Antiviral Activities of Heparan Sulfate Mimetic RAFT Polymers Against Mosquito-borne Viruses.

Mosquito-borne viruses are a major worldwide health problem associated with high morbidity and mortality rates and significant impacts on national healthcare budgets. The development of antiviral drugs for both the treatment and prophylaxis of these diseases is thus of considerable importance. To address the need for therapeutics with antiviral activity, a library of heparan sulfate mimetic polymers was screened against dengue virus (DENV), Yellow fever virus (YFV), Zika virus (ZIKV), and Ross River virus (RRV). The polymers were prepared by RAFT polymerization of various acidic monomers with a target MW of 20 kDa (average Mn ∼ 27 kDa by GPC). Among the polymers, poly(SS), a homopolymer of sodium styrenesulfonate, was identified as a broad spectrum antiviral with activity against all the tested viruses and particularly potent inhibition of YFV (IC50 = 310 pM). Our results further uncovered that poly(SS) exhibited a robust inhibition of ZIKV infection in both mosquito and human cell lines, which points out the potential functions of poly(SS) in preventing mosquito-borne viruses associated diseases by blocking viral transmission in their mosquito vectors and mitigating viral infection in patients.

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.

Inhibition of Pim kinases triggers a broad antiviral activity by affecting innate immunity and via the PI3K-Akt-mTOR axis the endolysosomal system.

Zoonoses such as ZIKV and SARS-CoV-2 pose a severe risk to global health. There is urgent need for broad antiviral strategies based on host-targets filling gaps between pathogen emergence and availability of therapeutic or preventive strategies. Significant reduction of pathogen titers decreases spread of infections and thereby ensures health systems not being overloaded and public life to continue. Based on previously observed interference with FGFR1/2-signaling dependent impact on interferon stimulated gene (ISG)-expression, we identified Pim kinases as promising druggable cellular target. We therefore focused on analyzing the potential of pan-Pim kinase inhibition to trigger a broad antiviral response. The pan-Pim kinase inhibitor AZD1208 exerted an extraordinarily high antiviral effect against various ZIKV isolates, SARS-CoV-2 and HBV. This was reflected by strong reduction in viral RNA, proteins and released infectious particles. Especially in case of SARS-CoV-2, AZD1208 led to a complete removal of viral traces in cells. Kinome-analysis revealed vast changes in kinase landscape upon AZD1208 treatment, especially for inflammation and the PI3K/Akt-pathway. For ZIKV, a clear correlation between antiviral effect and increase in ISG-expression was observed. Based on a cell culture model with impaired ISG-induction, activation of the PI3K-Akt-mTOR axis, leading to major changes in the endolysosomal equilibrium, was identified as second pillar of the antiviral effect triggered by AZD1208-dependent Pim kinase inhibition, also against HBV. We identified Pim-kinases as cellular target for a broad antiviral activity. The antiviral effect exerted by inhibition of Pim kinases is based on at least two pillars: innate immunity and modulation of the endolysosomal system.

Construction of exosome-loaded LL-37 and its protection against zika virus infection.

Zika virus (ZIKV) is an enveloped, single-stranded and positive-stranded RNA virus of the genus Flavivirus in the family Flaviviridae. ZIKV can cross the placental barrier and infect the fetus, causing microcephaly, congenital ZIKV syndrome, and even fetal death. ZIKV infection can also lead to testicular damage and male sterility. But no effective drugs and vaccines are available up to now. Previous studies have shown that the cathelicidin antimicrobial peptide LL-37 can protect against ZIKV infection. However, LL-37 is a secreted peptide, which can be easily degraded in vivo. We herein constructed exosome-loaded LL-37 (named LL-37-TM-exo and TM-LL-37-exo) using the transmembrane protein TM to load LL-37 onto the membrane of exosome. We found that exosome-loaded LL-37 could significantly inhibit ZIKV infection in vitro and in vivo, and LL-37-TM-exo had stronger antiviral activity than that of TM-LL-37-exo, which could significantly reduce ZIKV-induced testicular injury and sperm injury, and had broad-spectrum antiviral effect. Compared to free LL-37, exosome-loaded LL-37 showed a better serum stability, higher efficiency to cross the placental barrier, and stronger antiviral activity. The mechanism of exosome-loaded LL-37 against ZIKV infection was consistent with that of free LL-37, which could directly inactivate viral particles, reduce the susceptibility of host cells, and act on viral replication stage. Our study provides a novel strategy for the development of LL-37 against viral infection.

High-resolution RNA tertiary structures in Zika virus stem-loop A for the development of inhibitory small molecules.

Flaviviruses such as Zika (ZIKV) and dengue virus (DENV) are positive-sense RNA viruses belonging to Flaviviridae The flavivirus genome contains a 5' end stem-loop promoter sequence known as stem-loop A (SLA) that is recognized by the flavivirus polymerase NS5 during viral RNA synthesis and 5' guanosine cap methylation. The crystal structures of ZIKV and DENV SLAs show a well-defined fold, consisting of a bottom stem, side loop, and top stem-loop, providing unique interaction sites for small molecule inhibitors to disrupt the promoter function. To facilitate the identification of small molecule binding sites in flavivirus SLA, we determined high-resolution structures of the bottom and top stems of ZIKV SLA, which contain a single U- or G-bulge, respectively. Both bulge nucleotides exhibit multiple orientations, from folded back on the adjacent nucleotide to flipped out of the helix, and are stabilized by stacking or base triple interactions. These structures suggest that even a single unpaired nucleotide can provide flexibility to RNA structures, and its conformation is mainly determined by the stabilizing chemical environment. To facilitate discovery of small molecule inhibitors that interfere with the functions of ZIKV SLA, we screened and identified compounds that bind to the bottom and top stems of ZIKV SLA.

Boroleucine-Derived Covalent Inhibitors of the ZIKV Protease.

The Zika virus (ZIKV) remains a potential threat to the public health due to the lack of both an approved vaccination or a specific treatment. In this work, a series of peptidic inhibitors of the ZIKV protease with boroleucine as P1 residue was synthesized. The highest affinities with Ki values down to 8 nM were observed for compounds with basic residues in both P2 and P3 position and at the N-terminus. The low potency of reference compounds containing leucine, leucine-amide or isopentylamide as P1 residue suggested a covalent binding mode of the boroleucine-derived inhibitors. This was finally proven by crystal structure determination of the most potent inhibitor from this series in complex with the ZIKV protease.

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.

Discovery of New Zika Protease and Polymerase Inhibitors through the Open Science Collaboration Project OpenZika.

The Zika virus (ZIKV) is a neurotropic arbovirus considered a global threat to public health. Although there have been several efforts in drug discovery projects for ZIKV in recent years, there are still no antiviral drugs approved to date. Here, we describe the results of a global collaborative crowdsourced open science project, the OpenZika project, from IBM's World Community Grid (WCG), which integrates different computational and experimental strategies for advancing a drug candidate for ZIKV. Initially, molecular docking protocols were developed to identify potential inhibitors of ZIKV NS5 RNA-dependent RNA polymerase (NS5 RdRp), NS3 protease (NS2B-NS3pro), and NS3 helicase (NS3hel). Then, a machine learning (ML) model was built to distinguish active vs inactive compounds for the cytoprotective effect against ZIKV infection. We performed three independent target-based virtual screening campaigns (NS5 RdRp, NS2B-NS3pro, and NS3hel), followed by predictions by the ML model and other filters, and prioritized a total of 61 compounds for further testing in enzymatic and phenotypic assays. This yielded five non-nucleoside compounds which showed inhibitory activity against ZIKV NS5 RdRp in enzymatic assays (IC50 range from 0.61 to 17 µM). Two compounds thermally destabilized NS3hel and showed binding affinity in the micromolar range (Kd range from 9 to 35 µM). Moreover, the compounds LabMol-301 inhibited both NS5 RdRp and NS2B-NS3pro (IC50 of 0.8 and 7.4 µM, respectively) and LabMol-212 thermally destabilized the ZIKV NS3hel (Kd of 35 µM). Both also protected cells from death induced by ZIKV infection in in vitro cell-based assays. However, while eight compounds (including LabMol-301 and LabMol-212) showed a cytoprotective effect and prevented ZIKV-induced cell death, agreeing with our ML model for prediction of this cytoprotective effect, no compound showed a direct antiviral effect against ZIKV. Thus, the new scaffolds discovered here are promising hits for future structural optimization and for advancing the discovery of further drug candidates for ZIKV. Furthermore, this work has demonstrated the importance of the integration of computational and experimental approaches, as well as the potential of large-scale collaborative networks to advance drug discovery projects for neglected diseases and emerging viruses, despite the lack of available direct antiviral activity and cytoprotective effect data, that reflects on the assertiveness of the computational predictions. The importance of these efforts rests with the need to be prepared for future viral epidemic and pandemic outbreaks.

A cathelicidin antimicrobial peptide from Hydrophis cyanocinctus inhibits Zika virus infection by downregulating expression of a viral entry factor.

Zika virus (ZIKV) is a re-emerging flavivirus that causes conditions such as microcephaly and testis damage. The spread of ZIKV has become a major public health concern. Recent studies indicated that antimicrobial peptides are an ideal source for screening antiviral candidates with broad-spectrum antiviral activities, including against ZIKV. We herein found that Hc-CATH, a cathelicidin antimicrobial peptide identified from the sea snake Hydrophis cyanocinctus in our previous work, conferred protection against ZIKV infection in host cells and showed preventative efficacy and therapeutic efficacy in C57BL/6J mice, Ifnar1-/- mice, and pregnant mice. Intriguingly, we revealed that Hc-CATH decreased the susceptibility of host cells to ZIKV by downregulating expression of AXL, a TAM (TYRO3, AXL and MERTK) family kinase receptor that mediates ZIKV infection, and subsequently reversed the negative regulation of AXL on host's type I interferon response. Furthermore, we showed that the cyclo-oxygenase-2/prostaglandin E2/adenylyl cyclase/protein kinase A pathway was involved in Hc-CATH-mediated AXL downregulation, and Hc-CATH in addition directly inactivated ZIKV particles by disrupting viral membrane. Finally, while we found Hc-CATH did not act on the late stage of ZIKV infection, structure-function relationship studies revealed that α-helix and phenylalanine residues are key structural requirements for its protective efficacy against initial ZIKV infection. In summary, we demonstrate that Hc-CATH provides prophylactic and therapeutic efficacy against ZIKV infection via downregulation of AXL, as well as inactivating the virion. Our findings reveal a novel mechanism of cathelicidin against viral infection and highlight the potential of Hc-CATH to prevent and treat ZIKV infection.

Heparin Protects Human Neural Progenitor Cells from Zika Virus-Induced Cell Death While Preserving Their Differentiation into Mature Neuroglial Cells.

Zika virus (ZIKV) is an arbovirus member of the Flaviviridae family that causes severe congenital brain anomalies in infected fetuses. The key target cells of ZIKV infection, human neural progenitor cells (hNPCs), are highly permissive to infection that causes the inhibition of cell proliferation and induces cell death. We have previously shown that pharmaceutical-grade heparin inhibits virus-induced cell death with negligible effects on in vitro virus replication in ZIKV-infected hNPCs at the "high" multiplicity of infection (MOI) of 1. Here, we show that heparin inhibits formation of ZIKV-induced intracellular vacuoles, a signature of paraptosis, and inhibits necrosis and apoptosis of hNPCs grown as neurospheres (NS). To test whether heparin preserved the differentiation of ZIKV-infected hNPCs into neuroglial cells, hNPCs were infected at the MOI of 0.001. In this experimental condition, heparin inhibited ZIKV replication by ca. 2 log10, mostly interfering with virion attachment, while maintaining its protective effect against ZIKV-induced cytopathicity. Heparin preserved differentiation into neuroglial cells of hNPCs that were obtained from either human-induced pluripotent stem cells (hiPSC) or by fetal tissue. Quite surprisingly, multiple additions of heparin to hNPCs enabled prolonged virus replication while preventing virus-induced cytopathicity. Collectively, these results highlight the potential neuroprotective effect of heparin that could serve as a lead compound to develop novel agents for preventing the damage of ZIKV infection on the developing brain. IMPORTANCE ZIKV is a neurotropic virus that invades neural progenitor cells (NPCs), causing inhibition of their proliferation and maturation into neurons and glial cells. We have shown previously that heparin, an anticoagulant also used widely during pregnancy, prevents ZIKV-induced cell death with negligible inhibition of virus replication. Here, we demonstrate that heparin also exerts antiviral activity against ZIKV replication using a much lower infectious inoculum. Moreover, heparin interferes with different modalities of virus-induced cell death. Finally, heparin-induced prevention of virus-induced NPC death allows their differentiation into neuroglial cells despite the intracellular accumulation of virions. These results highlight the potential use of heparin, or pharmacological agents derived from it, in pregnant women to prevent the devastating effects of ZIKV infection on the developing brain of their fetuses.

Biocompatible and Selective Generation of Bicyclic Peptides.

Bicyclic peptides possess superior properties for drug discovery; however, their chemical synthesis is not straightforward and often neither biocompatible nor fully orthogonal to all canonical amino acids. The selective reaction between 1,2-aminothiols and 2,6-dicyanopyridine allows direct access to complex bicyclic peptides in high yield. The process can be fully automated using standard solid-phase peptide synthesis. Bicyclization occurs in water at physiological pH within minutes and without the need for a catalyst. The use of various linkers allows tailored bicyclic peptides with qualities such as plasma stability, conformational preorganization, and high target affinity. We demonstrate this for a bicyclic inhibitor of the Zika virus protease NS2B-NS3 as well as for bicyclic versions of the α-helical antimicrobial peptide aurein 1.2.

Nafamostat mesylate as a broad-spectrum candidate for the treatment of flavivirus infections by targeting envelope proteins.

Epidemics caused by flaviviruses occur globally; however, no antiviral drugs treating flaviviruses infections have yet been developed. Nafamostat (NM) is a protease inhibitor approved for pancreatitis and anti-coagulation. The anti-flavivirus potential of NM has yet to be determined. Here, utilizing in vitro and in vivo infection assays, we present that NM effectively inhibits Zika virus (ZIKV) and other flaviviruses in vitro. NM inhibited the production of ZIKV viral RNA and proteins originating from Asia and African lineage in human-, mouse- and monkey-derived cell lines and the in vivo anti-ZIKV efficacy of NM was verified. Mode-of-action analysis using time-of-drug-addition assay, infectivity inhibition assay, surface plasmon resonance assay, and molecular docking revealed that NM interacted with viral particles and blocked the early stage of infection by targeting the domain III of ZIKV envelope protein. Analysing the anti-flavivirus effects of NM-related compounds suggested that the antiviral effect depended on the unique structure of NM. These findings suggest the potential use of NM as an anti-flavivirus candidate, and a novel drug design approach targeting the flavivirus envelope protein.

Structure-Based Optimization and Characterization of Macrocyclic Zika Virus NS2B-NS3 Protease Inhibitors.

Zika virus (ZIKV) is a human pathogenic arbovirus. So far, neither a specific treatment nor a vaccination against ZIKV infections has been approved. Starting from our previously described lead structure, a series of 29 new macrocyclic inhibitors of the Zika virus protease containing different linker motifs have been synthesized. By selecting hydrophobic d-amino acids as part of the linker, numerous inhibitors with Ki values < 5 nM were obtained. For 12 inhibitors, crystal structures in complex with the ZIKV protease up to 1.30 Å resolution were determined, which contribute to the understanding of the observed structure-activity relationship (SAR). In immunofluorescence assays, an antiviral effect was observed for compound 26 containing a d-homocyclohexylalanine residue in its linker segment. Due to its excellent selectivity profile and low cytotoxicity, this inhibitor scaffold could be a suitable starting point for the development of peptidic drugs against the Zika virus and related flaviviruses.

SAR evolution towards potent C-terminal carboxamide peptide inhibitors of Zika virus NS2B-NS3 protease.

Zika virus (ZIKV) is a member of the Flaviviridae family that can cause neurological disorders and congenital malformations. The NS2B-NS3 viral serine protease is an attractive target for the development of new antiviral agents against ZIKV. We report here a SAR study on a series of substrate-like linear tripeptides that inhibit in a non-covalent manner the NS2B-NS3 protease. Optimization of the residues at positions P1, P2, P3 and of the N-terminal and C-terminal portions of the tripeptide allowed the identification of inhibitors with sub-micromolar potency with phenylglycine as arginine-mimicking group and benzylamide as C-terminal fragment. Further SAR exploration and application of these structural changes to a series of peptides having a 4-substituted phenylglycine residue at the P1 position led to potent compounds showing double digit nanomolar inhibition of the Zika protease (IC50 = 30 nM) with high selectivity against trypsin-like proteases and the proteases of other flavivirus, such as Dengue 2 virus (DEN2V) and West Nile virus (WNV).

Antiviral effects of azithromycin: A narrative review.

Viral infections have a great impact on human health. The urgent need to find a cure against different viruses led us to investigations in a vast range of drugs. Azithromycin (AZT), classified as a macrolide, showed various effects on different known viruses such as severe acute respiratory syndrome coronavirus (SARS-CoV), Zika, Ebola, Enterovirus (EVs) and Rhinoviruses (RVs), and Influenza A previously; namely, these viruses, which caused global concerns, are considered as targets for AZT different actions. Due to AZT background in the treatment of known viral infections mentioned above (which is described in this study), in the early stages of COVID-19 (a new zoonotic disease caused by a novel coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)) development, AZT drew attention to itself due to its antiviral and immunomodulatory effects as a valuable candidate for COVID-19 treatment. AZT usage instructions for treating different viral infections have always been under observation, and COVID-19 is no exception. There are still debates about the use of AZT in COVID-19 treatment. However, eventually, novel researches convinced WHO to announce the discontinuation of AZT use (alone or in combination with hydroxychloroquine) in treating SARS-CoV-2 infection. This research aims to study the structure of all of the viruses mentioned above and the molecular and clinical effects of AZT against the virus.

Targeting Host PIM Protein Kinases Reduces Mayaro Virus Replication.

Mayaro virus (MAYV) manipulates cell machinery to successfully replicate. Thus, identifying host proteins implicated in MAYV replication represents an opportunity to discover potential antiviral targets. PIM kinases are enzymes that regulate essential cell functions and also appear to be critical factors in the replication of certain viruses. In this study we explored the consequences of PIM kinase inhibition in the replication of MAYV and other arboviruses. Cytopathic effects or viral titers in samples from MAYV-, Chikungunya-, Una- or Zika-infected cells treated with PIM kinase inhibitors were evaluated using an inverted microscope or plaque-forming assays. The expression of viral proteins E1 and nsP1 in MAYV-infected cells was assessed using an immunofluorescence confocal microscope or Western blot. Our results revealed that PIM kinase inhibition partially prevented MAYV-induced cell damage and also promoted a decrease in viral titers for MAYV, UNAV and ZIKV. The inhibitory effect of PIM kinase blocking was observed for each of the MAYV strains tested and also occurred as late as 8 h post infection (hpi). Finally, PIM kinase inhibition suppressed the expression of MAYV E1 and nsP1 proteins. Taken together, these findings suggest that PIM kinases could represent an antiviral target for MAYV and other arboviruses.

Intracellular translocation of HMGB1 is important for Zika virus replication in Huh7 cells.

Neonatal microcephaly and adult Guillain-Barré syndrome are severe complications of Zika virus (ZIKV) infection. The robustly induced inflammatory cytokine expressions in ZIKV-infected patients may constitute a hallmark for severe disease. In the present study, the potential role of high mobility group box 1 protein (HMGB1) in ZIKV infection was investigated. HMGB1 protein expression was determined by the enzyme-linked immunosorbent assay (ELISA) and immunoblot assay. HMGB1's role in ZIKV infection was also explored using treatment with dexamethasone, an immunomodulatory drug, and HMGB1-knockdown (shHMGB1) Huh7 cells. Results showed that the Huh7 cells were highly susceptible to ZIKV infection. The infection was found to induce HMGB1 nuclear-to-cytoplasmic translocation, resulting in a > 99% increase in the cytosolic HMGB1 expression at 72-h post-infection (h.p.i). The extracellular HMGB1 level was elevated in a time- and multiplicity of infection (MOI)-dependent manner. Treatment of the ZIKV-infected cells with dexamethasone (150 µM) reduced HMGB1 extracellular release in a dose-dependent manner, with a maximum reduction of 71 ± 5.84% (P < 0.01). The treatment also reduced virus titers by over 83 ± 0.50% (P < 0.01). The antiviral effects, however, were not observed in the dexamethasone-treated shHMGB1 cells. These results suggest that translocation of HMGB1 occurred during ZIKV infection and inhibition of the translocation by dexamethasone coincided with a reduction in ZIKV replication. These findings highlight the potential of targeting the localization of HMGB1 in affecting ZIKV infection.

Identification of potential ZIKV NS2B-NS3 protease inhibitors from Andrographis paniculata: An insilico approach.

Andrographis paniculata is a widely used medicinal plant for treating a variety of human infections. The plant's bioactives have been shown to have a variety of biological activities in various studies, including potential antiviral, anticancer, and anti-inflammatory effects in a variety of experimental models. The present investigation identifies a potent antiviral compound from the phytochemicals of Andrographis paniculata against Zika virus using computational docking simulation. The ZIKV NS2B-NS3 protease, which is involved in viral replication, has been considered as a promising target for Zika virus drug development. The bioactives from Andrographis paniculata, along with standard drugs as control were screened for their binding energy using AutoDock 4.2 against the viral protein. Based on the higher binding affinity the phytocompounds Bisandrographolide A (-11.7), Andrographolide (-10.2) and Andrographiside (-9.7) have convenient interactions at the binding site of target protein (ZIKV NS2B-NS3 protease) in comparison with the control drug. In addition, using insilico tools, the selected high-scoring molecules were analysed for pharmacological properties such as ADME (Absorption, Distribution, Metabolism, and Excretion profile) and toxicity. Andrographolide was reported to have strong pharmacodynamics properties and target accuracy based on the Lipinski rule and lower binding energy. The selected bioactives showed lower AMES toxicity and has potent antiviral activity against zika virus targets. Further, MD simulation studies validated Bisandrographolide A & Andrographolide as a potential hit compound by exhibiting good binding with the target protein. The compounds exhibited good hydrogen bonds with ZIKV NS2B-NS3 protease. As a result, bioactives from the medicinal plant Andrographis paniculata can be studied in vitro and in vivo to develop an antiviral phytopharmaceutical for the successful treatment of zika virus.Communicated by Ramaswamy H. Sarma.

NS2B-NS3 protease inhibitors as promising compounds in the development of antivirals against Zika virus: A systematic review.

Zika virus (ZIKV) infections are associated with severe neurological complications and are a global public health concern. There are no approved vaccines or antiviral drugs to inhibit ZIKV replication. NS2B-NS3 protease (NS2B-NS3 pro), which is essential for viral replication, is a promising molecular target for anti-ZIKV drugs. We conducted a systematic review to identify compounds with promising effects against ZIKV; we discussed their pharmacodynamic and pharmacophoric characteristics. The online search, performed using the PubMed/MEDLINE and SCOPUS databases, yielded 56 articles; seven relevant studies that reported nine promising compounds with inhibitory activity against ZIKV NS2B-NS3 pro were selected. Of these, five (niclosamide, nitazoxanide, bromocriptine, temoporfin, and novobiocin) are currently available on the market and have been tested for off-label use against ZIKV. The 50% inhibitory concentration values of these compounds for the inhibition of NS2B-NS3 pro ranged at 0.38-21.6 µM; most compounds exhibited noncompetitive inhibition (66%). All compounds that could inhibit the NS2B-NS3 pro complex showed potent in vitro anti-ZIKV activity with a 50% effective concentration ranging 0.024-50 µM. The 50% cytotoxic concentration of the compounds assayed using A549, Vero, and WRL-69 cell lines ranged at 0.6-1388.02 µM and the selectivity index was 3.07-1698. This review summarizes the most promising antiviral agents against ZIKV that have inhibitory activity against viral proteases.

The Screening of Phytochemicals Against NS5 Polymerase to Treat Zika Virus Infection: Integrated Computational Based Approach.

BACKGROUND: The recent Zika Virus (ZIKV) outbreak provides a spur for new, efficient, and safe anti-Zika Virus agents. RNA-dependent RNA polymerase (RdRp) is critical amongst the seven non-structural proteins for viral replication and considered an attractive drug target. METHODS: In this study, molecular docking approach was used to rationally screen the library of 5000 phytochemicals to find inhibitors against NS5 RdRp. LigX tool was used to analyze the 2D plots of receptor-ligand interactions. The top-ranked compounds were then subjected to in-silico pharmacokinetic study. RESULTS: The compounds namely Polydatin, Dihydrogenistin, Liquiritin, Rhapontin and Cichoriin were successfully bound inside the pocket of NS5 RdRp. Polydatin was the leading phytochemical that showed high docking score -18.71 (kcal/mol) and bonding interaction at the active-site of NS5 RdRp. They were subjected to analyze drug-like properties that further reinforced their validation and showed that they have more capability to attach with the receptor as compared to SOFOSBUVIR control drug. MD simulation of the top two complexes was performed and the simulated complexes showed stability and ligands were kept within the bonding pocket. CONCLUSION: The study might facilitate the development of a natural and cost-effective drug against ZIKV. Further validation, however, is necessary to confirm its effectiveness and its biocompatibility.