Selective serotonin reuptake inhibitor fluoxetine inhibits replication of human enteroviruses B and D by targeting viral protein 2C

Enterovirus D68 and Human Respiratory Infections

Enterovirus D68 (EV-D68) is a member of the species Enterovirus D in the genus Enterovirus of the Picornaviridae family. EV-D68 was first isolated in the United States in 1962 and is primarily an agent of respiratory disease. Infections with EV-D68 have been rarely reported until recently, when reports of EV-D68 associated with respiratory disease increased notably worldwide. An outbreak in 2014 in the United States, for example, involved more than 1,000 cases of severe respiratory disease that occurred across almost all states. Phylogenetic analysis of all EV-D68 sequences indicates that the circulating strains of EV-D68 can be classified into two lineages, lineage 1 and lineage 2. In contrast to the prototype Fermon strain, all circulating strains have deletions in their genomes. Respiratory illness associated with EV-D68 infection ranges from mild illness that just needs outpatient service to severe illness requiring intensive care and mechanical ventilation. To date, there are no specific medicines and vaccines to treat or prevent EV-D68 infection. This review provides a detailed overview about our current understanding of EV-D68-related virology, epidemiology and clinical syndromes, pathogenesis, and laboratory diagnostics.

Antiviral activity of micafungin against enterovirus 71

Background

Enterovirus 71 (EV71) is a major causative agent of hand-foot-mouth disease (HFMD) and also causes severe neurological complications, leading to fatality in young children. However, no effective therapy is currently available for the treatment of this infection.

Methods

We identified small-molecule inhibitors of EV71 from a screen of 968 Food and Drug Administration (FDA)-approved drugs, with which clinical application for EV71-associated diseases would be more feasible, using EV71 subgenomic replicon system. Primary hits were extensively evaluated for their antiviral activities in EV71-infected cells.

Results

We identified micafungin, an echinocandin antifungal drug, as a novel inhibitor of EV71. Micafungin potently inhibits the proliferation of EV71 as well as the replication of EV71 replicon in cells with a low micromolar IC₅₀ (~5 μM). The strong antiviral effect of micafungin on EV71 replicon and the result from time-of-addition experiment demonstrated a targeting of micafungin on virion-independent intracellular process(es) during EV71 infection. Moreover, an extensive analysis excluded the involvement of 2C and 3A proteins, IRES-dependent translation, and also that of polyprotein processing in the antiviral effect of micafungin.

Conclusions

Our research revealed a new indication of micafungin as an effective inhibitor of EV71, which is the first case reporting antiviral activity of micafungin, an antifungal drug.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0557-8) contains supplementary material, which is available to authorized users.

The Emergence of Enterovirus-D68

Enterovirus-D68 (EV-D68) is a unique enterovirus, similar to human rhinoviruses, spread via the respiratory route and primarily causing respiratory disease. Increasing clusters of EV-D68 associated respiratory disease have been reported since 2008, with the largest reported outbreak occurring in North America in 2014. Epidemiologic data and biological plausibility support an association of EV-D68 with the neurologic condition, acute flaccid myelitis. Diagnosis requires EV-D68 specific PCR or viral sequencing of respiratory specimens. Treatment consists of supportive care, as there are no currently available effective vaccines or antiviral therapies. Further research is needed to prepare for future EV-D68 outbreaks of respiratory or neurologic disease.

Screening of a Library of FDA-Approved Drugs Identifies Several Enterovirus Replication Inhibitors That Target Viral Protein 2C

Enteroviruses (EVs) represent many important pathogens of humans. Unfortunately, no antiviral compounds currently exist to treat infections with these viruses. We screened the Prestwick Chemical Library, a library of approved drugs, for inhibitors of coxsackievirus B3, identified pirlindole as a potent novel inhibitor, and confirmed the inhibitory action of dibucaine, zuclopenthixol, fluoxetine, and formoterol. Upon testing of viruses of several EV species, we found that dibucaine and pirlindole inhibited EV-B and EV-D and that dibucaine also inhibited EV-A, but none of them inhibited EV-C or rhinoviruses (RVs). In contrast, formoterol inhibited all enteroviruses and rhinoviruses tested. All compounds acted through the inhibition of genome replication. Mutations in the coding sequence of the coxsackievirus B3 (CV-B3) 2C protein conferred resistance to dibucaine, pirlindole, and zuclopenthixol but not formoterol, suggesting that 2C is the target for this set of compounds. Importantly, dibucaine bound to CV-B3 protein 2C in vitro, whereas binding to a 2C protein carrying the resistance mutations was reduced, providing an explanation for how resistance is acquired.

Mechanism of Poliovirus Resistance to Host Phosphatidylinositol-4 Kinase III β Inhibitor

Phosphatidylinositol-4 kinase III β (PI4KB) and oxysterol-binding protein (OSBP) family I have been identified as the major targets of anti-enterovirus drug candidates. Resistance mutations in poliovirus (PV) to these inhibitors have been identified in viral 3A protein, represented by a G5318A (3A-Ala70Thr) mutation, but the mechanism of viral resistance to host PI4KB/OSBP inhibitors remained unknown. In this study, we found that a G5318A mutation enhances the basal levels of phosphatidylinositol 4-phosphate (PI4P) and of the 3A protein and decreases the levels of the 3AB protein during PV replication. The 3A protein acted as a major effector responsible for the resistance to PI4KB inhibitor, but did not enhance the PI4KB activity in vitro in contrast to the 2C, 2BC, 3AB, and 3D proteins. The 3AB protein acted as the primary target of a G5318A mutation and also as an effector. We identified novel resistance mutations to a PI4KB inhibitor [C5151U (3A-T14M) and C5366U (3A-H86Y) mutations] and found that there is a positive correlation between the extent of the resistance phenotype and the levels of the 3A proteins. These results suggested that the 3A protein overproduced by enhanced processing of the 3AB protein with the resistance mutations overcomes the inhibitory effect of PI4KB inhibitor on PV replication independently of the hyperactivation of the PI4KB/OSBP pathway.

Enteroviruses in the early 21st century: new manifestations and challenges

PURPOSE OF REVIEW

Enteroviruses cause a wide variety of diseases with neurologic, respiratory, skin, and gastrointestinal findings. The purpose of this review is to clarify changes in the classification of enteroviruses, provide information about recent disease outbreaks, and to summarize progress toward the treatment and prevention of these infections.

RECENT FINDINGS

Enteroviruses are now classified into four distinct species. New variants of coxsackievirus B1, enterovirus-A71, and enterovirus-D68 (EV-D68) have emerged as causes of recent outbreaks in the United States and other countries, including more severe disease manifestations than previously described. EV-D68 now commonly circulates in the United States, and has been linked to severe respiratory disease and associated with acute flaccid myelitis (AFM). Overcoming enormous political and logistical challenges, fewer than 100 cases of polio have been reported in 2015, and the initiation of 'endgame' strategies appears imminent. Unfortunately, treatment for enterovirus infections remains supportive, although the recently completed pleconaril trial in newborns suggests that antiviral therapy may reduce mortality in neonatal disease.

SUMMARY

Clinicians should be aware of the respiratory and neurological manifestations associated with EV-D68 and the potential for severe disease seen with other recently described enterovirus variants. Healthcare professionals should recognize the utility of rapid diagnostic methods and progress toward prevention and treatment of enterovirus infections.

Discovery of Structurally Diverse Small-Molecule Compounds with Broad Antiviral Activity against Enteroviruses

Antiviral drugs do not currently exist for the treatment of enterovirus infections, which are often severe and potentially life-threatening. We conducted high-throughput molecular screening and identified a structurally diverse set of compounds that inhibit the replication of coxsackievirus B3, a commonly encountered enterovirus. These compounds did not interfere with the function of the viral internal ribosome entry site or with the activity of the viral proteases, but they did drastically reduce the synthesis of viral RNA and viral proteins in infected cells. Sequence analysis of compound-resistant mutants suggests that the viral 2C protein is targeted by most of these compounds. These compounds demonstrated antiviral activity against a panel of the most commonly encountered enteroviruses and thus represent potential leads for the development of broad-spectrum anti-enteroviral drugs.

2014 outbreak of enterovirus D68 in North America

Enterovirus D68 (EV-D68) is an emerging picornavirus which causes severe respiratory disease, predominantly in children. In 2014, the largest and most widespread outbreak of EV-D68 described to date was reported in North America. Hospitals throughout the United States and Canada reported surges in patient volumes and resource utilization from August to October, 2014. In the US a total of 1,153 infections were confirmed in 49 states, although this is an underestimate of the likely millions of cases that occurred but were not tested. EV-D68 was detected in 14 patients who died; the role of the virus in these deaths is unknown. A possible association between EV-D68 and cases of acute flaccid paralysis with spinal cord gray matter lesions, known as acute flaccid myelitis, was observed during the outbreak and is under investigation. The 2014 outbreak of EV-D68 in North America demonstrates the public health importance of this emerging pathogen.

Synergistic antiviral activity of gemcitabine and ribavirin against enteroviruses

Enteroviruses are major causative agents of various human diseases, and some of them are currently considered to be an enormous threat to public health. However, no effective therapy is currently available for the treatment of these infections. We identified gemcitabine, a nucleoside-analog drug used for cancer treatment, from a screen of bioactive chemicals as a novel inhibitor of coxsackievirus B3 (CVB3) and enterovirus 71 (EV71). Gemcitabine potently inhibited the proliferation of CVB3 and EV71, as well as the replication of CVB3 and EV71 replicons, in cells with a low micromolar IC50 (1-5 μM). Its strong inhibitory effect was also observed in cells infected with human rhinoviruses, demonstrating broad-spectrum antiviral effects on enteroviruses. Mechanistically, an extensive analysis excluded the involvement of 2C, 3A, IRES-dependent translation, and also that of polyprotein processing in the antiviral effects of gemcitabine. Importantly, gemcitabine in combination with ribavirin, an antiviral drug currently being used against a few RNA viruses, exhibited a synergistic antiviral effect on the replication of CVB3 and EV71 replicons. Consequently, our results clearly demonstrate a new indication for gemcitabine as an effective broad-spectrum inhibitor of enteroviruses and strongly suggest a new therapeutic strategy using gemcitabine alone or in combination with ribavirin for the treatment of various diseases associated with enterovirus infection.

In Vitro Efficacy of Antiviral Compounds against Enterovirus D68

In 2014, the United States experienced a large outbreak of severe respiratory illness associated with enterovirus D68 (EV-D68). We used a homogeneous, cell-based assay to assess the antiviral activity of compounds developed for EV/rhinovirus infection or other indications. Three of 15 compounds were highly active against all four strains tested (the prototype and three 2014 strains), with 50% effective concentrations of 0.0012 to 0.027 μM. Additional studies are needed to assess their in vivo efficacy against EV-D68.

Management of the 2014 Enterovirus 68 Outbreak at a Pediatric Tertiary Care Center

PURPOSE

Enterovirus 68 (EV-D68) is an uncommonly recognized cause of acute respiratory tract infections. During the late summer of 2014, an international EV-D68 outbreak occurred. We review the steps of outbreak recognition and management in the context of 1 hospital's experience with the EV-D68 outbreak.

METHODS

We reviewed the role of Children's Mercy Hospital as one of the first hospitals to recognize the 2014 EV-D68 outbreak in the United States. The steps of outbreak management were applied to real-life examples as the outbreak unfolded at our hospital.

FINDINGS

Management of the 2014 EV-D68 outbreak was a multifaceted effort requiring close coordination with hospitals, local and state health departments, and the Centers for Disease Control and Prevention. The importance of clear and frequent communication is highlighted both intra- and interinstitutionally. Increased respiratory disease-related pediatric admissions at hospitals nationally were attributed to EV-D68. Outcomes for these children, including the association of EV-D68 with acute flaccid myelitis, remain under investigation.

IMPLICATIONS

Following the steps of outbreak management is critical to providing optimal patient care and ensuring the health of the public. During the 2014 EV-D68 outbreak, close adherence to outbreak principles led to swift recognition of illness, rapid diagnostic measures, institution of appropriate therapies, and dissemination of information to health care providers and the public. Equally important was the subsequent identification of an increase in acute flaccid myelitis cases against the backdrop of an increase in EV-D68 detections nationally. Future prospective studies are needed to determine the true burden of EV-D68 disease, potential vaccines and therapeutics, and outcomes of children with EV-D68 infection.

Replication and Inhibitors of Enteroviruses and Parechoviruses

The Enterovirus (EV) and Parechovirus genera of the picornavirus family include many important human pathogens, including poliovirus, rhinovirus, EV-A71, EV-D68, and human parechoviruses (HPeV). They cause a wide variety of diseases, ranging from a simple common cold to life-threatening diseases such as encephalitis and myocarditis. At the moment, no antiviral therapy is available against these viruses and it is not feasible to develop vaccines against all EVs and HPeVs due to the great number of serotypes. Therefore, a lot of effort is being invested in the development of antiviral drugs. Both viral proteins and host proteins essential for virus replication can be used as targets for virus inhibitors. As such, a good understanding of the complex process of virus replication is pivotal in the design of antiviral strategies goes hand in hand with a good understanding of the complex process of virus replication. In this review, we will give an overview of the current state of knowledge of EV and HPeV replication and how this can be inhibited by small-molecule inhibitors.

Persistent infection of human pancreatic cells with Coxsackievirus B4 is cured by fluoxetine

Group B Coxsackieviruses (CVB) are involved in various acute clinical features and they can play a role in the development of chronic diseases like type 1 diabetes. The persistence of CVB has been described in vitro and in vivo in various models. Fluoxetine was reported to inhibit the replication of CVB1-3, which prompted us to study the in vitro antiviral activity of fluoxetine against CVB4 in models of acute infection. In addition we took advantage of a chronically CVB4-infected Panc-1 cell line to evaluate the antiviral effect of fluoxetine in a model of persistent CVB4 infection. An inhibition of the CVB4 replication was obtained when fluoxetine was added at 5.48μM to Hep-2 cell cultures. No inhibitory effect was observed when CVB4 was mixed with fluoxetine for 2h and filtered to eliminate fluoxetine before inoculation to cells, or when cells were treated up to 96h and washed before viral inoculation. Fluoxetine (5.48μM) reduced viral replication by more than 50% in acutely infected Panc-1 cell cultures. A dramatic decrease of infectious particles levels in supernatants of Panc-1 cells chronically infected with CVB4 was obtained a few days after treatment with fluoxetine and no infectious viral particle was found as soon as day 21 of treatment, and intracellular enteroviral RNA was undetectable by RT-PCR after three weeks of treatment. These data display that fluoxetine can inhibit the replication of CVB4 and can cure Panc-1 cells chronically infected with CVB4.

Antivirals against enteroviruses: a critical review from a public-health perspective

The enteroviruses (EVs) of the Picornaviridae family are the most common viral pathogens known. Most EV infections are mild and self-limiting but manifestations can be severe in children and immunodeficient individuals. Antiviral development is actively pursued to benefit these high-risk patients and, given the alarming problem of antimicrobial drug resistance, antiviral drug resistance is a public-health concern. Picornavirus antivirals can be used off-label or as part of outbreak control measures. They may be used in the final stages of poliovirus eradication and to mitigate EV-A71 outbreaks. We review the potential emergence of drug-resistant strains and their impact on EV transmission and endemic circulation. We include non-picornavirus antivirals that inhibit EV replication, for example, ribavirin, a treatment for infection with HCV, and amantadine, a treatment for influenza A. They may have spurred resistance emergence in HCV or influenza A patients who are unknowingly coinfected with EV. The public-health challenge is always to find a balance between individual benefit and the long-term health of the larger population.

A thiazepino[4,5-a]benzimidazole derivative hampers the RNA replication of Eurasian serotypes of foot-and-mouth disease virus

The stamping-out policy for the control of foot-and-mouth disease virus (FMDV) in countries that are free from FMD without vaccination has a dramatic socio-economic impact, huge animal welfare issues and may result in the loss of farm animal genetic resources. As an alternative to pre-emptive culling or emergency vaccination we further explore the possibility to use antiviral drugs in the event of an FMD outbreak. In the present study, we tested the in vitro cytotoxicity and anti-FMDV activity of 1,2,4,5-tetrahydro-[1,4]thiazepino[4,5-a]benzimidazole. The molecule was shown to inhibit the replication of reference strains of the Eurasian FMDV serotypes O, A, C and Asia but not the FMDV serotypes from the South African Territories (SAT) neither a related picornavirus, i.e. swine vesicular disease virus. The molecule can be added until 2h post inoculation in a 'single replication cycle experiment' without losing its antiviral activity. The genetic characterization of progressively selected resistant FMD viruses shows that the molecule presumably interacts with the non-structural 2C protein of FMDV. Further studies are required on the use of this molecule in vivo.

Understanding virus replication is key to develop antiviral drugs

Frank van Kuppeveld* speaks to James Potticary, Commissioning Editor: Frank van Kuppeveld is a Professor of Molecular Virology at the Faculty of Veterinary Medicine, Utrecht University (The Netherlands). Having published over 100 original research papers, he is also the scientific coordinator of the European Training Network on (+)RNA Virus Replication and Antiviral Drug Development (EUVIRNA) consortium, a European training network for young researchers in the field of RNA viruses and antiviral drug development. van Kuppeveld spoke to Future Virology about his own contributions to the molecular virology field, as well as discussing the progress of the EUVIRNA training network.

Fluoxetine a novel anti-hepatitis C virus agent via ROS-, JNK-, and PPARβ/γ-dependent pathways

More than 20% of chronic hepatitis C (CHC) patients receiving interferon-alpha (IFN-α)-based anti-hepatitis C virus (HCV) therapy experienced significant depression, which was relieved by treatment with fluoxetine. However, whether and how fluoxetine affected directly the anti-HCV therapy remained unclear. Here, we demonstrated that fluoxetine inhibited HCV infection and blocked the production of reactive oxygen species (ROS) and lipid accumulation in Huh7.5 cells. Fluoxetine facilitated the IFN-α-mediated antiviral actions via activations of signal transducer and activator of transcription (STAT)-1 and c-Jun amino-terminal kinases (JNK). Alternatively, fluoxetine elevated peroxisome proliferator-activated receptor (PPAR) response element activity under HCV infection. The inhibitory effects of fluoxetine on HCV infection and lipid accumulation, but not production of ROS, were partially reversed by the PPAR-β, -γ, and JNK antagonists. Furthermore, fluoxetine intervention to the IFN-α-2b regimen facilitated to reduce HCV titer and alanine transaminase level for CHC patients. Therefore, fluoxetine intervention to the IFN-α-2b regimen improved the efficacy of anti-HCV treatment, which might be related to blockades of ROS generation and lipid accumulation and activation of host antiviral JNK/STAT-1 and PPARβ/γ signals.

Screening and identification of inhibitors against influenza A virus from a US drug collection of 1280 drugs

Infection with influenza A virus is still a global concern since it causes significant mortality, morbidity and economic loss. New burst pandemics and rapid emergence of drug-resistance strains in recent years call for novel antiviral therapies. One promising way to overcome this problem is searching new inhibitors among thousands of drugs approved in the clinic for the treatment of different diseases or approved to be safe by clinical trials. In the present work, a collection of 1280 compounds, most of which have been clinically used in human or animal, were screened for anti-influenza activity and 41 hits (SI>4.0) were obtained. Next the 18 hit compounds with SI >10.0 were tested for antiviral activity against 7 other influenza virus strains in canine-originated MDCK cells, 9 compounds exhibited broad antiviral spectrum. The antiviral effects of the 9 compounds were also confirmed in human-originated A549 cells and chicken-originated DF1 cells, by infectious virus yield reduction assay and indirect immunofluorescent assay. Results from the time of addition assay showed that the 9 candidates impaired different stages of influenza virus life cycle, indicating they are novel inhibitors with different mechanisms compared with the existing M2 ion-channel blockers or neuraminidase (NA) inhibitors. Taken together, our findings provide 9 novel drug candidates for the treatment of influenza virus infection. Further mechanism of action study of these inhibitors may lead to the discovery of new anti-influenza targets and structure-activity relationship (SAR) study can be initiated to improve the efficacy of these new classes of influenza inhibitors.