Zika antiviral chemotherapy: identification of drugs and promising starting points for drug discovery from an FDA-approved library

Identification of novel anti-ZIKV drugs from viral-infection temporal gene expression profiles

Zika virus (ZIKV) infections are typically asymptomatic but cause severe neurological complications (e.g. Guillain-Barré syndrome in adults, and microcephaly in newborns). There are currently no specific therapy or vaccine options available to prevent ZIKV infections. Temporal gene expression profiles of ZIKV-infected human brain microvascular endothelial cells (HBMECs) were used in this study to identify genes essential for viral replication. These genes were then used to identify novel anti-ZIKV agents and validated in publicly available data and functional wet-lab experiments. Here, we found that ZIKV effectively evaded activation of immune response-related genes and completely reprogrammed cellular transcriptional architectures. Knockdown of genes, which gradually upregulated during viral infection but showed distinct expression patterns between ZIKV- and mock infection, discovered novel proviral and antiviral factors. One-third of the 74 drugs found through signature-based drug repositioning and cross-reference with the Drug Gene Interaction Database (DGIdb) were known anti-ZIKV agents. In cellular assays, two promising antiviral candidates (Luminespib/NVP-AUY922, L-161982) were found to reduce viral replication without causing cell toxicity. Overall, our time-series transcriptome-based methods offer a novel and feasible strategy for antiviral drug discovery. Our strategies, which combine conventional and data-driven analysis, can be extended for other pathogens causing pandemics in the future.

Chelerythrine chloride inhibits Zika virus infection by targeting the viral NS4B protein

Zika virus (ZIKV) is a mosquito-borne virus that has re-emerged as a significant threat to global health in the recent decade. Whilst infections are primarily asymptomatic, the virus has been associated with the manifestation of severe neurological complications. At present, there is still a lack of approved antivirals for ZIKV infections. In this study, chelerythrine chloride, a benzophenanthridine alkaloid, was identified from a mid-throughput screen conducted on a 502-compound natural products library to be a novel and potent inhibitor of ZIKV infection in both in-vitro and in-vivo assays. Subsequent downstream studies demonstrated that the compound inhibits a post-entry step of the viral replication cycle and is capable of disrupting viral RNA synthesis and protein expression. The successful generation and sequencing of a ZIKV resistant mutant revealed that a single S61T mutation on the viral NS4B allowed ZIKV to overcome chelerythrine chloride inhibition. Further investigation revealed that chelerythrine chloride could directly inhibit ZIKV protein synthesis, and that the NS4B-S61T mutation confers resistance to this inhibition. This study has established chelerythrine chloride as a potential candidate for further development as a therapeutic agent against ZIKV infection.

Natural Products and Derivatives as Potential Zika virus Inhibitors: A Comprehensive Review

Zika virus (ZIKV) is an arbovirus whose infection in humans can lead to severe outcomes. This article reviews studies reporting the anti-ZIKV activity of natural products (NPs) and derivatives published from 1997 to 2022, which were carried out with NPs obtained from plants (82.4%) or semisynthetic/synthetic derivatives, fungi (3.1%), bacteria (7.6%), animals (1.2%) and marine organisms (1.9%) along with miscellaneous compounds (3.8%). Classes of NPs reported to present anti-ZIKV activity include polyphenols, triterpenes, alkaloids, and steroids, among others. The highest values of the selectivity index, the ratio between cytotoxicity and antiviral activity (SI = CC₅₀/EC₅₀), were reported for epigallocatechin gallate (SI ≥ 25,000) and anisomycin (SI ≥ 11,900) obtained from Streptomyces bacteria, dolastane (SI = 1246) isolated from the marine seaweed Canistrocarpus cervicorni, and the flavonol myricetin (SI ≥ 862). NPs mostly act at the stages of viral adsorption and internalization in addition to presenting virucidal effect. The data demonstrate the potential of NPs for developing new anti-ZIKV agents and highlight the lack of studies addressing their molecular mechanisms of action and pre-clinical studies of efficacy and safety in animal models. To the best of our knowledge, none of the active compounds has been submitted to clinical studies.

Differential Susceptibility of Fetal Retinal Pigment Epithelial Cells, hiPSC- Retinal Stem Cells, and Retinal Organoids to Zika Virus Infection

Zika virus (ZIKV) causes microcephaly and congenital eye disease. The cellular and molecular basis of congenital ZIKV infection are not well understood. Here, we utilized a biologically relevant cell-based system of human fetal retinal pigment epithelial cells (FRPEs), hiPSC-derived retinal stem cells (iRSCs), and retinal organoids to investigate ZIKV-mediated ocular cell injury processes. Our data show that FRPEs were highly susceptible to ZIKV infection exhibiting increased apoptosis, whereas iRSCs showed reduced susceptibility. Detailed transcriptomics and proteomics analyses of infected FRPEs were performed. Nucleoside analogue drug treatment inhibited ZIKV replication. Retinal organoids were susceptible to ZIKV infection. The Asian genotype ZIKV exhibited higher infectivity, induced profound inflammatory response, and dysregulated transcription factors involved in retinal organoid differentiation. Collectively, our study shows that ZIKV affects ocular cells at different developmental stages resulting in cellular injury and death, further providing molecular insight into the pathogenesis of congenital eye disease.

Natural products as Zika antivirals

Zika virus (ZIKV) is an arbovirus belonging to the flavivirus genus and is transmitted in Aedes mosquito vectors. Since its discovery in humans in 1952 in Uganda, ZIKV has been responsible for many outbreaks in South America, Africa, and Asia. Patients infected with ZIKV are usually asymptomatic; mild symptoms include fever, joint and muscle pain, and fatigue. However, severe infections may have neurological implications, such as Guillain-Barré syndrome and fetal microcephaly. To date, there are no existing approved therapeutic drugs or vaccines against ZIKV infections; treatments mainly target the symptoms of infection. Preventive measures against mosquito breeding are the main strategy for limiting the spread of the virus. Antiviral drug research for the treatment of ZIKV infection has been rapidly developing, with many drug candidates emerging from drug repurposing studies, and compound screening. In particular, several studies have demonstrated the potential of natural products as antivirals for ZIKV infection. Hence, this paper will review recent advances in natural products in ZIKV antiviral drug discovery.

In-Depth Characterization of Zika Virus Inhibitors Using Cell-Based Electrical Impedance

In this study, we use electric cell-substrate impedance sensing (ECIS), an established cell-based electrical impedance (CEI) technology, to decipher the kinetic cytopathic effect (CPE) induced by Zika virus (ZIKV) in susceptible human A549 lung epithelial cells and to evaluate several classes of compounds with reported antiviral activity (two entry inhibitors and two replication inhibitors). To validate the assay, we compare the results with those obtained with more traditional in vitro methods based on cell viability and viral yield readouts. We demonstrate that CEI can detect viral infection in a sensitive manner and can be used to determine antiviral potency. Moreover, CEI has multiple benefits compared to conventional assays: the technique is less laborious and better at visualizing the dynamic antiviral activity profile of the compounds, while also it has the ability to determine interesting time points that can be selected as endpoints in assays without continuous readout. We describe several parameters to characterize the compounds' cytotoxicity and their antiviral activity profile. In addition, the CEI patterns provide valuable additional information about the presumed mechanism of action of these compounds. Finally, as a proof of concept, we used CEI to evaluate the antiviral activity of a small series of compounds, for which we demonstrate that the sulfonated polymer PRO2000 inhibits ZIKV with a response profile representative for a viral entry inhibitor. Overall, we demonstrate for the first time that CEI is a powerful technology to evaluate and characterize compounds against ZIKV replication in a real-time, label-free, and noninvasive manner. IMPORTANCE Zika virus can cause serious disease in humans. Unfortunately, no antiviral drugs are available to treat infection. Here, we use an impedance-based method to continuously monitor virus infection in-and damage to-human cells. We can determine the Zika viral dose with this technique and also evaluate whether antiviral compounds protect the cells from damage caused by virus replication. We also show that this technique can be used to further unravel the characteristics of these compounds, such as their toxicity to the cells, and that it might even give further insight in their mechanism of antiviral action. Finally, we also find a novel Zika virus inhibitor, PRO2000. Overall, in this study, we use the impedance technology to-for the first time-evaluate compounds with anti-Zika virus properties, and therefore it can add valuable information in the further search for antiviral drugs.

Dihydrofolate reductase, thymidylate synthase, and serine hydroxy methyltransferase: successful targets against some infectious diseases

Parasitic diseases have a serious impact on the world in terms of health and economics and are responsible for worldwide mortality and morbidity. The present review features the hybrid targeting involving three main enzymes for the treatment of different parasitic diseases. The enzymes Dihydrofolate reductase, thymidylate synthase, and Serine hydroxy methyltransferase play an essential role in the folate pathway. The present review focuses on these enzymes, which can be targeted against several diseases. It shed light on the past, present, and future of these targets, and it can be assessed that these targets can play a significant role against several infectious diseases. For combating viral and protozoal infectious diseases, these targets in combination should be addressed.

Can anti-parasitic drugs help control COVID-19?

Novel COVID-19 is a public health emergency that poses a serious threat to people worldwide. Given the virus spreading so quickly, novel antiviral medications are desperately needed. Repurposing existing drugs is the first strategy. Anti-parasitic drugs were among the first to be considered as a potential treatment option for this disease. Even though many papers have discussed the efficacy of various anti-parasitic drugs in treating COVID-19 separately, so far, no single study comprehensively discussed these drugs. This study reviews some anti-parasitic recommended drugs to treat COVID-19, in terms of function and in vitro as well as clinical results. Finally, we briefly review the advanced techniques, such as artificial intelligence, that have been used to find effective drugs for the treatment of COVID-19.

Facile method for delivering chikungunya viral replicons into mosquitoes and mammalian cells

Reverse genetics is an important tool in the elucidation of viral replication and the development of countermeasures; however, these methods are impeded by laborious and inefficient replicon delivery methods. This paper demonstrates the use of a baculovirus to facilitate the efficient delivery of autonomous CHIKV replicons into mosquito and mammalian cells in vitro as well as adult mosquitoes in vivo. The efficacy of this approach was verified via co-localization among an eGFP reporter, nsP1, and dsRNA as well as through the inhibition of an RNA-dependent RNA polymerase (RdRp) null mutation (DDAA) in nsP4, or the treatment of a known antiviral compound (6-azauridine). We also investigated the correlation between CHIKV replicon-launched eGFP expression and the effectiveness of CHIKV replicon variants in inducing IFN-β expression in human cell lines. This delivery method based on a single vector is applicable to mosquito and mammalian cells in seeking to decipher the mechanisms underlying CHIKV replication, elucidate virus-host interactions, and develop antivirals. This study presents an effective alternative to overcome many of the technological issues related to the study and utilization of autonomous arbovirus replicons.

Flavonoids from Pterogyne nitens as Zika virus NS2B-NS3 protease inhibitors

Although the widespread epidemic of Zika virus (ZIKV) and its neurological complications are well-known there are still no approved drugs available to treat this arboviral disease or vaccine to prevent the infection. Flavonoids from Pterogyne nitens have already demonstrated anti-flavivirus activity, although their target is unknown. In this study, we virtually screened an in-house database of 150 natural and semi-synthetic compounds against ZIKV NS2B-NS3 protease (NS2B-NS3p) using docking-based virtual screening, as part of the OpenZika project. As a result, we prioritized three flavonoids from P. nitens, quercetin, rutin and pedalitin, for experimental evaluation. We also used machine learning models, built with Assay Central® software, for predicting the activity and toxicity of these flavonoids. Biophysical and enzymatic assays generally agreed with the in silico predictions, confirming that the flavonoids inhibited ZIKV protease. The most promising hit, pedalitin, inhibited ZIKV NS2B-NS3p with an IC50 of 5 μM. In cell-based assays, pedalitin displayed significant activity at 250 and 500 µM, with slight toxicity in Vero cells. The results presented here demonstrate the potential of pedalitin as a candidate for hit-to-lead (H2L) optimization studies towards the discovery of antiviral drug candidates to treat ZIKV infections.

Emerging paradigms of viral diseases and paramount role of natural resources as antiviral agents

In the current scenario, the increasing prevalence of diverse microbial infections as well as emergence and re-emergence of viral epidemics with high morbidity and mortality rates are major public health threat. Despite the persistent production of antiviral drugs and vaccines in the global market, viruses still remain as one of the leading causes of deadly human diseases. Effective control of viral diseases, particularly Zika virus disease, Nipah virus disease, Severe acute respiratory syndrome, Coronavirus disease, Herpes simplex virus infection, Acquired immunodeficiency syndrome, and Ebola virus disease remain promising goal amidst the mutating viral strains. Current trends in the development of antiviral drugs focus solely on testing novel drugs or repurposing drugs against potential targets of the viruses. Compared to synthetic drugs, medicines from natural resources offer less side-effect to humans and are often cost-effective in the productivity approaches. This review intends not only to emphasize on the major viral disease outbreaks in the past few decades and but also explores the potentialities of natural substances as antiviral traits to combat viral pathogens. Here, we spotlighted a comprehensive overview of antiviral components present in varied natural sources, including plants, fungi, and microorganisms in order to identify potent antiviral agents for developing alternative therapy in future.

Zika virus pathogenesis and current therapeutic advances

Zika virus (ZIKV) is an emerging arthropod-borne flavivirus that, upon infection, results in teratogenic effects and neurological disorders. ZIKV infections pose serious global public health concerns, prompting scientists to increase research on antivirals and vaccines against the virus. These efforts are still ongoing as the pathogenesis and immune evasion mechanisms of ZIKV have not yet been fully elaborated. Currently, no specific vaccines or drugs have been approved for ZIKV; however, some are undergoing clinical trials. Notably, several strategies have been used to develop antivirals, including drugs that target viral and host proteins. Additionally, drug repurposing is preferred since it is less costly and takes less time than other strategies because the drugs used have already been approved for human use. Likewise, different platforms have been evaluated for the design of vaccines, including DNA, mRNA, peptide, protein, viral vectors, virus-like particles (VLPSs), inactivated-virus, and live-attenuated virus vaccines. These vaccines have been shown to induce specific humoral and cellular immune responses and reduce viremia and viral RNA both in vitro and in vivo. Importantly, most of these vaccines have entered clinical trials. Understanding the viral disease mechanism will provide better strategies for developing therapeutic agents against ZIKV. This review provides a comprehensive summary of the viral pathogenesis of ZIKV and current advancements in the development of vaccines and drugs against this virus.

Antiviral Compounds for Blocking Arboviral Transmission in Mosquitoes

Mosquito-borne arthropod-borne viruses (arboviruses) such as the dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) are important human pathogens that are responsible for significant global morbidity and mortality. The recent emergence and re-emergence of mosquito-borne viral diseases (MBVDs) highlight the urgent need for safe and effective vaccines, therapeutics, and vector-control approaches to prevent MBVD outbreaks. In nature, arboviruses circulate between vertebrate hosts and arthropod vectors; therefore, disrupting the virus lifecycle in mosquitoes is a major approach for combating MBVDs. Several strategies were proposed to render mosquitoes that are refractory to arboviral infection, for example, those involving the generation of genetically modified mosquitoes or infection with the symbiotic bacterium Wolbachia. Due to the recent development of high-throughput screening methods, an increasing number of drugs with inhibitory effects on mosquito-borne arboviruses in mammalian cells were identified. These antivirals are useful resources that can impede the circulation of arboviruses between arthropods and humans by either rendering viruses more vulnerable in humans or suppressing viral infection by reducing the expression of host factors in mosquitoes. In this review, we summarize recent advances in small-molecule antiarboviral drugs in mammalian and mosquito cells, and discuss how to use these antivirals to block the transmission of MBVDs.

Sofosbuvir inhibits yellow fever virus in vitro and in patients with acute liver failure

INTRODUCTION AND OBJECTIVES

Direct antiviral agents (DAAs) are very efficient in inhibiting hepatitis C virus and might be used to treat infections caused by other flaviviruses whose worldwide detection has recently increased. The aim of this study was to verify the efficacy of DAAs in inhibiting yellow fever virus (YFV) by using drug repositioning (a methodology applied in the pharmaceutical industry to identify new uses for approved drugs).

MATERIALS AND METHODS

Three DAAs were evaluated: daclatasvir, sofosbuvir and ledipasvir or their combinations. For in vitro assays, the drugs were diluted in 100% dimethyl sulfoxide. Vaccine strain 17D and a 17D strain expressing the reporter fluorescent protein were used in the assays. A fast and reliable cell-based screening assay using Vero cells or Huh-7 cells (a hepatocyte-derived carcinoma ell line) was carried out. Two patients who acquired yellow fever virus with acute liver failure were treated with sofosbuvir for one week as a compassionate use.

RESULTS

Using a high-content screening assay, we verified that sofosbuvir presented the best antiviral activity against YFV. Moreover, after an off-label treatment with sofosbuvir, the two female patients diagnosed with yellow fever infection displayed a reduction in blood viremia and an improvement in the course of the disease, which was observed in the laboratory medical parameters related to disease evolution.

CONCLUSIONS

Sofosbuvir may be used as an option for treatment against YFV until other drugs are identified and approved for human use. These results offer insights into the role of nonstructural protein 5 (NS5) in YFV inhibition and suggest that nonstructural proteins may be explored as drug targets for YFV treatment.

Identification of Inhibitors of ZIKV Replication

Zika virus (ZIKV) was identified in 1947 in the Zika forest of Uganda and it has emerged recently as a global health threat, with recurring outbreaks and its associations with congenital microcephaly through maternal fetal transmission and Guillain-Barré syndrome. Currently, there are no United States (US) Food and Drug Administration (FDA)-approved vaccines or antivirals to treat ZIKV infections, which underscores an urgent medical need for the development of disease intervention strategies to treat ZIKV infection and associated disease. Drug repurposing offers various advantages over developing an entirely new drug by significantly reducing the timeline and resources required to advance a candidate antiviral into the clinic. Screening the ReFRAME library, we identified ten compounds with antiviral activity against the prototypic mammarenavirus lymphocytic choriomeningitis virus (LCMV). Moreover, we showed the ability of these ten compounds to inhibit influenza A and B virus infections, supporting their broad-spectrum antiviral activity. In this study, we further evaluated the broad-spectrum antiviral activity of the ten identified compounds by testing their activity against ZIKV. Among the ten compounds, Azaribine (SI-MTT = 146.29), AVN-944 (SI-MTT = 278.16), and Brequinar (SI-MTT = 157.42) showed potent anti-ZIKV activity in post-treatment therapeutic conditions. We also observed potent anti-ZIKV activity for Mycophenolate mofetil (SI-MTT = 20.51), Mycophenolic acid (SI-MTT = 36.33), and AVN-944 (SI-MTT = 24.51) in pre-treatment prophylactic conditions and potent co-treatment inhibitory activity for Obatoclax (SI-MTT = 60.58), Azaribine (SI-MTT = 91.51), and Mycophenolate mofetil (SI-MTT = 73.26) in co-treatment conditions. Importantly, the inhibitory effect of these compounds was strain independent, as they similarly inhibited ZIKV strains from both African and Asian/American lineages. Our results support the broad-spectrum antiviral activity of these ten compounds and suggest their use for the development of antiviral treatment options of ZIKV infection.

OR, Fontes W, Castro MS. Biological Properties of a Novel Multifunctional Host Defense Peptide from the Skin Secretion of the Chaco Tree Frog, Boana raniceps

In recent years, the number of new antimicrobial drugs launched on the market has decreased considerably even though there has been an increase in the number of resistant microbial strains. Thus, antimicrobial resistance has become a serious public health problem. Amphibian skin secretions are a rich source of host defense peptides, which generally are cationic and hydrophobic molecules, with a broad-spectrum of activity. In this study, one novel multifunctional defense peptide was isolated from the skin secretion of the Chaco tree frog, Boana raniceps. Figainin 2 (¹FLGAILKIGHALAKTVLPMVTNAFKPKQ²⁸) is cationic and hydrophobic, adopts an α-helical structure in 50% (v/v) trifluoroethanol (TFE), and is thermally stable. This peptide exhibited activity against Gram-negative and Gram-positive pathogenic bacteria arboviruses, T. cruzi epimastigotes; however, it did not show activity against yeasts. Figainin 2 also showed antiproliferative activity on cancer cells, is moderately active on human erythrocytes, and activates the oxidative burst in human neutrophils.

FDA-Approved Drugs Efavirenz, Tipranavir, and Dasabuvir Inhibit Replication of Multiple Flaviviruses in Vero Cells

Vector-borne flaviviruses (VBFs) affect human health worldwide, but no approved drugs are available specifically to treat VBF-associated infections. Here, we performed in silico screening of a library of U.S. Food and Drug Administration-approved antiviral drugs for their interaction with Zika virus proteins. Twelve hit drugs were identified by the docking experiments and tested in cell-based antiviral assay systems. Efavirenz, tipranavir, and dasabuvir at micromolar concentrations were identified to inhibit all VBFs tested; i.e., two representatives of mosquito-borne flaviviruses (Zika and West Nile viruses) and one representative of flaviviruses transmitted by ticks (tick-borne encephalitis virus). The results warrant further research into these drugs, either individually or in combination, as possible pan-flavivirus inhibitors.

Labyrinthopeptins Exert Broad-Spectrum Antiviral Activity through Lipid-Binding-Mediated Virolysis

To counteract the serious health threat posed by known and novel viral pathogens, drugs that target a variety of viruses through a common mechanism have attracted recent attention due to their potential in treating (re)emerging infections, for which direct-acting antivirals are not available. We found that labyrinthopeptins A1 and A2, the prototype congeners of carbacyclic lanthipeptides, inhibit the proliferation of diverse enveloped viruses, including dengue virus, Zika virus, West Nile virus, hepatitis C virus, chikungunya virus, Kaposi's sarcoma-associated herpesvirus, cytomegalovirus, and herpes simplex virus, in the low micromolar to nanomolar range. Mechanistic studies on viral particles revealed that labyrinthopeptins induce a virolytic effect through binding to the viral membrane lipid phosphatidylethanolamine (PE). These effects are enhanced by a combined equimolar application of both labyrinthopeptins, and a clear synergism was observed across a concentration range corresponding to 10% to 90% inhibitory concentrations of the compounds. Time-resolved experiments with large unilamellar vesicles (LUVs) reveal that membrane lipid raft compositions (phosphatidylcholine [PC]/PE/cholesterol/sphingomyelin at 17:10:33:40) are particularly sensitive to labyrinthopeptins in comparison to PC/PE (90:10) LUVs, even though the overall PE amount remains constant. Labyrinthopeptins exhibited low cytotoxicity and had favorable pharmacokinetic properties in mice (half-life [t _1/2] = 10.0 h), which designates them promising antiviral compounds acting by an unusual viral lipid targeting mechanism.IMPORTANCE For many viral infections, current treatment options are insufficient. Because the development of each antiviral drug is time-consuming and expensive, the prospect of finding broad-spectrum antivirals that can fight multiple, diverse viruses-well-known viruses as well as (re)emerging species-has gained attention, especially for the treatment of viral coinfections. While most known broad-spectrum agents address processes in the host cell, we found that targeting lipids of the free virus outside the host cell with the natural products labyrinthopeptin A1 and A2 is a viable strategy to inhibit the proliferation of a broad range of viruses from different families, including chikungunya virus, dengue virus, Zika virus, Kaposi's sarcoma-associated herpesvirus, and cytomegalovirus. Labyrinthopeptins bind to viral phosphatidylethanolamine and induce virolysis without exerting cytotoxicity on host cells. This represents a novel and unusual mechanism to tackle medically relevant viral infections.

Computer-Assisted and Data Driven Approaches for Surveillance, Drug Discovery, and Vaccine Design for the Zika Virus

Human life has been at the edge of catastrophe for millennia due diseases which emerge and reemerge at random. The recent outbreak of the Zika virus (ZIKV) is one such menace that shook the global public health community abruptly. Modern technologies, including computational tools as well as experimental approaches, need to be harnessed fast and effectively in a coordinated manner in order to properly address such challenges. In this paper, based on our earlier research, we have proposed a four-pronged approach to tackle the emerging pathogens like ZIKV: (a) Epidemiological modelling of spread mechanisms of ZIKV; (b) assessment of the public health risk of newly emerging strains of the pathogens by comparing them with existing strains/pathogens using fast computational sequence comparison methods; (c) implementation of vaccine design methods in order to produce a set of probable peptide vaccine candidates for quick synthesis/production and testing in the laboratory; and (d) designing of novel therapeutic molecules and their laboratory testing as well as validation of new drugs or repurposing of drugs for use against ZIKV. For each of these stages, we provide an extensive review of the technical challenges and current state-of-the-art. Further, we outline the future areas of research and discuss how they can work together to proactively combat ZIKV or future emerging pathogens.

Using Macaques to Address Critical Questions in Zika Virus Research

Zika virus (ZIKV) and nonhuman primates have been inextricably linked since the virus was first discovered in a sentinel rhesus macaque in Uganda in 1947. Soon after ZIKV was epidemiologically associated with birth defects in Brazil late in 2015, researchers capitalized on the fact that rhesus macaques are commonly used to model viral immunity and pathogenesis, quickly establishing macaque models for ZIKV infection. Within months, the susceptibility of pregnant macaques to experimental ZIKV challenge and ZIKV-associated abnormalities in fetuses was confirmed. This review discusses key unanswered questions in ZIKV immunity and in the pathogenesis of thecongenital Zika virus syndrome. We focus on those questions that can be best addressed in pregnant nonhuman primates and lessons learned from developing macaque models for ZIKV amid an active epidemic.

High-Throughput Screening Identifies Mixed-Lineage Kinase 3 as a Key Host Regulatory Factor in Zika Virus Infection

The Zika virus (ZIKV) life cycle involves multiple steps and requires interactions with host factors. However, the inability to systematically identify host regulatory factors for ZIKV has hampered antiviral development and our understanding of pathogenicity. Here, using a bioactive compound library with 2,659 small molecules, we applied a high-throughput and imaging-based screen to identify host factors that modulate ZIKV infection. The screen yielded hundreds of hits that markedly inhibited or potentiated ZIKV infection in SNB-19 glioblastoma cells. Among the hits, URMC-099, a mixed-lineage kinase 3 (MLK3) inhibitor, significantly facilitated ZIKV replication in both SNB-19 cells and the neonatal mouse brain. Using gene silencing and overexpression, we further confirmed that MLK3 was a host restriction factor against ZIKV. Mechanistically, MLK3 negatively regulated ZIKV replication through induction of the inflammatory cytokines interleukin-6 (IL-6), IL-8, tumor necrosis factor alpha (TNF-α), and monocyte chemoattractant protein 1 (MCP-1) but did not modulate host interferon-related pathways. Importantly, ZIKV activated the MLK3/MKK7/Jun N-terminal protein kinase (JNK) pathway in both SNB-19 cells and neonatal mouse brain. Together, these findings reveal a critical role for MLK3 in regulating ZIKV infection and facilitate the development of anti-ZIKV therapeutics by providing a number of screening hits.IMPORTANCE Zika fever, an infectious disease caused by the Zika virus (ZIKV), normally results in mild symptoms. Severe infection can cause Guillain-Barré syndrome in adults and birth defects, including microcephaly, in newborns. Although ZIKV was first identified in Uganda in 1947 in rhesus monkeys, a widespread epidemic of ZIKV infection in South and Central America in 2015 and 2016 raised major concerns. To date, there is no vaccine or specific medicine for ZIKV. The significance of our research is the systematic discovery of small molecule candidates that modulate ZIKV infection, which will allow the development of antiviral therapeutics. In addition, we identified MLK3, a key mediator of host signaling pathways that can be activated during ZIKV infection and limits virus replication by inducing multiple inflammatory cytokines. These findings broaden our understanding of ZIKV pathogenesis.

Therapeutic Advances Against ZIKV: A Quick Response, a Long Way to Go

Zika virus (ZIKV) is a mosquito-borne flavivirus that spread throughout the American continent in 2015 causing considerable worldwide social and health alarm due to its association with ocular lesions and microcephaly in newborns, and Guillain-Barré syndrome (GBS) cases in adults. Nowadays, no licensed vaccines or antivirals are available against ZIKV, and thus, in this very short time, the scientific community has conducted enormous efforts to develop vaccines and antivirals. So that, different platforms (purified inactivated and live attenuated viruses, DNA and RNA nucleic acid based candidates, virus-like particles, subunit elements, and recombinant viruses) have been evaluated as vaccine candidates. Overall, these vaccines have shown the induction of vigorous humoral and cellular responses, the decrease of viremia and viral RNA levels in natural target organs, the prevention of vertical and sexual transmission, as well as that of ZIKV-associated malformations, and the protection of experimental animal models. Some of these vaccine candidates have already been assayed in clinical trials. Likewise, the search for antivirals have also been the focus of recent investigations, with dozens of compounds tested in cell culture and a few in animal models. Both direct acting antivirals (DAAs), directed to viral structural proteins and enzymes, and host acting antivirals (HAAs), directed to cellular factors affecting all steps of the viral life cycle (binding, entry, fusion, transcription, translation, replication, maturation, and egress), have been evaluated. It is expected that this huge collaborative effort will produce affordable and effective therapeutic and prophylactic tools to combat ZIKV and other related still unknown or nowadays neglected flaviviruses. Here, a comprehensive overview of the advances made in the development of therapeutic measures against ZIKV and the questions that still have to be faced are summarized.

Identification of anti-flaviviral drugs with mosquitocidal and anti-Zika virus activity in Aedes aegypti

Zika virus (ZIKV), an emerging arbovirus belonging to the genus Flavivirus, is transmitted by Aedes mosquitoes. ZIKV infection can cause microcephaly of newborn babies and Guillain-Barré syndrome in adults. Because no licensed vaccine or specific antiviral treatment is available for ZIKV infection, the most commonly used approach to control the spread of ZIKV is suppression of the mosquito vector population. A novel proposed strategy to block arthropod virus (arbovirus) transmission is based on the chemical inhibition of virus infection in mosquitoes. However, only a few drugs and compounds have been tested with such properties. Here we present a comprehensive screen of 55 FDA-approved anti-flaviviral drugs for potential anti-ZIKV and mosquitocidal activity. Four drugs (auranofin, actinomycin D (Act-D), bortezomib and gemcitabine) were toxic to C6/36 cells, and two drugs (5-fluorouracil and mycophenolic acid (MPA)) significantly reduced ZIKV production in C6/36 cells at 2 μM and 0.5 μM, respectively. Three drugs (Act-D, cyclosporin A, ivermectin) exhibited a strong adulticidal activity, and six drugs (U18666A, retinoic acid p-hydroxyanilide (4-HPR), clotrimazole, bortezomib, MPA, imatinib mesylate) significantly suppressed ZIKV infection in mosquito midguts. Some of these FDA-approved drugs may have potential for use for the development of ZIKV transmission-blocking strategies.

Lipophilic statins inhibit Zika virus production in Vero cells

Zika virus (ZIKV) is a mosquito-borne member of the Flaviviridae family. ZIKV infection has been associated with neurological complications such as microcephaly in newborns and Guillain-Barré syndrome in adults; thus, therapeutic agents are urgently needed. Statins are clinically approved for lowering cholesterol levels to prevent cardiovascular disease but have shown potential as antiviral drugs. In this study, we explored the possibility of utilizing statins as anti-ZIKV drugs. We found that, generally, lipophilic statins (atorvastatin, cerivastatin, fluvastatin, lovastatin, mevastatin, and simvastatin) could reduce ZIKV production in vitro and result in smaller foci of infection. Time-of-drug-addition assay revealed that early treatment with statins is more beneficial than late treatment; however, statins could not completely inhibit the entry stage of ZIKV infection. Furthermore, individual lipophilic statins differed in anti-ZIKV capacity, with fluvastatin being the most efficient at low concentrations. Taken together, this study shows that statins or their derivatives have the potential to be used as anti-ZIKV therapeutic agents.

Antiviral Agents in Development for Zika Virus Infections

In 1947, Zika virus (ZIKV), a mosquito-borne flavivirus was identified in Uganda and subsequently spread to Asia and the Pacific regions. In 2015, it was introduced in Brazil causing an important social and sanitary alarm due to its increased virulence and rapid dissemination. Importantly, ZIKV infections have been associated with severe neurological complications such as Guillain–Barré syndrome and microcephaly in fetuses and newborns. Although enormous efforts were made by investigators in the development of effective countermeasures against ZIKV, there is still no approved specific antiviral drug for the treatment of ZIKV infections. Herein, we review several anti ZIKV candidates including drugs targeting both the virus (structural proteins and enzymes) and cellular elements.

Lipid Metabolism as a Source of Druggable Targets for Antiviral Discovery against Zika and Other Flaviviruses

The Zika virus (ZIKV) is a mosquito-borne flavivirus that can lead to birth defects (microcephaly), ocular lesions and neurological disorders (Guillain-Barré syndrome). There is no licensed vaccine or antiviral treatment against ZIKV infection. The effort to understand the complex interactions of ZIKV with cellular networks contributes to the identification of novel host-directed antiviral (HDA) candidates. Among the cellular pathways involved in infection, lipid metabolism gains attention. In ZIKV-infected cells lipid metabolism attributed to intracellular membrane remodeling, virion morphogenesis, autophagy modulation, innate immunity and inflammation. The key roles played by the cellular structures associated with lipid metabolism, such as peroxisomes and lipid droplets, are starting to be deciphered. Consequently, there is a wide variety of lipid-related antiviral strategies that are currently under consideration, which include an inhibition of sterol regulatory element-binding proteins (SREBP), the activation of adenosine-monophosphate activated kinase (AMPK), an inhibition of acetyl-Coenzyme A carboxylase (ACC), interference with sphingolipid metabolism, blockage of intracellular cholesterol trafficking, or a treatment with cholesterol derivatives. Remarkably, most of the HDAs identified in these studies are also effective against flaviviruses other than ZIKV (West Nile virus and dengue virus), supporting their broad-spectrum effect. Considering that lipid metabolism is one of the main cellular pathways suitable for pharmacological intervention, the idea of repositioning drugs targeting lipid metabolism as antiviral candidates is gaining force.

Secondary Metabolites of Actinomycetes and their Antibacterial, Antifungal and Antiviral Properties

The growing resistance of microorganisms towards antibiotics has become a serious global problem. Therapeutics with novel chemical scaffolds and/or mechanisms of action are urgently needed to combat infections caused by multidrug resistant pathogens, including bacteria, fungi and viruses. Development of novel antimicrobial agents is still highly dependent on the discovery of new natural products. At present, most antimicrobial drugs used in medicine are of natural origin. Among the natural producers of bioactive substances, Actinobacteria continue to be an important source of novel secondary metabolites for drug application. In this review, the authors report on the bioactive antimicrobial secondary metabolites of Actinobacteria that were described between 2011 and April 2018. Special attention is paid to the chemical scaffolds, biological activities and origin of these novel antibacterial, antifungal and antiviral compounds. Arenimycin C, chromopeptide lactone RSP 01, kocurin, macrolactins A1 and B1, chaxamycin D as well as anthracimycin are regarded as the most effective compounds with antibacterial activity. In turn, the highest potency among selected antifungal compounds is exhibited by enduspeptide B, neomaclafungins A-I and kribelloside D, while ahmpatinin i Bu, antimycin A1a, and pentapeptide 4862F are recognized as the strongest antiviral agents.

Anti-Zika Activity of a Library of Synthetic Carbohydrate Receptors

Zika virus (ZIKV), a mosquito-borne flavivirus, is a global health concern because of its association with severe neurological disorders. Currently, there are no antiviral therapies that have been specifically approved to treat ZIKV, and there is an urgent need to develop effective anti-ZIKV agents. Here, we report anti-ZIKV activity of 16 synthetic carbohydrate receptors (SCRs) that inhibit ZIKV infection in Vero and HeLa cells. Using a ZIKV reporter virus particle-based infection assay, our data demonstrates these SCRs are highly potent with IC₅₀s as low as 0.16 μM and negligible toxicity at several-fold higher concentrations. Time-of-addition studies showed that these SCRs inhibit the early stages of the virus infection, which is consistent with the proposed mode of action, where the SCRs likely inhibit binding between the virus and cell-surface glycans, thereby preventing viral entry into the cells and, as such, this study demonstrates a potential new strategy against ZIKV.

Strategies for Zika drug discovery

Zika virus (ZIKV) can cause devastating congenital syndrome in fetuses from pregnant women and autoimmune disorder Guillain-Barré syndrome in adults. No clinically approved vaccine or drug is currently available for ZIKV. This unmet medical need has motivated a global effort to develop countermeasures. Several promising ZIKV vaccine candidates have already entered clinical trials. In contrast, antiviral development of ZIKV is lagging behind. Here, we review the overall strategies for ZIKV drug discovery, including (i) repurposing of clinically approved drugs, (ii) viral replication-based phenotypic screening for inhibitors, and (iii) targeted drug discovery of viral proteins. Along with vaccines, the development of antiviral treatment will provide a complementary means to control ZIKV infections.

Antimalarial drugs and their metabolites are potent Zika virus inhibitors

Studies aimed at repurposing existing drugs revealed that some antimalarial compounds possess anti-Zika virus (anti-ZIKV) activity. Here, we further tested 14 additional antimalarial drugs and their metabolites or analogs for anti-ZIKV activity using a phenotypic screening approach. We identified four compounds with varying anti-ZIKV activity, including a metabolite of amodiaquine termed desethylamodiaquine (DAQ) and N-desethylchloroquine (DECQ), a metabolite of chloroquine, which both exhibited low micromolar effective concentrations against three different ZIKV strains. Two other compounds termed dihydroartemisinin (DHA) and quinidine (QD) exhibited only partial inhibition of ZIKV replication. Characterization of the inhibitory mechanisms of DAQ and DECQ showed that both drugs target the entry step as well as postentry events of the viral replication cycle. These hits represent attractive starting points for future optimization of new anti-ZIKV drug candidates derived from antimalarial drugs and their analogs.

Zika Virus: Origins, Pathological Action, and Treatment Strategies

The Zika virus (ZIKV) global epidemic prompted the World Health Organization to declare it a 2016 Public Health Emergency of International Concern. The overwhelming experience over the past several years teaches us that ZIKV and the associated neurological complications represent a long-term world-wide challenge to public health. Although the number of ZIKV cases in the Western Hemisphere has dropped since 2016, the need for basic research and anti-ZIKV drug development remains strong. Re-emerging viruses like ZIKV are an ever-present threat in the 21st century where fast transcontinental travel lends itself to viral epidemics. Here, we first present the origin story for ZIKV and review the rapid progress researchers have made toward understanding of the ZIKV pathology and in the design, re-purposing, and testing–particularly in vivo–drug candidates for ZIKV prophylaxis and therapy ZIKV. Quite remarkably, a short, but intensive, drug-repurposing effort has already resulted in several readily available FDA-approved drugs that are capable of effectively combating the virus in infected adult mouse models and, most importantly, in both preventing maternal-fetal transmission and severe microcephaly in newborns in pregnant mouse models.

High Throughput and Computational Repurposing for Neglected Diseases

Purpose

Neglected tropical diseases (NTDs) represent are a heterogeneous group of communicable diseases that are found within the poorest populations of the world. There are 23 NTDs that have been prioritized by the World Health Organization, which are endemic in 149 countries and affect more than 1.4 billion people, costing these developing economies billions of dollars annually. The NTDs result from four different causative pathogens: protozoa, bacteria, helminth and virus. The majority of the diseases lack effective treatments. Therefore, new therapeutics for NTDs are desperately needed.

Methods

We describe various high throughput screening and computational approaches that have been performed in recent years. We have collated the molecules identified in these studies and calculated molecular properties.

Results

Numerous global repurposing efforts have yielded some promising compounds for various neglected tropical diseases. These compounds when analyzed as one would expect appear drug-like. Several large datasets are also now in the public domain and this enables machine learning models to be constructed that then facilitate the discovery of new molecules for these pathogens.

Conclusions

In the space of a few years many groups have either performed experimental or computational repurposing high throughput screens against neglected diseases. These have identified compounds which in many cases are already approved drugs. Such approaches perhaps offer a more efficient way to develop treatments which are generally not a focus for global pharmaceutical companies because of the economics or the lack of a viable market. Other diseases could perhaps benefit from these repurposing approaches.

Electronic supplementary material

The online version of this article (10.1007/s11095-018-2558-3) contains supplementary material, which is available to authorized users.

Investigational drugs for the treatment of Zika virus infection: a preclinical and clinical update

INTRODUCTION

The Zika virus (ZIKV) infection results in severe neurological complications and has emerged as a threat to public health worldwide. No drugs or vaccines are available for use in the clinic and the need for novel and effective therapeutic agents is urgent.

AREAS COVERED

This review describes the latest progress of antiviral development for the treatment of ZIKV infection; it primarily focuses on the literature describing 20 potential anti-ZIKV drugs/agents currently being tested in vivo or in clinical trials. The paper also discusses the need for novel ZIKV inhibitors and the critical issues for successful antiviral drug development.

EXPERT OPINION

So far, 20 compounds have been tested in vivo and three in the clinical trials; progressing these compounds to the clinic is a challenge. Novel ZIKV inhibitors that target virus or host factors are urgently needed. Knowledge-driven drug repurposing, structure-based discovery, RNA interference, long noncoding RNAs, miRNAs, and peptide inhibitors may pave the way for the discovery of such novel agents.

Research Models and Tools for the Identification of Antivirals and Therapeutics against Zika Virus Infection

Zika virus recently re-emerged and caused global outbreaks mainly in Central Africa, Southeast Asia, the Pacific Islands and in Central and South America. Even though there is a declining trend, the virus continues to spread throughout different geographical regions of the world. Since its re-emergence in 2015, massive advances have been made regarding our understanding of clinical manifestations, epidemiology, genetic diversity, genomic structure and potential therapeutic intervention strategies. Nevertheless, treatment remains a challenge as there is no licensed effective therapy available. This review focuses on the recent advances regarding research models, as well as available experimental tools that can be used for the identification and characterization of potential antiviral targets and therapeutic intervention strategies.

Development and Validation of a Phenotypic High-Content Imaging Assay for Assessing the Antiviral Activity of Small-Molecule Inhibitors Targeting Zika Virus

Zika virus (ZIKV) has been linked to the development of microcephaly in newborns, as well as Guillain-Barré syndrome. There are currently no drugs available to treat ZIKV infection, and accordingly, there is an unmet medical need for the discovery of new therapies. High-throughput drug screening efforts focusing on indirect readouts of cell viability are prone to a higher frequency of false positives in cases where the virus is viable in the cell but the cytopathic effect (CPE) is reduced or delayed. Here, we describe a fast and label-free phenotypic high-content imaging assay to detect cells affected by the virus-induced CPE using automated imaging and analysis. Protection from the CPE correlates with a decrease in viral antigen production, as observed by immunofluorescence. We trained our assay using a collection of nucleoside analogues with activity against ZIKV; the previously reported antiviral activities of 2'-C-methylribonucleosides and ribavirin against the Zika virus in Vero cells were confirmed using our developed method. To validate the ability of our assay to reveal new anti-ZIKV compounds, we profiled a novel library of 24 natural product derivatives and found compound 1 to be an inhibitor of the ZIKV-induced cytopathic effect; the activity of the compound was confirmed in human fetal neural stem cells (NSCs). The described technique can be easily leveraged as a primary screening assay for profiling of the activities of large compound libraries against ZIKV and can be expanded to other ZIKV strains and other cell lines displaying morphological changes upon ZIKV infection.

Host-Directed Antivirals: A Realistic Alternative to Fight Zika Virus

Zika virus (ZIKV), a mosquito-borne flavivirus, was an almost neglected pathogen until its introduction in the Americas in 2015, where it has been responsible for a threat to global health, causing a great social and sanitary alarm due to its increased virulence, rapid spread, and an association with severe neurological and ophthalmological complications. Currently, no specific antiviral therapy against ZIKV is available, and treatments are palliative and mainly directed toward the relief of symptoms, such as fever and rash, by administering antipyretics, anti-histamines, and fluids for dehydration. Nevertheless, lately, search for antivirals has been a major aim in ZIKV investigations. To do so, screening of libraries from different sources, testing of natural compounds, and repurposing of drugs with known antiviral activity have allowed the identification of several antiviral candidates directed to both viral (structural proteins and enzymes) and cellular elements. Here, we present an updated review of current knowledge about anti-ZIKV strategies, focusing on host-directed antivirals as a realistic alternative to combat ZIKV infection.

Zika virus, vaccines, and antiviral strategies

INTRODUCTION

Zika virus (ZIKV) recently emerged as a global public health emergency of international concern. ZIKV is responsible for severe neurological complications in adults and infection during pregnancy and can lead to congenital Zika syndrome. There is no licensed vaccine or drug to prevent or treat ZIKV infection. Areas covered: The aim of this article is to provide an overview and update of the progress of research on anti-ZIKV vaccine and medications until the end of 2017, with a special emphasis on drugs that can be used during pregnancy. Expert commentary: Development of new vaccines and drugs is challenging and several points particular to ZIKV infections augment this difficulty: (1) Cross-reactions between ZIKV and other flaviviruses, the impact of ZIKV vaccination on subsequent flavivirus infections, and vice-versa, is unknown, (2) Drugs against ZIKV should be safe in pregnant women, and (3) Evaluation of the efficacy of vaccine and drugs against ZIKV in clinical trials phase II-IV will be complicated due to the decline of ZIKV circulation.

The A-Z of Zika drug discovery

Despite the recent outbreak of Zika virus (ZIKV), there are still no approved treatments, and early-stage compounds are probably many years away from approval. A comprehensive A-Z review of the recent advances in ZIKV drug discovery efforts is presented, highlighting drug repositioning and computationally guided compounds, including discovered viral and host cell inhibitors. Promising ZIKV molecular targets are also described and discussed, as well as targets belonging to the host cell, as new opportunities for ZIKV drug discovery. All this knowledge is not only crucial to advancing the fight against the Zika virus and other flaviviruses but also helps us prepare for the next emerging virus outbreak to which we will have to respond.

Male germ cells support long-term propagation of Zika virus

Evidence of male-to-female sexual transmission of Zika virus (ZIKV) and viral RNA in semen and sperm months after infection supports a potential role for testicular cells in ZIKV propagation. Here, we demonstrate that germ cells (GCs) are most susceptible to ZIKV. We found that only GCs infected by ZIKV, but not those infected by dengue virus and yellow fever virus, produce high levels of infectious virus. This observation coincides with decreased expression of interferon-stimulated gene Ifi44l in ZIKV-infected GCs, and overexpression of Ifi44l results in reduced ZIKV production. Using primary human testicular tissue, we demonstrate that human GCs are also permissive for ZIKV infection and production. Finally, we identified berberine chloride as a potent inhibitor of ZIKV infection in both murine and human testes. Together, these studies identify a potential cellular source for propagation of ZIKV in testes and a candidate drug for preventing sexual transmission of ZIKV.

The antimalarial drug amodiaquine possesses anti-ZIKA virus activities

Zika virus (ZIKV) outbreak has emerged as a global health threat, particularly in tropical areas, over the past few years. No antiviral therapy or vaccine is available at present. For these reasons, repurposing clinically approved drugs against ZIKV infection may provide rapid and cost-effective global health benefits. Here, we explored this strategy and screened eight FDA-approved drugs for antiviral activity against ZIKV using a cell-based assay. Our results show that the antimalarial drug amodiaquine has anti-ZIKV activity with EC₅₀ at low micromolar concentrations in cell culture. We further characterized amodiaquine antiviral activity against ZIKV and found that it targets early events of the viral replication cycle. Altogether, our results suggest that amodiaquine may be efficacious for the treatment of ZIKV infection.

Zika virus outbreak: a review of neurological complications, diagnosis, and treatment options

Zika virus (ZIKV) is an arbovirus transmitted mainly by mosquitos of Aedes species. The virus has emerged in recent years and spread throughout North and South Americas. The recent outbreak of ZIKV started in Brazil (2015) has resulted in infections surpassing a million mark. Contrary to the previous beliefs that Zika causes mildly symptomatic infections fever, headache, rash, arthralgia, and conjunctivitis, the recent outbreak associated ZIKV to serious neurological complications such as microcephaly, Guillain-Barré syndrome, and eye infections. The recent outbreak has resulted in an astonishing number of microcephaly cases in fetus and infants. Consequently, numerous studies were conducted using in vitro cell and in vivo animal models. These studies showed clear links between ZIKV infections and neurological abnormalities. Diagnosis methods based on nucleic acid and serological detection facilitated rapid and accurate identification of ZIKV infections. New transmission modalities such as sexual and transplacental transmission were uncovered. Given the seriousness of ZIKV infections, WHO declared the development of safe and effective vaccines and new antiviral drugs as an urgent global health priority. Rapid work in this direction has led to the identification of several vaccine and antiviral drug candidates. Here, we review the remarkable progress made in understanding the molecular links between ZIKV infections and neurological irregularities, new diagnosis methods, potential targets for antiviral drugs, and the current state of vaccine development.

Ophthalmologic Manifestations Associated With Zika Virus Infection

Vision plays an important role in the development of communication, social interaction, spatial awareness, and the motor skills needed to explore the environment. In the past 2 years, researchers have described the broad spectrum of clinical features that comprise congenital Zika syndrome (CZS). The ocular manifestations are considered 1 important pillar of this new entity. The most characteristic ophthalmic findings include chorioretinal scars and focal pigmentary changes seen in the macular region. Since these findings were first reported, other researchers have validated and extended them, leading to a more complete picture of the spectrum of ocular manifestations related to CZS. In this article, we summarize the current knowledge on the ocular implications of CZS and emphasize the importance of early rehabilitation to enhance visual performance in affected children.

Comparative analysis of different cell systems for Zika virus (ZIKV) propagation and evaluation of anti-ZIKV compounds in vitro

A strong correlation between Zika virus (ZIKV) infection and severe neurological disease in newborns and occasionally adults has emerged in the Brazilian outbreak. Efficient human cell-based assays are required to test candidate inhibitors of ZIKV replication. The aim of this work was to investigate ZIKV propagation and quantification in different cell lines. The human (U87, A549, Huh7), mosquito (C6/36) and monkey (VERO E6) cell lines tested were all permissive to ZIKV infection. When assessed by plaque forming units (PFU) in three different target cell lines, the maximal production of ZIKV was achieved in Huh7 at day 3 post-infection (6.38±0.44 log₁₀PFU/ml). The C6/36 cell line showed a low and slow production of virus when compared with other cell lines. A549 readout cells generated a larger number of plaques compared to Huh7 but not to VERO E6 cells. ZIKV PFU and RNA titers showed the highest correlation when Huh7 and A549 were used as the producer and readout cells, respectively. Also, U87 cells produced ZIKV RNA titers which were highly correlated with PFU independently from the readout cell line. Using the best virus-cell system, sofosbuvir and ribavirin EC₅₀ were 1.2μM and 1.1μM when measured through plaque assay, and 4.2μM and 5.2μM when measured by quantitative real time PCR (qRT-PCR), respectively. In summary, ZIKV can efficiently infect different human cell lines and rapidly reach peak viral titers. Overall, A549 cells appear to be as efficient as the VERO E6 gold standard for plaque assay allowing the use of human, rather than simian, cells for evaluating candidate anti-ZIKV compounds by the reference assay. The possibility to replace the labor-intensive plaque assay with the more rapid and easy-to-perform qRT-PCR is appealing and warrants further investigation.

Zika Virus: What Have We Learnt Since the Start of the Recent Epidemic?

Zika is a viral disease transmitted mainly by mosquitoes of the genus Aedes. In recent years, it has expanded geographically, changing from an endemic mosquito-borne disease across equatorial Asia and Africa, to an epidemic disease causing large outbreaks in several areas of the world. With the recent Zika virus (ZIKV) outbreaks in the Americas, the disease has become a focus of attention of public health agencies and of the international research community, especially due to an association with neurological disorders in adults and to the severe neurological and ophthalmological abnormalities found in fetuses and newborns of mothers exposed to ZIKV during pregnancy. A large number of studies have been published in the last 3 years, revealing the structure of the virus, how it is transmitted and how it affects human cells. Many different animal models have been developed, which recapitulate several features of ZIKV disease and its neurological consequences. Moreover, several vaccine candidates are now in active preclinical development, and three of them have already entered phase I clinical trials. Likewise, many different compounds targeting viral and cellular components are being tested in in vitro and in experimental animal models. This review aims to discuss the current state of this rapidly growing literature from a multidisciplinary perspective, as well as to present an overview of the public health response to Zika and of the perspectives for the prevention and treatment of this disease.

Ocular effects of Zika virus-a review

Zika virus was considered an innocent pathogen while restricted to the African and Asian population; however, after reaching the Americas in March 2015, it became a global threat. Despite usually causing mild or no symptoms in infected adults, Zika virus displays a different behavior toward fetuses. When infected during gestation, fetuses have their immature neural cells killed by the virus and consequently have devastating findings at birth. In the past year the drastic effects of Zika virus infection in newborns include neurological, ophthalmological, audiological, and skeletal abnormalities. These findings represent a new entity called congenital Zika syndrome. We summarize the ocular findings of congenital Zika Syndrome, as well as the current understanding of the illness, systemic manifestations, laboratory investigation, differential diagnosis, prophylaxis, and treatment for this disorder.

The Race To Find Antivirals for Zika Virus

Zika virus (ZIKV), a flavivirus transmitted by mosquitoes, was an almost neglected pathogen until its introduction in the Americas in 2015 and its subsequent explosive spread throughout the continent, where it has infected millions of people. The virus has caused social and sanitary alarm, mainly due to its association with severe neurological disorders (Guillain-Barré syndrome and microcephaly in fetuses and newborns). Nowadays, no specific antiviral therapy against ZIKV is available. However, during the past months, a great effort has been made to search for antiviral candidates using different approaches and methodologies, ranging from testing specific compounds with known antiviral activity to the screening of libraries with hundreds of bioactive molecules. The identified antiviral candidates include drugs targeting viral components as well as cellular ones. Here, an updated review of what has been done in this line is presented.

The Race To Find Antivirals for Zika Virus

Zika virus (ZIKV), a flavivirus transmitted by mosquitoes, was an almost neglected pathogen until its introduction in the Americas in 2015 and its subsequent explosive spread throughout the continent, where it has infected millions of people. The virus has caused social and sanitary alarm, mainly due to its association with severe neurological disorders (Guillain-Barré syndrome and microcephaly in fetuses and newborns). Nowadays, no specific antiviral therapy against ZIKV is available. However, during the past months, a great effort has been made to search for antiviral candidates using different approaches and methodologies, ranging from testing specific compounds with known antiviral activity to the screening of libraries with hundreds of bioactive molecules. The identified antiviral candidates include drugs targeting viral components as well as cellular ones. Here, an updated review of what has been done in this line is presented.