Effects of the oxoaporphine alkaloid hernandonine on dengue virus. Evidence for its mechanisms of action

BACKGROUND

Dengue, caused by the dengue virus (Orthoflavivirus dengue, encompassing DENV types 1-4), is a member of the Flaviviridae family. The symptoms of dengue range from subclinical or mild manifestations to potentially fatal complications. The management of severe dengue is exceptionally challenging due to the absence of effective antiviral medications. In this context, natural products, whether in the form of pure compounds or standardized plant extracts, have emerged as a promising source for the development of novel antiviral therapeutics. Hernandonine, an oxoaporphine alkaloid found in Hernandia nymphaeifolia (C. Presl) Kubitzki. serves both as a metabolite and an inhibitor of human immunodeficiency virus type 1 (HIV-1) integrase.

PURPOSE

This study investigated the ability of hernandonine to inhibit DENV infection and explored its potential mechanisms.

STUDY DESIGN

To assess the in vitro anti-DENV activity, cells or induced pluripotent stem cell (iPSC)-derived cerebral organoids were exposed to hernandonine before or after infection with DENV. Along with hernandonine, the endocytosis modulators, genistein, wortmannin, Methyl-β-cyclodextrin (MβCD) and lovastatin, were used in the assays.

METHODS

The DENV infectivity and virion production in cells or cerebral organoids treated with compounds were determined. Various methods, including cell and cerebral organoids imaging, protein and gene detection were conducted to explore their antiviral mechanisms.

RESULTS

The results revealed notable antiviral properties of hernandonine, particularly in inhibiting DENV during the early stages of infection. Mechanistic analysis demonstrated that, akin to genistein, wortmannin, methyl-β-cyclodextrin (MβCD), and lovastatin, hernandonine exerted an influence on cholesterol-rich lipid rafts. It also restrained the pseudopodial movement ability of cells, potentially through the downregulation of cytoskeleton and endocytosis regulatory genes or protein expression. Moreover, hernandonine's virucidal activity was demonstrated. Hernandonine's inhibition of DENV infection was further validated in a disease-relevant iPSC-derived cerebral organoids model, a novel DENV-2 infection system worthy of further application.

CONCLUSION

This study evidenced the potential of hernandonine as a novel candidate in the fight against DENV infection.

Structure-based identification of small-molecule inhibitors that target the DIII domain of the Dengue virus glycoprotein E pan-serotypically

Dengue viral infection is caused by the Dengue virus, which spreads to humans through the bite of infected mosquitos. Dengue affects over half of the global population, with an estimated 500 million infections per year. Despite this, no effective treatment is currently available, however, several promising candidates are undergoing pre-clinical/clinical testing. The existence of four major serotypes is an important challenge in the development of drugs and vaccines to combat Dengue virus infection. Hence, the drug/vaccine thereby developed should neutralize all the four serotypes equally. However, there is no pan-serotype specific treatment for Dengue virus, thereby emphasizing the need for the identification of novel drug-like compounds that can target all serotypes of the Dengue virus equally. To this end, we employed virtual screening methodologies to find drug-like compounds that target the domain III of glycoprotein E. Most importantly, domain III of E protein is involved in viral fusion with the host membrane and is also targeted by neutralizing antibodies. Our study found two small molecule drug-like compounds (out of the 3 million compounds screened) having similar binding affinity with all four serotypes. The compounds thereby identified exhibit favourable drug like properties and can be developed as a treatment for Dengue virus.

Dengue Envelope Protein as a Cytotoxic Factor Inducing Hemorrhage and Endothelial Cell Death in Mice

Dengue virus (DENV) infection, prevalent in tropical and subtropical regions, can progress to dengue hemorrhagic fever (DHF), which increases mortality during secondary infections. DHF is characterized by endothelial damage and vascular leakage. Despite its severity, no specific antiviral treatments exist, and the viral factors responsible for endothelial damage remain unclear. This study examines the role of the DENV envelope protein domain III (EIII) in inducing endothelial apoptosis using a mouse model. Additionally, we aim to explore whether cell death-inducing pathways could serve as drug targets to ameliorate EIII-induced endothelial injury and hemorrhage. In vitro experiments using human endothelial HMEC-1 cells demonstrated that both recombinant EIII (rEIII) and DENV markedly induced caspase-3-mediated endothelial cell death, an effect that was attenuated by co-treatment with chondroitin sulfate B (CSB), N-acetyl cysteine (NAC), and the caspase-3 inhibitor z-DEVD-FMK. In vivo, sequential injections of rEIII and anti-platelet immunoglobulin in mice, designed to mimic the clinical phase of DHF with peak viremia followed by an increase in DENV-induced Ig, including autoantibodies, revealed that these dual treatments markedly triggered caspase-3-dependent apoptosis in vascular endothelial cells at hemorrhage sites. Treatments with z-DEVD-FMK effectively reduced DHF-like symptoms such as thrombocytopenia, hemorrhage, inflammation, hypercoagulation, and endothelial damage. Additionally, CSB and NAC alleviated hemorrhagic symptoms in the mice. These results suggest that targeting EIII, reactive oxygen species, and caspase-3-mediated apoptosis could offer potential therapeutic strategies for addressing EIII-induced hemorrhagic pathogenesis.

Efficacy of human interleukin-11 analogs for treating dengue fever-associated thrombocytopenia: a prospective cohort

AIM

Dengue fever (DF), carried by Aedes mosquitoes, affects millions worldwide. Platelet-inducing human IL-11 analogues may be effective in treating DF-associated thrombocytopenia.

METHODOLOGY

A prospective study was done at Dr. Ziauddin Hospital, a tertiary care hospital in Karachi, Pakistan, from September 2023 to April 30, 2024.

RESULTS

This study recruited 300 DF patients characterized by thrombocytopenia (platelet count < 30,000), including 159 in the treatment and 141 in the control group. The median age of patients was 34 ± 11.05 years, with 187 males (62.3%) and 113 females (37.7%). The treatment group had a higher proportion of fever (80%, p < 0.0001) and headache (96%, p = 0.012) compared to the control group; however, no significant changes were observed in other clinical parameters between the two groups. Following treatment for 5 days, platelet counts of the treatment group increased significantly in response to IL-11 treatment compared to the control group at all time intervals (day 0, day 1, day 2, day 3, day 4, and day 5). Following treatment, males consistently exhibited higher platelet counts than females (all p < 0.05). In addition, patients admitted on day 3 of their course of illness showed a significantly slow response to the treatment compared to those admitted on day 5. Although young individuals exhibited a significant increase in platelet count, the age showed no significant intergroup differences.

CONCLUSIONS

IL-11 analogs have promising potential for treating DF-associated thrombocytopenia. Additional investigation is necessary to refine administration protocols and examine the wider therapeutic ramifications of IL-11 in managing DF.

Exploring the antiviral inhibitory activity of Niloticin against the NS2B/NS3 protease of Dengue virus (DENV2)

Dengue virus (DENV2) is the cause of dengue disease and a worldwide health problem. DENV2 replicates in the host cell using polyproteins such as NS3 protease in conjugation with NS2B cofactor, making NS3 protease a promising antiviral drug-target. This study investigated the efficacy of 'Niloticin' against NS2B/NS3-protease. In silico and in vitro analyses were performed which included interaction of niloticin with NS2B/NS3-protease, protein stability and flexibility, mutation effect, betweenness centrality of residues and analysis of cytotoxicity, protein expression and WNV NS3-protease activity. Similar like acyclovir, niloticin forms strong H-bonds and hydrophobic interactions with residues LEU149, ASN152, LYS74, GLY148 and ALA164. The stability of the niloticin-NS2B/NS3-protease complex was found to be stable compared to the apo NS2B/NS3-protease in structural deviation, PCA, compactness and FEL analysis. The IC50 value of niloticin was 0.14 μM in BHK cells based on in vitro cytotoxicity analysis and showed significant activity at 2.5 μM in a concentration-dependent manner. Western blotting and qRT-PCR analyses showed that niloticin reduced DENV2 protein transcription in a dose-dependent manner. Besides, niloticin confirmed the inhibition of NS3-protease by the SensoLyte 440 WNV protease detection kit. These promising results suggest that niloticin could be an effective antiviral drug against DENV2 and other flaviviruses.

7D, a small molecule inhibits dengue infection by increasing interferons and neutralizing-antibodies via CXCL4:CXCR3:p38:IRF3 and Sirt1:STAT3 axes respectively

There are a limited number of effective vaccines against dengue virus (DENV) and significant efforts are being made to develop potent anti-virals. Previously, we described that platelet-chemokine CXCL4 negatively regulates interferon (IFN)-α/β synthesis and promotes DENV2 replication. An antagonist to CXCR3 (CXCL4 receptor) reversed it and inhibited viral replication. In a concurrent search, we identified CXCR3-antagonist from our compound library, namely 7D, which inhibited all serotypes of DENV in vitro. With a half-life of ~2.85 h in plasma and no significant toxicity, 7D supplementation (8 mg/kg-body-weight) to DENV2-infected IFNα/β/γR-/-AG129 or wild-type C57BL6 mice increased synthesis of IFN-α/β and IFN-λ, and rescued disease symptoms like thrombocytopenia, leukopenia and vascular-leakage, with improved survival. 7D, having the property to inhibit Sirt-1 deacetylase, promoted acetylation and phosphorylation of STAT3, which in-turn increased plasmablast proliferation, germinal-center maturation and synthesis of neutralizing-antibodies against DENV2 in mice. A STAT3-inhibitor successfully inhibited these effects of 7D. Together, these observations identify compound 7D as a stimulator of IFN-α/β/λ synthesis via CXCL4:CXCR3:p38:IRF3 signaling, and a booster for neutralizing-antibody generation by promoting STAT3-acetylation in plasmablasts, capable of protecting dengue infection.

Exploring antiviral activity of Betanin and Glycine Betaine against dengue virus type-2 in transfected Hela cells

Dengue virus (DENV) infection is a worldwide public health concern infecting approximately 400 million individuals and about 40,000 mortalities yearly. Despite this, no licensed or readily available antiviral medication is currently available specifically for DENV infection, and therapy is typically symptomatic. Therefore, the objective of the study was to investigate the antiviral activity of Beta vulgaris L. phytoconstituents against DENV-2 targeting NS3 protein. The antiviral activity of phytochemicals was examined through virtual ligand-based screening, antiviral inhibition and dosage response assays, western blotting analysis and MD simulations. We conducted toxicological, and pharmacokinetic analysis to assess plant-based natural compound's efficacy, safety, and non-toxic doses. Molecular docking and MD simulation results revealed that the nonstructural protein-3 (NS3) might prove as a funamental target for Betanin and Glycine Betaine against Dengue virus. Betanin and Glycine betaine were initially studied for their non-toxic doses in HeLa, CHO, and Vero cells via MTT assay. HeLa cells were transiently transfected with cloned vector pcDNA3.1/Zeo(+)/DENV-2 NS3 along with non-toxic doses (80 μM-10 μM) of selected phytochemicals. The dose-response assay illustrated downregulated expression of DENV-2 NS3 gene after administration of Betanin (IC50 = 4.35 μM) and Glycine Betaine (IC50 = 4.49 μM). Dose response analysis of Betanin (80 μM-10 μM) depicted the significant inhibition of NS3 protein expression as well. These results suggested downregulated expression of DENV-2 NS3 at mRNA and protein level portraying the DENV replication inhibition. Based on our study findings, NS3 protease is depicted as distinctive DENV-2 inhibitor target. We will channel our study further into in vitro characterization employing the mechanistic study to understand the role of host factors in anti-flavi therapeutic.

Inhibition of dengue virus infection in vitro by fucoidan and polysaccharide extract from marine alga Sargassum spp

Dengue virus (DENV) infection poses a global health threat, leading to severe conditions with the potential for critical outcomes. Currently, there are no specific drugs available whereas the vaccine does not offer comprehensive protection across all DENV serotypes. Therefore, the development of potential antiviral agents is necessary to reduce the severity risk and interrupt the transmission circuit. The search for effective antiviral agents against DENV has predominantly focused on natural resources, particularly those demonstrating diverse biological activities and high safety profiles. Cyanobacteria and algae including Leptolyngbya sp., Spirulina sp., Chlorella sp., and Sargassum spp., which are prevalent species in Thailand, have been reported for their diverse biological activities and high safety profiles. However, their anti-DENV activity has not been documented. In this study, the screening assay was performed to compare the antiviral activity against DENV of crude polysaccharide and ethanolic extracts derived from 4 species of cyanobacteria and algae in Vero cells. Polysaccharide extracts from Sargassum spp. were the most effective in inhibiting DENV-2 infection under co-infection conditions, where the virus was exposed to the extract at the time of infection. Treatment of the extract significantly reduced the ability of DENV to bind to the host cells to 47.87 ± 3.88 % while treatment upon virus binding step had no antiviral effect suggesting the underlaying mechanism of the extract on interfering virus binding step. Fucoidan, a key bioactive substance in Sargassum polysaccharide, showed to reduce DENV-2 infection to 26.59 ± 5.01 %, 20.46 ± 6.58 % under the co-infection condition in Vero and A549 cells, respectively. In accompanied with Sargassum polysaccharide, fucoidan disturbed the virus binding to the host cells. These findings warrant further development and exploration of the Sargassum-derived polysaccharide, fucoidan, as a promising candidate for combating DENV infections.

Dengue virus: pathogenesis and potential for small molecule inhibitors

Dengue, caused by dengue virus (DENV), is now endemic in nearly 100 countries and infection incidence is reported in another 30 countries. Yearly an estimated 400 million cases and 2200 deaths are reported. Effective vaccines against DENV are limited and there has been significant focus on the development of effective antiviral against the disease. The World Health Organization has initiated research programs to prioritize the development and optimization of antiviral agents against several viruses including Flaviviridae. A significant effort has been taken by the researchers to develop effective antivirals against DENV. Several potential small-molecule inhibitors like efavirenz, tipranavir and dasabuvir have been tested against envelope and non-structural proteins of DENV, and are in clinical trials around the world. We recently developed one small molecule, namely 7D, targeting the host PF4-CXCR3 axis. 7D inhibited all 4 serotypes of DENV in vitro and specifically DENV2 infection in two different mice models. Although the development of dengue vaccines remains a high priority, antibody cross reactivity among the serotypes and resulting antibody-dependent enhancement (ADE) of infection are major concerns that have limited the development of effective vaccine against DENV. Therefore, there has been a significant emphasis on the development of antiviral drugs against dengue. This review article describes the rescue effects of some of the small molecule inhibitors to viral/host factors associated with DENV pathogenesis.

Antiviral Effect of Microalgae Phaeodactylum tricornutum Protein Hydrolysates against Dengue Virus Serotype 2

Dengue, caused by the dengue virus (DENV), is a global health threat transmitted by Aedes mosquitoes, resulting in 400 million cases annually. The disease ranges from mild to severe, with potential progression to hemorrhagic dengue. Current research is focused on natural antivirals due to challenges in vector control. This study evaluates the antiviral potential of peptides derived from the microalgae Phaeodactylum tricornutum, known for its bioactive compounds. Microalgae were cultivated under controlled conditions, followed by protein extraction and hydrolysis to produce four peptide fractions. These fractions were assessed for cytotoxicity via the MTT assay and antiviral activity against DENV serotype 2 using flow cytometry and plaque formation assays. The 10-30 kDa peptide fraction, at 150 and 300 μg/mL concentrations, demonstrated no cytotoxicity and significantly reduced the percentage of infected cells and viral titers. These findings suggest that peptides derived from Phaeodactylum tricornutum exhibit promising antiviral activity against dengue virus serotype 2, potentially contributing to developing new therapeutic approaches for dengue.

Anti-dengue therapeutic potential of Tinospora cordifolia and its bioactives

ETHNOPHARMACOLOGICAL RELEVANCE

Dengue is one of the most prevalent mosquito-borne viral infections. Moreover, due to the absence of appropriate curative and preventive measures against it, the mortality rate is increasing alarmingly. However, remarkable docking and clinical advances have been achieved with plant-based natural and conventional therapeutics. Tinospora cordifolia is one of the highly explored panaceas at the local level for its effective anti-dengue formulations.

AIM OF THE STUDY

The present article aims for critical assessment of the data available on the anti-dengue therapeutic use of T. cordifolia. Efforts have also been made on the clinical and in-silico anti-dengue efficacy of this plant. The phytochemistry and the antiviral machinery of the plant are also emphasized.

MATERIALS AND METHODS

The present article is the outcome of the literature survey on the anti-dengue effect of T. cordifolia. A literature survey was conducted from 2011 to 2024 using different databases with appropriate keywords.

RESULTS

The present study confirms the anti-dengue potential of T. cordifolia. The plant can suppress the initiation of 'cytokine storm', vascular leakage and inhibition of various structural and NS proteins to exert its anti-dengue potential. Berberine and magnoflorine phytocompounds were highly explored for their anti-dengue potential.

CONCLUSIONS

The present study concluded that T. cordifolia serves as an effective therapeutic agent for treating dengue. Further in-silico and clinical studies are needed so that stable, safe and efficacious anti-dengue drug can be developed. Besides, a precise antiviral mechanism of T. cordifolia against DENV infection is still needed.

Dengue Virus dependence on glucokinase activity and glycolysis Confers Sensitivity to NAD(H) biosynthesis inhibitors

Viruses have developed sophisticated strategies to control metabolic activity of infected cells in order to supply replication machinery with energy and metabolites. Dengue virus (DENV), a mosquito-borne flavivirus responsible for dengue fever, is no exception. Previous reports have documented DENV interactions with metabolic pathways and shown in particular that glycolysis is increased in DENV-infected cells. However, underlying molecular mechanisms are still poorly characterized and dependence of DENV on this pathway has not been investigated in details yet. Here, we identified an interaction between the non-structural protein 3 (NS3) of DENV and glucokinase regulator protein (GCKR), a host protein that inhibits the liver-specific hexokinase GCK. NS3 expression was found to increase glucose consumption and lactate secretion in hepatic cell line expressing GCK. Interestingly, we observed that GCKR interaction with GCK decreases DENV replication, indicating the dependence of DENV to GCK activity and supporting the role of NS3 as an inhibitor of GCKR function. Accordingly, in the same cells, DENV replication both induces and depends on glycolysis. By targeting NAD(H) biosynthesis with the antimetabolite 6-Amino-Nicotinamide (6-AN), we decreased cellular glycolytic activity and inhibited DENV replication in hepatic cells. Infection of primary organotypic liver cultures (OLiC) from hamsters was also inhibited by 6-AN. Altogether, our results show that DENV has evolved strategies to control glycolysis in the liver, which could account for hepatic dysfunctions associated to infection. Besides, our findings suggest that lowering intracellular availability of NAD(H) could be a valuable therapeutic strategy to control glycolysis and inhibit DENV replication in the liver.

An in-silico receptor-pharmacophore based multistep molecular docking and simulation study to evaluate the inhibitory potentials against NS1 of DENV-2

DENV-2 strain is the most fatal and infectious of the five dengue virus serotypes. The non-structural protein NS1 encoded by its genome is the most significant protein required for viral pathogenesis and replication inside the host body. Thus, targeting the NS1 protein and designing an inhibitor to limit its stability and secretion is a propitious attempt in our fight against dengue. Four novel inhibitors are designed to target the conserved cysteine residues (C55, C313, C316, and C329) and glycosylation sites (N130 and N207) of the NS1 protein in an attempt to halt the spread of the dengue infection in the host body altogether. Numerous computer-aided drug designing techniques including molecular docking, molecular dynamics simulation, virtual screening, principal component analysis, and dynamic cross-correlation matrix were employed to determine the structural and functional activity of the NS1-inhibitor complexes. From our analysis, it was evident that the extent of structural and atomic level fluctuations of the ligand-bound protein exhibited a declining trend in contrast to unbound protein which was prominently noticeable through the RMSD, RMSF, Rg, and SASA graphs. The ADMET analysis of the four ligands revealed a promising pharmacokinetics and pharmacodynamic profile, along with good bioavailability and toxicity properties. The proposed drugs when bound to the targeted cavities resulted in stable conformations in comparison to their unbound state, implying they have good affinity promising effective drug action. Thus, they can be tested in vitro and used as potential anti-dengue drugs.Communicated by Ramaswamy H. Sarma.

Identification of 3, 4-dihydroxy complexes as potential antiviral via DFT, molecular docking, molecular dynamics and MM/PBSA against rabies and dengue receptors

The quest to identify antiviral drug candidates for dengue and rabies viral diseases is a great challenge for the researchers. While different research is being conducted on the repurposed drugs against these two viruses, no drug compound has gained success in treating them. Therefore, in this study, 3, 4-dihydroxy complexes have been virtually designed to investigate their antiviral properties and analyze their efficiency in interaction with the concerned viral diseases. DFT calculations are carried out to study the electronic and thermodynamic properties to understand the stability and reactivity of the reported compounds. These compounds were subjected to molecular docking studies to understand the binding interactions with NS5 Dengue virus mRNA 2'-O-methyltransferase and phosphoprotein C-terminal domain of Rabies virus. MD simulation, hydrogen bond analysis, and MM/PBSA were performed at 100 ns to support the obtained docking results.Communicated by Ramaswamy H. Sarma.

mRNA-encoded Cas13 can be used to treat dengue infections in mice

Dengue is a major global health threat, and there are no approved antiviral agents. Prior research using Cas13 only demonstrated dengue mitigation in vitro. Here we demonstrate that systemic delivery of mRNA-encoded Cas13a and guide RNAs formulated in lipid nanoparticles can be used to treat dengue virus (DENV) 2 and 3 in mice. First, we identified guides against DENV 2 and 3 that demonstrated in vitro efficacy. Next, we confirmed that Cas13 enzymatic activity is necessary for DENV 2 or DENV 3 mitigation in vitro. Last, we show that a single dose of lipid-nanoparticle-formulated mRNA-encoded Cas13a and guide RNA, administered 1 day post-infection, promotes survival of all infected animals and serum viral titre decreases on days 2 and 3 post-infection after lethal challenge in mice. Off-target analysis in mice using RNA sequencing showed no collateral cleavage. Overall, these data demonstrate the potential of mRNA-encoded Cas13 as a pan-DENV drug.

Tanreqing injection demonstrates anti-dengue activity through the regulation of the NF-κB-ICAM-1/VCAM-1 axis

BACKGROUND

Tanreqing injection (TRQ) has been employed in clinical practice as a treatment for dengue fever (DF). Nevertheless, the precise pharmacological mechanism underlying its efficacy remains elusive.

METHOD

Network pharmacology, molecular docking, transcriptome sequencing, and experimental evaluation were employed to analyze and study the inhibitory potential of TRQ against dengue virus (DENV).

RESULT

We found that TRQ inhibited the replication of DENV in human umbilical vein endothelial cells, Huh-7 cells, and Hep3B cells. In addition, TRQ prolonged the survival duration of AG129 mice infected with DF, decreased the viral load in serum and organs, and alleviated organ damage. Subsequently, ultra-high-performance liquid chromatography-tandem mass spectrometry analysis of TRQ was performed to identify 314 targets associated with 36 active compounds present in TRQ. Integration of multiple databases yielded 47 DF-related genes. Then, 15 hub targets of TRQ in DF were determined by calculating the network topology parameters (Degree). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that these pathways were primarily enriched in the processes of cytokine activation and leukocyte cross-endothelial migration, with significant enrichment of cell adhesion molecules. Molecular docking revealed favorable binding affinity between TRQ's key active compounds and the predicted hub targets. Transcriptome sequencing results showed TRQ's ability to restore the expression of vascular cell adhesion molecule-1 (VCAM-1) post-DENV infection. Finally, TRQ was found to modulate the immune status by regulating the nuclear factor kappa-B (NF-κB)- intercellular cell adhesion molecule-1 (ICAM-1)/VCAM-1 axis, as well as reduce immune cell alterations, inflammatory factor secretion, vascular permeability, and bleeding tendencies induced by DENV infection.

CONCLUSION

Our research suggests that TRQ exerts therapeutic effects on DF by regulating the NF-κB-ICAM-1/VCAM-1 axis.

Pan-serotype dengue virus inhibitor JNJ-A07 targets NS4A-2K-NS4B interaction with NS2B/NS3 and blocks replication organelle formation

Dengue fever represents a significant medical and socio-economic burden in (sub)tropical regions, yet antivirals for treatment or prophylaxis are lacking. JNJ-A07 was described as highly active against the different genotypes within each serotype of the disease-causing dengue virus (DENV). Based on clustering of resistance mutations it has been assumed to target DENV non-structural protein 4B (NS4B). Using a photoaffinity labeling compound with high structural similarity to JNJ-A07, here we demonstrate binding to NS4B and its precursor NS4A-2K-NS4B. Consistently, we report recruitment of the compound to intracellular sites enriched for these proteins. We further specify the mechanism-of-action of JNJ-A07, which has virtually no effect on viral polyprotein cleavage, but targets the interaction between the NS2B/NS3 protease/helicase complex and the NS4A-2K-NS4B cleavage intermediate. This interaction is functionally linked to de novo formation of vesicle packets (VPs), the sites of DENV RNA replication. JNJ-A07 blocks VPs biogenesis with little effect on established ones. A similar mechanism-of-action was found for another NS4B inhibitor, NITD-688. In summary, we unravel the antiviral mechanism of these NS4B-targeting molecules and show how DENV employs a short-lived cleavage intermediate to carry out an early step of the viral life cycle.

In silico homology modeling of dengue virus non-structural 4B (NS4B) protein and its molecular docking studies using triterpenoids

BACKGROUND

Dengue fever has become a significant worldwide health concern, because of its high morbidity rate and the potential for an increase in mortality rates due to lack of adequate treatment. There is an immediate need for the development of effective medication for dengue fever.

METHODS

Homology modeling of dengue virus (DENV) non-structural 4B (NS4B) protein was performed by SWISS-MODEL to predict the 3D structure of the protein. Structure validation was conducted using PROSA, PROCHECK, Ramachandran plot, and VERIFY-3D. MOE software was used to find out the in-Silico inhibitory potential of the five triterpenoids against the DENV-NS4B protein.

RESULTS

The SWISS-MODEL was employed to predict the three-dimensional protein structure of the NS4B protein. Through molecular docking, it was found that the chosen triterpenoid NS4B protein had a high binding affinity interaction. It was observed that the NS4B protein binding energy for 15-oxoursolic acid, betulinic acid, ursolic acid, lupeol, and 3-o-acetylursolic acid were - 7.18, - 7.02, - 5.71, - 6.67 and - 8.00 kcal/mol, respectively.

CONCLUSIONS

NS4B protein could be a promising target which showed good interaction with tested triterpenoids which can be developed as a potential antiviral drug for controlling dengue virus pathogenesis by inhibiting viral replication. However, further investigations are necessary to validate and confirm their efficacy.

In-silico screening and identification of potential drug-like compounds for dengue-associated thrombocytopenia from Carica papaya leaf extracts

Dengue virus is a mosquito-borne pathogen that causes a variety of illnesses ranging from mild fever to severe and fatal dengue haemorrhagic fever or dengue shock syndrome. One of the major clinical manifestations of severe dengue infection is thrombocytopenia. The dengue non-structural protein 1 (NS1) is the primary protein that stimulates immune cells via toll-like receptor 4 (TLR4), induces platelets, and promotes aggregation, which could result in thrombocytopenia. The leaf extracts of Carica papaya seem to have therapeutic benefits in managing thrombocytopenia associated with dengue. The present study focuses on understanding the underlying mechanism of the use of papaya leaf extracts in treating thrombocytopenia. We have identified 124 phytocompounds that are present in the papaya leaf extract. The pharmacokinetics, molecular docking, binding free energy calculations, and molecular dynamic simulations were performed to investigate the drug-like properties, binding affinities, and interaction of phytocompounds with NS1 protein as well as the interactions of NS1 with TLR4. Three phytocompounds were found to bind with the ASN130, a crucial amino acid residue in the active site of the NS1 protein. Thus, we conclude that Rutin, Myricetin 3-rhamnoside, or Kaempferol 3-(2''-rhamnosylrutinoside) may serve as promising molecules by ameliorating thrombocytopenia in dengue-infected patients by interfering the interaction of NS1 with TLR4. These molecules can serve as drugs in the management of dengue-associated thrombocytopenia after verifying their effectiveness and assessing the drug potency, through additional in-vitro assays.Communicated by Ramaswamy H. Sarma.

Synthesis and dengue inhibition potential of new uridine derivatives: The DENV 2 inhibitors

Dengue is an important arboviral infection worldwide for which presently there is no specific medicine. Evidence suggests there are four serotypes of dengue virus (DENV1-4), of which DENV 2 is considered to cause the most sever dengue. Therefore, this study was aimed to develop the new uridine derivatives (NUDs) against dengue virus (DENV 2). In current study 2-(3,4-dihydroxy-5-(hydroxymethyl)-tetrahydrofuran-2-yl)-4-((substituted cyclohexa-2,5-dienylidene)methyl)-1,2,4-triazine-3,5(2H,4H)-dione (2a-f), were obtained via reaction of substituted uridine (1) and different aromatic aldehydes separately. Synthesized NUDs were further characterized using FTIR, 1H & 13C-NMR, mass and element analysis data. Characterized NUDs were assessed for their inhibition potential against DENV 2. Synthesized NUDs were also evaluated for their cytotoxicity towards Vero cells by MTT assay method. This investigation successfully synthesized NUDs 2a-f and reported their high inhibitory activity against DENV 2. The synthesized NUDs exhibited negligible cytotoxicity. High anti-viral activity against DENV 2 serotype and least/no cytotoxicity of NUDs suggests their importance in the treatment of dengue. Present study recommends that in future these NUDs must be investigated for their clinical importance to establish them as a choice for dengue treatment.

Prescribing antibiotics for children with dengue infection in Taiwan: who are at risk and who are high prescribers?

Inappropriate antibiotic use contributes to antimicrobial resistance, a global public health threat. The non-specific manifestations of dengue, itself a growing public health threat, lead to avoidable empiric antibiotic prescription, particularly in children. In this national pooled population-based cross-sectional study, we evaluated child and physician characteristics associated with antibiotics prescription in confirmed dengue cases in Taiwan. Linking national health care insurance claims and reports of confirmed dengue cases from 2008 to 2015, there were 7086 children with confirmed dengue with 21 744 outpatient visits and 2520 inpatient admissions. We assessed the presence of antibiotic prescription in outpatient and inpatient settings separately a week before or after the confirmation date. Logistic regression models with generalized estimating equations were applied to identify patient, practitioner, and other factors associated with antibiotic prescription. A total of 29.4% of children <18 years old with dengue who did not have a concomitant bacterial infection were prescribed antibiotics during the 14-day assessment period. Antibiotics prescription was reduced from 13.5% to 6.3% and from 43.2% to 19.3% in outpatient and inpatient settings, respectively, after dengue was confirmed. Young children were more likely to receive antibiotics. Significant variations in antibiotic prescribing across physicians were observed only in outpatient settings: physicians ≥60 years old and physicians practicing at clinics and in non-urban facilities were more likely to prescribe antibiotics. Antibiotics were less likely to be prescribed during an exceptional 2-year epidemic than in other years. Antibiotic prescribing for dengue, an arboviral infection affecting half of the global population, was shown to occur in 29% of paediatric cases in Taiwan. That potentially avoidable antibiotic consumption could be reduced by improving antibiotic stewardship, informed by understanding the conditions under which antibiotics are prescribed and the availability of prevention strategies for viral diseases, including dengue. We identified a number of such factors in this national population-based study.

Protocol to evaluate the antiviral effect of FDA-approved drugs against dengue virus in Huh7 cells and AG129 mice

Finding an effective therapy against diseases caused by flaviviruses remains a challenge. Here, we present a protocol to test Food and Drug Administration-approved drugs that inhibit host nuclear protein import, promoting a reduction of dengue infection. We describe steps for analyzing the drug effect on nuclear import inhibition of cellular and viral proteins by confocal microscopy or western blotting. We then describe procedures for measuring the antiviral drug effects on virus-infected cells by flow cytometry and testing drug efficacy in dengue-infected AG129 mice by survival assays. For complete details on the use and execution of this protocol, please refer to Palacios-Rápalo et al.1.

Repurposing of therapeutic antibodies against dengue virus envelope protein receptor binding domain

Dengue virus (DENV) is the leading cause of numerous deaths every year due to its high infectivity. In this study we have tried to target the DENV envelope protein receptor binding domain, the region crucial for binding to host receptors which leads to membrane fusion and entry of the viral genome into the human host cell. We have taken 13 known FDA approved antiviral therapeutic antibodies from therapeutic antibody database and tried to repurpose them against the DENV envelope protein. Based on the humanness analysis, 10 antibodies were selected against the DENV envelope protein. Computational affinity maturation of the 10 selected antibodies was performed to increase their binding affinity and specificity against the DENV envelope protein which ultimately led to 8 mutant antibodies having better binding affinity than the native ones. Molecular Dynamics (MD) simulation shows that, the stability of the complexes involving both the native and mutant antibodies were found to be the same although the binding energy between the protein and the respective antibodies was seen to improve upon computational affinity maturation. Contact analyses show similar robustness of the interaction for both the mutant and native antibodies during complex formation with the DENV envelope protein. This has led to the selection of total 18 antibodies including 10 natural and 8 affinity matured mutants which have a high probability of interacting with the DENV envelope protein. Finally, based on all these analyses along with heated MD simulation, Bamlanivimab, Etesivimab and Tixagevimab with a mutation of residue 100 of the heavy chain from serine to tyrosine were selected as prospective therapeutic antibodies to combat DENV infection. This study may open a new avenue in designing therapeutics to combat Dengue viral infection.

Antiviral activity of pimecrolimus against dengue virus type 2 infection in vitro and in vivo

Dengue virus (DENV) infection is a public health concern in several countries and is associated with severe diseases, such as dengue hemorrhagic fever and dengue shock syndrome. DENVs are transmitted to humans via the bites of infected Aedes mosquitoes, and no antiviral therapeutics are currently available. In this work, we aimed to identify antiviral drugs against DENV type 2 (DENV2) infections and selected pimecrolimus as a potential antiviral drug candidate. Pimecrolimus significantly inhibited DENV2-mediated cell death and replication in vitro. We also confirmed a decrease in the number of plaques formed as well as in the envelope protein levels of DENV2. The time-of-addition and course experiments revealed that pimecrolimus inhibited DENV2 infection during the early stages of the virus replication cycle. In an experimental mouse model, orally administered pimecrolimus alleviated body weight loss and lethality caused by DENV2 infection, which we used as readouts of the drug's antiviral potency. Furthermore, pimecrolimus significantly inhibited the DENV2 load and ameliorated focal necrosis in the liver and spleen. Taken together, our in vitro and in vivo findings suggest that pimecrolimus is a promising antiviral drug candidate for the treatment of DENV2 infection.

In silico design of peptide inhibitors for Dengue virus to treat Dengue virus-associated infections

Dengue virus is a single positive-strand RNA virus that is composed of three structural proteins including capsid, envelope, and precursor membrane while seven non-structural proteins (NS1, NS2A, NS2B, NS3A, NS3B, NS4, and NS5). Dengue is a viral infection caused by the dengue virus (DENV). DENV infections are asymptomatic or produce only mild illness. However, DENV can occasionally cause more severe cases and even death. There is no specific treatment for dengue virus infections. Therapeutic peptides have several important advantages over proteins or antibodies: they are small in size, easy to synthesize, and have the ability to penetrate the cell membranes. They also have high activity, specificity, affinity, and less toxicity. Based on the known peptide inhibitor, the current study designs peptide inhibitors for dengue virus envelope protein using an alanine and residue scanning technique. By replacing I21 with Q21, L14 with H14, and V28 with K28, the binding affinity of the peptide inhibitors was increased. The newly designed peptide inhibitors with single residue mutation improved the binding affinity of the peptide inhibitors. The inhibitory capability of the new promising peptide inhibitors was further confirmed by the utilization of MD simulation and free binding energy calculations. The molecular dynamics simulation demonstrated that the newly engineered peptide inhibitors exhibited greater stability compared to the wild-type peptide inhibitors. According to the binding free energies MM(GB)SA of these developed peptides, the first peptide inhibitor was the most effective against the dengue virus envelope protein. All peptide derivatives had higher binding affinities for the envelope protein and have the potential to treat dengue virus-associated infections. In this study, new peptide inhibitors were developed for the dengue virus envelope protein based on the already reported peptide inhibitor.