Inhibition Of Zika Virus Research Articles

Endogenous ZAP is associated with altered Zika virus infection phenotype

The zinc finger antiviral protein 1 (ZAP) has broad antiviral activity. ZAP is an interferon (IFN)-stimulated gene, which itself may enhance type I IFN antiviral response. In a previous study, Zika virus was identified as ZAP-resistant and not sensitive to ZAP antiviral activity. Here, we found that ZAP was associated with the inhibition of Zika virus in Vero cells, in the absence of a robust type I IFN system because Vero cells are deficient for IFN-alpha and -beta. Also, quantitative RNA-seq data indicated that endogenous ZAP is associated with altered global gene expression both in the steady state and during Zika virus infection. Further studies are warranted to elucidate this IFN-alpha and -beta independent anti-Zika virus activity and involvement of ZAP.

ZIKV Inhibitors Based on Pyrazolo[3,4-d]pyridazine-7-one Core: Rational Design, In Vitro Evaluation, and Theoretical Studies.

The Zika virus (ZIKV) is believed to cause birth defects, and no anti-ZIKV drugs have been approved by medical organizations to date. Starting from antimicrobial lead compounds with a pyrazolo[3,4-d]pyridazine-7-one scaffold, we synthesized 16 derivatives and screened their ability to interfere with ZIKV infection utilizing a cell-based phenotypic assay. Of these, five compounds showed significant inhibition of ZIKV with a selective index value greater than 4.6. In particular, compound 9b showed the best anti-ZIKV activity with a selectivity index of 22.4 (half-maximal effective concentration = 25.6 μM and 50% cytotoxic concentration = 572.4 μM). Through the brine shrimp lethality bioassay, 9b, 10b, 12, 17a, and 19a showed median lethal dose values in a range of 87.2-100.3 μg/mL. Compound 9b was also targeted to the NS2B-NS3 protease of ZIKV using molecular docking protocols, in which it acted as a noncompetitive inhibitor and strongly bound to five key amino acids (His51, Asp75, Ser135, Ala132, Tyr161). Utilizing the pharmacophore model of 9b, the top 20 hits were identified as prospective inhibitors of NS2B-NS3 protease, and six of them were confirmed for their stability with the protease via redocking and molecular dynamics simulations.

Therapeutic targeting of organelles for inhibition of Zika virus replication in neurons

Zika virus (ZIKV) is an arbovirus belonging to the family Flaviviridae. Since 2015, ZIKV infection has emerged as a leading cause of virus-induced placental insufficiency, microcephaly and other neuronal complications. Currently, no therapeutics have been approved to treat ZIKV infection. In this study, we examined how targeted inhibition of cellular organelles or trafficking processes affected ZIKV infection and replication in neural progenitor cells. We found that blocking endocytosis, Golgi function or structural filaments like actin or microtubules had moderate effects on virus replication. However, inducing endoplasmic reticulum (ER) stress by treatment with Thapsigargin substantially inhibited virus production, suggesting the ER might be a candidate cellular target. Further analysis showed that sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCA) was important for ZIKV inhibition. Collectively, these studies indicate that targeting the SERCA-dependent ER stress pathway may be useful to develop antivirals to inhibit ZIKV replication.

Antiviral activity of ouabain against a Brazilian Zika virus strain

Zika virus (ZIKV) is an emerging arbovirus associated with neurological disorders. Currently, no specific vaccines or antivirals are available to treat the ZIKV infection. Ouabain, a cardiotonic steroid known as Na+/K+-ATPase inhibitor, has been previously described as an immunomodulatory substance by our group. Here, we evaluated for the first time the antiviral activity of this promising substance against a Brazilian ZIKV strain. Vero cells were treated with different concentrations of ouabain before and after the infection with ZIKV. The antiviral effect was evaluated by the TCID50 method and RT-qPCR. Ouabain presented a dose-dependent inhibitory effect against ZIKV, mainly when added post infection. The reduction of infectious virus was accompanied by a decrease in ZIKV RNA levels, suggesting that the mechanism of ZIKV inhibition by ouabain occurred at the replication step. In addition, our in silico data demonstrated a conformational stability and favorable binding free energy of ouabain in the biding sites of the NS5-RdRp and NS3-helicase proteins, which could be related to its mechanism of action. Taken together, these data demonstrate the antiviral activity of ouabain against a Brazilian ZIKV strain and evidence the potential of cardiotonic steroids as promising antiviral agents.

A platform of assays for the discovery of anti-Zika small-molecules with activity in a 3D-bioprinted outer-blood-retina model.

The global health emergency posed by the outbreak of Zika virus (ZIKV), an arthropod-borne flavivirus causing severe neonatal neurological conditions, has subsided, but there continues to be transmission of ZIKV in endemic regions. As such, there is still a medical need for discovering and developing therapeutical interventions against ZIKV. To identify small-molecule compounds that inhibit ZIKV disease and transmission, we screened multiple small-molecule collections, mostly derived from natural products, for their ability to inhibit wild-type ZIKV. As a primary high-throughput screen, we used a viral cytopathic effect (CPE) inhibition assay conducted in Vero cells that was optimized and miniaturized to a 1536-well format. Suitably active compounds identified from the primary screen were tested in a panel of orthogonal assays using recombinant Zika viruses, including a ZIKV Renilla luciferase reporter assay and a ZIKV mCherry reporter system. Compounds that were active in the wild-type ZIKV inhibition and ZIKV reporter assays were further evaluated for their inhibitory effects against other flaviviruses. Lastly, we demonstrated that wild-type ZIKV is able to infect a 3D-bioprinted outer-blood-retina barrier tissue model and disrupt its barrier function, as measured by electrical resistance. One of the identified compounds (3-Acetyl-13-deoxyphomenone, NCGC00380955) was able to prevent the pathological effects of the viral infection on this clinically relevant ZIKV infection model.

Identification of Ascomycin against Zika virus infection through screening of natural product library

Zika virus (ZIKV) infection could lead to Guillain-Barré syndrome in adults and microcephaly in the newborns from infected pregnant women. To date, there is no specific drug for the treatment of ZIKV infection. In this study, we sought to screen inhibitors against ZIKV infection from a natural product library. A ZIKV replicon was used to screen a library containing 1680 natural compounds. We explored the antiviral mechanism of the compound candidate in vitro and in vivo infection models. Ascomycin, a macrolide from Streptomyces hygroscopicus, was identified with inhibitory effect against ZIKV in Vero cells (IC50 = 0.11 μM), hepatoma cell Huh7 (IC50 = 0.38 μM), and glioblastoma cell SNB-19 (IC50 = 0.06 μM), far below the cytotoxic concentrations. Mechanistic study revealed that Ascomycin suppressed ZIKV RNA replication step during the life cycle and the regulation of calcineurin-NFAT pathway maybe involved in this inhibitory effect, independent of innate immunity activation. Moreover, we found that Ascomycin also inhibited the infection of other Flaviviridae members, such as hepatitis C virus and dengue virus. Ascomycin reduced ZIKV load in blood by up to 3500-fold in A129 mice. Meanwhile, the infection in the mice brain was undetectable by immunohistochemistry staining. Together, these findings reveal a critical role of Ascomycin in the inhibition of ZIKV and related viruses, facilitating the development of novel antiviral agents.

An Integrated Systems Biology Approach Identifies the Proteasome as A Critical Host Machinery for ZIKV and DENV Replication

The Zika virus (ZIKV) and dengue virus (DENV) flaviviruses exhibit similar replicative processes but have distinct clinical outcomes. A systematic understanding of virus–host protein–protein interaction networks can reveal cellular pathways critical to viral replication and disease pathogenesis. Here we employed three independent systems biology approaches toward this goal. First, protein array analysis of direct interactions between individual ZIKV/DENV viral proteins and 20,240 human proteins revealed multiple conserved cellular pathways and protein complexes, including proteasome complexes. Second, an RNAi screen of 10,415 druggable genes identified the host proteins required for ZIKV infection and uncovered that proteasome proteins were crucial in this process. Third, high-throughput screening of 6016 bioactive compounds for ZIKV inhibition yielded 134 effective compounds, including six proteasome inhibitors that suppress both ZIKV and DENV replication. Integrative analyses of these orthogonal datasets pinpoint proteasomes as critical host machinery for ZIKV/DENV replication. Our study provides multi-omics datasets for further studies of flavivirus–host interactions, disease pathogenesis, and new drug targets.

Repurposing of Potent Mtase Inhibitors Against ZIKV Utilizing Structure-Based Molecular Docking

Zika is an Aedes mosquito vector-borne pandemic viral disease. It is a goal for the scientists to destroy the virus completely by generating potent inhibitors. To explore the disease mechanism, various zika viral targets were explored. One of the major targets is Methyltransferase (Mtase), which is common with zika virus (ZIKV), dengue virus (DENV), and West Nile virus (WNV) belonging to the family of Flaviviridae. Therefore, an attempt has been made here to quest dengue virus and West Nile virus Mtase inhibitors, which could be repurposed on Zika virus inhibition by structure-based docking studies. The mode of interactions of 25 DENV and WNV inhibitors has been compared with natural reference drug sinefungin, which is a specific dengue virus and West Nile virus methyl transferase inhibitor. The docking results of compound numbers 4, 6, 10, 12, 13, 17, 18, and 20 exhibit the same mode of interaction with sinefungin. Therefore, these compounds could be proposed for a further experimental investigation to combat zika.

Therapeutic Applications of Peptides against Zika Virus: A Review.

Zika Virus (ZIKV) belongs to the class of flavivirus that can be transmitted by Aedes mosquitoes. The number of Zika virus caused cases of acute infections, neurological disorders and congenital microcephaly are rapidly growing and therefore, in 2016, the World Health Organization declared a global "Public Health Emergency of International Concern". Anti-ZIKV therapeutic and vaccine development strategies are growing worldwide in recent years, however, no specific and safe treatment is available till date to save the human life. Currently, development of peptide therapeutics against ZIKV has attracted rising attention on account of their high safety concern and low development cost, in comparison to small therapeutic molecules and antibody-based anti-viral drugs. In present review, an overview of ZIKV inhibition by peptide-based inhibitors including E-protein derived peptides, antimicrobial peptides, frog skin peptides and probiotic peptides has been discussed. Peptides inhibitors have also been reported to act against NS5, NS2B-NS3 protease and proteasome in order to inhibit ZIKV infection. Recent advances in peptide-based therapeutics and vaccine have been reviewed and their future promise against ZIKV infections has been explored.

The Robust Restriction of Zika Virus by Type-I Interferon in A549 Cells Varies by Viral Lineage and Is Not Determined by IFITM3.

Type-I interferon (IFN-I) is a major antiviral host response but its impact on Zika virus (ZIKV) replication is not well defined, particularly as it relates to different circulating strains. Interferon stimulated genes (ISGs) that inhibit ZIKV, such as IFITM3, have been identified largely using overexpression studies. Here, we tested whether diverse ZIKV strains differed in their susceptibility to IFN-I-mediated restriction and the contribution of IFITM3 to this restriction. We identified a robust IFN-I-mediated antiviral effect on ZIKV replication (>100-fold reduction) in A549 cells, a commonly used cell line to study ZIKV replication. The extent of inhibition depended on the IFN-I type and the virus strain tested. Viruses from the American pathogenic outbreak were more sensitive to IFNα (p = 0.049) and IFNβ (p = 0.09) than African-lineage strains, which have not been linked to severe pathogenesis. Knocking out IFITM3 expression did not dampen the IFN-I antiviral effect and only high overexpression of IFITM3 led to ZIKV inhibition. Moreover, IFITM3 expression levels in different cells were not associated with IFN-mediated ZIKV inhibition. Taken together, our findings indicate that there is a robust IFN-I-mediated antiviral effect on ZIKV infection, particularly for American viruses, that is not due to IFITM3. A549 cells, which are a commonly used cell line to study ZIKV replication, present an opportunity for the discovery of novel antiviral ISGs against ZIKV.

Doratoxylon apetalum, an Indigenous Medicinal Plant from Mascarene Islands, Is a Potent Inhibitor of Zika and Dengue Virus Infection in Human Cells.

Zika virus (ZIKV) and Dengue virus (DENV) are mosquito-borne viruses of the Flavivirus genus that could cause congenital microcephaly and hemorrhage, respectively, in humans, and thus present a risk to global public health. A preventive vaccine against ZIKV remains unavailable, and no specific antiviral drugs against ZIKV and DENV are licensed. Medicinal plants may be a source of natural antiviral drugs which mostly target viral entry. In this study, we evaluate the antiviral activity of Doratoxylum apetalum, an indigenous medicinal plant from the Mascarene Islands, against ZIKV and DENV infection. Our data indicated that D. apetalum exhibited potent antiviral activity against a contemporary epidemic strain of ZIKV and clinical isolates of four DENV serotypes at non-cytotoxic concentrations in human cells. Time-of-drug-addition assays revealed that D. apetalum extract acts on ZIKV entry by preventing the internalisation of virus particles into the host cells. Our data suggest that D. apetalum-mediated ZIKV inhibition relates to virus particle inactivation. We suggest that D. apetalum could be a promising natural source for the development of potential antivirals against medically important flaviviruses.

A Viperin Mutant Bearing the K358R Substitution Lost its Anti-ZIKA Virus Activity.

Interferon-induced viperin (VP) was identified as playing an important role in the innate immune response against Zika virus (ZIKV). The 361 amino acid long human VP protein comprises of a highly conserved C-terminal region, which has been associated with VP antiviral properties against ZIKV. In the present study, we sought to determine whether the very last C-terminal amino-acid residues of VP might play a role in VP-mediated ZIKV inhibition. To address this issue, a recombinant human viperin (rVPwt) was overexpressed by transfection in human epithelial A549 cells. We confirmed that transient overexpression of rVPwt prior to ZIKV infection dramatically reduced viral replication in A549 cells. Deletion of the last 17 C-terminal amino acids of VP resulted in a higher expression level of mutant protein compared to wild-type VP. Mutational analysis revealed that residue substitution at positions 356 to 360 with five alanine led to the same phenotype. The charged residues Asp356, Lys358, and Asp360 were then identified to play a role in the weak level of VPwt protein in A549 cells. Mutant VP bearing the D360A substitution partially rescued ZIKV growth in A549 cells. Remarkably, a single Lys-to-Arg substitution at position 358 was sufficient to abrogate VP antiviral activity against ZIKV. In conclusion, our study showed that Asp356, Lys358, and Asp360 may have an influence on biochemical properties of VP. Our major finding was that Lys358 was a key amino-acid in VP antiviral properties against ZIKV.

Extract prepared from the leaves of Ocimum basilicum inhibits the entry of Zika virus.

The recent Zika virus (ZIKV) outbreaks and rapid spread in tropical Latin America since introduction to Brazil in 2014, and now appearing cases in the USA, are alarming. World Health Organization (WHO) has considered transmission of ZIKV, a serious public health problem because of the increasing number of outbreaks. There are currently no drugs approved for the treatment of ZIKV infection. Discovery of safe and effective drugs are hampered by the risk in treating pregnant woman and toxicity to the fetus. Sweet basil, known as Ocimum basilicum in the scientific community, is a very well-known medicinal herb. Numerous studies have documented its beneficial activity against a great variety of human pathogens ranging from bacteria and virus to fungus and protozoans. Although, basil extracts and oils have been tested successfully against other viruses, its application to tackle ZIKV infection has not been exploited at all. In this study, we report for the first time that highly diluted ethanol extracts prepared from basil leaves can effectively inhibit ZIKV replication in Vero E6 cells with a half maximal inhibitory concentration (IC50) value of 1:134. The diluted extract as well as the amount of ethanol that goes into its preparation have been found to be completely non-toxic to the above mentioned cell line. The extract seems to inhibit the virus at the step of attachment and entry into the host cell. The specific inhibition of ZIKV observed using the basil leaf extract suggests a new alternative mode of treatment against flavivirus. Keywords: Zika virus; basil extract; antiviral.

Variable Inhibition of Zika Virus Replication by Different Wolbachia Strains in Mosquito Cell Cultures.

Mosquito-borne arboviruses are a major source of human disease. One strategy to reduce arbovirus disease is to reduce the mosquito's ability to transmit virus. Mosquito infection with the bacterial endosymbiont Wolbachia pipientis wMel is a novel strategy to reduce Aedes mosquito competency for flavivirus infection. However, experiments investigating cyclic environmental temperatures have shown a reduction in maternal transmission of wMel, potentially weakening the integration of this strain into a mosquito population relative to that of other Wolbachia strains. Consequently, it is important to investigate additional Wolbachia strains. All Zika virus (ZIKV) suppression studies are limited to the wMel Wolbachia strain. Here we show ZIKV inhibition by two different Wolbachia strains: wAlbB (isolated from Aedes albopictus mosquitoes) and wStri (isolated from the planthopper Laodelphax striatellus) in mosquito cells. Wolbachia strain wStri inhibited ZIKV most effectively. Single-cycle infection experiments showed that ZIKV RNA replication and nonstructural protein 5 translation were reduced below the limits of detection in wStri-containing cells, demonstrating early inhibition of virus replication. ZIKV replication was rescued when Wolbachia was inhibited with a bacteriostatic antibiotic. We observed a partial rescue of ZIKV growth when Wolbachia-infected cells were supplemented with cholesterol-lipid concentrate, suggesting competition for nutrients as one of the possible mechanisms of Wolbachia inhibition of ZIKV. Our data show that wAlbB and wStri infection causes inhibition of ZIKV, making them attractive candidates for further in vitro mechanistic and in vivo studies and future vector-centered approaches to limit ZIKV infection and spread.IMPORTANCE Zika virus (ZIKV) has swiftly spread throughout most of the Western Hemisphere. This is due in large part to its replication in and spread by a mosquito vector host. There is an urgent need for approaches that limit ZIKV replication in mosquitoes. One exciting approach for this is to use a bacterial endosymbiont called Wolbachia that can populate mosquito cells and inhibit ZIKV replication. Here we show that two different strains of Wolbachia, wAlbB and wStri, are effective at repressing ZIKV in mosquito cell lines. Repression of virus growth is through the inhibition of an early stage of infection and requires actively replicating Wolbachia Our findings further the understanding of Wolbachia viral inhibition and provide novel tools that can be used in an effort to limit ZIKV replication in the mosquito vector, thereby interrupting the transmission and spread of the virus.

Discovery of host-targeted covalent inhibitors of dengue virus

We report here on an approach targeting the host reactive cysteinome to identify inhibitors of host factors required for the infectious cycle of Flaviviruses and other viruses. We used two parallel cellular phenotypic screens to identify a series of covalent inhibitors, exemplified by QL-XII-47, that are active against dengue virus. We show that the compounds effectively block viral protein expression and that this inhibition is associated with repression of downstream processes of the infectious cycle, and thus significantly contributes to the potent antiviral activity of these compounds. We demonstrate that QL-XII-47's antiviral activity requires selective, covalent modification of a host target by showing that the compound's antiviral activity is recapitulated when cells are preincubated with QL-XII-47 and then washed prior to viral infection and by showing that QL-XII-47R, a non-reactive analog, lacks antiviral activity at concentrations more than 20-fold higher than QL-XII-47's IC90. QL-XII-47's inhibition of Zika virus, West Nile virus, hepatitis C virus, and poliovirus further suggests that it acts via a target mediating inhibition of these other medically relevant viruses. These results demonstrate the utility of screens targeting the host reactive cysteinome for rapid identification of compounds with potent antiviral activity.

Inhibition of Zika virus by Wolbachia in Aedes aegypti.

Through association with cases of microcephaly in 2015, Zika virus (ZIKV) has transitioned from a relatively unknown mosquito-transmitted pathogen to a global health emergency, emphasizing the need to improve existing mosquito control programs to prevent future disease outbreaks. The response to Zika must involve a paradigm shift from traditional to novel methods of mosquito control, and according to the World Health Organization should incorporate the release of mosquitoes infected with the bacterial endosymbiont Wolbachia pipientis. In our recent paper [Dutra, HLC et al., Cell Host & Microbe 2016] we investigated the potential of Wolbachia infections in Aedes aegypti to restrict infection and transmission of Zika virus recently isolated in Brazil. Wolbachia is now well known for its ability to block or reduce infection with a variety of pathogens in different mosquito species including the dengue (DENV), yellow fever, and chikungunya viruses, and malaria-causing Plasmodium, and consequently has great potential to control mosquito-transmitted diseases across the globe. Our results demonstrated that the wMel Wolbachia strain in Brazilian Ae. aegypti is a strong inhibitor of ZIKV infection, and furthermore appears to prevent transmission of infectious viral particles in mosquito saliva, which highlights the bacterium’s suitability for more widespread use in Zika control.

In vitro Inhibition of Zika Virus by Metadichol®, A Novel Nano Emulsion Lipid

Objective: To show the antiviral activity of Metadichol® against Zika virus by an in-vitro assay. Methods: The primary Anti-Zika virus assay was performed using real-time RT-qPCR (TaqMan) to measure extracellular Zika virus RNA copy number associated with virions released from vero cells. The ‘vero’ cell line (kidney epithelial cells extracted from an African green monkey) treated with antiviral test articles is infected with Zika virus followed by Zika virus associated RNA measurement in the cell culture supernatant. Antiviral compounds blocking any step of viral replication such as transcription, translation, encapsidation, the particle assembly and release were identified and characterized using this sensitive assay system. Findings: Metadichol® [1,2] in vitro assays, inhibited the Zika Virus with a EC50 of 1.48 µg/ml. Conclusion: Metadichol is a safe and effective inhibitor for enveloped viruses in humans. Since it is known to bind to the vitamin D receptor (VDR), its action mechanism likely involves the competitive displacement of virus particles from VDR’s on host cell membranes. Metabolism studies of long chain alcohol in fibroblasts suggest that very long chain fatty alcohols, fatty aldehydes, and fatty acids are reversibly interconverted in a fatty alcohol cycle [3]. Metadichol consists of natural components of common foods (classified as GRAS), Metadichol has no known negative side effects. The inhibition of Zika virus by Metadichol is not surprising, given that we have recently published the results of Metadichol which showed broad-spectrum antiviral activity against Dengue, Ebola, H1N1, SARS, Chikungunya and other enveloped viruses [4].