and the dynamics during an infection has inspired researchers in the development of a wide spectrum of antiviral strategies. Practically every stage in the viral life cycle and every viral gene product is a potential target. In addition, several strategies are targeting host proteins that play an essential role in the viral life cycle. This review summarizes the main genetic approaches taken in such antiviral strategies.

About the nature of RNA interference

In the context of yet unclarified issues of RNA interference (RNAi), it is discussed that RNAi-induced histone modification may not only have the purpose of inactivating native genes by blocking their transcription in the sense direction but may also simultaneously trigger transcription of the corresponding antisense strand to form double-stranded RNA for posttranscriptional gene-silencing in cells lacking RNA replicase activities. Invading foreign genetic traits may be posttranscriptionally silenced through complementary transcripts from specific, highly variable genomic regions, which are able to finally match any given sequence by the appropriate recombination and processing of their transcripts. The information to fight these traits may additionally become anchored in the genome, to provide at least a temporary "immunity" and may be inherited at least for a few generations. It is further proposed that: (1) RNA viruses evolved from constituents of the RNAi machinery through the capture of functions essential for their maintenance and replication and (2) viruses and RNAi are mutually interacting components of a universal and predominant genetic steering system that is involved in the modulation of gene expression on the cellular level and simultaneously constitutes a driving force for evolution, particularly in imperfect organisms. Such a model would deliver explanations for yet unresolved issues of RNAi, the clarification of which will have a significant impact on its future medical and biotechnological application.

EpCAM is overexpressed in breast cancer and is a potential target for breast cancer gene therapy

EpCAM (epithelial cell adhesion molecule) is a cell surface molecule that is known to be highly expressed in colon and other epithelial carcinomas. EpCAM is involved in cell-to-cell adhesion and has been the target of antibody therapy in several clinical trials. To assess the value of EpCAM as a novel target for breast cancer gene therapy, we performed real-time reverse transcription-PCR to quantify the level of EpCAM mRNA expression in normal breast tissue and primary and metastatic breast cancers. We found that EpCAM is overexpressed 100- to 1000-fold in primary and metastatic breast cancer. Silencing EpCAM gene expression with EpCAM short interfering RNA (siRNA) resulted in a 35-80% decrease in the rate of cell proliferation in four different breast cancer cell lines. EpCAM siRNA treatment decreased cell migration by 91.8% and cell invasion by 96.4% in the breast cancer cell line MDA-MB-231 in vitro. EpCAM siRNA treatment was also associated with an increase in the detergent-insoluble protein fraction of E-cadherin, alpha-catenin, and beta-catenin, consistent with the known biology of EpCAM as a regulator of cell adhesion. Our hypothesis is that modulation of EpCAM expression can affect cell migration, invasion, and proliferation by enhancing E-cadherin-mediated cell-to-cell adhesion. These data provide compelling evidence that EpCAM is a potential novel target for breast cancer gene therapy and offer insights into the mechanisms associated with EpCAM gene silencing.

Inhibition of luciferase expression in hepatocellular carcinoma cells by short hairpin RNA

AIM: To construct a recombinant plasmid containing short hairpin RNA of luciferase in order to suppress the expression of luciferase gene in hepatocellular carcinoma cells line Bel-7402.

METHODS: Two inverted repeating oligonucleotides, double-stranded DNA which dropped temperature were designed, and then cloned into PGE-1 vector digesting by the double restricted endoenzymes to generate the plasmids pshRNA-luc, pshRNA-luc and pCMV-luc, which were cotransfected into hepatocellular carcinoma cells line Bel-7402 to detect effect of luciferase expression.

RESULTS: The size of the PCR product was 652 bp. DNA sequencing showed the sequence of recombinant plasmids pshRNA-luc was successfully constructed. The recombinant plasmids suppressed the expression of luciferase gene by 86% in Bel-7402 cells (P <0.01).

CONCLUSION: Short hairpin RNA of luciferase can efficiently suppress its expression in hepatocellular carcinoma cells Bel-7402.

RNA interference directed against Poly(ADP-Ribose) polymerase 1 efficiently suppresses human immunodeficiency virus type 1 replication in human cells

We established small interfering RNA (siRNA) directed against poly(ADP-ribose) polymerase 1 (PARP-1) that effectively reduces the expression of PARP-1 in two human cell lines. Established siRNA against PARP-1 significantly suppressed human immunodeficiency virus type 1 (HIV-1) replication, as well as the activation of the integrated HIV-1 long terminal repeat promoter. These results indicate that PARP-1 is required for efficient HIV-1 replication in human cells. We propose that PARP-1 may serve as a cellular target for RNA interference-mediated gene silencing to inhibit HIV-1 replication.

Effects of length and location on the cellular response to double-stranded RNA

Since double-stranded RNA (dsRNA) has not until recently generally been thought to be deliberately expressed in cells, it has commonly been assumed that the major source of cellular dsRNA is viral infections. In this view, the cellular responses to dsRNA would be natural and perhaps ancient antiviral responses. While the cell may certainly react to some dsRNAs as an antiviral response, this does not represent the only response or even, perhaps, the major one. A number of recent observations have pointed to the possibility that dsRNA molecules are not seen only as evidence of viral infection or recognized for degradation because they cannot be translated. In some instances they may also play important roles in normal cell growth and function. The purpose of this review is to outline our current understanding of the fate of dsRNA in cells, with a focus on the apparent fact that their fates and functions appear to depend critically not only on where in the cell dsRNA molecules are found, but also on how long they are and perhaps on how abundant they are.

Emerging Technologies: Trendy RNA Tools for Aging Research

Aging is an inevitable biological phenomenon. Attempts to understand its mechanisms and, consequently, to therapeutically decelerate or even reverse the process are limited by its daunting complexity. Rapid and robust functional genomic tools suited to a wide array of experimental model systems are needed to dissect the interplay of individual genes during aging. In this article, we review principles that transcend the view of RNA, from a molecule merely mediating the flow of genetic information, into a unique molecular tool. In the form of catalytic molecular scissors (ribozymes), antibody-like antagonists (aptamers) and gene silencers (interfering RNAs, RNAi) can be effectively used to dissect biofunctions conserved throughout the evolution. In this review, application of recent RNA tools in aging research is discussed.

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Hepatitis C virus NS3 protein up-regulates expression of thioredoxin reductase 1 gene

AIM: To investigate the transactivating effect of HCV NS3 protein on TXNRD1 gene promoter and the molecular biological mechanisms of HCV NS3 protein in HCV pathogeneicity.

METHODS: Polymerase chain reaction (PCR) technique was employed to amplify the sequence of TXNRD1 promoter from HepG2 genomic DNA, and the product was subcloned into pCAT3-Basic by Kpn I and Xho I, named pCAT3-TXNRD1p. pCAT3-TXNRD1p was transfected into the hepatoblastoma cell line HepG2, then cotransfected with pcDNA3.1(-)-NS3 by FuGENE 6 transfection reagents. The HepG2 cells transfected with pCAT3-Basic was used as negative control. The activity of CAT in HepG2 cells transfected was detected by an ELISA kit after 48 hours, which reflected the transactivating function of HCV NS3 protein to TXNRD1 gene promoter.

RESULTS: The expression vector pcDNA3.1(-)-NS3 and report vector pCAT3-TXNRD1p were constructed and confirmed by restriction enzyme digestion and sequencing. The expression of CAT in HepG2 cells co-transfected with pCAT3-TXNRD1p and pcDNA3.1(-)-NS3 is 9 times as higher as that of pCAT3-Basic, and twice as higher as that of pCAT3-TXNRD1p.

CONCLUSION: HCV NS3 protein can transactivate TXNRD1 promoter, and therefore up-regulate the expression of TXNRD1 gene.

Effect of siRNA targeting survivin gene on biological behavior of hepatocellular carcinoma

AIM: To study the influence of siRNA targeting survivin on the biological behavior of hepatocellular carcinoma (HCC).

METHODS: One pair of 21 bp reverse repeated motifs of survivin target sequence with 9 spacer were synthesized and inserted into plasmid psilencer 2.1 to generate siRNA eukaryotic expression vector. After stable transfection into HepG2 cells, the biological behaviors of the survivin siRNA transfected HCC cells were observed.

RESULTS: The recombinant plasmid Psilence(+)-survivin was successfully constructed. survivin mRNA and protein expression inhibitory ratio reached 73% and 75% respectively. It was demonstrated that transfected cells with survivin siRNA were inhibited on growth and increased on apoptosis. Subsequent study in nude mouse model demonstrated lower succeeding rate in cells transfected with survivin siRNA and the tumor size from 9-30 day was 0.10±0.01 cm³, 0.30±0.03 cm³, 0.39±0.11 cm³, 0.45±0.13 cm³, 0.49±0.07 cm³, 0.58±0.01 cm³ 0.60±0.10 cm³, and 0.65±0.07 cm³ respectively. The difference was obvious (P < 0.01).

CONCLUSION: siRNA targeting survivin gene can specifically suppress survivin expression in HepG2 cells and inhibit tumor cells growth both in vivo and in vitro. This provides a theory basis to reverse the drug resistance in tumor cells.

Construction and expression of eukaryotic vector bearing fusion gene of HBV PreS2S and Fc fragment

AIM: To construct and express a recombinant eukaryotic expression vector bearing fusion gene of HBV S2S and Fc fragment.

METHODS: The technique of splicing by overlapping extension and twice PCR were used, and fusion gene fragment was obtained and cloned into pGEM-T Easy TA cloning vector to get suited enzyme sites. Recombinant eukaryotic expression vector pcDNA3 S2S/Fc was constructed by double adhesive terminal ligation. Then the recombinant vector was transferred into SP2/0 cells by using Lipofectamine.

RESULTS: The recombinant vector was identified by digestion with restriction enzymes and confirmed by DNA sequencing analysis. And the vector bearing fusion gene could be expressed in eukaryotic cells detected by indirect immunofluotescence technique.

CONCLUSION: The relative efficient expression of the fusion gene in SP2/0 cells may provide an experimental basis for specific immunotherapy for HBV infection.

Therapeutic effects of recombinant human augmenter of liver regeneration on murine liver damage caused by carbon tetrachloride

AIM: To explore the therapeutic effects of recombinant human augmenter of liver regeneration (ALR) on CCl₄ liver damage of mice.

METHODS: The recombinant human ALR was prepared by standard procedure of fermentation and chromatography techniques. Chemical liver damage model of mice was established by CCl₄. The mice were divided into two groups: group one was treated by recombinant ALR, 2 mg/kg or 20 g, 1/12 h, 4 times, and group two was treated by normal saline as control. After treatment, the mice were sacrificed for collecting the blood sample. For evaluation of chemical liver damage, the serum ALT and AST levels were determined by an autobiochemical processor.

RESULTS: The CCl₄ liver damage model was established. After the treatment with recombinant human ALR, the ALT and AST levels in treated groups were significantly decreased as compared with the group treated with normal saline (ALT: 991 U/L vs 2134 U/L, P < 0.01; AST: 938 U/L vs 1873 U/L, P < 0.01), indicating the potent therapeutic effects of recombinant human ALR on mice model of chemical damage caused by CCl₄.

CONCLUSION: Recombinant human ALR is successfully prepared and effective in the treatment of murine CCl₄ liver damage.