Polypyrimidine Tract-Binding Protein Enhances Zika Virus Translation by Binding to the 5'UTR of Internal Ribosomal Entry Site

Objectives To identify the 5'untranslated region of Zika virus(ZIKV 5'UTR)RNA-binding proteins and to investigate the impact of the binding protein on the activity of internal ribosomal entry site(IRES)located in ZIKV 5'UTR and virus production.Methods Interacting proteins in U251 cells were captured using tRSA-tagged ZIKV 5'UTR RNA and tRSA-ZIKV 5'UTR RNA-binding proteins were visualized by SDS-PAGE silver staining,Subsequently,liquid chromatographytandem mass spectrometry(LC-MS/MS),bioinformatics analysis,and Western blot were used to identify the candidate proteins binding to ZIKV 5'UTR.Dicistronic expression assay and plaque forming assay were performed to analyze the effect of the binding protein on ZIKV IRES activity and ZIKV production,respecitvely.Results tRSA RNA pull-down assay,LC-MS/MS,and Western blot analysis showed that polypyrimidine tractbinding protein(PTB)bound to the ZIKV 5'UTR.Furthermore,dual luciferase reporter assay revealed that overexpression of PTB significantly enhanced the IRES activity of ZIKV(t=10.220,P<0.001),while PTB knockdown had the opposite effect(t=4.897,P<0.01).Additionally,virus plaque forming assay demonstrated that up-regulation of PTB expression significantly enhanced viral titer(t=6.400,P<0.01),whereas reducing PTB expression level weakened virus infectivity(t=5.055,P<0.01).Conclusion PTB positively interacts with the ZIKV 5'UTR and enhances IRES activity and virus production.

Synchronous Detection of DNA/RNA of Four Shrimp Viruses by Real-time Fluorescence Quantitative RT-PCR

[ Objective] This study aimed to establish a simultaneous detection method of shrimp viruses by real-time fluorescence quantitative RT-PCR, to improve the efficiency of inspection and quarantine. [ Method] A novel real-time fluorescence quantitative RT-PCR assay was established and optimized for simultaneously detecting DNA/RNA of four shrimp viruses （WSSV, IHHNV, TSV and YHV ）. [ Result] The optimized real-time fluorescence quantitative RT-PCR system gener- ated typical amplification curves with high amplification efficiencies （E = 1.06, 1.07, 0.92 and 0.92, respectively）, good hnear relationship （ r = 1 ）, uniform repeatability （ standard deviation = 0.05 - 0.46 ; variation coefficient = 0.26% - 1.62% ） and high sensitivity, exhibiting no significant differences compared with re- al-time fluorescence quantitative PCR （average error of Ct value = 0.04 -0.40; T = 0.53 -2.50; P 〉 0.05 ）. The total detection time was about 1 h. [ Conclusion] The optimized real-time fluorescence quantitative RT-PCR system can be used for rapid detection of WSSV, IHHNV, TSV and YHV.

Construction Strategy and Affecting Factors of Positive-Strand RNA Virus Infectious Clone

Construction of infectious clones by full-length cDNA is basic and key for recovering RNA virus and is core of reverse genetics.In this article,basic consideration and key technology were viewed and factors affecting infectivity of clones were also summarized.Some research advances were briefly introduced about positive-strand RNA viruses infectious clones.Finally,this article also reviewed the application of infectious clones.

AAV-mediated expression of p65shRNA and bone morphogenetic protein 4 synergistically enhances chondrocyte regeneration

BACKGROUND:Adeno-associated virus(AAV)gene therapy has been proven to be reliable and safe for the treatment of osteoarthritis in recent years.However,given the complexity of osteoarthritis pathogenesis,single gene manipulation for the treatment of osteoarthritis may not produce satisfactory results.Previous studies have shown that nuclear factorκB could promote the inflammatory pathway in osteoarthritic chondrocytes,and bone morphogenetic protein 4(BMP4)could promote cartilage regeneration.OBJECTIVE:To test whether combined application of AAV-p65shRNA and AAV-BMP4 will yield the synergistic effect on chondrocytes regeneration and osteoarthritis treatment.METHODS:Viral particles containing AAV-p65-shRNA and AAV-BMP4 were prepared.Their efficacy in inhibiting inflammation in chondrocytes and promoting chondrogenesis was assessed in vitro and in vivo by transfecting AAV-p65-shRNA or AAV-BMP4 into cells.The experiments were divided into five groups:PBS group;osteoarthritis group;AAV-BMP4 group;AAV-p65shRNA group;and BMP4-p65shRNA 1:1 group.Samples were collected at 4,12,and 24 weeks postoperatively.Tissue staining,including safranin O and Alcian blue,was applied after collecting articular tissue.Then,the optimal ratio between the two types of transfected viral particles was further investigated to improve the chondrogenic potential of mixed cells in vivo.RESULTS AND CONCLUSION:The combined application of AAV-p65shRNA and AAV-BMP4 together showed a synergistic effect on cartilage regeneration and osteoarthritis treatment.Mixed cells transfected with AAV-p65shRNA and AAV-BMP4 at a 1:1 ratio produced the most extracellular matrix synthesis(P<0.05).In vivo results also revealed that the combination of the two viruses had the highest regenerative potential for osteoarthritic cartilage(P<0.05).In the present study,we also discovered that the combined therapy had the maximum effect when the two viruses were administered in equal proportions.Decreasing either p65shRNA or BMP4 transfected cells resulted in less collagen II synthesis.This implies that inhibiting inflammation by p65shRNA and promoting regeneration by BMP4 are equally important for osteoarthritis treatment.These findings provide a new strategy for the treatment of early osteoarthritis by simultaneously inhibiting cartilage inflammation and promoting cartilage repair.

Ambisense polarity of genome RNA of orthomyxoviruses and coronaviruses

Influenza viruses and coronaviruses have linear single-stranded RNA genomes with negative and positive sense polarities and genes encoded in viral genomes are expressed in these viruses as positive and negative genes,respectively.Here we consider a novel gene identified in viral genomes in opposite direction,as positive in influenza and negative in coronaviruses,suggesting an ambisense genome strategy for both virus families.Noteworthy,the identified novel genes colocolized in the same RNA regions of viral genomes,where the previously known opposite genes are encoded,a so-called ambisense stacking architecture of genes in virus genome.It seems likely,that ambisense gene stacking in influenza and coronavirus families significantly increases genetic potential and virus diversity to extend virus-host adaptation pathways in nature.These data imply that ambisense viruses may have a multivirion mechanism,like"a dark side of the Moon",allowing production of the heterogeneous population of virions expressed through positive and negative sense genome strategies.

Antiviral Effect of Ribonuclease from <i>Bacillus pumilus</i>against Phytopathogenic Rna-Viruses

Background: Viruses can cause different diseases in plants. To prevent viral infections, plants are treated with chemical compounds and antiviral agents. Chemical antiviral agents usually have narrow specificity, which limits their wide application. Alternative antiviral strategy is associated with the use of microbial enzymes, which are less toxic and are readily decomposed without accumulation of harmful substances. The aim of this work is to study the effect of Bacillus pumilus ribonuclease on various phytopathogenic viruses with specific focus on the ability of enzyme to eliminate them from plant explants in vitro. Materials and methods: Extracellular ribonuclease of B. pumilus is tested as an antiviral agent. To study the antiviral effect of RNase, depending on concentration and the time of application several plant-virus model systems are used. Virus detection is conducted by serological testing and RT-PCR. Results: Bacillus pumilus ribonuclease possesses antiviral activity against plant Rna-viruses RCMV (red clover mottle virus), PVX (Potato Virus X) and AMV (Alfalfa Mosaic Virus). The maximum inhibitory effect against actively replicating viruses is observed when plants are treated with the enzyme in the concentration of 100 ug/ml prior to infection. In case of local necrosis ribonuclease in the concentration of 1 ug/ml completely inhibits the development of RCMV virus on bean plants. The enzyme is able to penetrate plants and inhibit the development of viral infection, inhibiting effect for untreated surfaces decreased on average for 20%. It is also found that B. pumilus ribonuclease protects apical explants of sprouts of potato tubers from PVM and PVS viruses. Conclusion: B. pumilus ribonuclease possesses antiviral activity against plant Rna-viruses and produces viruses-free plants in the apical meristem culture.

Serum hepatitis B virus RNA is a predictor of HBeAg seroconversion and virological response with entecavir treatment in chronic hepatitis B patients

BACKGROUND Characteristics of alterations of serum hepatitis B virus(HBV) RNA in different chronic hepatitis B(CHB) patients still cannot be fully explained. Whether HBV RNA can predict HBeAg seroconversion is still controversial.AIM To investigate whether HBV RNA can predict virological response or HBeAg seroconversion during entecavir(ETV) treatment when HBV DNA is undetectable.METHODS The present study evaluated 61 individuals who were diagnosed and treated with long-term ETV monotherapy at the Department of Infectious Diseases of Peking University First Hospital(China) from September 2006 to December 2007.Finally, 30 treatment-naive individuals were included. Serum HBV RNA were extracted from 140 μL serum samples at two time points. Then they were reverse transcribed to cDNA with the HBV-specific primer. The product was quantified by real-time quantitative PCR(RT-PCR) using TAMARA probes. Statistical analyses were performed with IBM SPSS 20.0.RESULTS Level of serum HBV RNA at baseline was 4.15 ± 0.90 log10 copies/mL. HBV RNA levels showed no significant difference between the virological response(VR)and partial VR(PVR) groups at baseline(P = 0.940). Serum HBV RNA significantly decreased among patients who achieved a VR during ETV therapy(P < 0.001). The levels of HBV RNA in both HBeAg-positive patients with seroconversion group and those with no seroconversion increased after 24 wk of treatment. Overall, HBV RNA significantly but mildly correlated to HBsAg(r =0.265, P = 0.041), and HBV RNA was not correlated to HBV DNA(r = 0.242, P =0.062). Furthermore, serum HBV RNA was an independent indicator for predicting HBeAg seroconversion and virological response. HBeAg seroconversion was more likely in CHB patients with HBV RNA levels below4.12 log10 copies/mL before treatment.CONLUSION The level of serum HBV RNA could predict HBeAg seroconversion and PVR during treatment. In the PVR group, the level of serum HBV RNA tends to be increasing.

Inhibition of hepatitis B virus gene expression and replication by artificial microRNA

AIM: To investigate the inhibitory effects of hepatitis B virus (HBV) replication and expression by transfecting artificial microRNA (amiRNA) into HepG2.2.15 cells. METHODS: Three amiRNA-HBV plasmids were constructed and transfected into HepG2.2.15 cells. HBV antigen secretion was detected in the cells with transient and stable transfection by time-resolved fluoroimmunoassays (TRFIA). HBV DNA replication was examined by ? uorescence quantitative PCR, and the level of HBV S mRNA was measured by semi- quantitative RT-PCR. RESULTS: The efficiency of transient transfection of the vectors into 2.2.15 cells was 55%-60%. All the vectors had significant inhibition effects on HBsAg and HBeAg at 72 h and 96 h after transfection (P < 0.01 for all). The secretion of HBsAg and HBeAg into the supernatant was inhibited by 49.8% ± 4.7% and 39.9% ± 6.7%, respectively, at 72 h in amiRNA- HBV-S608 plasmid transfection group. The copy of HBV DNA within culture supernatant was also significantly decreased at 72 h and 96 h after transfection (P <0.01 for all). In the cells with stable transfection, the secretion of HBsAg and HBeAg into the supernatant was significantly inhibited in all three transfection groups (P < 0.01 for all, vs negative control). The copies of HBV DNA were inhibited by 33.4% ± 3.0%, 60.8% ± 2.3% and 70.1% ± 3.3%, respectively. CONCLUSION: In HepG2.2.15 cells, HBV replication and expression could be inhibited by artif icial microRNA targeting the HBV S coding region. Vector-based artificial microRNA could be a promising therapeutic approach for chronic HBV infection.

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

AIM： To observe the inhibition of hepatitis B virus replication and expression by transfecting vector-based small interference RNA （siRNA） pGenesiI-HBV X targeting HBV X gene region into HepG2.2.15 cells. METHODS：pGenesil-HBV X was constructed and transfected into HepG2.2.15 cells via lipofection. HBV antigen secretion was determined 24, 48, and 72 h after transfection by time-resolved immunofluorometric assays （TRFIA）. HBV replication was examined by fluorescence quantitative PCR, and the expression of cytoplasmic viral proteins was determined by immunohistochemistry. RESULTS： The secretion of HBsAg and HBeAg into the supernatant was found to be inhibited by 28.5% and 32.2% （P 〈 0.01）, and by 38.67% （P 〈 0.05） and 42.86% （P 〈 0.01） at 48 h and 72 h after pGenesil-HBV X transfection, respectively. Immunohistochemical staining for cytoplasmic HBsAg showed a similar decline in HepG2.2.15 cells 48 h after transfection. The number of HBV genomes within culture supernatants was also significantly decreased 48 h and 72 h post-transfection as quantified by fluorescence PCR （P 〈 0.05）. CONCLUSION： In HepG2.2.15 cells, HBV replication and expression is inhibited by vector-based siRNA pGenesil- HBV X targeting the HBV X coding region.

Hepatitis B virus pathogenesis: Fresh insights into hepatitis B virus RNA

Hepatitis B virus(HBV) is still a worldwide health concern. While divergent factors are involved in its pathogenesis, it is now clear that HBV RNAs, principally templates for viral proteins and viral DNAs, have diverse biological functions involved in HBV pathogenesis. These functions include viral replication, hepatic fibrosis and hepatocarcinogenesis. Depending on the sequence similarities, HBV RNAs may act as sponges for host mi RNAs and may deregulate mi RNA functions, possibly leading to pathological consequences. Some parts of the HBV RNA molecule may function as viralderived mi RNA, which regulates viral replication. HBV DNA can integrate into the host genomic DNA and produce novel viral-host fusion RNA, which may have pathological functions. To date, elimination of HBVderived covalently closed circular DNA has not been achieved. However, RNA transcription silencing may be an alternative practical approach to treat HBVinduced pathogenesis. A full understanding of HBV RNA transcription and the biological functions of HBV RNA may open a new avenue for the development of novel HBV therapeutics.

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.

Combination of small interfering RNA and lamivudine on inhibition of human B virus replication in HepG2.2.15 cells

AIM: To observe the inhibition of hepatitis B virus (HBV) replication and expression by combination of siRNA and lamivudine in HepG2.2.15 cells. METHODS: Recombinant plasmid psil-HBV was constructed and transfected into HepG2.2.15 cells. The transfected cells were cultured in lamivudine-containing medium (0.05 μmol/L) and harvested at 48, 72 and 96 h. The concentration of HBeAg and HBsAg was determined using ELISA. HBV DNA replication was examined by real- time PCR and the level of HBV mRNA was measured by RT-PCR. RESULTS: In HepG2.2.15 cells treated with combination of siRNA and lamivudine, the secretion of HBeAg and HBsAg into the supernatant was found to be inhibited by 91.80% and 82.40% (2.89 ± 0.48 vs 11.73 ± 0.38, P < 0.05; 4.59 ± 0.57 vs 16.25 ± 0.48, P < 0.05) at 96 h, respectively; the number of HBV DNA copies within culture medium was also significantly decreased at 96 h (1.04 ± 0.26 vs 8.35 ± 0.33, P < 0.05). Moreover, mRNA concentration in HepG2.2.15 cells treated with combination of siRNA and lamivudine was obviously lower compared to those treated either with siRNA or lamivudine (19.44 ± 0.17 vs 33.27 ± 0.21 or 79.9 ± 0.13, P < 0.05). CONCLUSION: Combination of siRNA and lamivudine is more effective in inhibiting HBV replication as compared to the single use of siRNA or lamivudine in HepG2.2.15 cells.

Lentivirus vectors construction of SiRNA targeting interference GPC3 gene and its biological effects on liver cancer cell lines Huh-7

Objective:To build GPC3 gene short hairpin interference RNA(shRNA)slow virus veclor.observe expression of Huh-7 GPC3 gene in human liver cell line proliferation apoptosis and the effect of GPC3 gene influencing on liver cancer cell growth,and provide theoretical basis for genc therapy of liver cancer.Methods:Hepatocellular carcinoma cell line Huh-7 wsa transfected by a RNA interference technique.GPC3 gene expression in a variety of liver cancer cell lines was detected by fluorescence quantitative PCR.Targeted GPC3 gene seqnences of small interfering RNA(siRNA)PGC-shRNA-GPC3 were restructured.Stable expression cell linse of siRNA were screened and established with the heplp of liposomes(lipofectamine^(TM2000))as carrier transfcetion of human liver cell lines.In order to validate siRNA interference efficiency.GPC3 siRNA mRNA expression was detected after transfection by using RT-PCR and Western blot.The absorbance value of the cells of blank group,untransfection group and transfection group,the cell cycle and cell apoptosis were calculated,and effects of GPC3 gene nn Huh-7 cell proliferation and apoptosis were observed.Results:In the liver cancer cell lines Huh-7 GPC3 gene showed high expression.PGC-shRNA-GPC3 recombinant plasmid was constructde successfully via sequencing validation.Stable recombinant plasmid transfected into liver cancer cell linse Huh-7can obviously inhibit GPC3 mRNA expression level.Conclusions:The targeted GPC3 siRNA can effectively inhibit the expression of GPC3.

Combination of small interfering RNAs mediates greater suppression on hepatitis B virus cccDNA in HepG2.2.15 cells

AIM： To observe the inhibition of hepatitis B virus （HBV） replication and expression in HepG2.2.15 cells by combination of small interfering RNAs （siRNAs）. METHODS： Recombinant plasmid psiI-HBV was constructed and transfected into HepG2.2.15 cells. At 48 h, 72 h and 96 h after transfection, culture media were collected and cells were harvested for HBV replication assay. HBsAg and HBeAg in the cell culture medium were detected by enzyme-linked immunoadsorbent assay （ELISA）. Intracellular viral DNA and covalently closed circular DNA （cccDNA） were quantified by real-time polymerase chain reaction （PCR）. HBV viral mRNA was reverse transcribed and quantified by reverse-transcript PCR （RT-PCR）. RESULTS： siRNAs showed marked anti-HBV effects. siRNAs could specifically inhibit the expression of HBsAg and the replication of HBV DNA in a dosedependent manner. Furthermore, combination of siRNAs, compared with individual use of each siRNA, exerted a stronger inhibition on antigen expression and viral replication. More importantlycombination of siRNAs significantly suppressed HBV cccDNA amplification. CONCLUSION： Combination of siRNAs mediates a stronger inhibition on viral replication and antigenexpression in HepG2.2.15 cells, especially on cccDNA amplification.

Expressing p20 hairpin RNA of Citrus tristeza virus confers Citrus aurantium with tolerance/resistance against stem pitting and seedling yellow CTV strains

The Citrus tristeza virus (CTV) uses 3 silencing suppressor genes, p20, p23 and p25, to resist the attacks from its Citrus hosts. Inactivating these genes is therefore obviously a potential defensive option in addition to the current control strat-egies including aphid management and the use of mild strain cross protection. In this study, we cloned partial DNA frag-ments from the three genes, and used them to construct vectors for expressing hairpin RNAs (hpRNAs). To facilitate the formation of hpRNAs, the constructs were introduced in a loop structure. Fol owing transformation of sour orange (Citrus aurantium) with these constructs, 8 p20 hpRNA (hp20) and 1 p25 hpRNA (hp25) expressing lines were obtained. The 7 hp20 transgenic lines were further characterized. Their reactions to CTV were tested fol owing inoculation with CT14A and/or TR-L514, both of which are severe strains. Results showed that 3 lines (hp20-5, hp20-6 and hp20-8) were completely resistant to TR-L514 under greenhouse conditions for no detectable viral load was found in their leaves by PCR. However, they exhibited only partial suppression of TR-L514 under screen house conditions since the virus was detected in their leaves, though 2 months later compared to non-transgenic controls. Further tests showed that hp20-5 was tolerant also to CT14A under screen house conditions. The growth of hp20-5 was much better than others including the controls that were concurrently chal enged with CT14A. These results showed that expressing p20 hpRNA was sufifcient to confer sour orange with CTV resistance/tolerance.

High-throughput RNA interference screens integrative analysis: Towards a comprehensive understanding of the virus-host interplay

Viruses are extremely heterogeneous entities; the size and the nature of their genetic information, as well as the strategies employed to amplify and propagate their genomes, are highly variable. However, as obligatory intracellular parasites, replication of all viruses relies on the host cell. Having co-evolved with their host for several million years, viruses have developed very sophisticated strategies to hijack cellular factors that promote virus uptake, replication, and spread. Identification of host cell factors(HCFs) required for these processes is a major challenge for researchers, but it enables the identification of new, highly selective targets for anti viral therapeutics. To this end, the establishment of platforms enabling genome-wide high-throughput RNA interference(HT-RNAi) screens has led to the identification of several key factors involved in the viral lifecycle. A number of genome-wide HT-RNAi screens have been performed for major human pathogens. These studies enable first inter-viral comparisons related to HCF requirements. Although several cellular functions appear to be uniformly required for the life cycle of most viruses tested(such as the proteasome and the Golgi-mediated secretory pathways), some factors, like the lipid kinase Phosphatidylinositol 4-kinase Ⅲα in the case of hepatitis C virus, are selectively required for individual viruses. However, despite the amount of data available, we are still far away from a comprehensive understanding of the interplay between viruses and host factors. Major limitations towards this goal are the low sensitivity and specificity of such screens, resulting in limited overlap between different screens performed with the same virus. This review focuses on how statistical and bioinformatic analysis methods applied to HTRNAi screens can help overcoming these issues thus increasing the reliability and impact of such studies.

Eight key long non-coding RNAs predict hepatitis virus positive hepatocellular carcinoma as prognostic targets

BACKGROUND Hepatitis B virus,together with hepatitis C virus,has been recognized as the leading causes of hepatocellular carcinoma(HCC).Long non-coding RNAs(lncRNAs)have been suggested in increasing studies to be the potential prognostic factors for HCC.However,the role of combined application of lncRNAs in estimating overall survival(OS)for hepatitis virus positive HCC(VHCC)is uncertain.AIM To construct an lncRNA signature related to the OS of VHCC patients to enhance the accuracy of prognosis prediction.METHODS The expression patterns of lncRNAs,as well as related clinical data were collected from 149 VHCC patients from The Cancer Genome Atlas database.The R package was adopted to obtain the differentially expressed lncRNAs(DElncRNAs).LncRNAs significantly associated with OS were screened by means of univariate Cox regression analysis,so as to construct a least absolute shrinkage and selection operator(LASSO)model.Subsequently,the constructed lncRNA signature was developed and validated.Afterwards,the prognostic nomogram was established,which combined the as-established lncRNA signature as well as the clinical features.Meanwhile,subgroup analysis stratified by the virus type was also performed.Finally,the above-mentioned lncRNAs were enriched to corresponding pathways according to the markedly coexpressed genes.RESULTS A total of 1420 DElncRNAs were identified,among which 406 were significant in univariate Cox regression analysis.LASSO regression confirmed 8 out of the 406 lncRNAs,including AC005722.2,AC107959.3,AL353803.1,AL589182.1,AP000844.2,AP002478.1,FLJ36000,and NPSR1-AS1.Then,the prognostic risk score was calculated.Our results displayed a significant association between the risk model and the OS of VHCC[hazard ratio=1.94,95%confidence interval(CI):1.61-2.34,log-rank P=2e-10].The inference tree suggested that the established lncRNA signature was useful in the risk stratification of VHCC.Furthermore,a nomogram was plotted,and the concordance index of internal validation was 0.763(95%CI:0.700-0.826).Moreover,the subgroup analysis regarding etiology confirmed this risk model.In addition,the Wnt signaling pathway,angiogenesis,the p53 pathway,and the PI3 kinase pathway were the remarkably enriched pathways.CONCLUSION An eight-lncRNA signature has been established to predict the prognosis for VHCC,which contributes to providing a novel foundation for the targeted therapy of VHCC.

Host RNA circles and the origin of hepatitis delta virus

Recent reports show that many cellular RNAs are processed to form circular species that are relatively abundant and resistant to host nucleases.In some cases,such circles actually bind host microRNAs.Such depletion of available microRNAs appears to have biological roles;for instance,in homeostasis and disease.These findings regarding host RNA circles support a speculative reappraisal of the origin and mode of replication of hepatitis delta virus,hepatitis delta virus(HDV),an agent with a small circular RNA genome;specifically,it is proposed that in hepatocytes infected with hepatitis B virus(HBV),some viral RNA species are processed to circular forms,which by a series of chance events lead to an RNA that can be both replicated by host enzymes and assembled,using HBV envelope proteins,to form particles some of which are infectious.Such a model also may provide some new insights into the potential pathogenic potential of HDV infections.In return,new insights into HDV might provide information leading to a better understanding of the roles of the host RNA circles.

Inhibition of hepatitis C virus replication by single-stranded RNA structural mimics

AIM: To examine the effect of hepatitis C virus (HCV) structural mimics of regulatory regions of the genome on HCV replication.METHODS: HCV RNA structural mimics were constructed and tested in a HCV genotype 1b aBB7 replicon,and a Japanese fulminant hepatitis-1 (JFH-1) HCV genotype 2a infection model.All sequences were computer-predicted to adopt stem-loop structures identical to the corresponding elements in full-length viral RNA.Huh7.5 cells bearing the BB7 replicon or infected with JFH-1 virus were transfected with expression vectors generating HCV mimics and controls.Cellular HCV RNA and protein levels were quantified by real-time polymerase chain reaction and Western blotting,respectively.To evaluate possible antisense effects,complementary RNAs spanning a mimic were prepared.RESULTS: In the BB7 genotype 1b replicon system,mimics of the polymerase (NS-5B),X and BA regions inhibited replication by more than 90%,50%,and 60%,respectively.In the JFH-1 genotype 2 infection system,mimics that were only 74% and 46% identical in sequence relative to the corresponding region in JFH-1 inhibited HCV replication by 91.5% and 91.2%,respectively,as effectively as a mimic with complete identity to HCV genotype 2a.The inhibitory effects were confirmed by NS3 protein levels.Antisense RNA molecules spanning the 74% identical mimic had no significant effects.CONCLUSION: HCV RNA structural mimics can inhibit HCV RNA replication in replicon and infectious HCV systems and do so independent of close sequence identity with the target.

Circulating microRNAs as non-invasive biomarkers for hepatitis B virus liver fibrosis

Viruses can alter the expression of host microRNAs(miRNA s) and modulate the immune response during a persistent infection. The dysregulation of host miRNA s by hepatitis B virus(HBV) contributes to the proinflammatory and profibrotic changes within the liver. Multiple studies have documented the differential regulation of intracellular and circulating miRNA s during different stages of HBV infection. Circulating miRNA s found in plasma and/or extracellular vesicles can integrate data on viral-host interactions and on the associated liver injury. Hence, the detection of circulating miRNA s in chronic HBV hepatitis could offer a promising alternative to liver biopsy, as their expression is associated with HBV replication, the progression of liver fibrosis,and the outcome of antiviral treatment. The current review explores the available data on miRNA involvement in HBV pathogenesis with an emphasis on their potential use as biomarkers for liver fibrosis.