Pathway analysis of host responses to dengue virus serotype 2 infection and inhibition of viral envelope protein by naringenin from Ganoderma lucidum.

Dengue fever cases are spiking over the last two decades. Incessant efforts are still being made to gain deeper insights on this arboviral disease and to identify bioactive antivirals. In this study, bioinformatics analysis was conducted to identify the differentially expressed genes (DEGs) in the expression profiling datasets of dengue virus serotype 2 (DENV2) patients. We found overexpressed genes in dengue patients that can interrupt cell cycle progression and phase transitions of mitosis inside the host to favour the viral replication process. These DEGs were associated with the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways such as cell cycle and DNA replication. A protein interaction network consisting of these significant pathways was also constructed using STRING. Futher, the traditional Chinese medicine (TCM) compounds from Ganoderma lucidum were screened to target DENV2 envelope protein, which was crucial for viral fusion activity. Docking, orbital energy, and toxicity prediction analysis revealed that naringenin was the best antiviral candidate. Following molecular dynamics simulations, the predicted binding energy of the protein-naringenin system using the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach was slightly greater than the control system. It is recommended to perform in vitro inhibition of naringenin against DENV2 and use our findings to complement the experimental data obtained.

Molecular Characterization and Identification of Potential Inhibitors for 'E' Protein of Dengue Virus.

Dengue is an arthropod-borne acute febrile illness caused by Dengue Virus (DENV), a member of Flaviviridae. Severity of the infection ranges from mild self-limiting illness to severe life-threatening hemorrhagic fever (DHF) and dengue shock syndrome (DSS). To date, there is no specific antiviral therapy established to treat the infection. The current study reports the epidemiology of DENV infections and potential inhibitors of DENV 'E' protein. Among the various serotypes, DENV-2 serotype was observed more frequently, followed by DENV-4, DENV-1, and DENV-3. New variants of existing genotypes were observed in DENV-1, 2, and 4 serotypes. Predominantly, the severe form of dengue was attributable to DENV-2 infections, and the incidence was more common in males and pediatric populations. Both the incidence and the disease severity were more common among the residents of non-urban environments. Due to the predominantly self-limiting nature of primary dengue infection and folk medicine practices of non-urban populations, we observed a greater number of secondary dengue cases than primary dengue cases. Hemorrhagic manifestations were more in secondary dengue in particularly in the pediatric group. Through different computational methods, ligands RGBLD1, RGBLD2, RGBLD3, and RGBLD4 are proposed as potential inhibitors in silico against DENV-1, -2, -3, and -4 serotypes.

Heme oxygenase-1 inhibits DENV-induced endothelial hyperpermeability and serves as a potential target against dengue hemorrhagic fever.

Dengue virus (DENV) is a cause of vascular endothelial dysfunction and vascular leakage, which are characterized as hallmarks of dengue hemorrhagic fever or dengue shock syndrome, which become a severe global health emergency with substantial morbidity and mortality. Currently, there are still no promising therapeutics to alleviate the dengue-associated vascular hemorrhage in a clinical setting. In the present study, we first observed that heme oxygenase-1 (HO-1) expression level was highly suppressed in severe DENV-infected patients. In contrast, the overexpression of HO-1 could attenuate DENV-induced pathogenesis, including plasma leakage and thrombocytopenia, in an AG129 mouse model. Our data indicate that overexpression of HO-1 or its metabolite biliverdin can maintain endothelial integrity upon DENV infection in vitro and in vivo. We further characterized the positive regulatory effect of HO-1 on the endothelial adhesion factor vascular endothelial-cadherin to decrease DENV-induced endothelial hyperpermeability. Subsequently, we confirmed that two medicinal plant-derived compounds, andrographolide, and celastrol, widely used as a nutritional or medicinal supplement are useful to attenuate DENV-induced plasma leakage through induction of the HO-1 expression in DENV-infected AG129 mice. In conclusion, our findings reveal that induction of the HO-1 signal pathway is a promising option for the treatment of DENV-induced vascular pathologies.

Vitamin D Regulates the Expression of Immune and Stress Response Genes in Dengue Virus-infected Macrophages by Inducing Specific MicroRNAs.

BACKGROUND: The pathogenesis associated with Dengue virus (DENV) infection is marked by the impairment of host immune response. Consequently, the modulation of immune response has emerged as an important therapeutic target for the control of DENV infection. Vitamin D has been shown to regulate the immune response in DENV infection, although the molecular mechanism remains poorly understood. Post-transcriptional regulation of mRNA by miRNAs offers an opportunity to gain insight into the immunomodulation mediated by vitamin D. OBJECTIVE: Previously, it has been observed that a high dose of vitamin D (4000 IU) decreased DENV-2 infection and inflammatory response in monocyte-derived macrophages (MDMs). Here, we examine whether high or low doses of vitamin D supplements exert differential effect on miRNA expression in DENV-infected macrophages. METHODS: We analyzed miRNA expression profiles in MDMs isolated from healthy individuals who were given either 1000 or 4000 IU/day of vitamin D for 10 days. MDMs before or after vitamin D supplementation were challenged with DENV-2, and miRNAs profiles were analyzed by qPCR arrays. RESULTS: DENV-2 infected MDMs supplemented with 4000 IU, showed up-regulation of miR-374a-5p, miR-363-3p, miR-101-3p, miR-9-5p, miR-34a-5p, miR-200a-3p, and the family of miRNAs miR-21-5p, and miR-590-p. The miRNA profile and predicted target mRNAs suggested regulatory pathways in MDMs obtained from healthy donors who received higher doses of vitamin D. These DENV-2 infected MDMs expressed a unique set of miRNAs that target immune and cellular stress response genes. CONCLUSION: The results suggest vitamin D dose-dependent differential expression of miRNAs target key signaling pathways of the pathogenesis of dengue disease.

High-Throughput Screening Assays for Dengue Antiviral Drug Development.

Dengue is an arthropod-borne viral disease that has become endemic and a global threat in over 100 countries. The increase in prevalence would require a long-term measure to control outbreaks. Sanofi Pasteur has licensed the tetravalent dengue vaccine (Dengvaxia) in certain dengue endemic countries. However, the efficacy of the vaccine is limited against certain dengue serotypes and can only be used for individuals from the age from 9 to 45 years old. Over the years, there has been intense research conducted on the development of antivirals against dengue virus (DENV) through either inhibiting the virus replication or targeting the host cell mechanism to block the virus entry. However, no approved antiviral drug against dengue is yet available. In this chapter, we describe the dengue antiviral development workflow including (i) prophylactic, (ii) virucidal, and (iii) postinfection assays that are employed in the antiviral drug screening process against DENV. Further, we demonstrate different methods that can be used to enumerate the reduction in virus foci number including foci-forming unit reduction assay (FFURA), estimation of viral RNA copy number through quantitative real-time PCR, and a high-throughput enzyme linked immunosorbent assay (ELISA)-based quantification of virus particles.

Antiviral Role of Phenolic Compounds against Dengue Virus: A Review.

Phenolic compounds have been related to multiple biological activities, and the antiviral effect of these compounds has been demonstrated in several viral models of public health concern. In this review, we show the antiviral role of phenolic compounds against dengue virus (DENV), the most widespread arbovirus globally that, after its re-emergence, has caused multiple epidemic outbreaks, especially in the last two years. Twenty phenolic compounds with anti-DENV activity are discussed, including the multiple mechanisms of action, such as those directed against viral particles or viral proteins, host proteins or pathways related to the productive replication viral cycle and the spread of the infection.

A Targeted Computational Screen of the SWEETLEAD Database Reveals FDA-Approved Compounds with Anti-Dengue Viral Activity.

Affordable and effective antiviral therapies are needed worldwide, especially against agents such as dengue virus that are endemic in underserved regions. Many antiviral compounds have been studied in cultured cells but are unsuitable for clinical applications due to pharmacokinetic profiles, side effects, or inconsistent efficacy across dengue serotypes. Such tool compounds can, however, aid in identifying clinically useful treatments. Here, computational screening (Rapid Overlay of Chemical Structures) was used to identify entries in an in silico database of safe-in-human compounds (SWEETLEAD) that display high chemical similarities to known inhibitors of dengue virus. Inhibitors of the dengue proteinase NS2B/3, the dengue capsid, and the host autophagy pathway were used as query compounds. Three FDA-approved compounds that resemble the tool molecules structurally, cause little toxicity, and display strong antiviral activity in cultured cells were selected for further analysis. Pyrimethamine (50% inhibitory concentration [IC50] = 1.2 µM), like the dengue proteinase inhibitor ARDP0006 to which it shows structural similarity, inhibited intramolecular NS2B/3 cleavage. Lack of toxicity early in infection allowed testing in mice, in which pyrimethamine also reduced viral loads. Niclosamide (IC50 = 0.28 µM), like dengue core inhibitor ST-148, affected structural components of the virion and inhibited early processes during infection. Vandetanib (IC50 = 1.6 µM), like cellular autophagy inhibitor spautin-1, blocked viral exit from cells and could be shown to extend survival in vivo Thus, three FDA-approved compounds with promising utility for repurposing to treat dengue virus infections and their potential mechanisms were identified using computational tools and minimal phenotypic screening.IMPORTANCE No antiviral therapeutics are currently available for dengue virus infections. By computationally overlaying the three-dimensional (3D) chemical structures of compounds known to inhibit dengue virus over those of compounds known to be safe in humans, we identified three FDA-approved compounds that are attractive candidates for repurposing as antivirals. We identified targets for two previously identified antiviral compounds and revealed a previously unknown potential anti-dengue compound, vandetanib. This computational approach to analyze a highly curated library of structures has the benefits of speed and cost efficiency. It also leverages mechanistic work with query compounds used in biomedical research to provide strong hypotheses for the antiviral mechanisms of the safer hit compounds. This workflow to identify compounds with known safety profiles can be expanded to any biological activity for which a small-molecule query compound has been identified, potentially expediting the translation of basic research to clinical interventions.

Phylogenetically based establishment of a dengue virus panel, representing all available genotypes, as a tool in dengue drug discovery.

Dengue fever is the most widespread of the human arbovirus diseases, with approximately one third of the world's population at risk of infection. Dengue viruses are members of the genus Flavivirus (family Flaviviridae) and, antigenically, they separate as four closely related serotypes (1-4) that share 60-75% amino acid homology. This genetic diversity complicates the process of antiviral drug discovery. Thus, currently no approved dengue-specific therapeutic treatments are available. With the aim of providing an efficient tool for dengue virus drug discovery, a collection of nineteen dengue viruses, representing the genotypic diversity within the four serotypes, was developed. After phylogenetic analysis of the full-length genomes, we selected relevant strains from the EVAg collection at Aix-Marseille University and completed the virus collection, using a reverse genetic system based on the infectious sub-genomic amplicons technique. Finally, we evaluated this dengue virus collection against three published dengue inhibitory compounds. NITD008, which targets the highly conserved active site of the viral NS5 polymerase enzyme, exhibited similar antiviral potencies against each of the different dengue genotypes in the panel. Compounds targeting less conserved protein subdomains, such as the capsid inhibitor ST-148, or SDM25N, a ∂ opioid receptor antagonist which indirectly targets NS4B, exhibited larger differences in potency against the various genotypes of dengue viruses. These results illustrate the importance of a phylogenetically based dengue virus reference panel for dengue antiviral research. The collection developed in this study, which includes such representative dengue viruses, has been made available to the scientific community through the European Virus Archive to evaluate novel DENV antiviral candidates.

Nucleoside Analogs with Selective Antiviral Activity against Dengue Fever and Japanese Encephalitis Viruses.

Dengue virus (DENV) and Japanese encephalitis virus (JEV) are important arthropod-borne viruses from the Flaviviridae family. DENV is a global public health problem with significant social and economic impacts, especially in tropical and subtropical areas. JEV is a neurotropic arbovirus endemic to east and southeast Asia. There are no U.S. FDA-approved antiviral drugs available to treat or to prevent DENV and JEV infections, leaving nearly one-third of the world's population at risk for infection. Therefore, it is crucial to discover potent antiviral agents against these viruses. Nucleoside analogs, as a class, are widely used for the treatment of viral infections. In this study, we discovered nucleoside analogs that possess potent and selective anti-JEV and anti-DENV activities across all serotypes in cell-based assay systems. Both viruses were susceptible to sugar-substituted 2'-C-methyl analogs with either cytosine or 7-deaza-7-fluoro-adenine nucleobases. Mouse studies confirmed the anti-DENV activity of these nucleoside analogs. Molecular models were assembled for DENV serotype 2 (DENV-2) and JEV RNA-dependent RNA polymerase replication complexes bound to nucleotide inhibitors. These models show similarities between JEV and DENV-2, which recognize the same nucleotide inhibitors. Collectively, our findings provide promising compounds and a structural rationale for the development of direct-acting antiviral agents with dual activity against JEV and DENV infections.

Computational screening of medicinal plant phytochemicals to discover potent pan-serotype inhibitors against dengue virus.

Emergence of Dengue as one of the deadliest viral diseases prompts the need for development of effective therapeutic agents. Dengue virus (DV) exists in four different serotypes and infection caused by one serotype predisposes its host to another DV serotype heterotypic re-infection. We undertook virtual ligand screening (VLS) to filter compounds against DV that may inhibit inclusively all of its serotypes. Conserved non-structural DV protein targets such as NS1, NS3/NS2B and NS5, which play crucial role in viral replication, infection cycle and host interaction, were selected for screening of vital antiviral drug leads. A dataset of plant based natural antiviral derivatives was developed. Molecular docking was performed to estimate the spatial affinity of target compounds for the active sites of DV's NS1, NS3/NS2B and NS5 proteins. The drug likeliness of the screened compounds was followed by ADMET analysis whereas the binding behaviors were further elucidated through molecular dynamics (MD) simulation experiments. VLS screened three potential compounds including Canthin-6-one 9-O-beta-glucopyranoside, Kushenol W and Kushenol K which exhibited optimal binding with all the three conserved DV proteins. This study brings forth novel scaffolds against DV serotypes to serve as lead molecules for further optimization and drug development against all DV serotypes with equal effect against multiple disease causing DV proteins. We therefore anticipate that the insights given in the current study could be regarded valuable towards exploration and development of a broad-spectrum natural anti-dengue therapy.

Evaluation of anti-dengue activity of Carica papaya aqueous leaf extract and its role in platelet augmentation.

Dengue disease is characterized by a marked decrease in platelet count, which is life threatening. In the present study, we investigated the antiviral activity of an aqueous extract of Carica papaya leaves (PLE) against dengue virus (DENV) and its effect on platelet augmentation. The anti-dengue activity of PLE in DENV-infected THP-1 cells was examined by immunoblotting and flow cytometry. The effect of PLE on erythrocyte damage was investigated using hemolytic and anti-hemolytic assays. Virus-infected THP-1 cells were assayed for IFN-α secretion. The effect of PLE on platelet augmentation in rats with cyclophosphamide-induced thrombocytopenia was also investigated. The platelet count of blood from the retro-orbital plexus of rats was determined on the 1st, 4th, 7th, 11th and 14th day of study. On the 14th day, the rats were sacrificed for histopathological examination of the liver, kidney and spleen. Plasma of thrombocytopenic rats was tested for thrombopoietin (TPO) and IL-6 secretion. The data suggest that PLE significantly decreases the expression of the envelope and NS1 proteins in DENV-infected THP-1 cells. A marked decrease in intracellular viral load upon PLE treatment confirmed its antiviral activity. This also resulted in a significant decrease in erythrocyte damage and hydrogen-peroxide-induced lipid peroxidation. A significant increase in the number of platelets was found in thrombocytopenic rats treated with PLE, along with an increase in IL-6 and TPO levels. These findings suggest that PLE can potentially be used as an antiviral agent, as it helps in platelet augmentation and exhibits antiviral activity against DENV.

Luteolin escape mutants of dengue virus map to prM and NS2B and reveal viral plasticity during maturation.

We previously showed that luteolin, a well-known plant-derived component found in the "heat clearing" class of Traditional Chinese Medicine (TCM) herbs, is an uncompetitive inhibitor (Ki 58.6 µM) of the host proprotein convertase furin, an endoprotease that is required for maturation of flaviviruses in the trans-Golgi compartment. Luteolin also weakly inhibited recombinant dengue virus NS2B/NS3 protease (Ki 140.36 µM) non-competitively. In order to further explore the mechanism of inhibition we isolated resistant mutants by continuous passaging of DENV2 in the presence of increasing concentrations of luteolin. Nucleotide sequence analysis of the luteolin-resistant escape mutants revealed nucleotide changes that lead to amino acid substitutions in the prM (T79R) and NS2B (I114M) genes. These mutations were introduced into a DENV2 infectious clone and tested for replication in Huh-7 cells. Interestingly we found that the replication kinetics of prM T19R-NS2B I114M double-mutant (DM) was similar to wild-type virus (WT). On the other hand the prM T79R single mutant (SM1) was attenuated and the NS2B I114M single mutant (SM2) showed enhanced replication. Time of drug addition assay with luteolin showed that the mutant viruses were able to produce more mature virions than WT in the order DM > SM2>SM1>WT. Exogenous addition of furin to purified immature WT or mutant viruses revealed that luteolin blocked the prM cleavage of WT and SM2 at a similar level. On the other hand the SM1 immature virus showed some cleavage while the DM immature virus revealed efficient furin cleavage of prM even in the presence of 50 µM luteolin. Our findings suggest that luteolin inhibition of furin may occur at host/pathogen interface that permits the virus to escape the suppression by mutating key residue that may lead to an altered interface.

Alpha-mangostin inhibits both dengue virus production and cytokine/chemokine expression.

Since severe dengue virus (DENV) infection in humans associates with both high viral load and massive cytokine production - referred to as "cytokine storm", an ideal drug for treatment of DENV infection should efficiently inhibit both virus production and cytokine expression. In searching for such an ideal drug, we discovered that α-mangostin (α-MG), a major bioactive compound purified from the pericarp of the mangosteen fruit (Garcinia mangostana Linn), which has been used in traditional medicine for several conditions including trauma, diarrhea, wound infection, pain, fever, and convulsion, inhibits both DENV production in cultured hepatocellular carcinoma HepG2 and Huh-7 cells, and cytokine/chemokine expression in HepG2 cells. α-MG could also efficiently inhibit all four serotypes of DENV. Treatment of DENV-infected cells with α-MG (20µM) significantly reduced the infection rates of four DENV serotypes by 47-55%. α-MG completely inhibited production of DENV-1 and DENV-3, and markedly reduced production of DENV-2 and DENV-4 by 100 folds. Furthermore, it could markedly reduce cytokine (IL-6 and TNF-α) and chemokine (RANTES, MIP-1ß, and IP-10) transcription. These actions of α-MG are more potent than those of antiviral agent (ribavirin) and anti-inflammatory drug (dexamethasone). Thus, α-MG is potential to be further developed as therapeutic agent for DENV infection.

Luteolin restricts dengue virus replication through inhibition of the proprotein convertase furin.

In many countries afflicted with dengue fever, traditional medicines are widely used as panaceas for illness, and here we describe the systematic evaluation of a widely known natural product, luteolin, originating from the "heat clearing" class of herbs. We show that luteolin inhibits the replication of all four serotypes of dengue virus, but the selectivity of the inhibition was weak. In addition, ADE-mediated dengue virus infection of human cell lines and primary PBMCs was inhibited. In a time-of-drug-addition study, luteolin was found to reduce infectious virus particle formation, but not viral RNA synthesis, in Huh-7 cells. During the virus life cycle, the host protease furin cleaves the pr moiety from prM protein of immature virus particles in the trans-Golgi network to produce mature virions. Analysis of virus particles from luteolin-treated cells revealed that prM was not cleaved efficiently. Biochemical interrogation of human furin showed that luteolin inhibited the enzyme activity in an uncompetitive manner, with Ki value of 58.6 µM, suggesting that treatment may restrict the virion maturation process. Luteolin also exhibited in vivo antiviral activity in mice infected with DENV, causing reduced viremia. Given the mode of action of luteolin and its widespread source, it is possible that it can be tested in combination with other dengue virus inhibitors.

Low sensitivity of the tourniquet test for differential diagnosis of dengue: an analysis of 28,000 trials in patients.

BACKGROUND: The aim of this study was to evaluate the utility of the tourniquet test (TT) for dengue diagnosing. To our knowledge, no previous study with such a large sample, of this duration, with as many laboratory methods referenced, or relating the results of the TT to the 2009 WHO classification of severity has been conducted thus far. METHODS: In this study, we analyzed the records of 119,589 suspected dengue cases in a Brazilian city, with 30,670 confirmed cases. The Cohen's Kappa test was applied to evaluate the degree of agreement between the tests, and the sensitivity and specificity was calculated for the TT. RESULTS: Twenty-eight thousand six hundred thirty-five TT were performed. No association between the outcome of the TT and greater severity of infection, according to the 2009 guideline, was observed (P = 0.28); furthermore, relevant agreement with the final diagnosis (κ = 0.01; 95 % CI = 0.00 to 0.02) or individually with the IgM enzyme-linked immunoassay was not observed (κ = 0.05; 95 % CI = 0.04 to 0.06), and was even lower with PCR (κ = 0.27; 95 % CI = 0.06 to 0.49). Most importance of the TT was shown in relation to specificity (88.9 %; 95 % CI = 0.88 to 0.89) and negative predictive value (70.3 %; CI 95 % = 0.70 to 0.71). CONCLUSIONS: TT was more effective in detecting cases that were truly negative than positive. These results suggest that the TT should not be used as diagnosis of dengue.

Enhanced sensing of dengue virus DNA detection using O2 plasma treated-silicon nanowire based electrical biosensor.

Dengue Virus (DENV) has become one of the most serious arthropod-borne viral diseases, causing death globally. The existing methods for DENV detection suffer from the late stage treatment due to antibodies-based detection which is feasible only after five days following the onset of the illness. Here, we demonstrated the highly effective molecular electronic based detection utilizing silicon nanowire (SiNW) integrated with standard complementary metal-oxide-semiconductor (CMOS) process as a sensing device for detecting deoxyribonucleic acid (DNA) related to DENV in an early stage diagnosis. To transform the fabricated devices as a functional sensing element, three-step procedure consist of SiNW surface modification, DNA immobilization and DNA hybridization were employed. The detection principle works by detecting the changes in current of SiNW which bridge the source and drain terminal to sense the immobilization of probe DNA and their hybridization with target DNA. The oxygen (O2) plasma was proposed as an effective strategy for increasing the binding amounts of target DNA by modified the SiNW surface. It was found that the detection limit of the optimized O2 plasma treated-SiNW device could be reduced to 1.985 × 10-14 M with a linear detection range of the sequence-specific DNA from 1.0 × 10-9 M to 1.0 × 10-13 M. In addition, the developed biosensor device was able to discriminate between complementary, single mismatch and non-complementary DNA sequences. This highly sensitive assay was then applied to the detection of reverse transcription-polymerase chain reaction (RT-PCR) product of DENV-DNA, making it as a potential method for disease diagnosis through electrical biosensor.

Casamino acids facilitate the secretion of recombinant dengue virus serotype-3 envelope domain III in Pichia pastoris.

BACKGROUND: Dengue is a viral disease spread to humans by mosquitoes. Notably, there are four serotypes of dengue viruses (DENV) that places ~40 % of the global population at risk of infection. However, lack of a suitable drug or a preventive vaccine exacerbates the matter further. Envelope domain-III (EDIII) antigen of dengue virus (DENV) has garnered much attention as a promising vaccine candidate for dengue, in addition to its use as a diagnostic intermediate. Hence developing a method for efficient production of high quality recombinant EDIII is important for research and industrial purpose. RESULTS: In this work, a Pichia pastoris system was optimized for the secretory over-expression of DENV serotype-3 EDIII under the control of methanol inducible AOX1 promoter. Temperature alone had a significant impact upon the amount of secretory EDIII, with 2.5-fold increase upon reducing the induction temperature from 30 to 20 °C. However surprisingly, supplementation of culture media with Casamino acids (CA), further augmented secretory EDIII titer, with a concomitant drop of intracellular EDIII levels at both temperatures. Though, reduction in intracellular retention of EDIII was more prominent at 20 °C than 30 °C. This suggests that CA supplementation facilitates overexpressing P. pastoris cells to secrete more EDIII by reducing the proportion retained intracellularly. Moreover, a bell-shaped correlation was observed between CA concentration and secretory EDIII titer. The maximum EDIII expression level of 187 mg/L was achieved under shake flask conditions with induction at 20 °C in the presence of 1 % CA. The overall increase in EDIII titer was ~9-fold compared to un-optimized conditions. Notably, mouse immune-sera, generated using this purified EDIII antigen, efficiently neutralized the DENV. CONCLUSIONS: The strategy described herein could enable fulfilling the mounting demand for recombinant EDIII as well as lay direction to future studies on secretory expression of recombinant proteins in P. pastoris with CA as a media supplement.

Dengue human infection models to advance dengue vaccine development.

Dengue viruses (DENV) currently infect approximately 400 million people each year causing millions to seek care and overwhelming the health care infrastructure in endemic areas. Vaccines to prevent dengue and therapeutics to treat dengue are not currently available. The efficacy of the most advanced candidate vaccine against symptomatic dengue in general and DENV-2 in particular was much lower than expected, despite the ability of the vaccine to induce neutralizing antibody against all four DENV serotypes. Because seroconversion to the DENV serotypes following vaccination was thought to be indicative of induced protection, these results have made it more difficult to assess which candidate vaccines should or should not be evaluated in large studies in endemic areas. A dengue human infection model (DHIM) could be extremely valuable to down-select candidate vaccines or therapeutics prior to engaging in efficacy trials in endemic areas. Two DHIM have been developed to assess the efficacy of live attenuated tetravalent (LATV) dengue vaccines. The first model, developed by the Laboratory of Infectious Diseases at the U. S. National Institutes of Health, utilizes a modified DENV-2 strain DEN2Δ30. This virus was derived from the DENV-2 Tonga/74 that caused only very mild clinical infection during the outbreak from which it was recovered. DEN2Δ30 induced viremia in 100%, rash in 80%, and neutropenia in 27% of the 30 subjects to whom it was given. The Walter Reed Army Institute of Research (WRAIR) is developing a DHIM the goal of which is to identify DENV that cause symptomatic dengue fever. WRAIR has evaluated seven viruses and has identified two that meet dengue fever criteria. Both of these models may be very useful in the evaluation and down-selection of candidate dengue vaccines and therapeutics.

Identifying initiation and elongation inhibitors of dengue virus RNA polymerase in a high-throughput lead-finding campaign.

Dengue virus (DENV) is the most significant mosquito-borne viral pathogen in the world and is the cause of dengue fever. The DENV RNA-dependent RNA polymerase (RdRp) is conserved among the four viral serotypes and is an attractive target for antiviral drug development. During initiation of viral RNA synthesis, the polymerase switches from a "closed" to "open" conformation to accommodate the viral RNA template. Inhibitors that lock the "closed" or block the "open" conformation would prevent viral RNA synthesis. Herein, we describe a screening campaign that employed two biochemical assays to identify inhibitors of RdRp initiation and elongation. Using a DENV subgenomic RNA template that promotes RdRp de novo initiation, the first assay measures cytosine nucleotide analogue (Atto-CTP) incorporation. Liberated Atto fluorophore allows for quantification of RdRp activity via fluorescence. The second assay uses the same RNA template but is label free and directly detects RdRp-mediated liberation of pyrophosphates of native ribonucleotides via liquid chromatography-mass spectrometry. The ability of inhibitors to bind and stabilize a "closed" conformation of the DENV RdRp was further assessed in a differential scanning fluorimetry assay. Last, active compounds were evaluated in a renilla luciferase-based DENV replicon cell-based assay to monitor cellular efficacy. All assays described herein are medium to high throughput, are robust and reproducible, and allow identification of inhibitors of the open and closed forms of DENV RNA polymerase.

The utilization of SiNWs/AuNPs-modified indium tin oxide (ITO) in fabrication of electrochemical DNA sensor.

This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel.