Zika Virus Replication Research Articles

Self-Organized Nanoparticles of Random and Block Copolymers of Sodium 2-(Acrylamido)-2-methyl-1-propanesulfonate and Sodium 11-(Acrylamido)undecanoate as Safe and Effective Zika Virus Inhibitors.

A series of anionic homopolymers, poly(sodium 2-(acrylamido)-2-methyl-1-propanesulfonate) (PAMPS) and amphiphilic copolymers of AMPS and sodium 11-(acrylamido)undecanoate (AaU), both block (PAMPS75-b-PAaUn), and random (P(AMPSm-co-AaUn)), were synthesized and their antiviral activity against Zika virus (ZIKV) was evaluated. Interestingly, while the homopolymers showed limited antiviral activity, the copolymers are very efficient antivirals. This observation was explained considering that under the conditions relevant to the biological experiments (pH 7.4 PBS buffer) the macromolecules of these copolymers exist as negatively charged (zeta potential about −25 mV) nanoparticles (4–12 nm) due to their self-organization. They inhibit the ZIKV replication cycle by binding to the cell surface and thereby blocking virus attachment to host cells. Considering good solubility in aqueous media, low toxicity, and high selectivity index (SI) of the PAMPS-b-PAaU copolymers, they can be considered promising agents against ZIKV infections.

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.

Endogenous cathelicidin is required for protection against ZIKV-caused testis damage via inactivating virons

Cathelicidins have been shown to effectively inhibit flavivirus replication in vitro. However, the effects of mouse and human endogenous cathelicidins on flavivirus infection in vivo are rarely known. We herein found that mouse endogenous cathelicidin CRAMP was significantly up-regulated upon Zika virus (ZIKV) infection. CRAMP deficiency markedly exacerbated ZIKV replication in testis, and aggravated ZIKV-induced testicular damage and spermatic damage in mice, indicating that endogenous cathelicidin is required for protection against ZIKV-caused male infertility in mice. In vitro antiviral assay showed that both mouse cathelidin CRAMP and human cathelicidin LL-37 obviously reduced ZIKV-caused cytopathic effect and inhibited ZIKV replication in Vero cells. Antiviral mechanism revealed that they both directly inactivated ZIKV virons by binding to ZIKV virons and inducing the leakage of ZIKV genomic RNA, consequently inactivated ZIKV virons. In vivo antiviral assay indicated that both of them effectively inhibited ZIKV replication in C57BL/6J and IFNα/β receptor-deficient (Ifnar1−/−) mice when CRAMP or LL-37 was intravenously injected in parallel with or at 1 h after intravenous injection of ZIKV, implying that CRAMP and LL-37 effectively inactivated ZIKV particles and exhibited therapeutic potential against ZIKV infection in vivo. Our findings reveal that endogenous cathelicidin CRAMP and LL-37 act as inactivators of ZIKV, and effectively protect against ZIKV replication and ZIKV-induced male infertility, highlighting their potential for therapy of ZIKV infection.

Gain-of-function genetic screening identifies the antiviral function of TMEM120A via STING activation

Zika virus (ZIKV) infection can be associated with neurological pathologies, such as microcephaly in newborns and Guillain-Barre syndrome in adults. Effective therapeutics are currently not available. As such, a comprehensive understanding of virus-host interactions may guide the development of medications for ZIKV. Here we report a human genome-wide overexpression screen to identify host factors that regulate ZIKV infection and find TMEM120A as a ZIKV restriction factor. TMEM120A overexpression significantly inhibits ZIKV replication, while TMEM120A knockdown increases ZIKV infection in cell lines. Moreover, Tmem120a knockout in mice facilitates ZIKV infection in primary mouse embryonic fibroblasts (MEF) cells. Mechanistically, the antiviral activity of TMEM120A is dependent on STING, as TMEM120A interacts with STING, promotes the translocation of STING from the endoplasmic reticulum (ER) to ER-Golgi intermediate compartment (ERGIC) and enhances the phosphorylation of downstream TBK1 and IRF3, resulting in the expression of multiple antiviral cytokines and interferon-stimulated genes. In summary, our gain-of-function screening identifies TMEM120A as a key activator of the antiviral signaling of STING.

Front Cover: Bithiazole Inhibitors of Phosphatidylinositol 4‐Kinase (PI4KIIIβ) as Broad‐Spectrum Antivirals Blocking the Replication of SARS‐CoV‐2, Zika Virus, and Human Rhinoviruses (ChemMedChem 23/2021)

The Front Cover shows bithiazole derivatives acting as broad-spectrum antiviral agents (BSAAs) by targeting human host cells. These molecules block the replication of human rhinoviruses (hRVs) and Zika virus (ZIKV) via inhibition of the intracellular protein PI4KIIIβ while the inhibition of SARS-CoV-2 entry and replication seems to be connected with the modulation of an additional target. Cover design by Marco Radi. More information can be found in the Communication by Maria Grazia Martina, Marco Radi et al.

Synthesis, structure-activity relationship and antiviral activity of indole-containing inhibitors of Flavivirus NS2B-NS3 protease.

Zika virus belongs to the Flavivirus family of RNA viruses, which include other important human pathogens such as dengue and West Nile virus. There are no approved antiviral drugs for these viruses. The highly conserved NS2B-NS3 protease of Flavivirus is essential for the replication of these viruses and it is therefore a drug target. Compound screen followed by medicinal chemistry optimization yielded a novel series of 2,6-disubstituted indole compounds that are potent inhibitors of Zika virus protease (ZVpro) with IC50 values as low as 320nM. The structure-activity relationships of these and related compounds are discussed. Enzyme kinetics studies show the inhibitor 66 most likely exhibited a non-competitive mode of inhibition. In addition, this series of ZVpro inhibitors also inhibit the NS2B-NS3 protease of dengue and West Nile virus with reduced potencies. The most potent compounds 66 and 67 strongly inhibited Zika virus replication in cells with EC68 values of 1-3μM. These compounds are novel pharmacological leads for further drug development targeting Zika virus.

Starvation at the larval stage increases the vector competence of Aedes aegypti females for Zika virus.

Aedes aegypti is the primary vector of Zika virus (ZIKV), a flavivirus which typically presents itself as febrile-like symptoms in humans but can also cause neurological and pregnancy complications. The transmission cycle of mosquito-borne arboviruses such as ZIKV requires that various key tissues in the female mosquito get productively infected with the virus before the mosquito can transmit the virus to another vertebrate host. Following ingestion of a viremic blood-meal from a vertebrate, ZIKV initially infects the midgut epithelium before exiting the midgut after blood-meal digestion to disseminate to secondary tissues including the salivary glands. Here we investigated whether smaller Ae. aegypti females resulting from food deprivation as larvae exhibited an altered vector competence for blood-meal acquired ZIKV relative to larger mosquitoes. Midguts from small ‘Starve’ and large ‘Control’ Ae. aegypti were dissected to visualize by transmission electron microscopy (TEM) the midgut basal lamina (BL) as physical evidence for the midgut escape barrier showing Starve mosquitoes with a significantly thinner midgut BL than Control mosquitoes at two timepoints. ZIKV replication was inhibited in Starve mosquitoes following intrathoracic injection of virus, however, Starve mosquitoes exhibited a significantly higher midgut escape and population dissemination rate at 9 days post-infection (dpi) via blood-meal, with more virus present in saliva and head tissue than Control by 10 dpi and 14 dpi, respectively. These results indicate that Ae. aegypti developing under stressful conditions potentially exhibit higher midgut infection and dissemination rates for ZIKV as adults, Thus, variation in food intake as larvae is potentially a source for variable vector competence levels of the emerged adults for the virus.

In vitro antiviral activity against Zika virus from a natural product of the Brazilian red seaweed Bryothamnion triquetrum.

Zika virus (ZIKV) is an arthropod-borne flavivirus that reemerged in 2007 and, since then, has caused several outbreaks and spread to over 80 countries worldwide. Along with this, ZIKV infections have been associated with severe clinical outcomes, including neurological manifestations, especially in newborns, posing a major threat to human health. However, there are no licensed vaccines or specific antiviral agents available yet; thereby, there is an urgent need for the discovery of novel therapeutic strategies to fight this infection. In this context, seaweeds are proven sources of biologically relevant products, including antiviral ones, that remain poorly explored. Herein, we evaluated the antiviral potential of the dichloromethane extract of the red seaweed Bryotamnion triquetrum against ZIKV. MTT assay was carried out to evaluate the extract's toxicity in Vero cells, while standard plaque assays were performed for viral titer quantification in the antiviral assays. The B. triquetrum extract possessed great inhibitory activity on the ZIKV replication in Vero cells, with an EC50 of 1.38 µg/ml and a higher selectivity index than ribavirin (289.85 and 75.20, respectively), a licensed antiviral drug. The investigation of its mechanism of action revealed a moderate virucidal effect while it strongly impaired virus replication at both early and late steps of the virus replication cycle with moderate inhibition at the attachment stage. Finally, the B. triquetrum extract presented a remarkable synergistic effect with ribavirin at suboptimal concentrations, which also highlights the promising antiviral potential of this product as a drug candidate to combat ZIKV infection. Keywords: Rhodophyta; Algae; arbovirus; antiviral; Zika.

Limited replication of human cytomegalovirus in a trophoblast cell line

Several viruses, including human cytomegalovirus (HCMV), are thought to replicate in the placenta. However, there is little understanding of the molecular mechanisms involved in HCMV replication in this tissue. We investigated replication of HCMV in the extravillous trophoblast cell line SGHPL-4, a commonly used model of HCMV replication in the placenta. We found limited HCMV protein expression and virus replication in SGHPL-4 cells. This was associated with a lack of trophoblast progenitor cell protein markers in SGHPL-4 cells, suggesting a relationship between trophoblast differentiation and limited HCMV replication. We proposed that limited HCMV replication in trophoblast cells is advantageous to vertical transmission of HCMV, as there is a greater opportunity for vertical transmission when the placenta is intact and functional. Furthermore, when we investigated the replication of other vertically transmitted viruses in SGHPL-4 cells we found some limitation to replication of Zika virus, but not herpes simplex virus. Thus, limited replication of some, but not all, vertically transmitted viruses may be a feature of trophoblast cells.

High-throughput Antiviral Assays to Screen for Inhibitors of Zika Virus Replication.

Antiviral drug discovery requires the development of reliable biochemical and cellular assays that can be performed in high-throughput screening (HTS) formats. The flavivirus non-structural (NS) proteins are thought to co-translationally assemble on the endoplasmic reticulum (ER) membranes, forming the replication complex (RC). The NS3 and NS5 are the most studied enzymes of the RC and constitute the main targets for drug development due to their crucial roles in viral genome replication. NS3 protease domain, which requires NS2B as its cofactor, is responsible for the cleavage of the immature viral polyprotein into the mature NS proteins, whereas NS5 RdRp domain is responsible for the RNA replication. Herein, we describe in detail the protocols used in replicon-based screenings and enzymatic assays to test large compound libraries for inhibitors of the Zika virus (ZIKV) replication. Replicons are self-replicating subgenomic systems expressed in mammalian cells, in which the viral structural genes are replaced by a reporter gene. The inhibitory effects of compounds on viral RNA replication can be easily evaluated by measuring the reduction in the reporter protein activity. The replicon-based screenings were performed using a BHK-21 ZIKV replicon cell line expressing Renilla luciferase as a reporter gene. To characterize the specific targets of identified compounds, we established in-vitro fluorescence-based assays for recombinantly expressed NS3 protease and NS5 RdRp. The proteolytic activity of the viral protease was measured by using the fluorogenic peptide substrate Bz-nKRR-AMC, while the NS5 RdRp elongation activity was directly detected by the increase of the fluorescent signal of SYBR Green I during RNA elongation, using the synthetic biotinylated self-priming template 3'UTR-U30 (5'-biotin-U30-ACUGGAGAUCGAUCUCCAGU-3').

High-throughput Antiviral Assays to Screen for Inhibitors of Zika Virus Replication

High-throughput Antiviral Assays to Screen for Inhibitors of Zika Virus Replication

In vitro and in vivo characterization of erythrosin B and derivatives against Zika virus

Zika virus (ZIKV) causes significant human diseases without specific therapy. Previously we found erythrosin B, an FDA-approved food additive, inhibited viral NS2B−NS3 interactions, leading to inhibition of ZIKV infection in cell culture. In this study, we performed pharmacokinetic and in vivo studies to demonstrate the efficacy of erythrosin B against ZIKV in 3D mini-brain organoid and mouse models. Our results showed that erythrosin B is very effective in abolishing ZIKV replication in the 3D organoid model. Although pharmacokinetics studies indicated that erythrosin B had a low absorption profile, mice challenged by a lethal dose of ZIKV showed a significantly improved survival rate upon oral administration of erythrosin B, compared to vehicle control. Limited structure−activity relationship studies indicated that most analogs of erythrosin B with modifications on the xanthene ring led to loss or reduction of inhibitory activities towards viral NS2B−NS3 interactions, protease activity and antiviral efficacy. In contrast, introducing chlorine substitutions on the isobenzofuran ring led to slightly increased activities, suggesting that the isobenzofuran ring is well tolerated for modifications. Cytotoxicity studies indicated that all derivatives are nontoxic to human cells. Overall, our studies demonstrated erythrosin B is an effective antiviral against ZIKV both in vitro and in vivo.

Hide and Seek: The Interplay Between Zika Virus and the Host Immune Response.

Zika virus (ZIKV) received worldwide attention over the past decade when outbreaks of the disease were found to be associated with severe neurological syndromes and congenital abnormalities. Unlike most other flaviviruses, ZIKV can spread through sexual and transplacental transmission, adding to the complexity of Zika pathogenesis and clinical outcomes. In addition, the spread of ZIKV in flavivirus-endemic regions, and the high degree of structural and sequence homology between Zika and its close cousin Dengue have raised questions on the interplay between ZIKV and the pre-existing immunity to other flaviviruses and the potential immunopathogenesis. The Zika epidemic peaked in 2016 and has affected over 80 countries worldwide. The re-emergence of large-scale outbreaks in the future is certainly a possibility. To date, there has been no approved antiviral or vaccine against the ZIKV. Therefore, continuing Zika research and developing an effective antiviral and vaccine is essential to prepare the world for a future Zika epidemic. For this purpose, an in-depth understanding of ZIKV interaction with many different pathways in the human host and how it exploits the host immune response is required. For successful infection, the virus has developed elaborate mechanisms to escape the host response, including blocking host interferon response and shutdown of certain host cell translation. This review provides a summary on the key host factors that facilitate ZIKV entry and replication and the mechanisms by which ZIKV antagonizes antiviral innate immune response and involvement of adaptive immune response leading to immunopathology. We also discuss how ZIKV modulates the host immune response during sexual transmission and pregnancy to induce infection, how the cross-reactive immunity from other flaviviruses impacts ZIKV infection, and provide an update on the current status of ZIKV vaccine development.

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.

Actions of Camptothecin Derivatives on Larvae and Adults of the Arboviral Vector Aedes aegypti.

Mosquito-borne viruses including dengue, Zika, and Chikungunya viruses, and parasites such as malaria and Onchocerca volvulus endanger health and economic security around the globe, and emerging mosquito-borne pathogens have pandemic potential. However, the rapid spread of insecticide resistance threatens our ability to control mosquito vectors. Larvae of Aedes aegypti were screened with the Medicines for Malaria Venture Pandemic Response Box, an open-source compound library, using INVAPP, an invertebrate automated phenotyping platform suited to high-throughput chemical screening of larval motility. We identified rubitecan (a synthetic derivative of camptothecin) as a hit compound that reduced A. aegypti larval motility. Both rubitecan and camptothecin displayed concentration dependent reduction in larval motility with estimated EC50 of 25.5 ± 5.0 µM and 22.3 ± 5.4 µM, respectively. We extended our investigation to adult mosquitoes and found that camptothecin increased lethality when delivered in a blood meal to A. aegypti adults at 100 µM and 10 µM, and completely blocked egg laying when fed at 100 µM. Camptothecin and its derivatives are inhibitors of topoisomerase I, have known activity against several agricultural pests, and are also approved for the treatment of several cancers. Crucially, they can inhibit Zika virus replication in human cells, so there is potential for dual targeting of both the vector and an important arbovirus that it carries.

Discovery of Genes that Modulate Flavivirus Replication in an Interferon-Dependent Manner

Establishment of the interferon (IFN)-mediated antiviral state provides a crucial initial line of defense against viral infection. Numerous genes that contribute to this antiviral state remain to be identified. Using a loss-of-function strategy, we screened an original library of 1156 siRNAs targeting 386 individual curated human genes in stimulated microglial cells infected with Zika virus (ZIKV), an emerging RNA virus that belongs to the flavivirus genus. The screen recovered twenty-one potential host proteins that modulate ZIKV replication in an IFN-dependent manner, including the previously known IFITM3 and LY6E. Further characterization contributed to delineate the spectrum of action of these genes towards other pathogenic RNA viruses, including Hepatitis C virus and SARS-CoV-2. Our data revealed that APOL3 acts as a proviral factor for ZIKV and several other related and unrelated RNA viruses. In addition, we showed that MTA2, a chromatin remodeling factor, possesses potent flavivirus-specific antiviral functions induced by IFN. Our work identified previously unrecognized genes that modulate the replication of RNA viruses in an IFN-dependent manner, opening new perspectives to target weakness points in the life cycle of these viruses.

Myxovirus resistance protein A activates type I IFN signaling pathway to inhibit Zika virus replication

Myxovirus resistance protein A(MxA), one of the dynamin superfamily of large guanosine triphosphatase and a classical interferon stimulated gene (ISG) induced by type I interferons (IFNs), plays antiviral role in various virus infections. However, the effect of MxA on Zika virus (ZIKV) infection and its underlying mechanism remain elusive. In this study, we aimed to explore the role of MxA in ZIKV infection and its potential mechanisms. MxA overexpression was achieved by transfection with plasmid. The levels of MxA expression and ZIKV replication were assayed by both qRT-PCR and western blot. The activation status of Jak/STAT signaling pathway was evaluated at three levels: phosphorylation of STAT1 and STAT2(p-STAT1, p-STAT2) (western blot), activity of interferon sensitive response element (ISRE) (dual luciferase reporter gene assay), and the expression levels of ISGs (qRT-PCR). Our results showed that MxA overexpression inhibited ZIKV replication with no effect on virus entry. The expression levels of retinoic acid inducible gene I (RIG-I), melanoma differentiation-associated gene-5(MDA5), Toll-like receptor3(TLR3) and interferon regulatory Factor 3(IRF3), as well as IFNα and IFNβ, were increased in parallel with MxA upregulation. Interestingly, the inhibitory effect of MxA on ZIKV replication was abolished in type I IFN receptor (IFNAR) deficient cells (U5A). These data collectively supported that MxA inhibits ZIKV replication through activation of the type I IFN signaling pathway.

Placental Autophagy and Viral Replication Co-localize in Human and Non-human Primate Placentae Following Zika Virus Infection: Implications for Therapeutic Interventions.

Multiple studies have shown both induction and inhibition of autophagy during Zika virus (ZIKV) infection. While some have proposed mechanisms by which autophagic dysregulation might facilitate ZIKV vertical transmission, there is a lack of in situ data in human and non-human primate models. This is an especially pertinent question as autophagy-inhibitors, such as hydroxychloroquine, have been proposed as potential therapeutic agents aimed at preventing vertical transmission of ZIKV and other RNA viruses. Given the paucity of pre-clinical data in support of either autophagic enhancement or inhibition of placental ZIKV viral infection, we sought to assess cellular, spatial, and temporal associations between placental ZIKV infection and measures of autophagy in human primary cell culture and congenital infection cases, as well as an experimental non-human primate (marmoset, Callithrix jacchus) model. Primary trophoblast cells were isolated from human placentae (n = 10) and infected in vitro with ZIKV. Autophagy-associated gene expression (ULK-1, BECN1, ATG5, ATG7, ATG12, ATG16L1, MAP1LC3A, MAP1LC3B, p62/SQSTM1) was then determined by TaqMan qPCR to determine fold-change with ZIKV-infection. In in vivo validation experiments, autophagy genes LC3B and p62/SQSTM1 were probed using in situ hybridization (ISH) in the placentae of human Congenital Zika Syndrome (CZS) cases (n = 3) and ZIKV-infected marmoset placenta (n = 1) and fetal tissue (n = 1). Infected and uninfected villi were compared for mean density and co-localization of autophagic protein markers. Studies of primary cultured human trophoblasts revealed decreased expression of autophagy genes ATG5 and p62/SQSTM1 in ZIKV-infected trophoblasts [ATG5 fold change (±SD) 0.734-fold (±0.722), p = 0.036; p62/SQSTM1 0.661-fold (±0.666), p = 0.029]. Histologic examination by ISH and immunohistochemistry confirmed spatial association of autophagy and ZIKV infection in human congenital infection cases, as well as marmoset placental and fetal tissue samples. When quantified by densitometric data, autophagic protein LC3B, and p62/SQSTM1 expression in marmoset placenta were significantly decreased in in situ ZIKV-infected villi compared to less-infected areas [LC3B mean 0.951 (95% CI, 0.930-0.971), p = 0.018; p62/SQSTM1 mean 0.863 (95% CI, 0.810-0.916), p = 0.024]. In the current study, we observed that in the non-transformed human and non-human primate placenta, disruption (specifically down-regulation) of autophagy accompanies later ZIKV replication in vitro, in vivo, and in situ. The findings collectively suggest that dysregulated autophagy spatially and temporally accompanies placental ZIKV replication, providing the first in situ evidence in relevant primate pre-clinical and clinical models for the importance of timing of human therapeutic strategies aimed at agonizing/antagonizing autophagy. These studies have likely further implications for other congenitally transmitted viruses, particularly the RNA viruses, given the ubiquitous nature of autophagic disruption and dysregulation in host responses to viral infection during pregnancy.

In Vitro Inhibition of Zika Virus Replication with Amantadine and Rimantadine Hydrochlorides

Zika virus (ZIKV) is a mosquito-borne flavivirus in which human infection became relevant during recent outbreaks in Latin America due to its unrecognized association with fetal neurological disorders. Currently, there are no approved effective antivirals or vaccines for the treatment or prevention of ZIKV infections. Amantadine and rimantadine are approved antivirals used against susceptible influenza A virus infections that have been shown to have antiviral activity against other viruses, such as dengue virus (DENV). Here, we report the in vitro effectiveness of both amantadine and rimantadine hydrochlorides against ZIKV replication, resulting in a dose-dependent reduction in viral titers of a ZIKV clinical isolate and two different ZIKV reference strains. Additionally, we demonstrate similar in vitro antiviral activity of these drugs against DENV-1 and yellow fever virus (YFV), although at higher drug concentrations for the latter. ZIKV replication was inhibited at drug concentrations well below cytotoxic levels of both compounds, as denoted by the high selectivity indexes obtained with the tested strains. Further work is absolutely needed to determine the potential clinical use of these antivirals against ZIKV infections, but our results suggest the existence of a highly conserved mechanism across flavivirus, susceptible to be blocked by modified more specific adamantane compounds.

Flavonoids as Molecules With Anti-Zika virus Activity.

Zika virus (ZIKV) is an arthropod-born virus that is mainly transmitted to humans by mosquitoes of the genus Aedes spp. Since its first isolation in 1947, only a few human cases had been described until large outbreaks occurred on Yap Island (2007), French Polynesia (2013), and Brazil (2015). Most ZIKV-infected individuals are asymptomatic or present with a self-limiting disease and nonspecific symptoms such as fever, myalgia, and headache. However, in French Polynesia and Brazil, ZIKV outbreaks led to the diagnosis of congenital malformations and microcephaly in newborns and Guillain-Barré syndrome (GBS) in adults. These new clinical presentations raised concern from public health authorities and highlighted the need for anti-Zika treatments and vaccines to control the neurological damage caused by the virus. Despite many efforts in the search for an effective treatment, neither vaccines nor antiviral drugs have become available to control ZIKV infection and/or replication. Flavonoids, a class of natural compounds that are well-known for possessing several biological properties, have shown activity against different viruses. Additionally, the use of flavonoids in some countries as food supplements indicates that these molecules are nontoxic to humans. Thus, here, we summarize knowledge on the use of flavonoids as a source of anti-ZIKV molecules and discuss the gaps and challenges in this area before these compounds can be considered for further preclinical and clinical trials.