Exploration of the anti-enterovirus activity of a series of pleconaril/pirodavir-like compounds

Pterostilbene Exhibits Broad-Spectrum Antiviral Activity by Targeting the Enterovirus Capsid, Inactivating Viral Particles, Blocking Viral Binding, and Protecting Mice From Lethal EV-A71 Challenge

Human enteroviruses (EVs) are a major public health issue worldwide owing to their potential to cause respiratory illnesses, hand-foot-and-mouth disease, and severe neurological complications. Currently, no effective drugs or multivalent vaccines are available. Pterostilbene (Pte), a naturally occurring compound found in blueberries and other plants, is a type of stilbene with a similar structure to resveratrol. Pterostilbene exerts antioxidant, anti-inflammatory, and anticancer properties. However, few studies have explored its antiviral activity. This study aimed to investigate the anti-enteroviral effect and mechanisms of Pte against EV-A71 and EV-D68. Cytotoxicity and antiviral assays were performed to assess the safety of Pte to cells and its antiviral effects against enteroviruses. Viral attachment, inactivation assays, cellular receptor binding, western blotting, time-of-addition and time-of-removal assays, particle stability thermal release assay, and molecular docking were performed to elucidate the antiviral mechanisms of Pte. Additionally, we validated the antiviral effects of Pte using in vivo experiments. Among the stilbenes examined, Pte exerted a broad-spectrum inhibitory effect on various enteroviruses, including EV-A71, EV-D68, and coxsackieviruses at 40 μM, without cytotoxicity. Mechanistically, Pte significantly inhibited enteroviral attachment, inactivated viral particles, blocked viral binding to its receptors, and increased virion stability. Molecular docking analysis revealed that Pte occupied a hydrophobic pocket in viral protein 1, indicating a strong binding affinity and acting as an efficient inhibitor. Notably, sequence alignment of multiple enteroviruses indicated that the Pte-interacting residues in VP1 were highly conserved. In vivo studies demonstrated that oral administration of Pte significantly alleviated infection symptoms and reduced mortality in hSCARB2 transgenic mice. Pte possesses potential application as a broad-efficacy antiviral drug against enteroviral infections.

Discovery of A-967079 as an Enterovirus D68 Antiviral by Targeting the Viral 2C Protein

Enterovirus D68 (EV-D68) has had several outbreaks worldwide, yet no FDA-approved antiviral is available for treating this viral infection. EV-D68 infection typically leads to respiratory illnesses and, in severe cases, can cause neurological complications and even death, particularly in children. This study identified a small molecule, A-967079, as an EV-D68 antiviral through phenotypical screening. A-967079 has shown potent and broad-spectrum antiviral activity with a high selectivity index against multiple strains of EV-D68. Pharmacological characterization of the mechanism of action involving time-of-addition, resistance selection, and differential scanning fluorimetry assays suggests that viral 2C protein is the drug target. Overall, A-967079 represents a promising candidate for further development as an EV-D68 antiviral.

Insights into enterovirus a-71 antiviral development: from natural sources to synthetic nanoparticles

Enteroviruses are pathogens responsible for several diseases, being enterovirus A71 (EVA71) the second leading cause of hand, foot, and mouth disease (HFMD), especially in Asia-Pacific countries. HFMD is mostly common in infants and children, with mild symptoms. However, the disease can result in severe nervous system disorders in children as well as in immunosuppressed adults. The virus is highly contagious, and its transmission occurs via fecal-oral, oropharyngeal secretions, and fomites. The EVA71 burdens the healthy systems and economies around the world, however, up to date, there is no antiviral approved to treat infected individuals and the existent vaccines are not available or approved to be used worldwide. In this context, an extensive literature research was conducted to describe and summarize the recent advances in natural and/or synthetic compounds with antiviral activity against EVA71. The summarized data presented here might simply encourage the future studies in EVA71 antiviral development, by encouraging further research encompassing these compounds or even the application of the techniques and technologies to improve or produce new antiviral molecules.

Direct-Acting Antivirals and Host-Targeting Approaches against Enterovirus B Infections: Recent Advances

Enterovirus B (EV-B)-related diseases, which can be life threatening in high-risk populations, have been recognized as a serious health problem, but their clinical treatment is largely supportive, and no selective antivirals are available on the market. As their clinical relevance has become more serious, efforts in the field of anti-EV-B inhibitors have greatly increased and many potential antivirals with very high selectivity indexes and promising in vitro activities have been discovered. The scope of this review encompasses recent advances in the discovery of new compounds with anti-viral activity against EV-B, as well as further progress in repurposing drugs to treat these infections. Current progress and future perspectives in drug discovery against EV-Bs are briefly discussed and existing gaps are spotlighted.

Multifunctionality of structural proteins in the enterovirus life cycle

Members of the genus Enterovirus have a significant effect on human health, especially in infants and children. Since the viral genome has limited coding capacity, Enteroviruses subvert a range of cellular processes for viral infection via the interaction of viral proteins and numerous cellular factors. Intriguingly, the capsid-receptor interaction plays a crucial role in viral entry and has significant implications in viral pathogenesis. Moreover, interactions between structural proteins and host factors occur directly or indirectly in multiple steps of viral replication. In this review, we focus on the current understanding of the multifunctionality of structural proteins in the viral life cycle, which may constitute valuable targets for antiviral and therapeutic interventions.

Evaluation of the virucidal effects of rosmarinic acid against enterovirus 71 infection via in vitro and in vivo study

BACKGROUND

Although enterovirus 71 (EV71) is an important public health threat, especially in the Asia-Pacific region, there are still no effective drugs or vaccines to treat and prevent EV71 infection. Therefore, it is critical to develop prophylactic and therapeutic agents against EV71. Rosmarinic acid (RA), a phytochemical, has been discovered to possess a broad spectrum of biological activities.

METHODS

The virucidal effects of RA on EV71 were determined by MTT, western blot, median cell culture infectious dose, apoptosis detection, plaque reduction, semi-quantitative real-time polymerase chain reaction, immunofluorescence detection, molecular docking analysis, and mouse protection assay.

RESULTS

RA showed a strong protective effect against EV71 infection in human rhabdomyosarcoma cells when the multiplicity of infection was 1, with a low IC50 value (4.33 ± 0.18 μM) and high therapeutic index (340). RA not only protected cells from EV71-induced cytopathic effects, but also from EV71-induced apoptosis. The results of time-of-addition analysis demonstrated that the inhibitory activity of RA was highest at the early stage of viral infection. Consistent with this, the infectivity of EV71 in the early stage of viral infection also was observed to be limited in neonatal mice treated with RA. Further, molecular docking predicts that RA could replace the natural pocket factor within the VP1 capsid-binding hydrophobic pocket.

CONCLUSIONS

This study suggests that RA has the potential to be developed as an antiviral agent against initial EV71 infection to prevent or reduce EV71-induced pathogenesis and complications, since RA can effectively reduce EV71 infection in the early stages of viral infection.

Automated cell-based luminescence assay for profiling antiviral compound activity against enteroviruses

We describe the development, optimisation, and validation of an automated, cell-based and high-throughput screening assay using existing luminescence-based ATPlite reagents for identifying antiviral compounds that inhibit enterovirus replication. Antiviral efficacy was determined by measuring the ATP levels in cells that were protected from the viral cytopathic effect (CPE) by the antiviral compounds pleconaril and rupintrivir. CPE-based assay conditions were optimised at a cell density of 5000 cells/well and a viral infection dose of 100 CCID₅₀ in 384-well plates. The assay exhibited excellent robustness, with Z'-factor values between 0.75 and 0.82, coefficients of variation between 0.33% and 1.45%, and signal-to-background ratios ranging from 6.92 to 22.6 when testing three enterovirus A71 isolates circulating in China. The assay was also suitable for screening other picornaviruses, such as poliovirus, coxsackievirus, echovirus, and parechovirus.

Inhibition of herpes simplex virus 1 (HSV-1) and poliovirus (PV-1) by bacteriocins from lactococcus lactis subsp. lactis and enterococcus durans strains isolated from goat milk

Bacteriocins have unusual inhibitory activity, including antiviral properties, and this can be exploited to give alternative applications. Semi-purified bacteriocins of six lactic acid bacteria (LAB) strains isolated from goat milk (two Lactococcus lactis: GLc03 and GLc05, and four Enterococcus durans: GEn09, GEn12, GEn14 and GEn17) were tested for cytotoxicity in Vero cells (50% Cytotoxicity Concentration: CC₅₀), and for their antiviral activities against herpes simplex virus 1 (HVS-1) and poliovirus (PV-1). Semi-purified bacteriocins presented low cytotoxicity, with CC₅₀ varying from 256.2 µg/mL (GLc05) to 1084.5 µg/mL (GEn14). CC₁₀ was determined for all isolates (GLc03: 36.9 µg/mL; GLc05: 51.2 µg/mL; GEn09: 88.1 µg/mL; GEn12: 99.9 µg/mL; GEn14: 275 µg/mL; and GEn17: 62.2 µg/mL) and considered for antiviral activity assays. Antiviral activity before virus adsorption was recorded against PV-1 for GLc05 (4.9%), GEn09 (3.4%), GEn12 (24.7%) and GEn17 (23.5%), and against HSV-1 for GEn12 (27.9%), GEn14 (58.7%) and GEn17 (39.2%). Antiviral activity after virus adsorption was identified against PV-1 for GLc05 (32.7%), GEn09 (91.0%), GEn12 (93.7%) and GEn17 (57.2%), and against HSV-1 for GEn17 (71.6%). The results obtained indicate the potential of some bacteriocins, particularly those produced by E. durans strains investigated in the present study, in viral inhibition and their application as new antiviral agents.

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.