The potential of RNA-binding proteins as host-targeting antivirals against RNA viruses

RNA-binding proteins (RBPs) are essential regulators of cellular RNA processes, including RNA stability, translation, and post-translational regulation. During viral infections, RBPs are key regulators of the viral cycle due to their interaction with both host and viral RNAs. Herein, we initially explore the roles of specific RBP families, namely heterogeneous nuclear ribonucleoproteins (hnRNPs), DEAD-box helicases, human antigen R (HuR), and the eukaryotic initiation factors of the eIF4F complex, in viral RNA replication, translation, and assembly. Next, we examine the potential of these RBPs as host-targeting antivirals against pandemic-prone RNA viruses that have been gaining momentum in recent years. Targeting RBPs could disrupt cellular homeostasis, leading to unintended effects on host cells; however, RBPs have been successfully targeted mainly in anticancer therapies, showcasing that their modulation can be safely achieved by drug repurposing. By disrupting key viral-RBP interactions or modulating RBP functions, such therapeutic interventions aim to inhibit viral propagation and restore normal host processes. Thus, conceivable benefits of targeting RBPs as alternative antiviral strategies include their broad-spectrum activity and potential for combination therapies with conventional antivirals, reduced or delayed resistance development, and concomitant enhancement of host immune responses. Our discussion also highlights the broader implications of leveraging host-directed therapies in an attempt to overcome viral resistance. Finally, we emphasise the need for continued innovation to refine these strategies for broad-spectrum antiviral applications.

Clinical features and outcomes of patients with acute myeloid leukemia: the single-center experience of 668 patients in China

OBJECTIVE

To investigate efficacy and prognostic factors in the treatment of adult newly-diagnosed acute myeloid leukemia (AML) with or without allogeneic hematopoietic stem cell transplantation (Allo-HSCT).

METHODS

We retrospectively analyzed 668 patients with newly-diagnosed AML (non-M3 type) in the Department of Hematology at Shanghai Changhai Hospital from January 2012 to December 2021. Based on different induction chemotherapy regimens, patients were categorized into an IA (idarubicin, IDA + cytarabine, Ara-C) (3 + 7, regimen) group (n = 303) and a DA (daunorubicin, DNR + cytarabine, Ara-C) (3 + 7, regimen) group (n = 365) with or without allo-HSCT. Minimal residual disease (MRD), complete response (CR), overall response rate (ORR), progression-free survival (PFS), overall survival (OS), and adverse effects (AE) were analyzed and compared. Characteristics significantly associated with overall or progression-free survival (OS or PFS) upon univariate analysis were subsequently included in a Cox proportional hazard model.

RESULTS

This study used data from 668 AML patients. After induction therapy, the CR rate in the IA group was 70.63% and ORR was 79.87%, which were significantly higher than those in the DA group (with a CR rate of 56.99% and an ORR of 70.14%) (P = 0.0002 and P = 0.0035, respectively). There were no significant differences in drug safety between the two chemotherapy regimens used in IA and DA (P > 0.05). The recurrence rate was lower in patients with an MRD < 0.001 than in patients with an MRD ≥ 0.001. A continuous negative MRD during the period is significant because it is associated with prolonged OS and PFS of AML patients. Data from 100 patients in the two groups who underwent allo-HSCT were analyzed using univariate analysis and the Cox proportional hazards model. From the multivariate analysis, MRD was found to be the only independent predictor of OS (P = 0.042; HR 1; 95%CI 0.00-0.76).

CONCLUSION

In the treatment of adult AML patients, IA regimen is associated with a high CR rate and ORR rate and does not increase treatment-related toxicity. IA regimen prolongs OS and PFS in AML patients and reduces the likelihood of leukemia cells' subsequent infiltration into the central nervous system. There is a high correlation between the level of MRD after treatment and the patient's bone marrow recurrence. To obtain superior treatment effects for patients undergoing allo-HSCT, the MRD should be reduced to less than 0.001 before pretreatment. A negative MRD before allo-HSCT can prolong OS in patients with AML. We examined the clinical characteristics and outcomes of AML patients in China, finding novel information on prognostic factors and primary treatment of AML that may be applicable in routine clinical practice.

Readers of RNA Modification in Cancer and Their Anticancer Inhibitors

Cancer treatment has always been a challenge for humanity. The inadequacies of current technologies underscore the limitations of our efforts against this disease. Nevertheless, the advent of targeted therapy has introduced a promising avenue, furnishing us with more efficacious tools. Consequently, researchers have turned their attention toward epigenetics, offering a novel perspective in this realm. The investigation of epigenetics has brought RNA readers to the forefront, as they play pivotal roles in recognizing and regulating RNA functions. Recently, the development of inhibitors targeting these RNA readers has emerged as a focal point in research and holds promise for further strides in targeted therapy. In this review, we comprehensively summarize various types of inhibitors targeting RNA readers, including non-coding RNA (ncRNA) inhibitors, small-molecule inhibitors, and other potential inhibitors. We systematically elucidate their mechanisms in suppressing cancer progression by inhibiting readers, aiming to present inhibitors of readers at the current stage and provide more insights into the development of anticancer drugs.

Advances in anti-EV-A71 drug development research

BACKGROUND

Enterovirus A71 (EV-A71) is capable of causing hand, foot and mouth disease (HFMD), which may lead to neurological sequelae and even death. As EV-A71 is resistant to environmental changes and mutates easily, there is still a lack of effective treatments or globally available vaccines.

AIM OF REVIEW

For more than 50 years since the HFMD epidemic, related drug research has been conducted. Progress in this area can promote the further application of existing potential drugs and develop more efficient and safe antiviral drugs, and provide useful reference for protecting the younger generation and maintaining public health security.

KEY SCIENTIFIC CONCEPTS OF REVIEW

At present, researchers have identified hundreds of EV-A71 inhibitors based on screening repurposed drugs, targeted structural design, and rational modification of previously effective drugs as the main development strategies. This review systematically introduces the current potential drugs to inhibit EV-A71 infection, including viral inhibitors targeting key sites such as the viral capsid, RNA-dependent RNA polymerase (RdRp), 2C protein, internal ribosome entry site (IRES), 3C proteinase (3Cpro), and 2A proteinase (2Apro), starting from each stage of the viral life cycle. Meanwhile, the progress of host-targeting antiviral drugs and their development are summarized in terms of regulating host immunity, inhibiting autophagy or apoptosis, and regulating the cellular redox environment. In addition, the current clinical methods for the prevention and treatment of HFMD are summarized and discussed with the aim of providing support and recommendations for the treatment of enterovirus infections including EV-A71.

Antiviral activity of SP81 peptide against Enterovirus A71 (EV-A71)

The hand, food, and mouth disease (HFMD) is primarily caused by Enterovirus A71 (EV-A71). EV-A71 outbreaks in the Asia Pacific have been associated with severe neurological disease and high fatalities. Currently, there are no FDA-approved antivirals for the treatment of EV-A71 infections. In this study, the SP81 peptide, derived from the VP1 capsid protein of EV-A71 was shown to be a promising antiviral candidate for the treatment of EV-A71 infections. SP81 peptide was non-toxic to RD cells up to 45 μM, with a half-maximal cytotoxic concentration (CC50) of 90.32 μM. SP81 peptide exerted antiviral effects during the pre- and post-infection stages with 50% inhibitory concentrations (IC50) of 4.529 μM and 1.192 μM, respectively. Direct virus inactivation of EV-A71 by the SP81 peptide was also observed with an IC50 of 8.076 μM. Additionally, the SP81 peptide exhibited direct virus inactivation of EV-A71 at 95% upon the addition of the SP81 peptide within 5 min. This study showed that the SP81 peptide exhibited significant inhibition of EV-A71 and could serve as a promising antiviral agent for further clinical development against EV-A71 infections.

Small Molecules Targeting Viral RNA

The majority of antivirals available target viral proteins; however, RNA is emerging as a new and promising antiviral target due to the presence of highly structured RNA in viral genomes fundamental for their replication cycle. Here, we discuss methods for the identification of RNA-targeting compounds, starting from the determination of RNA structures either from purified RNA or in living cells, followed by in silico screening on RNA and phenotypic assays to evaluate viral inhibition. Moreover, we review the small molecules known to target the programmed ribosomal frameshifting element of SARS-CoV-2, the internal ribosomal entry site of different viruses, and RNA elements of HIV.

Advances and Breakthroughs in IRES-Directed Translation and Replication of Picornaviruses

Viruses lack the properties to replicate independently due to the limited resources encoded in their genome; therefore, they hijack the host cell machinery to replicate and survive. Picornaviruses get the prerequisite for effective protein synthesis through specific sequences known as internal ribosome entry sites (IRESs). In the past 2 decades, significant progress has been made in identifying different types of IRESs in picornaviruses. This review will discuss the past and current findings related to the five different types of IRESs and various internal ribosome entry site trans-acting factors (ITAFs) that either promote or suppress picornavirus translation and replication. Some IRESs are inefficient and thus require ITAFs. To achieve their full efficiency, they recruit various ITAFs, which enable them to translate more effectively and efficiently, except type IV IRES, which does not require any ITAFs. Although there are two kinds of ITAFs, one promotes viral IRES-dependent translation, and the second type restricts. Picornaviruses IRESs are classified into five types based on their use of sequence, ITAFs, and initiation factors. Some ITAFs regulate IRES activity by localizing to the viral replication factories in the cytoplasm. Also, some drugs, chemicals, and herbal extracts also regulate viral IRES-dependent translation and replication. Altogether, this review will elaborate on our understanding of the past and recent advancements in the IRES-dependent translation and replication of picornaviruses. IMPORTANCE The family Picornaviridae is divided into 68 genera and 158 species. The viruses belonging to this family range from public health importance, such as poliovirus, enterovirus A71, and hepatitis A virus, to animal viruses of great economic importance, such as foot-and-mouth disease virus. The genomes of picornaviruses contain 5' untranslated regions (5' UTRs), which possess crucial and highly structured stem-loops known as IRESs. IRES assemble the ribosomes and facilitate the cap-independent translation. Virus-host interaction is a hot spot for researchers, which warrants deep insight into understanding viral pathogenesis better and discovering new tools and ways for viral restriction to improve human and animal health. The cap-independent translation in the majority of picornaviruses is modulated by ITAFs, which bind to various IRES regions to initiate the translation. The discoveries of ITAFs substantially contributed to understanding viral replication behavior and enhanced our knowledge about virus-host interaction more effectively than ever before. This review discussed the various types of IRESs found in Picornaviridae, past and present discoveries regarding ITAFs, and their mechanism of action. The herbal extracts, drugs, and chemicals, which indicated their importance in controlling viruses, were also summarized. In addition, we discussed the movement of ITAFs from the nucleus to viral replication factories. We believe this review will stimulate researchers to search for more novel ITAFs, drugs, herbal extracts, and chemicals, enhancing the understanding of virus-host interaction.

Hand, Foot, and Mouth Disease Challenges and Its Antiviral Therapeutics

Hand, Foot, and Mouth Disease (HFMD) is an infectious disease caused by enteroviruses (EVs) and is extremely contagious and prevalent among infants and children under 5 years old [...].

Drug Repositioning for Hand, Foot, and Mouth Disease

Hand, foot, and mouth disease (HFMD) is a highly contagious disease in children caused by a group of enteroviruses. HFMD currently presents a major threat to infants and young children because of a lack of antiviral drugs in clinical practice. Drug repositioning is an attractive drug discovery strategy aimed at identifying and developing new drugs for diseases. Notably, repositioning of well-characterized therapeutics, including either approved or investigational drugs, is becoming a potential strategy to identify new treatments for virus infections. Various types of drugs, including antibacterial, cardiovascular, and anticancer agents, have been studied in relation to their therapeutic potential to treat HFMD. In this review, we summarize the major outbreaks of HFMD and the progress in drug repositioning to treat this disease. We also discuss the structural features and mode of action of these repositioned drugs and highlight the opportunities and challenges of drug repositioning for HFMD.

Diverse roles of heterogeneous nuclear ribonucleoproteins in viral life cycle

Understanding the host-virus interactions helps to decipher the viral replication strategies and pathogenesis. Viruses have limited genetic content and rely significantly on their host cell to establish a successful infection. Viruses depend on the host for a broad spectrum of cellular RNA-binding proteins (RBPs) throughout their life cycle. One of the major RBP families is the heterogeneous nuclear ribonucleoproteins (hnRNPs) family. hnRNPs are typically localized in the nucleus, where they are forming complexes with pre-mRNAs and contribute to many aspects of nucleic acid metabolism. hnRNPs contain RNA binding motifs and frequently function as RNA chaperones involved in pre-mRNA processing, RNA splicing, and export. Many hnRNPs shuttle between the nucleus and the cytoplasm and influence cytoplasmic processes such as mRNA stability, localization, and translation. The interactions between the hnRNPs and viral components are well-known. They are critical for processing viral nucleic acids and proteins and, therefore, impact the success of the viral infection. This review discusses the molecular mechanisms by which hnRNPs interact with and regulate each stage of the viral life cycle, such as replication, splicing, translation, and assembly of virus progeny. In addition, we expand on the role of hnRNPs in the antiviral response and as potential targets for antiviral drug research and development.

hnRNP A1 in RNA metabolism regulation and as a potential therapeutic target

Abnormal RNA metabolism, regulated by various RNA binding proteins, can have functional consequences for multiple diseases. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is an important RNA binding protein, that regulates various RNA metabolic processes, including transcription, alternative splicing of pre-mRNA, translation, miRNA processing and mRNA stability. As a potent splicing factor, hnRNP A1 can regulate multiple splicing events, including itself, collaborating with other cooperative or antagonistical splicing factors by binding to splicing sites and regulatory elements in exons or introns. hnRNP A1 can modulate gene transcription by directly interacting with promoters or indirectly impacting Pol II activities. Moreover, by interacting with the internal ribosome entry site (IRES) or 3'-UTR of mRNAs, hnRNP A1 can affect mRNA translation. hnRNP A1 can alter the stability of mRNAs by binding to specific locations of 3'-UTR, miRNAs biogenesis and Nonsense-mediated mRNA decay (NMD) pathway. In this review, we conclude the selective sites where hnRNP A1 binds to RNA and DNA, and the co-regulatory factors that interact with hnRNP A1. Given the dysregulation of hnRNP A1 in diverse diseases, especially in cancers and neurodegeneration diseases, targeting hnRNP A1 for therapeutic treatment is extremely promising. Therefore, this review also provides the small-molecule drugs, biomedicines and novel strategies targeting hnRNP A1 for therapeutic purposes.

Targeting non-structural proteins of Hepatitis C virus for predicting repurposed drugs using QSAR and machine learning approaches

Hepatitis C virus (HCV) infection causes viral hepatitis leading to hepatocellular carcinoma. Despite the clinical use of direct-acting antivirals (DAAs) still there is treatment failure in 5-10% cases. Therefore, it is crucial to develop new antivirals against HCV. In this endeavor, we developed the "Anti-HCV" platform using machine learning and quantitative structure-activity relationship (QSAR) approaches to predict repurposed drugs targeting HCV non-structural (NS) proteins. We retrieved experimentally validated small molecules from the ChEMBL database with bioactivity (IC50/EC50) against HCV NS3 (454), NS3/4A (495), NS5A (494) and NS5B (1671) proteins. These unique compounds were divided into training/testing and independent validation datasets. Relevant molecular descriptors and fingerprints were selected using a recursive feature elimination algorithm. Different machine learning techniques viz. support vector machine, k-nearest neighbour, artificial neural network, and random forest were used to develop the predictive models. We achieved Pearson's correlation coefficients from 0.80 to 0.92 during 10-fold cross validation and similar performance on independent datasets using the best developed models. The robustness and reliability of developed predictive models were also supported by applicability domain, chemical diversity and decoy datasets analyses. The "Anti-HCV" predictive models were used to identify potential repurposing drugs. Representative candidates were further validated by molecular docking which displayed high binding affinities. Hence, this study identified promising repurposed drugs viz. naftifine, butalbital (NS3), vinorelbine, epicriptine (NS3/4A), pipecuronium, trimethaphan (NS5A), olodaterol and vemurafenib (NS5B) etc. targeting HCV NS proteins. These potential repurposed drugs may prove useful in antiviral drug development against HCV.

Enterovirus A71 antivirals: Past, present, and future

Enterovirus A71 (EV-A71) is a significant human pathogen, especially in children. EV-A71 infection is one of the leading causes of hand, foot, and mouth diseases (HFMD), and can lead to neurological complications such as acute flaccid myelitis (AFM) in severe cases. Although three EV-A71 vaccines are available in China, they are not broadly protective and have reduced efficacy against emerging strains. There is currently no approved antiviral for EV-A71. Significant progress has been made in developing antivirals against EV-A71 by targeting both viral proteins and host factors. However, viral capsid inhibitors and protease inhibitors failed in clinical trials of human rhinovirus infection due to limited efficacy or side effects. This review discusses major discoveries in EV-A71 antiviral development, analyzes the advantages and limitations of each drug target, and highlights the knowledge gaps that need to be addressed to advance the field forward.

Molecular profiling of individual FDA-approved clinical drugs identifies modulators of nonsense-mediated mRNA decay

Nonsense-mediated mRNA decay (NMD) degrades transcripts with premature stop codons. Given the prevalence of nonsense single nucleotide polymorphisms (SNPs) in the general population, it is urgent to catalog the effects of clinically approved drugs on NMD activity: any interference could alter the expression of nonsense SNPs, inadvertently inducing adverse effects. This risk is higher for patients with disease-causing nonsense mutations or an illness linked to dysregulated nonsense transcripts. On the other hand, hundreds of disorders are affected by cellular NMD efficiency and may benefit from NMD-modulatory drugs. Here, we profiled individual FDA-approved drugs for their impact on cellular NMD efficiency using a sensitive method that directly probes multiple endogenous NMD targets for a robust readout of NMD modulation. We found most FDA-approved drugs cause unremarkable effects on NMD, while many elicit clear transcriptional responses. Besides several potential mild NMD modulators, the anticancer drug homoharringtonine (HHT or omacetaxine mepesuccinate) consistently upregulates various endogenous NMD substrates in a dose-dependent manner in multiple cell types. We further showed translation inhibition mediates HHT's NMD effect. In summary, many FDA drugs induce transcriptional changes, and a few impact global NMD, and direct measurement of endogenous NMD substrate expression is robust to monitor cellular NMD.

Antidepressant Sertraline Is a Broad-Spectrum Inhibitor of Enteroviruses Targeting Viral Entry through Neutralization of Endolysosomal Acidification

Enterovirus 71 (EV71) is an etiological agent of hand foot and mouth disease and can also cause neurological complications in young children. However, there are no approved drugs as of yet to treat EV71 infections. In this study, we conducted antiviral drug screening by using a Food and Drug Administration (FDA)-approved drug library. We identified five drugs that showed dose-dependent inhibition of viral replication. Sertraline was further characterized because it exhibited the most potent antiviral activity with the highest selectivity index among the five hits. The antiviral activity of sertraline was noted for other EV serotypes. The drug’s antiviral effect is not likely associated with its approved indications as an antidepressant and its mode-of-action as a selective serotonin reuptake inhibitor. The time-of-addition assay revealed that sertraline inhibited an EV71 infection at the entry stage. We also showed that sertraline partitioned into acidic compartments, such as endolysosomes, to neutralize the low pH levels. In agreement with the findings, the antiviral effect of sertraline could be greatly relieved by exposing virus-infected cells to extracellular low-pH culture media. Ultimately, we have identified a use for an FDA-approved antidepressant in broad-spectrum EV inhibition by blocking viral entry through the alkalization of the endolysosomal route.

Heat Shock Protein A6, a Novel HSP70, Is Induced During Enterovirus A71 Infection to Facilitate Internal Ribosomal Entry Site-Mediated Translation

Enterovirus A71 (EV-A71) is a human pathogen causing hand, foot, and mouth disease (HFMD) in children. Its infection can lead to severe neurological diseases or even death in some cases. While being produced in a large quantity during infection, viral proteins often require the assistance from cellular chaperones for proper folding. In this study, we found that heat shock protein A6 (HSPA6), whose function in viral life cycle is scarcely studied, was induced and functioned as a positive regulator for EV-A71 infection. Depletion of HSPA6 led to the reductions of EV-A71 viral proteins, viral RNA and virions as a result of the downregulation of internal ribosomal entry site (IRES)-mediated translation. Unlike other HSP70 isoforms such as HSPA1, HSPA8, and HSPA9, which regulate all phases of the EV-A71 life, HSPA6 was required for the IRES-mediated translation only. Unexpectedly, the importance of HSPA6 in the IRES activity could be observed in the absence of viral proteins, suggesting that HSPA6 facilitated IRES activity through cellular factor(s) instead of viral proteins. Intriguingly, the knockdown of HSPA6 also caused the reduction of luciferase activity driven by the IRES from coxsackievirus A16, echovirus 9, encephalomyocarditis virus, or hepatitis C virus, supporting that HSPA6 may assist the function of a cellular protein generally required for viral IRES activities.

Multi-conformation representation of Mpro identifies promising candidates for drug repurposing against COVID-19

The COVID-19 main protease (Mpro), one of the conserved proteins of the novel coronavirus is crucial for its replication and so is a very lucrative drug target. Till now, there is no drug molecule that has been convincingly identified as the inhibitor of the function of this protein. The current pandemic situation demands a shortcut to quickly reach to a lead compound or a drug, which may not be the best but might serve as an interim solution at least. Following this notion, the present investigation uses virtual screening to find a molecule which is alraedy approved as a drug for some other disease but could be repurposed to inhibit Mpro. The potential of the present method of work to identify such a molecule, which otherwise would have been missed out, lies in the fact that instead of just using the crystallographically identified conformation of the receptor’s ligand binding pocket, molecular dynamics generated ensemble of conformations has been used. It implicitly included the possibilities of “induced-fit” and/or “population shift” mechanisms of ligand fitting. As a result, the investigation has not only identified antiviral drugs like ribavirin, ritonavir, etc., but it has also captured a wide variety of drugs for various other diseases like amrubicin, cangrelor, desmopressin, diosmin, etc. as the potent possibilities. Some of these ligands are versatile to form stable interactions with various different conformations of the receptor and therefore have been statistically surfaced in the investigation. Overall the investigation offers a wide range of compounds for further testing to confirm their scopes of applications to combat the COVID-19 pandemic.

Evaluation of potential anti-RNA-dependent RNA polymerase (RdRP) drugs against the newly emerged model of COVID-19 RdRP using computational methods

INTRODUCTION

Despite all the efforts to treat COVID-19, no particular cure has been found for this virus. Since developing antiviral drugs is a time-consuming process, the most effective approach is to evaluate the approved and under investigation drugs using in silico methods. Among the different targets within the virus structure, as a vital component in the life cycle of coronaviruses, RNA-dependent RNA polymerase (RdRP) can be a critical target for antiviral drugs. The impact of the existence of RNA in the enzyme structure on the binding affinity of anti-RdRP drugs has not been investigated so far.

METHODS

In this study, the potential anti-RdRP effects of a variety of drugs from two databases (Zinc database and DrugBank) were evaluated using molecular docking. For this purpose, the newly emerged model of COVID-19 (RdRP) post-translocated catalytic complex (PDB ID: 7BZF) that consists of RNA was chosen as the target.

RESULTS

The results indicated that idarubicin (IDR), a member of the anthracycline antibiotic family, and fenoterol (FNT), a known beta-2 adrenergic agonist drug, tightly bind to the target enzyme and could be used as potential anti-RdRP inhibitors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These outcomes revealed that due to the ligand-protein interactions, the presence of RNA in this structure could remarkably affect the binding affinity of inhibitor compounds.

CONCLUSION

In silico approaches, such as molecular docking, could effectively address the problem of finding appropriate treatment for COVID-19. Our results showed that IDR and FNT have a significant affinity to the RdRP of SARS-CoV-2; therefore, these drugs are remarkable inhibitors of coronaviruses.

Enterovirus D68 Antivirals: Past, Present, and Future

Enterovirus D68 (EV-D68) is an RNA virus that causes respiratory illnesses mainly in children. In severe cases, it can lead to neurological complications such as acute flaccid myelitis (AFM). EV-D68 belongs to the enterovirus genera of the Picornaviridae family, which also includes many other significant human pathogens such as poliovirus, enterovirus A71, and rhinovirus. There are currently no vaccines or antivirals against EV-D68. In this review, we present the current understanding of the link between EV-D68 and AFM, the mechanism of viral replication, and recent progress in developing EV-D68 antivirals by targeting various viral proteins and host factors that are essential for viral replication. The future directions of EV-D68 antiviral drug discovery and the criteria for drugs to reach clinical trials are also discussed.

Broad-Spectrum Host-Based Antivirals Targeting the Interferon and Lipogenesis Pathways as Potential Treatment Options for the Pandemic Coronavirus Disease 2019 (COVID-19)

The ongoing Coronavirus Disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) signals an urgent need for an expansion in treatment options. In this study, we investigated the anti-SARS-CoV-2 activities of 22 antiviral agents with known broad-spectrum antiviral activities against coronaviruses and/or other viruses. They were first evaluated in our primary screening in VeroE6 cells and then the most potent anti-SARS-CoV-2 antiviral agents were further evaluated using viral antigen expression, viral load reduction, and plaque reduction assays. In addition to remdesivir, lopinavir, and chloroquine, our primary screening additionally identified types I and II recombinant interferons, 25-hydroxycholesterol, and AM580 as the most potent anti-SARS-CoV-2 agents among the 22 antiviral agents. Betaferon (interferon-β1b) exhibited the most potent anti-SARS-CoV-2 activity in viral antigen expression, viral load reduction, and plaque reduction assays among the recombinant interferons. The lipogenesis modulators 25-hydroxycholesterol and AM580 exhibited EC50 at low micromolar levels and selectivity indices of >10.0. Combinational use of these host-based antiviral agents with virus-based antivirals to target different processes of the SARS-CoV-2 replication cycle should be evaluated in animal models and/or clinical trials.

Insights into idarubicin antimicrobial activity against methicillin-resistant Staphylococcus aureus

BACKGROUND

MRSA is a major concern in community settings and in health care. The emergence of biofilms and persister cells substantially increases its antimicrobial resistance. It is very urgent to develop new antimicrobials to solve this problem.

OBJECTIVE

Idarubicin was profiled to assess its antimicrobial effects in vitro and in vivo, and the underlying mechanisms.

METHODS

We investigated the antimicrobial effects of idarubicin against MRSA by time-kill analysis. The antibiofilm efficacy of idarubicin was assessed by crystal violet and XTT staining, followed by laser confocal microscopy observation. The mechanisms underlying the antimicrobial effects were studied by transmission electron microscopy, all-atom molecular dynamic simulations, SYTOX staining, surface plasma resonance, and DNA gyrase inhibition assay. Further, we addressed the antimicrobial efficacy in wound and subcutaneous abscess infection in vivo.

RESULTS

Idarubicin kills MRSA cells by disrupting the lipid bilayers and interrupting the DNA topoisomerase IIA subunits, and idarubicin shows synergistic antimicrobial effects with fosfomycin. Through synergy with a single dose treatment fosfomycin and the addition of the cell protector amifostine, the cytotoxicity and cardiotoxicity of idarubicin were significantly reduced without affecting its antimicrobial effects. Idarubicin alone or in combination with fosfomycin exhibited considerable efficacy in a subcutaneous abscess mouse model of MRSA infection. In addition, idarubicin also showed a low probability of causing resistance and good postantibiotic effects.

CONCLUSIONS

Idarubicin and its analogs have the potential to become a new class of antimicrobials for the treatment of MRSA-related infections.

Antivirals and vaccines for Enterovirus A71

Enterovirus A71 (EV-A71) is an important emerging virus posing a threat to children under five years old. EV-A71 infection in infants or young children can cause hand-foot-and-mouth disease, herpangina, or severe neurological complications. However, there are still no effective antivirals for treatment of these infections. In this review, we summarize the antiviral compounds developed to date based on various targets of the EV-A71 life cycle. Moreover, development of a vaccine would be the most effective approach to prevent EV-A71 infection. Therefore, we also summarize the development and clinical progress of various candidate EV-A71 vaccines, including inactivated whole virus, recombinant VP1 protein, synthetic peptides, viral-like particles, and live attenuated vaccines.

Stimulation of the Internal Ribosome Entry Site (IRES)-Dependent Translation of Enterovirus 71 by DDX3X RNA Helicase and Viral 2A and 3C Proteases

The translation of enterovirus 71 (EV71) is mediated by an internal ribosome entry site (IRES)-dependent manner. EV71 IRES comprises five highly structured domains (domains II-VI) in the 5′-untranslated region of the viral mRNA. A conserved AUG triplet residing in domain VI is proposed to be the ribosome entry site. It is thus envisaged that the highly structured conformation of domain VI may actually reduce the accessibility of the AUG triplet to the ribosome. This study identified a DEAD-box family RNA helicase, DDX3X, that positively regulated the EV71 IRES-dependent translation. The helicase activity of DDX3X was required for the stimulation of EV71 IRES activity; however, DDX3X was no longer important for the IRES activity when the secondary structure of domain VI was destabilized. DDX3X interacted with the truncated eIF4G which bound specifically to domain V. Thus, we proposed that DDX3X might bind to domain VI or a region nearby via the interaction with the truncated eIF4G, and subsequently unwound the secondary structure of domain VI to facilitate ribosome entry. Additionally, we demonstrated that the viral 2A^pro and 3C^pro enhanced the IRES-dependent translation via their protease activities. Together, these results indicate that DDX3X is an important RNA helicase involved in EV71 IRES-dependent translation and that IRES translation is enhanced by viral infection, partly mediated by viral protease activity.

Identifying novel antiviral targets against enterovirus 71: where are we?

Human enterovirus 71 (HEV71) has been considered as an essential human pathogen, which causes hand, foot and mouth disease in young children. Several HEV71 outbreaks have been observed in many Asia-Pacific countries for the past two decades with significant fatalities. However, there are no competent vaccines or antivirals against HEV71 infection to date. Thus, it is of critical priority to delve into the search for anti-HEV71 agents. Prior to this, there is a need to gain knowledge about the distinct targets of HEV71 that are available and that have been exploited for antiviral therapy. This review aims to provide a better understanding of HEV71 virology and feature potential antivirals for progressive clinical development with respect to their elucidated mechanistic actions.

Development of a fluorescence resonance energy transfer-based intracellular assay to identify novel enterovirus 71 antivirals

Enterovirus 71 (EV71) is considered one of the most virulent pathogens in the family Picornaviridae. However, there have been no effective treatments for the severe complications caused by EV71. Development of new drugs against targets that are essential for viral replication often requires screening large collections of compounds, for which a high-throughput screening platform is needed. In this study, a drug-screening platform was developed based on a genetically engineered cell line that displays fluorescence resonance energy transfer (FRET) and shows a real-time and quantifiable impairment of FRET upon EV71 infection. A library of small molecules consisting of 1280 compounds with defined bioactivities was used for screening drugs with anti-EV71 activity; accurate, rapid, and robust results were obtained from this screening procedure. Ten drugs were identified in the primary screening, and their antiviral activities were indicated by dose-dependent elevation of FRET. Among these, AC-93253, mitoxantrone and N-bromoacetamide had not been reported as enterovirus inhibitors, and it was confirmed that they were able to suppress viral yields in a dose-dependent manner. Taken together, these studies demonstrate the feasibility of this FRET-based platform for efficient screening and identification of novel compounds with activity against EV71 infection.