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.

First-in-human trial evaluating safety and pharmacokinetics of AT-752, a novel nucleotide prodrug with pan-serotype activity against dengue virus

AT-752 is a novel guanosine nucleotide prodrug inhibitor of the dengue virus (DENV) polymerase with sub-micromolar, pan-serotype antiviral activity. This phase 1, double-blind, placebo-controlled, first-in-human study evaluated the safety, tolerability, and pharmacokinetics of ascending single and multiple oral doses of AT-752 in healthy subjects. AT-752 was well tolerated when administered as a single dose up to 1,500 mg or when administered as multiple doses up to 750 mg three times daily (TID). No serious adverse events occurred, and the majority of treatment-emergent adverse events were mild in severity and resolved by the end of the study. In those receiving single ascending doses of AT-752, no pharmacokinetic sensitivity was observed in Asian subjects, and no food effect was observed. Plasma exposure of the guanosine nucleoside metabolite AT-273, the surrogate of the active triphosphate metabolite of the drug, increased with increasing dose levels of AT-752 and exhibited a long half-life of approximately 15-25 h. Administration of AT-752 750 mg TID led to a rapid increase in plasma levels of AT-273 exceeding the target in vitro 90% effective concentration (EC90) of 0.64 µM in inhibiting DENV replication, and maintained this level over the treatment period. The favorable safety and pharmacokinetic results support the evaluation of AT-752 as an antiviral for the treatment of dengue in future clinical studies.Registered at ClinicalTrials.gov (NCT04722627).

Dual action effects of ethyl-p-methoxycinnamate against dengue virus infection and inflammation via NF-κB pathway suppression

Dengue virus (DENV) infection can lead to severe outcomes through a virus-induced cytokine storm, resulting in vascular leakage and inflammation. An effective treatment strategy should target both virus replication and cytokine storm. This study identified Kaempferia galanga L. (KG) extract as exhibiting anti-DENV activity. The major bioactive compound, ethyl-p-methoxycinnamate (EPMC), significantly reduced DENV-2 infection, virion production, and viral protein synthesis in HepG2 and A549 cells, with half-maximal effective concentration (EC50) values of 22.58 µM and 6.17 µM, and impressive selectivity indexes (SIs) of 32.40 and 173.44, respectively. EPMC demonstrated efficacy against all four DENV serotypes, targeting the replication phase of the virus life cycle. Importantly, EPMC reduced DENV-2-induced cytokines (IL-6 and TNF-α) and chemokines (RANTES and IP-10), as confirmed by immunofluorescence and immunoblot analyses, indicating inhibition of NF-κB activation. EPMC's role in preventing excessive inflammatory responses suggests it as a potential candidate for dengue treatment. Absorption, distribution, metabolism, excretion, and toxicity (ADMET) and drug-likeness for EPMC were predicted using SwissADME and ProTox II servers, showing good drug-like properties without toxicity. These findings highlight KG extract and EPMC as promising candidates for future anti-dengue therapeutics, offering a dual-action approach by inhibiting virus replication and mitigating inflammatory reactions.

The Inhibition of NS2B/NS3 Protease: A New Therapeutic Opportunity to Treat Dengue and Zika Virus Infection

In the global pandemic scenario, dengue and zika viruses (DENV and ZIKV, respectively), both mosquito-borne members of the flaviviridae family, represent a serious health problem, and considering the absence of specific antiviral drugs and available vaccines, there is a dire need to identify new targets to treat these types of viral infections. Within this drug discovery process, the protease NS2B/NS3 is considered the primary target for the development of novel anti-flavivirus drugs. The NS2B/NS3 is a serine protease that has a dual function both in the viral replication process and in the elusion of the innate immunity. To date, two main classes of NS2B/NS3 of DENV and ZIKV protease inhibitors have been discovered: those that bind to the orthosteric site and those that act at the allosteric site. Therefore, this perspective article aims to discuss the main features of the use of the most potent NS2B/NS3 inhibitors and their impact at the social level.

Exploring the therapeutic potential of DV-B-120 as an inhibitor of dengue virus infection

Dengue fever, an infectious disease prevalent in subtropical and tropical regions, currently lacks effective small-molecule drugs as treatment. In this study, we used a fluorescence peptide cleavage assay to screen seven compounds to assess their inhibition of the dengue virus (DENV) NS2B-NS3 protease. DV-B-120 demonstrated superior inhibition of NS2B-NS3 protease activity and lower toxicity compared to ARDP0006. The selectivity index of DV-B-120 was higher than that of ARDP0006. In vivo assessments of the antiviral efficacy of DV-B-120 against DENV replication demonstrated delayed mortality of suckling mice treated with the compound, with 60-80% protection against life-threatening effects, compared to the outcomes of DENV-infected mice treated with saline. The lower clinical scores of DENV-infected mice treated with DV-B-120 indicated a reduction in acute-progressive illness symptoms, underscoring the potential therapeutic impact of DV-B-120. Investigations of DV-B-120's ability to restore the antiviral type I IFN response in the brain tissue of DENV-infected ICR suckling mice demonstrated its capacity to stimulate IFN and antiviral IFN-stimulated gene expression. DV-B-120 not only significantly delayed DENV-2-induced mortality and illness symptoms but also reduced viral numbers in the brain, ultimately restoring the innate antiviral response. These findings strongly suggest that DV-B-120 holds promise as a therapeutic agent against DENV infection and highlight its potential contribution in addressing the current lack of effective treatments for this infectious disease.IMPORTANCEThe prevalence of dengue virus (DENV) infection in tropical and subtropical regions is escalating due to factors like climate change and mosquito vector expansion. With over 300 million annual infections and potentially fatal outcomes, the urgent need for effective treatments is evident. While the approved Dengvaxia vaccine has variable efficacy, there are currently no antiviral drugs for DENV. This study explores seven compounds targeting the NS2B-NS3 protease, a crucial protein in DENV replication. These compounds exhibit inhibitory effects on DENV-2 NS2B-NS3, holding promise for disrupting viral replication and preventing severe manifestations. However, further research, including animal testing, is imperative to assess therapeutic efficacy and potential toxicity. Developing safe and potent treatments for DENV infection is critical in addressing the rising global health threat posed by this virus.

A Comprehensive Study to Unleash the Putative Inhibitors of Serotype2 of Dengue Virus: Insights from an In Silico Structure-Based Drug Discovery

Dengue fever is a mosquito-borne disease that claims the lives of millions of people around the world. A number of factors like disease's non-specific symptoms, increased viral mutation, growing antiviral drug resistance due to reduced susceptibility, unavailability of an effective vaccine for dengue, weak immunity against the virus, and many more are involved. Dengue belongs to the Flaviviridae family of viruses. The two species of the vector transmitting dengue are Aedes aegypti and Aedes albopictus, with the former one being dominant. Serotypes 2 of dengue fever are spread to the human body and cause severe illness. Recently, dengue has imposed an aggressive effect synergistically with the COVID-19 pandemic. As a result, we concentrated our efforts on finding a potential therapeutic. For this, we chose natural compounds to fight dengue fever, which is currently regarded as successful among many drug therapies. Following this, we started the in silico experiment with 922 plant extracts as lead compounds to fight serotype 2. In this study, we used SwissADME for analyzing ligand drug-likeness, pkCSM for designing an ADMET profile, Autodock vina 4.2 and Swissdock tools for molecular docking, and finally Desmond for molecular dynamics simulation. Ultimately 45 were found effective against the 2'O methyltransferase protein of serotype 2. CHEMBL376820 was found as possible therapeutic candidates for inhibiting methyltransferase protein in this thorough analysis. Nevertheless, more in vitro and in vivo research are required to substantiate their potential therapeutic efficacy.

Identification of natural antimicrobial peptides mimetic to inhibit Ca2+ influx DDX3X activity for blocking dengue viral infectivity

Viruses are microscopic biological entities that can quickly invade and multiply in a living organism. Each year, over 36,000 people die and nearly 400 million are infected with the dengue virus (DENV). Despite dengue being an endemic disease, no targeted and effective antiviral peptide resource is available against the dengue species. Antiviral peptides (AVPs) have shown tremendous ability to fight against different viruses. Accelerating antiviral drug discovery is crucial, particularly for RNA viruses. DDX3X, a vital cell component, supports viral translation and interacts with TRPV4, regulating viral RNA metabolism and infectivity. Its diverse signaling pathway makes it a potential therapeutic target. Our study focuses on inhibiting viral RNA translation by blocking the activity of the target gene and the TRPV4-mediated Ca2+ cation channel. Six major proteins from camel milk were first extracted and split with the enzyme pepsin. The antiviral properties were then analyzed using online bioinformatics programs, including AVPpred, Meta-iAVP, AMPfun, and ENNAVIA. The stability of the complex was assessed using MD simulation, MM/GBSA, and principal component analysis. Cytotoxicity evaluations were conducted using COPid and ToxinPred. The top ten AVPs, determined by optimal scores, were selected and saved for docking studies with the GalaxyPepDock tools. Bioinformatics analyses revealed that the peptides had very short hydrogen bond distances (1.8 to 3.6 Å) near the active site of the target protein. Approximately 76% of the peptide residues were 5-11 amino acids long. Additionally, the identified peptide candidates exhibited desirable properties for potential therapeutic agents, including a net positive charge, moderate toxicity, hydrophilicity, and selectivity. In conclusion, this computational study provides promising insights for discovering peptide-based therapeutic agents against DENV.

Carbazole to indolazepinone scaffold morphing leads to potent cell-active dengue antivirals

According to WHO, dengue virus is classed among major threats for future pandemics and remains at large an unmet medical need as there are currently no relevant antiviral drugs whereas vaccine developments have met with safety concerns, mostly due to secondary infections caused by antibody-dependant-enhancement in cross infections among the four dengue serotypes. This adds extra complexity in dengue antiviral research and has impeded the progress in this field. Following through our previous effort which born the allosteric, dual-mode inhibitor SP-471P (a carbazole derivative, EC50 1.1 μM, CC50 100 μM) we performed further optimisation while preserving the two arylamidoxime arms and the bromoaryl domain present in SP-471P. Examination of the relative positions of these functionalities within this three-point pharmacophore ultimately led us to an indolazepinone scaffold and our lead compound SP-1769B. SP-1769B is among the most cell-efficacious against all serotypes (DENV2/3 EC50 100 nM, DENV1/4 EC50 0.95-1.25 μM) and safest (CC50 > 100 μM) anti-dengue compounds in the literature that also completely inhibits a secondary ADE-driven infection.

Potential of several triazene derivatives against DENGUE viruses

Dengue fever is an infectious disease caused by the dengue virus (DENV), an RNA Flavivirus transmitted by the mosquitoes Aedes aegypti and Aedes albopictus widespread in tropical, subtropical and also temperate regions. Symptoms range from a simple cold to a severe, life-threatening haemorrhagic fever. According to the WHO, it affects around 390 million people per year. No antiviral treatment for DENV is available, and the Dengvaxia vaccine is only intended for people over 9 years of age who have contracted dengue one time in the past, and shows serotype-specific effectiveness. There is therefore a crying need to discover new molecules with antiviral power against flaviviruses. The present study was carried out to evaluate the anti-DENV activities and cytotoxicity of triazenes obtained by diazocopulation. Some triazenes were highly cytotoxic (16, and 25) to hepatocarcinoma Huh7 cells, whereas others displayed strong anti-DENV potential. The antiviral activity ranged from EC50 = 7.82 µM to 48.12 µM in cellulo, with a selectivity index (CC50/EC50) greater than 9 for two of the compounds (10, and 20). In conclusion, these new triazenes could serve as a lead to develop and optimize drugs against DENV.

Serum Stabilities and Antiviral Activities of Chemically Modified Peptides Against Dengue Serotypes 1-4

Dengue presents a major public health concern in over 100 countries due to the absence of an effective vaccine and antiviral therapy against all four dengue virus (DENV) serotypes. Several antiviral peptides were previously reported to inhibit at least three or all four DENV serotypes. Chemical modifications such as d-amino acid substitutions, polyethylene glycol (PEG)ylation, and cyclization could be applied to peptides to improve their biological activities and stability in serum. The PEGylated peptide 3 (PEG-P3) was identified to be the most promising antiviral candidate as it demonstrated good inhibitory effects against all four DENV serotypes during the pre- and post-infection stages, Based on the RP-HPLC and LC/MS analysis, peptide 4 was identified to be more stable in human serum than peptide 3, with 78.9 % and 41.6 % of the peptides remaining after 72 h of incubation in human serum, respectively. Both peptides were also able to retain their antiviral activities against specific DENV serotypes after 72 h incubation in human serum. PEG-P3 was found to be more stable than the unmodified peptide 3 with 89.4 % of PEG-P3 remaining in the human serum after 72 h of incubation. PEG-P3 was able to retain its inhibitory effects against DENV-1 to 4 after 72 h of incubation in human serum. This study provided insights into the antiviral activities and stabilities of the unmodified and chemically modified peptides in human serum.

Inhibition of cellular activation induced by platelet factor 4 via the CXCR3 pathway ameliorates Japanese encephalitis and dengue viral infections

BACKGROUND

Activated platelets secrete platelet factor 4 (PF4), which contributes to viral pathogenesis. Recently, we reported the proviral role of PF4 in replication of closely related flaviviruses, Japanese encephalitis virus (JEV) and dengue virus (DENV).

OBJECTIVES

This study aimed to investigate the detailed mechanism of PF4-mediated virus replication.

METHODS

PF4-/- or wild-type (WT) mice were infected with JEV, and host defense mechanisms, including autophagic/interferon (IFN) responses, were assessed. WT mice were pretreated with the CXCR3 antagonist AMG487 that inhibits PF4:CXCR3 pathway. This pathway was tested in PF4-/- monocytes infected with DENV or in monocytes isolated from patients with DENV infection.

RESULTS

PF4-/- mice infected with JEV showed reduced viral load and improved brain inflammation and survival. PF4-/- mice synthesized more IFN-α/β with higher expression of phosphorylated IRF3 in the brain. PF4 treatment decreased IRF-3/7/9 and IFN-α/β expression and suppressed autophagic LC3-II flux and lysosomal degradation of viral proteins in JEV-infected cells. PF4 increased the expression of P-mTOR, P-p38, and P-ULK1Ser757 and decreased expression of LC3-II. Decreased autophagosome-lysosome fusion in turn promoted DENV2 replication. The above processes were reversed by AMG487. Uninfected PF4-/- monocytes showed elevated LC3-II and autophagosome-lysosome fusion. Microglia of JEV-infected PF4-/- mice exhibited elevated LC3-II inversely related to viral load. Similarly, monocytes from PF4-/- mice showed reduced infection by DENV2. In patients with DENV infection, higher plasma PF4 and viral load were inversely correlated with LC3-II, LAMP-1, and lysosomal degradation of DENV-NS1 in monocytes during the febrile phase.

CONCLUSION

These studies suggest that PF4 deficiency or inhibition of the PF4:CXCR3 pathway prevents JEV and DENV infection. The studies also highlight the PF4:CXCR3 axis as a potential target to develop treatment regimens against flaviviruses.

Role of granulocyte colony stimulating factor (G-CSF) in dengue patients with severe thrombocytopenia

OBJECTIVE

To determine the effects of granulocyte colony-stimulating factor in improving platelet count in patients with dengue fever.

METHODS

The retrospective, cross-sectional study was conducted at Northwest General Hospital and Research Centre, Peshawar, Pakistan, between January 2021 and October 2022, and comprised dengue fever inpatients regardless of age and gender who received granulocyte colony-stimulating factor subcutaneously. The impact of colony-stimulating factor on platelet and white blood cell counts as well as any unfavourable consequences was assessed. Convenient sampling was used and a structured format was used for data collection. Data was analysed using SPSS 21.

RESULTS

Of the 100 patients, 67(67%) were males and 33(33%) were females. The largest age group was that of >55 years 31(31%), fever was present in all the 100(100%) cases, bleeding in 18(18%) and platelet count <30,000 in 83(83%) cases. Dengue fever was confirmed by rapid dengue nonstructural protein 1 antigen in 76(76%) cases, dengue immunoglobulin G antibody test 28(28%), and immunoglobulin M antibody test in 31(31%) cases. Overall, 72(72%) patients received only one dose of granulocyte colony-stimulating factor. Post-administration, a substantial rise in the median platelet and white blood cell counts was seen compared to the baseline (p<0.05) on day 2.

CONCLUSIONS

Granulocyte colony-stimulating factor helped increase platelet and white blood cell counts quickly in dengue fever patients.

Investigating Lycotoxin-An1a (An1a), a defense antiviral peptide from Alopecosa nagpag venom as prospective anti-dengue agent against DENV-2 NS2B-NS3 protease

Dengue fever is a global health concern with no effective therapy. Screening synthetic chemicals, animal-originated compounds, and phytocompounds against Dengue virus (DENV) targets has failed to find dengue antivirals. The current study examines animal drugs as antagonists against NS2B-NS3Pro, one of DENV's most promising therapeutic targets for dengue fever. Antiviral-Lycotoxin-An1a (An1a), a defence antiviral peptide isolated from the venom of Alopecosa nagpag, a toxic spider. Based on prior in vitro research, it was discovered that the venom peptide suppresses the action of DENV-2 NS2B-NS3Pro. An1a peptide with NS2B-NS3Pro wild type (WT) and two mutants (H51N and S135A) was tested for anti-dengue characteristics using in silico analysis. The WT NS2B-NS3Pro has a catalytic triad of His51, Asp75, and Ser135 in the active site, but the mutants have N51 instead of His51 and Ala135 instead of Ser135. The dynamic sites of the three proteases (WT, H51N, S135A) and the peptide toxin (An1a) were taken into account to achieve molecular docking of An1a with WT NS2B-NS3Pro in conjunction with H51N and S135A. Cluspro-2 performs rigid-flexible docking to predict peptide binding affinity, effectiveness, and inhibitory consistency. Since the ligand had a higher binding affinity, docking score, and molecular interaction network, MD simulations and MM-GBSA free energy calculations were used to investigate the stability of the three protein-peptide complexes. The computer-aided screening and manufacture of spider venom-based anti-dengue medicines yielded intriguing results in the preliminary studies. This study is significant in defining the ideal therapeutic candidate against dengue infections.

Suppression of dengue virus replication by the French maritime pine extract Pycnogenol®

Dengue virus (DENV) is mainly found in the tropics and infects approximately 400 million people annually. However, no clinically available therapeutic agents specific to dengue have been developed. Here, we examined the potential antiviral effects of the French maritime pine extract Pycnogenol® (PYC) against DENV because we previously found that the extract exerts antiviral effects on hepatitis C virus, which belongs to the Flavivirus family. First, we examined the efficacy of PYC against DENV1, 2, 3, and 4 serotypes and determined that it had a dose-dependent suppressive effect on the viral load, especially in the supernatant. This inhibitory effect of PYC may target the late stages of infection such as maturation and secretion, but not replication. Next, we examined the efficacy of PYC against DENV infection in type I interferon (IFN) receptor knockout mice (A129). As the propagation of DENV2 was the highest among the four serotypes, we used this serotype in our murine model experiments. We found that PYC significantly inhibited DENV2 replication in mice on day 4 without significantly decreasing body weight or survival ratio. We further examined the mechanism of action of PYC in DENV2 infection by characterizing the main PYC targets among the host (viral) factors and silencing them using siRNA. Silencing long noncoding-interferon-induced protein (lnc-IFI)-44, polycystic kidney disease 1-like 3 (Pkd1l3), and ubiquitin-specific peptidase 31 (Usp31) inhibited the replication of DENV2. Thus, the results of this study shed light on the inhibitory effects of PYC on DENV replication and its underlying mechanisms.

A Case Report of Cefixime, Paracetamol, and Nimesulide Induced Toxic Epidermal Necrolysis in a Woman with Dengue Infection without any Other Associated Comorbidities

BACKGROUND

Toxic Epidermal Necrolysis (TEN) is a rare, acute, and life-threatening mucocutaneous disease that occurs after the administration of certain drugs, resulting in extensive keratinocyte cell death, skin involvement at the dermal-epidermal junction, and extensive bullous skin eruptions and sloughing. Many published case reports have observed the presence of fever with a viral infection, drug, and/or genetic association as a possible trigger for TEN but associated with other comorbidities. Physicians still struggle to predict which individuals could be predisposed to TEN. The case report that we present had a history of multiple drug intake and fever due to dengue virus infection but was not associated with any other comorbidity.

CASE PRESENTATION

We present an unusual case of a 32-year-old woman of Western Indian origin who had developed dengue infection and suffered toxic epidermal necrolysis following a five-day course of a third-generation cephalosporin antibiotic, cefixime and a three-day course of 2 analgesic drugs, paracetamol (acetaminophen), and nimesulide, with the adverse event occurring on the fifth day of the dengue infection. The offending drugs were stopped, and patient survived with supportive management and hydration.

CONCLUSION

The presence of comorbidities may not always be the triggering factor for TEN, though it can affect patient outcomes. Rational drug use is always recommended for patient care. Further research is required to understand the pathomechanism behind the viral-drug-gene interaction.

Rapid diagnostic tests for dengue would reduce hospitalizations, healthcare costs and antibiotic prescriptions in Spain: A cost-effectiveness analysis

BACKGROUND

Current gold standard diagnostic techniques for dengue are expensive and time-consuming. Rapid diagnostic tests (RDTs) have been proposed as alternatives, although data about their potential impact in non-endemic areas is scarce.

METHODS

We performed a cost-effectiveness analysis comparing the costs of dengue RDTs to the current standard of care for the management of febrile returning travelers in Spain. Effectiveness was measured in terms of potential averted hospital admissions and reduction of empirical antibiotics, based on 2015-2020 dengue admissions at Hospital Clinic Barcelona (Spain).

RESULTS

Dengue RDTs were associated with 53.6% (95% CI: 33.9-72.5) reduction of hospital admissions and were estimated to save 289.08-389.31€ per traveler tested. Moreover, RDTs would have avoided the use of antibiotics in 46.4% (95% CI: 27.5-66.1) of dengue patients.

DISCUSSION

Implementation of dengue RDTs for the management of febrile travelers is a cost-saving strategy that would lead to a reduction of half of dengue admissions and a reduction of inappropriate antibiotics in Spain.

Molecular mechanism of ChaiShi JieDu granule in treating dengue based on network pharmacology and molecular docking: A review

Dengue fever is a frequently occurring infectious disease caused by the Dengue virus, prevalent in tropical and subtropical regions. Chaishi Jiedu Granules (CSJD) is an empirical prescription of the Eighth Affiliated Hospital of Guangzhou Medical University in the treatment of dengue fever, which has been widely used in the treatment of dengue fever, and has shown good efficacy in improving the clinical symptoms of patients. This study aims to explore the molecular mechanism of CSJD in treating dengue fever using network pharmacology, molecular docking techniques, and virtual screening methods. The results showed that luteolin, quercetin and other compounds in CSJD could target important targets related to dengue virus, including STAT3, AKT1, TNF, IL-6, and other key genes, thus playing an antiviral role. Among them, luteolin and wogonin in CSJD also inhibited dengue virus replication and reduced inflammation, and showed good binding force with IL-6 and TNF. Therefore, this study provides an important reference for the development of CSJD as a potential drug for dengue fever treatment and a new perspective for research and development in this field.

Synthesis of novel rhodamine type Anthrone Spiro-lactam (ASL) analogues and evaluation of antiviral activity against dengue and chikungunya viruses

A series of Rhodamine type Anthrone-Spirolactam (ASL) derivatives Benzylimin-Anthrone-Spirolactam (ASL-1 to ASL-10) and Benzamide-Anthrone-Spirolactam (ASL-11 and ASL-12) were synthesized via a simple condensation reaction between Anthrone Spiro-lactamine (2) and various aromatic aldehyde and acyl chlorides respectively. Since rhodamine-based compounds were reported to have antiviral activity, the ASL derivatives were examined for in vitro antiviral activity against dengue and chikungunya viruses. Among all the analogues, ASL-3, ASL-6, ASL-7, ASL-8, ASL-9 and ASL-10 were the most potent against dengue virus (DENV) and exerted around one log reduction in virus titre under post-treatment conditions. At the same time ASL-3 was effective under co-treatment conditions. Two analogues ASL-6 and ASL-12 exerted anti-chikungunya virus (CHIKV) activity under post-treatment conditions. In silico docking studies revealed that the ASL derivatives interacted with the proteins of DENV and CHIKV. Together, the results suggest the anti-DENV and CHIKV activity of ASL derivatives which may be exploited further for therapeutic purposes.

Virucidal activity of trehalose 6-monolaurate against dengue virus in vitro

Dengue fever is an acute febrile disease caused by dengue virus (DENV) infection. Over the past 60 years, DENV has spread throughout tropical regions and currently affects more than 50% of the world's population; however, there are as of yet no effective anti-DENV drugs for clinical treatment. A number of research teams have investigated derivatives of glycolipids as possible agents for the inhibition of DENV. Our objective in this research was to study the antiviral effects of trehalose 6-caprate (TMC), trehalose 6-monolaurate (TML), and trehalose 6-monooleate (TMO), based on reports that the corresponding glycosyl, trehalose, reduces the transmission of Zika virus (ZIKV). We also sought to elucidate the molecular mechanisms underlying inhibition using the RNA isolation and reverse transcription-quantitative polymerase chain reaction, western blot analysis, median tissue culture infectious dose (TCID50 ) assay, and immunofluorescence assay and immunochemistry staining, in vitro. This is the first study to demonstrate the TML-induced inhibition of DENV serotype 2 (DENV-2) in a dose-dependent manner. The inhibitory effects of TML in the pretreated, cotreated, and full-treated groups were confirmed using time of addition assays. We determined that TML restricted viral binding, entry, replication, and release. We also confirmed the efficacy of TML against three clinical isolates of DENV serotypes 1, 3, and 4 (DENV-1, DENV-3, and DENV-4). The findings obtained in this study identify TML as a promising candidate for the development of drugs to treat DENV infection.

Modelling the impact of JNJ-1802, a first-in-class dengue inhibitor blocking the NS3-NS4B interaction, on in-vitro DENV-2 dynamics

Dengue virus (DENV) is a public health challenge across the tropics and subtropics. Currently, there is no licensed prophylactic or antiviral treatment for dengue. The novel DENV inhibitor JNJ-1802 can significantly reduce viral load in mice and non-human primates. Here, using a mechanistic viral kinetic model calibrated against viral RNA data from experimental in-vitro infection studies, we assess the in-vitro inhibitory effect of JNJ-1802 by characterising infection dynamics of two DENV-2 strains in the absence and presence of different JNJ-1802 concentrations. Viral RNA suppression to below the limit of detection was achieved at concentrations of >1.6 nM, with a median concentration exhibiting 50% of maximal inhibitory effect (IC50) of 1.23x10-02 nM and 1.28x10-02 nM for the DENV-2/RL and DENV-2/16681 strains, respectively. This work provides important insight into the in-vitro inhibitory effect of JNJ-1802 and presents a first step towards a modelling framework to support characterization of viral kinetics and drug effect across different host systems.

Expanding the synthesis of a library of potent glucuronic acid glycodendrons for Dengue virus inhibition

Multivalent glycodendrons are valuable tools to mimic many structural and functional features of cell-surface glycoconjugates and its focal position scaffolds represent important components to increase specificity and affinity. Previous work in our group described the preparation of a tetravalent glucuronic acid dendron that binds with good affinity to Dengue virus envelope protein (KD = 22 μM). Herein, the chemical synthesis and binding analysis of a new library of potent glucuronic acid dendrons bearing different functional group at the focal position and different level of multivalency are described. Their chemical synthesis was performed sequentially in three stages and with good yields. Namely a) the chemical synthesis of the oligo and polyalkynyl scaffolds, b) assembling with fully protected glucuronic acid-based azide units by using a microwave assisted copper-catalysed azide-alkyne cycloaddition reaction and c) sequential deprotection of hydroxyl and carboxylic acid groups. Surface Plasmon Resonance studies have demonstrated that the valency and the focal position functional group exert influence on the interaction with Dengue virus envelope protein. Molecular modelling studies were carried out in order to understand the binding observed. This work reports an efficient glycodendrons chemical synthesis that provides appropriate focal position functional group and multivalence, that offer an easy and versatile strategy to find new active compounds against Dengue virus.

A sulfonamide chalcone inhibited dengue virus with a potential target at the SAM-binding site of viral methyltransferase

Dengue infection is a global health problem as climate change facilitates the spread of mosquito vectors. Infected patients could progress to severe plasma leakage and hemorrhagic shock, where current standard treatment remains supportive. Previous reports suggested that several flavonoid derivatives inhibited mosquito-borne flaviviruses. This work aimed to explore sulfonamide chalcone derivatives as dengue inhibitors and to identify molecular targets. We initially screened 27 sulfonamide chalcones using cell-based antiviral and cytotoxic screenings. Two potential compounds, SC22 and SC27, were identified with DENV1-4 EC50s in the range of 0.71-0.94 and 3.15-4.46 μM, and CC50s at 14.63 and 31.02 μM, respectively. The compounds did not show any elevation in ALT or Cr in C57BL/6 mice on the 1st, 3rd, and 7th days after being administered intraperitoneally with 50 mg/kg SC22 or SC27 in a single dose. Moreover, the SAM-binding site of NS5 methyltransferase was a potential target of SC27 identified by computational and enzyme-based assays. The main target of SC22 was in a late stage of viral replication, but the exact target molecule had yet to be identified. In summary, a sulfonamide chalcone, SC27, was a potential DENV inhibitor that targeted viral methyltransferase. Further investigation should be the study of the structure-activity relationship of SC27 derivatives for higher potency and lower toxicity.

Expanding the anti-flaviviral arsenal: Discovery of a baicalein-derived Compound with potent activity against DENV and ZIKV

With approximately 3.8 billion people at risk of infection in tropical and sub-tropical regions, Dengue ranks among the top ten threats worldwide. Despite the potential for severe disease manifestation and the economic burden it places on endemic countries, there is a lack of approved antiviral agents to effectively treat the infection. Flavonoids, including baicalein, have garnered attention for their antimicrobial properties. In this study, we took a rational and iterative approach to develop a series of baicalein derivatives with improved antiviral activity against Dengue virus (DENV). Compound 11064 emerged as a promising lead candidate, exhibiting antiviral activity against the four DENV serotypes and representative strains of Zika virus (ZIKV) in vitro, with attractive selectivity indices. Mechanistic studies revealed that Compound 11064 did not prevent DENV attachment at the cell surface, nor viral RNA synthesis and viral protein translation. Instead, the drug was found to impair the post-receptor binding entry steps (endocytosis and/or uncoating), as well as the late stage of DENV infection cycle, including virus assembly/maturation and/or exocytosis. The inability to raise DENV resistant mutants, combined with significant antiviral activity against an unrelated RNA virus (Enterovirus-A71) suggested that Compound 11064 targets the host rather than a viral protein, further supporting its broad-spectrum antiviral potential. Overall, Compound 11064 represents a promising antiviral candidate for the treatment of Dengue and Zika.

Role of N-acetylcysteine in liver injury due to dengue fever

Dengue fever (DF) is a common mosquito-borne viral infection which is endemic in Southeast Asia. Liver involvement may vary from asymptomatic elevation of liver enzymes to fulminant hepatitis. Although the valuable effects of N-acetylcysteine (NAC) in paracetamol toxicity and non-paracetamol liver failure have been extensively studied, its use in DF-associated hepatitis remains unclear. We made a literature search in an online format from libraries such as PubMed, Google Scholar, and EMBASE, and selected 33 articles including original research articles, case reports, and systemic analyses. The majority of the articles reviewed had a positive outcome but treatment strategies involved NAC together with supportive care. Hence, data on sole use of NAC from large randomised control trials remain unclear.

Liang-Ge-San inhibits dengue virus serotype 2 infection by reducing caveolin1-induced cytoplasmic heat shock protein 70 translocation into the plasma membrane

BACKGROUND

Dengue virus (DENV) is a major public health threat. However, there are no specific therapeutic drugs for DENV. Many Chinese heat-cleaning formulas, such as Liang-Ge-San (LGS), have been frequently used in the virus-induced diseases. The antiviral effect of LGS has not been reported yet.

PURPOSE

In this study, the effect of LGS on the inhibition of dengue virus serotype 2 (DENV-2) was investigated and the relevant mechanism was explored.

METHODS

High-performance liquid chromatography was applied to analyze the chemical characterization of LGS. The in vitro antiviral activities of LGS against DENV-2 were evaluated by time-of-drug-addition assay. The binding of heat shock protein 70 (Hsp70) and envelope (E) protein or caveolin1 (Cav1) were analyzed by immunofluorescence and immunoprecipitation assays. Then the role of Cav1 in the anti-DENV-2 effects of LGS was further examined. DENV-2 infected Institute of Cancer Research suckling mice (n = 10) and AG129 mice (n = 8) were used to examine the protective effects of LGS.

RESULTS

It was found that geniposide, liquiritin, forsythenside A, forsythin, baicalin, baicalein, rhein, and emodin maybe the characteristic components of LGS. LGS inhibited the early stage of DENV-2 infection, decreased the expression levels of viral E and non-structural protein 1 (NS1) proteins. LGS also reduced E protein and Hsp70 binding and attenuated the translocation of Hsp70 from cytoplasm to the cell membrane. Moreover, LGS decreased the binding of Hsp70 to Cav1. Further study showed that the overexpression of Cav1 reversed LGS-mediated E protein and Hsp70 inhibition in the plasma membrane. In the in vivo study, LGS was highly effective in prolonging the survival time, reducing viral loads.

CONCLUSION

This work demonstrates for the first time that LGS exerts anti-DENV-2 activity in vitro and in vivo. LGS decreases DENV-2-stimulated cytoplasmic Hsp70 translocation into the plasma membrane by Cav1 inhibition, thereby inhibiting the early stage of virus infection. These findings indicate that LGS may be a candidate for the treatment of DENV.

Safety, Tolerability, and Pharmacokinetics of JNJ-1802, a Pan-serotype Dengue Direct Antiviral Small Molecule, in a Phase 1, Double-Blind, Randomized, Dose-Escalation Study in Healthy Volunteers

BACKGROUND

Dengue is a growing global health threat with no specific antiviral drugs available for treatment or prophylaxis. This first-in-human, double-blind, randomized, placebo-controlled study aimed to examine the safety, tolerability, and pharmacokinetics of increasing single and multiple oral doses of JNJ-1802, a pan-serotype dengue antiviral small molecule.

METHODS

Eligible healthy participants (18-55 years of age) were randomized to receive oral JNJ-1802 in fasted conditions as (1) single doses (50-1200 mg; n = 29) or placebo (n = 10); or (2) once-daily doses (50-560 mg for 10 consecutive days or 400 mg for 31 days; n = 38) or placebo (n = 9). Safety and tolerability were evaluated throughout the study. Plasma and urine samples were collected at predetermined time points to characterize pharmacokinetics.

RESULTS

JNJ-1802 was generally safe and well-tolerated. One grade 3 adverse event (depression) was reported but not considered drug-related by the investigator. Two grade 2 events of rash occurred (multiple-dose part) that were considered very likely related to JNJ-1802 by the investigator and resolved. No clinically relevant changes were observed in laboratory tests, electrocardiograms, or vital signs.JNJ-1802 exposure after single or multiple doses increased dose-proportionally from 50 to 150 mg and less than dose-proportionally for higher doses. The terminal elimination half-life was 6.3-9.2 days and the accumulation factor was 4.3-7.3 after 10 days and 14.6 after 31 days with low amounts of unchanged drug in urine (<0.001% of the 400 mg dose).

CONCLUSIONS

Pharmacokinetics and safety results of JNJ-1802 support further clinical development for the treatment and prevention of dengue infection.

Nanomedicine as a potential novel therapeutic approach against the dengue virus

Dengue is an arbovirus infection which is transmitted by Aedes mosquitoes. Its prompt detection and effective treatment is a global health challenge. Various nanoparticle-based vaccines have been formulated to present immunogen (antigens) to instigate an immune response or prevent virus spread, but no specific treatment has been devised. This review explores the role of nanomedicine-based therapeutic agents against dengue virus, taking into consideration the applicable dengue virus assays that are sensitive, specific, have a short turnaround time and are inexpensive. Various kinds of metallic, polymeric and lipid nanoparticles with safe and effective profiles present an alternative strategy that could provide a better remedy for eradicating the dengue virus.

Quinazolinone Compounds Have Potent Antiviral Activity against Zika and Dengue Virus

Dengue (DENV) and Zika (ZIKV) viruses are important human pathogens, causing ∼100 million symptomatic infections each year. These infections carry a 20-fold increased incidence of serious neurological diseases, such as microcephaly in newborns (for ZIKV) and Guillain-Barré syndrome. Moreover, DENV can develop serious and possibly life-threatening dengue hemorrhagic fever in certain patients. Patients recovered from one of the four serotypes of DENV are still susceptible to other serotypes with a higher likelihood of serious disease because of antibody-dependent enhancement. Except for mosquito control, there have been no antiviral drugs to prevent and treat ZIKV/DENV infections. Phenotypic screening found that 2,3,6-trisubstituted quinazolinone compounds are novel inhibitors of ZIKV replication. Fifty-four analogues were synthesized, and their structure-activity relationships are discussed. Additional testing shows that compounds 22, 27, and 47 exhibited broad and potent activities against ZIKV and DENV with EC50 values as low as 86 nM with no significant cytotoxicity to mammalian cells.

Functionalized sulfonyl anthranilic acid derivatives inhibit replication of all the four dengue serotypes

Dengue virus (DENV), a mosquito-borne flavivirus, continues to be a major public health threat in many countries and no approved antiviral therapeutics are available yet. In this work, we designed and synthesized a series of sulfonyl anthranilic acid (SAA) derivatives using a ligand-based scaffold morphing approach of the 2,1-benzothiazine 2,2-dioxide core, previously used by us to develop DENV polymerase inhibitors resulting devoid of any cell-based antiviral activity. Several derivatives based on the new SAA chemotype exhibited potent inhibition against DENV infection in the cell-based assay but did not inhibit DENV NS5 polymerase activity in the in vitro de novo initiation and elongation assays. Notably, best compounds 26 and 39 showed EC50 values in the range of 0.54-1.36 μM against cells infected with the four dengue serotypes (DENV-1-4). Time-of-drug-addition assay revealed that analogue 26 is a post-entry replication inhibitor that appears to be specific for cells of primate origin, implicating a host target with a high barrier to resistance. In conclusion, SAA derivatives offer a valuable starting point for developing effective Dengue antiviral therapeutics.

AT-752 targets multiple sites and activities on the Dengue virus replication enzyme NS5

AT-752 is a guanosine analogue prodrug active against dengue virus (DENV). In infected cells, it is metabolized into 2'-methyl-2'-fluoro guanosine 5'-triphosphate (AT-9010) which inhibits RNA synthesis in acting as a RNA chain terminator. Here we show that AT-9010 has several modes of action on DENV full-length NS5. AT-9010 does not inhibit the primer pppApG synthesis step significantly. However, AT-9010 targets two NS5-associated enzyme activities, the RNA 2'-O-MTase and the RNA-dependent RNA polymerase (RdRp) at its RNA elongation step. Crystal structure and RNA methyltransferase (MTase) activities of the DENV 2 MTase domain in complex with AT-9010 at 1.97 Å resolution shows the latter bound to the GTP/RNA-cap binding site, accounting for the observed inhibition of 2'-O but not N7-methylation activity. AT-9010 is discriminated ∼10 to 14-fold against GTP at the NS5 active site of all four DENV1-4 NS5 RdRps, arguing for significant inhibition through viral RNA synthesis termination. In Huh-7 cells, DENV1-4 are equally sensitive to AT-281, the free base of AT-752 (EC50 ≈ 0.50 μM), suggesting broad spectrum antiviral properties of AT-752 against flaviviruses.

Identification and validation of novel non-nucleoside class of molecules inhibiting the dengue virus replication

There is currently no drug available to treat mosquito-borne dengue. The C-terminal RNA-dependent RNA polymerase (RdRp) domain in the non-structural type 5 (NS5) protein of the dengue virus (DENV) is essential for viral RNA synthesis and replication, and therefore, it is an attractive target for the anti-dengue drug development. We report herein the discovery and validation of two novel non-nucleoside classes of small molecules as DENV RdRp inhibitors. Firstly, using the refined X-ray structure of the DENV NS5 RdRp domain (PDB-ID: 4V0R), we conducted docking, binding free-energy studies, and short-scale molecular dynamics simulation to investigate the binding sites of known small molecules that led to the optimized protein-ligand complex. Subsequently, protein structure-based screening of a commercial database (∼500,000 synthetic compounds), pre-filtered for the drug-likeness, led to the top-ranked 171 molecules, which was then subjected to structural diversity analysis and clustering. This process led to six structurally distinct and best-scored compounds that were procured from the commercial vendor, and then subjected to the in vitro testing in the MTT and dengue infection assays. It revealed two unique and structurally unique compounds, KKR-D-02 and KKR-D-03, exhibiting 84 and 81% reductions, respectively, in DENV copy number in repeated assays in comparison to the virus-infected cell controls. These active compounds represent novel scaffolds for further structure-based discovery of novel candidate molecules for the intervention of dengue.Communicated by Ramaswamy H. Sarma.

Effect of Sauropus androgynus L. Merr. on dengue virus-2: An in vitro and in silico study

ETHNOPHARMACOLOGICAL RELEVANCE

Sauropus androgynus L. Merr. (Euphorbiaceae) commonly known as "multigreen" and "multivitamin" is consumed as a vegetable and used in traditional medicine to relieve fever.

AIM OF THE STUDY

This in vitro study is aimed to explore the activities of the lipophilic fraction of the leaves of S. androgynus (LFSA) against dengue (DENV), chikungunya (CHIKV) viruses and malaria (P. falciparum strain 3D7) parasite.

MATERIALS AND METHODS

The LFSA was analyzed by using GC-FID and GC-MS. The antiviral activity of LFSA was studied using the Vero CCL-81 cell line. The cytotoxicity assay was performed using 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). Focus forming unit (FFU), cell-based immunofluorescence (IFA) assays, and quantitative RT-PCR, were used to determine and confirm antiviral activity against DENV and CHIKV. The antiparasitic activity of LFSA was carried out against P. falciparum strain 3D7 grown in fresh O+ human erythrocytes culture.

RESULTS

Twelve compounds were identified in LFSA using GC/MS. The most abundant compound was squalene (36.9%), followed by vitamin E (12.5%) and linolenic acid (10.2%). Significant reduction in DENV titre was observed under pre- and post-infection treatment conditions at a concentration of 31.25 μg/ml, but no anti-malarial and anti-CHIKV activity was observed. The Autodock-Vina-based in-silico docking study revealed that β-sitosterol could form a strong interaction with the DENV E glycoprotein.

CONCLUSION

Our findings suggest that LFSA can inhibit DENV infection and might act as a potent prophylactic/therapeutic agent against DENV-2. In-silico results suggested that β-sitosterol may block the viral entry by inhibiting the fusion process.

Molecular Mechanisms of Antiviral Agents against Dengue Virus

Dengue is a major global health threat causing 390 million dengue infections and 25,000 deaths annually. The lack of efficacy of the licensed Dengvaxia vaccine and the absence of a clinically approved antiviral against dengue virus (DENV) drive the urgent demand for the development of novel anti-DENV therapeutics. Various antiviral agents have been developed and investigated for their anti-DENV activities. This review discusses the mechanisms of action employed by various antiviral agents against DENV. The development of host-directed antivirals targeting host receptors and direct-acting antivirals targeting DENV structural and non-structural proteins are reviewed. In addition, the development of antivirals that target different stages during post-infection such as viral replication, viral maturation, and viral assembly are reviewed. Antiviral agents designed based on these molecular mechanisms of action could lead to the discovery and development of novel anti-DENV therapeutics for the treatment of dengue infections. Evaluations of combinations of antiviral drugs with different mechanisms of action could also lead to the development of synergistic drug combinations for the treatment of dengue at any stage of the infection.

Blocking NS3-NS4B interaction inhibits dengue virus in non-human primates

Dengue is a major health threat and the number of symptomatic infections caused by the four dengue serotypes is estimated to be 96 million1 with annually around 10,000 deaths2. However, no antiviral drugs are available for the treatment or prophylaxis of dengue. We recently described the interaction between non-structural proteins NS3 and NS4B as a promising target for the development of pan-serotype dengue virus (DENV) inhibitors3. Here we present JNJ-1802-a highly potent DENV inhibitor that blocks the NS3-NS4B interaction within the viral replication complex. JNJ-1802 exerts picomolar to low nanomolar in vitro antiviral activity, a high barrier to resistance and potent in vivo efficacy in mice against infection with any of the four DENV serotypes. Finally, we demonstrate that the small-molecule inhibitor JNJ-1802 is highly effective against viral infection with DENV-1 or DENV-2 in non-human primates. JNJ-1802 has successfully completed a phase I first-in-human clinical study in healthy volunteers and was found to be safe and well tolerated4. These findings support the further clinical development of JNJ-1802, a first-in-class antiviral agent against dengue, which is now progressing in clinical studies for the prevention and treatment of dengue.

N-Phenylpyridine-3-Carboxamide and 6-Acetyl-1H-Indazole Inhibit the RNA Replication Step of the Dengue Virus Life Cycle

Dengue virus (DENV) is a Flavivirus that causes the most prevalent arthropod-borne viral disease. Clinical manifestation of DENV infection ranges from asymptomatic to severe symptoms that can lead to death. Unfortunately, no antiviral treatments against DENV are currently available. In order to identify novel DENV inhibitors, we screened a library of 1,604 chemically diversified fragment-based compounds using DENV reporter viruses that allowed quantification of viral replication in infected cells. Following a validation screening, the two best inhibitor candidates were N-phenylpyridine-3-carboxamide (NPP3C) and 6-acetyl-1H-indazole (6A1HI). The half maximal effective concentration of NPP3C and 6A1H1 against DENV were 7.1 μM and 6.5 μM, respectively. 6A1H1 decreased infectious DENV particle production up to 1,000-fold without any cytotoxicity at the used concentrations. While 6A1HI was DENV-specific, NPP3C also inhibited the replication of other flaviviruses such as West Nile virus and Zika virus. Structure-activity relationship (SAR) studies with 151 analogues revealed key structural elements of NPP3C and 6A1HI required for their antiviral activity. Time-of-drug-addition experiments identified a postentry step as a target of these compounds. Consistently, using a DENV subgenomic replicon, we demonstrated that these compounds specifically impede the viral RNA replication step and exhibit a high genetic barrier-to-resistance. In contrast, viral RNA translation and the de novo biogenesis of DENV replication organelles were not affected. Overall, our data unveil NPP3C and 6A1H1 as novel DENV inhibitors. The information revealed by our SAR studies will help chemically optimize NPP3C and 6A1H1 in order to improve their anti-flaviviral potency and to challenge them in in vivo models.

Quassinoids from Eurycoma longifolia with antiviral activities by inhibiting dengue virus replication

BACKGROUND

Dengue caused by dengue virus (DENV) spreads rapidly around the world. However, there are no worldwide licensed vaccines or specific antivirals to combat DENV infection. Quassinoids are the most characteristic components of Eurycoma longifolia, which have been reported to display a variety of biological activities. However, whether quassinoids exert anti-DENV activities remains unknown.

PURPOSE

To test the quassinoids of E. longifolia for their activity against DENV and to clarify the potential mechanisms.

METHODS

The quassinoids from E. longifolia were isolated by chromatography techniques, and their chemical structures were elucidated by spectroscopic analysis. The anti-DENV activities of quassinoids on baby hamster kidney cells BHK-21 were determined by lactate dehydrogenase (LDH) assay. The synthesis of progeny virus was measured by plaque assay. The expression levels of envelope protein (E) and non-structural protein 1 (NS1) were evaluated by qRT-PCR, Western blot and immunofluorescence assays. Molecular docking was used to screen the potential targets of the most active quassinoid against DENV-2, and surface plasmon resonance analysis was employed to confirm the direct binding between the most active quassinoid and potential target.

RESULTS

Twenty-four quassinoids, including three new quassinoids (1 - 3), were isolated from the ethanol extract of E. longifolia. Quassinoids 4, 5, 9, 11, 12, 15, 16, 17, 19 and 20 significantly reduced the LDH release at the stages of viral binding and entry or intracellular replication. Among them, 19 (6α-hydroxyeurycomalactone, 6α-HEL) exhibited the best anti-DENV-2 activities with an EC₅₀ value of 0.39 ± 0.02 μM. Further experiments suggested that 6α-HEL remarkably inhibited progeny virus synthesis and mRNA and protein expression levels of E and NS1 of DENV-2. Time-of-drug-addition assay suggested that 6α-HEL inhibited intracellular replication of DENV-2 at an early stage. Moreover, 6α-HEL was shown to interact with NS5-RdRp domain at a binding affinity of -8.15 kcal/mol. SPR assay further verified 6α-HEL bound to RdRp protein with an equilibrium dissociation constant of 1.49 × 10^-7 M.

CONCLUSION

Ten quassinoids from E. longifolia showed anti-DENV activities at processes of virus binding and entry or intracellular replication. The most active quassinoid 6α-HEL exerts the anti-DENV-2 activities at intracellular replication stage by directly targeting the NS5-RdRp protein. These results suggest that 6α-HEL could be a promising candidate for the treatment of DENV-2 infection.

Scaffold identification and drug repurposing for finding potential Dengue envelope inhibitors through ligand-based pharmacophore model

Most of the existing DENV entry inhibitors were discovered through structure-based, high-throughput screening techniques and optimization approaches by aiming β-OG pocket. However, the class of precise chemical scaffolds with superior antiviral activity targeting the early stages of virus infection that is considered to be beneficial in therapeutics and is still in process. In this study, ligand-based pharmacophore modeling using existing DENV entry inhibitors provided two best models, AADRR-2 and AAADR-2 (A- accepter, D- donor, R-ring) to screen public and DrugBank datasets. Further, approximately 36000 molecules were filtered using Zinc13 by employing the ideal validated models. Additionally, using β-OG binding pocket as target site, molecular docking experiments including induced-fit studies were conducted that provided further structurally divergent ligands. Moreover, the refined list of preferential hits were filtered out based on the best fitness score, binding energy and interaction paradigm, among them fused pyrimidine, hydrazone and biphenyl core comprising scaffolds were identified possessing profound interaction profile with key amino acid residues, ALA-50, GLN-200, PHE-193 and PHE-279 in 100 ns MD simulations. Additionally, the search for similar chemical fingerprints from DrugBank library was also carried out and Eltrombopag (Promacta/Revolade® prescribed in thrombocytopenia) was identified as a preferential β-OG pocket binder. The identified pyrazole-based hydrazone class of drug, Eltrombopag is in phase II clinical trials employed to treat dengue-mediated thrombocytopenia.Communicated by Ramaswamy H. Sarma.

Antiviral Potential of Traditional Unani Medicine with Special Emphasis on Dengue: A Review

Dengue fever has become a major public health concern. It is usually related to intravascular leaking, bleeding disorders, and thrombocytopenia and is recognized as a potent threat to humans. The scarcity of anti-dengue medication or vaccine for such a serious disease leads to an upsurge in the usage of traditional medicines for its proper management. India has diverse biodiversity and a long history of using plant-based remedies. Several medicinal plant extracts have been studied for producing anti-dengue viral activity. AYUSH traditional systems provide a plethora of plants that have been reported to be useful in the treatment of fever. Single and compound plant- based formulations in natural form have been used in Unani holistic approaches. This review serves as a new approach to illustrate the most recent evidence regarding the antiviral activity of various plants by providing scientific proof and also to validate the traditional formulations as effective treatments in dengue fever for global acceptance.

Drug repurposing toward the inhibition of RNA-dependent RNA polymerase of various flaviviruses through computational study

Numerous pathogens affecting human is present in the flavivirus family namely west nile, dengue, yellow fever, and zika which involves in development of global burden and distressing the environment economically. Till date, no approved drugs are available for targeting these viruses. The threat which urged the identification of small molecules for the inhibition of these viruses is the spreading of serious viral diseases. The recent outbreak of zika and dengue infections postured a solemn risk to worldwide public well-being. RNA-dependent RNA polymerase (RdRp) is the supreme adaptable enzymes of all the RNA viruses which is responsible for the replication and transcription of genome among the structural and nonstructural proteins of flaviviruses. It is understood that the RdRp of the flaviviruses are similar stating that the japanese encephalitis and west nile shares 70% identity with zika whereas the dengue serotype 2 and 3 shares the identity of 76% and 81%, respectively. In this study, we investigated the binding site of four flaviviral RdRp and provided insights into various interaction of the molecules using the computational approach. Our study helps in recognizing the potent compounds that could inhibit the viral protein as a common inhibitor. Additionally, with the conformational stability analysis, we proposed the possible mechanism of inhibition of the identified common small molecule toward RdRp of flavivirus. Finally, this study could be an initiative for the identification of common inhibitors and can be explored further for understanding the mechanism of action through in vitro studies for the study on efficacy.

Inhibitory Potential of Chromene Derivatives on Structural and Non-Structural Proteins of Dengue Virus

Dengue fever is a mosquito-borne viral disease that has become a serious health issue across the globe. It is caused by a virus of the Flaviviridae family, and it comprises five different serotypes (DENV-1 to DENV-5). As there is no specific medicine or effective vaccine for controlling dengue fever, there is an urgent need to develop potential inhibitors against it. Traditionally, various natural products have been used to manage dengue fever and its co-morbid conditions. A detailed analysis of these plants revealed the presence of various chromene derivatives as the major phytochemicals. Inspired by these observations, authors have critically analyzed the anti-dengue virus potential of various 4H chromene derivatives. Further, in silico, in vitro, and in vivo reports of these scaffolds against the dengue virus are detailed in the present manuscript. These analogues exerted their activity by interfering with various stages of viral entry, assembly, and replications. Moreover, these analogues mainly target envelope protein, NS2B-NS3 protease, and NS5 RNA-dependent RNA polymerase, etc. Overall, chromene-containing analogues exerted a potent activity against the dengue virus and the present review will be helpful for the further exploration of these scaffolds for the development of novel antiviral drug candidates.

Papaya Leaf Extracts as Potential Dengue Treatment: An In-Silico Study

Dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS) cause serious public health problems, with nearly 390 million people affected and 20,000 deaths per year in tropical and subtropical countries. Despite numerous attempts, no antiviral drug or vaccine is currently available to combat the manifestation. The challenge of discovering an efficient vaccine is enhanced by the surplus presence of efficient vectors and drug resistance from the virus. For centuries, papaya (Carica papaya) extracts have been traditionally used to treat DF, DHF, and DSS. In the present study, we systematically investigated seven compounds isolated from papaya leaf extract with regard to their potential as inhibitors for non-structural (NS) proteins, NS3 and NS5, which play a crucial role in viral RNA replication. The computational tools applied stretched across classical molecular docking, molecular dynamics (MD) simulations and SwissADME used to calculate binding affinities; binding free energies; Absorption, Distribution, Metabolism, and Excretion (ADME); and drug-likeness properties, thus, identifying Kaempferol, Chlorogenic acid, and Quercetin as potential candidates, with Kaempferol and Quercetin scoring best. Therefore, for the Kaempferol and Quercetin complexes, hybrid quantum mechanical/molecular mechanical (QM/MM) geometry and frequency calculations were performed, followed by the local mode analysis developed in our group to quantify Kaempferol-NS and Quercetin-NS hydrogen bonding. Given the non-toxic nature and the wide availability of the Kaempferol and Quercetin papaya extract in almost all of the susceptible regions, and our results showing high NS3 and NS5 binding affinities and energies, strong hydrogen bonding with both NS3 and NS5, and excellent ADME properties, we suggest Kaempferol and Quercetin as a strong NS3 and NS5 inhibitor to be further investigated in vitro.

Case of steroid refractory dengue myositis responsive to intravenous immunoglobulins

Dengue is an arbovirus infection that usually presents with the symptoms of high-grade fever, myalgia and rash. Dengue is spread by the Aedes aegypti mosquito and frequent outbreaks are being reported in regions like Pakistan, India and Sri Lanka. Although muscle ache is quite common with dengue fever, overt myositis is of very rare occurrence. Here, we report a case of a young girl who presented to us with serologically confirmed dengue infection, and having bilateral upper and lower limb weakness. Her raised creatine kinase, along with her electromyography pattern was suggestive of myositis. Her condition was steroid-resistant and responded only to intravenous immunoglobulin. She was discharged in a stable condition.

Glycyrrhizic Acid Derivatives Bearing Amino Acid Residues in the Carbohydrate Part as Dengue Virus E Protein Inhibitors: Synthesis and Antiviral Activity

Dengue virus (DENV) is one of the most geographically distributed mosquito-borne flaviviruses, like Japanese encephalitis virus (JEV), and Zika virus (ZIKV). In this study, a library of the known and novel Glycyrrhizic acid (GL) derivatives bearing amino acid residues or their methyl/ethyl esters in the carbohydrate part were synthesized and studied as DENV inhibitors in vitro using the cytopathic effect (CPE), viral infectivity and virus yield assays with DENV1 and DENV-2 in Vero E6 and A549 cells. Among the GL conjugates tested, compound hits GL-D-ValOMe 3, GL-TyrOMe 6, GL-PheOEt 11, and GL-LysOMe 21 were discovered to have better antiviral activity than GL, with IC50 values ranging from <0.1 to 5.98 μM on the in vitro infectivity of DENV1 and DENV2 in Vero E6 and A549 cells. Compound hits 3, 6, 11, and 21 had a concentration-dependent inhibition on the virus yield in Vero E6, in which GL-D-ValOMe 3 and GL-PheOEt 11 were the most active inhibitors of DENV2 yield. Meanwhile, the time-of-addition assay indicated that conjugates GL-D-ValOMe 3 and GL-PheOEt 11 exhibited a substantial decrease in the DENV2 attachment stage. Subsequently, chimeric single-round infectious particles (SRIPs) of DENV2 C-prM-E protein/JEV replicon and DENV2 prM-E/ZIKV replicon were utilized for the DENV envelope I protein-mediated attachment assay. GL conjugates 3 and 11 significantly reduced the attachment of chimeric DENV2 C-prM-E/JEV and DENV2 prM-E/ZIKV SRIPs onto Vero E6 cells in a concentration-dependent manner but did not impede the attachment of wild-type JEV CprME/JEV and ZIKV prM-E/ZIKV SRIPs, indicating the inhibition of Compounds 3 and 11 on DENV2 E-mediated attachment. Molecular docking data revealed that Compounds 3 and 11 have hydrophobic interactions within a hydrophobic pocket among the interfaces of Domains I, II, and the stem region of the DENV2 envelope (E) protein. These results displayed that Compounds 3 and 11 were the lead compounds targeting the DENV E protein. Altogether, our findings provide new insights into the structure−activity relationship of GL derivatives conjugated with amino acid residues and can be the new fundamental basis for the search and development of novel flavivirus inhibitors based on natural compounds.

Dengue virus NS4B protein as a target for developing antivirals

Dengue virus is an important pathogen affecting global population while no specific treatment is available against this virus. Effort has been made to develop inhibitors through targeting viral nonstructural proteins such as NS3 and NS5 with enzymatic activities. No potent inhibitors entering clinical studies have been developed so far due to many challenges. The genome of dengue virus encodes four membrane-bound nonstructural proteins which do not possess any enzymatic activities. Studies have shown that the membrane protein-NS4B is a validated target for drug discovery and several NS4B inhibitors exhibited antiviral activities in various assays and entered preclinical studies.. Here, we summarize the recent studies on dengue NS4B protein. The structure and membrane topology of dengue NS4B derived from biochemical and biophysical studies are described. Function of NS4B through protein-protein interactions and some available NS4B inhibitors are summarized. Accumulated studies demonstrated that cell-based assays play important roles in developing NS4B inhibitors. Although the atomic structure of NS4B is not obtained, target-based drug discovery approach become feasible to develop NS4B inhibitors as recombinant NS4B protein is available.

Randomized single oral dose phase 1 study of safety, tolerability, and pharmacokinetics of Iminosugar UV-4 Hydrochloride (UV-4B) in healthy subjects

Background

UV-4 (N-(9’-methoxynonyl)-1-deoxynojirimycin, also called MON-DNJ) is an iminosugar small-molecule oral drug candidate with in vitro antiviral activity against diverse viruses including dengue, influenza, and filoviruses and demonstrated in vivo efficacy against both dengue and influenza viruses. The antiviral mechanism of action of UV-4 is through inhibition of the host endoplasmic reticulum-resident α-glucosidase 1 and α-glucosidase 2 enzymes. This inhibition prevents proper glycan processing and folding of virus glycoproteins, thereby impacting virus assembly, secretion, and the fitness of nascent virions.

Methodology/Principal findings

Here we report a first-in-human, single ascending dose Phase 1a study to evaluate the safety, tolerability, and pharmacokinetics of UV-4 hydrochloride (UV-4B) in healthy subjects (ClinicalTrials.gov Identifier NCT02061358). Sixty-four subjects received single oral doses of UV-4 as the hydrochloride salt equivalent to 3, 10, 30, 90, 180, 360, 720, or 1000 mg of UV-4 (6 subjects per cohort), or placebo (2 subjects per cohort). Single doses of UV-4 hydrochloride were well tolerated with no serious adverse events or dose-dependent increases in adverse events observed. Clinical laboratory results, vital signs, and physical examination data did not reveal any safety signals. Dose-limiting toxicity was not observed; the maximum tolerated dose of UV-4 hydrochloride in humans has not yet been determined (>1000 mg). UV-4 was rapidly absorbed and distributed after dosing with the oral solution formulation used in this study. Median time to reach maximum plasma concentration ranged from 0.5–1 hour and appeared to be independent of dose. Exposure increased approximately in proportion with dose over the 333-fold dose range. UV-4 was quantifiable in pooled urine over the entire collection interval for all doses.

Conclusions/Significance

UV-4 is a host-targeted broad-spectrum antiviral drug candidate. At doses in humans up to 1000 mg there were no serious adverse events reported and no subjects were withdrawn from the study due to treatment-emergent adverse events. These data suggest that therapeutically relevant drug levels of UV-4 can be safely administered to humans and support further clinical development of UV-4 hydrochloride or other candidate antivirals in the iminosugar class.

Trial registration

ClinicalTrials.gov NCT02061358 https://clinicaltrials.gov/ct2/show/NCT02061358.

Styrylpyrone Derivative (SPD) Extracted from Goniothalamus umbrosus Binds to Dengue Virus Serotype-2 Envelope Protein and Inhibits Early Stage of Virus Replication

A study was conducted to investigate the anti-viral effect of a styrylpyrone derivative (SPD) called goniothalamin and the effects on the dengue virus serotype 2 (DENV-2) replication cycle. The SPD was prepared from the root of Goniothalamus umbrosus after purification with petroleum ether. The isolated SPD was then subjected to gas chromatography–mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) analyses for structure validation. The cytotoxicity of the SPD was evaluated using a cell viability assay, while the anti-viral activity of the SPD towards DENV-2 was confirmed by conducting a foci reduction assay which involved virus yield reduction, time-of-addition, and time removal assays. Transcriptomic analysis via quantitative real-time polymerase chain reaction (qRT-PCR) using the DENV-2 E gene was conducted to investigate the level of gene transcript. Immunocytochemistry analysis was used to investigate the effects of SPD treatment on protein E expression. Finally, software molecular docking of the SPD and E protein was also performed. The cytotoxicity assay confirmed that the SPD was not toxic to Vero cells, even at the highest concentration tested. In the time-of-addition assay, more than 80% foci reduction was observed when SPDs were administered at 2 h post-infection (hpi), and the reduction percentage then dropped with the delay of the treatment time, suggesting the inhibition of the early replication cycle. However, the time removal assay showed that more than 80% reduction could only be observed after 96 h post-treatment with the SPD. Treatment with the SPD reduced the progeny infectivity when treated for 24 h and was dose-dependent. The result showed that transcript level of the E gene in infected cells treated with the SPD was reduced compared to infected cells without treatment. In immunocytochemistry analysis, the DENV-2 E protein exhibited similar expression trends, shown by the gene transcription level. Molecular docking showed that the SPD can interact with E protein through hydrogen bonds and other interactions. Overall, this study showed that SPDs have the potential to be anti-DENV-2 via a reduction in viral progeny infectivity and a reduction in the expression of the DENV-2 E gene and protein at different phases of viral replication. SPDs should be further researched to be developed into an effective anti-viral treatment, particularly for early-phase dengue viral infection.

PD1 CD44 antiviral peptide as an inhibitor of the protein-protein interaction in dengue virus invasion

Dengue virus (DENV) infection is mediated by the interaction between the virus envelope protein and cellular receptors of the host cells. In this study, we designed peptides to inhibit protein-protein interaction between dengue virus and CD44 receptor, which is one of the receptors used by DENV for entry. In silico model complexes were designed between domain III of the viral envelope protein of dengue virus 2 and the domain of human CD44 receptor using ClusPro 2.0, (https://cluspro.bu.edu/login.php), and inhibition peptides were designed with Rosetta Online-Server(http://rosie.rosettacommons.org/peptiderive). We identified one linear antiviral peptide of 18 amino acids derived from the human CD44 receptor, PD1 CD44. It did not show hemolysis or toxicity in HepG2 or BHK cell lines, nor did it stimulate the release of IL-1β, IL-6, TNF-α, and IFN-γ, below 100 µM. It had an IC50 of 13.8 µM and maximum effective dose of 54.9 µM evaluated in BHK cells. The decrease in plaque-forming units/mL for DENV1, DENV2, DENV3, and DENV4 was 99.60%, 99.40%, 97.80%, and 70.50%, respectively, and similar results were obtained by RT-qPCR. Non-structural protein 1 release was decreased in pre- and co-treatment but not in post-treatment. Competition assays between the DN59 peptide, envelope protein, and the fragment of domain III "MDKLQLKGMSYSMCTGKF" of the viral envelope of DENV2 and PD1 CD44 showed that our peptide lost its antiviral activity. We demonstrated that our peptide decreased endosome formation, and we propose that it binds to the envelope protein of DENV, inhibiting viral invasion/fusion.

Azelnidipine Exhibits In Vitro and In Vivo Antiviral Effects against Flavivirus Infections by Targeting the Viral RdRp

Flaviviruses, represented by Zika and dengue virus (ZIKV and DENV), are widely present around the world and cause various diseases with serious consequences. However, no antiviral drugs have been clinically approved for use against them. Azelnidipine (ALP) is a dihydropyridine calcium channel blocker and has been approved for use as an antihypertensive drug. In the present study, ALP was found to show potent anti-flavivirus activities in vitro and in vivo. ALP effectively prevented the cytopathic effect induced by ZIKV and DENV and inhibited the production of viral RNA and viral protein in a dose-dependent manner. Moreover, treatment with 0.3 mg/kg of ALP protected 88.89% of mice from lethal challenge. Furthermore, using the time-of-drug-addition assay, the enzymatic inhibition assay, the molecular docking, and the surface plasmon resonance assay, we revealed that ALP acted at the replication stage of the viral infection cycle by targeting the viral RNA-dependent RNA polymerase. These findings highlight the potential for the use of ALP as an antiviral agent to combat flavivirus infections.

Efficacy of rupatadine in reducing the incidence of dengue haemorrhagic fever in patients with acute dengue: A randomised, double blind, placebo-controlled trial

BACKGROUND

Rupatadine was previously shown to reduce endothelial dysfunction in vitro, reduced vascular leak in dengue mouse models and to reduce the extent of pleural effusions and thrombocytopenia in patients with acute dengue. Therefore, we sought to determine the efficacy of rupatadine in reducing the incidence of dengue haemorrhagic fever (DHF) in patients with acute dengue.

METHODS AND FINDINGS

A phase 2, randomised, double blind, placebo controlled clinical trial was carried out in patients with acute dengue in Sri Lanka in an outpatient setting. Patients with ≤3 days since the onset of illness were either recruited to the treatment arm of oral rupatadine 40mg for 5 days (n = 123) or the placebo arm (n = 126). Clinical and laboratory features were measured daily to assess development of DHF and other complications. 12 (9.7%) patients developed DHF in the treatment arm compared to 22 (17.5%) who were on the placebo although this was not significant (p = 0.09, relative risk 0.68, 95% CI 0.41 to 1.08). Rupatadine also significantly reduced (p = 0.01) the proportion of patients with platelet counts <50,000 cells/mm3 and significantly reduced (p = 0.04) persisting vomiting, headache and hepatic tenderness (p<0.0001) in patients. There was a significant difference in the duration of illness (p = 0.0002) although the proportion of individuals who required hospital admission in both treatment arms. Only 2 patients on rupatadine and 3 patients on the placebo developed shock, while bleeding manifestations were seen in 6 patients on rupatadine and 7 patients on the placebo.

CONCLUSIONS

Rupatadine appeared to be safe and well tolerated and showed a trend towards a reducing proportion of patients with acute dengue who developed DHF. Its usefulness when used in combination with other treatment modalities should be explored.

TRIAL REGISTRATION

International Clinical Trials Registration Platform: SLCTR/2017/024.

Antiviral Activity of Rosmarinic Acid Against Four Serotypes of Dengue Virus

The present study was undertaken to evaluate the putative antiviral activity of Rosmarinic acid (RA) against four serotypes of dengue virus (DENV). Our previous in silico binding analysis revealed that RA binds strongly to the envelope domain III (EDIII) protein of all four DENV serotypes. We employed an in vitro Biolayer Interferometry-based OCTET™ platform to study the binding interaction of RA with EDIII protein of the four DENV serotypes. Additionally, a functional plaque assay was developed to investigate the potential inhibition of infection of the four DENV serotypes. Using OCTET™, the binding interaction of RA to DENV-EDIII protein of the four DENV serotypes demonstrates interaction which can be arranged in the following order: EDIII-DENV1 (Koff value of 1.05 s-1) > EDIII-DENV2 (Koff value of 5.63 × 10-01 s-1) > EDIII-DENV3 (Koff value of 4.63 × 10-02 s-1) > EDIII-DENV4 (Koff value of 3.53 × 10-02 s-1). Subsequently, the inhibiting ability of RA using plaque assay confirmed reduction in the number of plaques for all four serotypes, indicating the ability of RA not only to bind, but also to inhibit the infection of four serotypes in cell culture, while being non-toxic at the concentrations used in the study. However, the effect of RA was variable on different serotypes, demonstrating highest effect on DENV1 (EC50 = 13.73 µg/mL, SI ≥ 728) followed by DENV2 (EC50 = 77.74 µg/mL, SI  ≥ 129), DENV3 (EC50 = 244 µg/mL, SI ≥ 41) and DENV4 (EC50 = 280 µg/mL, SI ≥ 36).