Viral engagement with host receptors blocked by a novel class of tryptophan dendrimers that targets the 5-fold-axis of the enterovirus-A71 capsid

Investigating the multifaceted role of nucleolin in cellular function and Cancer: Structure, Regulation, and therapeutic implications

Nucleolin (NCL), a highly conserved and multifunctional phosphoprotein, is primarily localized in the nucleolus and participates in various cellular compartments, including the nucleoplasm, cytoplasm, and plasma membrane. Initially discovered in the 1970 s, NCL is integral to ribosome biogenesis through its roles in ribosomal RNA transcription, processing, and assembly. Beyond ribosome synthesis, NCL plays critical roles in cellular processes such as DNA and RNA metabolism, chromatin remodeling, and cell cycle regulation, underscoring its essentiality for cell viability. Structurally, NCL comprises multiple functional domains, which facilitates interaction with various kinases and other proteins. NCL's extensive post-translational modifications influence its localization and function. Importantly, NCL has emerged as a key player in multiple pathologies, particularly cancer, where it contributes to tumor growth, metastasis, and drug resistance. On the cell surface, NCL acts as a co-receptor for growth factors and other ligands, facilitating oncogenic signaling. Additionally, its regulation of non-coding RNAs, stabilization of oncogenic mRNAs, and involvement in immune evasion highlight its potential as a therapeutic target. This review provides an unexplored in-depth overview of NCL's structure, functions, and modifications, with a focus on its role in cancer biology and its therapeutic implications.

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.

Multiplexed multicolor antiviral assay amenable for high-throughput research

To curb viral epidemics and pandemics, antiviral drugs are needed with activity against entire genera or families of viruses. Here, we develop a cell-based multiplex antiviral assay for high-throughput screening against multiple viruses at once, as demonstrated by using three distantly related orthoflaviviruses: dengue, Japanese encephalitis and yellow fever virus. Each virus is tagged with a distinct fluorescent protein, enabling individual monitoring in cell culture through high-content imaging. Specific antisera and small-molecule inhibitors are employed to validate that multiplexing approach yields comparable inhibition profiles to single-virus infection assays. To facilitate downstream analysis, a kernel is developed to deconvolute and reduce the multidimensional quantitative data to three cartesian coordinates. The methodology is applicable to viruses from different families as exemplified by co-infections with chikungunya, parainfluenza and Bunyamwera viruses. The multiplex approach is expected to facilitate the discovery of broader-spectrum antivirals, as shown in a pilot screen of approximately 1200 drug-like small-molecules.

C-2 Thiophenyl Tryptophan Trimers Inhibit Cellular Entry of SARS-CoV-2 through Interaction with the Viral Spike (S) Protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, by infecting cells via the interaction of its spike protein (S) with the primary cell receptor angiotensin-converting enzyme (ACE2). To search for inhibitors of this key step in viral infection, we screened an in-house library of multivalent tryptophan derivatives. Using VSV-S pseudoparticles, we identified compound 2 as a potent entry inhibitor lacking cellular toxicity. Chemical optimization of 2 rendered compounds 63 and 65, which also potently inhibited genuine SARS-CoV-2 cell entry. Thermofluor and microscale thermophoresis studies revealed their binding to S and to its isolated receptor binding domain (RBD), interfering with the interaction with ACE2. High-resolution cryoelectron microscopy structure of S, free or bound to 2, shed light on cell entry inhibition mechanisms by these compounds. Overall, this work identifies and characterizes a new class of SARS-CoV-2 entry inhibitors with clear potential for preventing and/or fighting COVID-19.

Evaluation of 3D Human Intestinal Organoids as a Platform for EV-A71 Antiviral Drug Discovery

Enteroviruses are a leading cause of upper respiratory tract, gastrointestinal, and neurological infections. Management of enterovirus-related diseases has been hindered by the lack of specific antiviral treatment. The pre-clinical and clinical development of such antivirals has been challenging, calling for novel model systems and strategies to identify suitable pre-clinical candidates. Organoids represent a new and outstanding opportunity to test antiviral agents in a more physiologically relevant system. However, dedicated studies addressing the validation and direct comparison of organoids versus commonly used cell lines are lacking. Here, we described the use of human small intestinal organoids (HIOs) as a model to study antiviral treatment against human enterovirus 71 (EV-A71) infection and compared this model to EV-A71-infected RD cells. We used reference antiviral compounds such as enviroxime, rupintrivir, and 2'-C-methylcytidine (2'CMC) to assess their effects on cell viability, virus-induced cytopathic effect, and viral RNA yield in EV-A71-infected HIOs and cell line. The results indicated a difference in the activity of the tested compounds between the two models, with HIOs being more sensitive to infection and drug treatment. In conclusion, the outcome reveals the value added by using the organoid model in virus and antiviral studies.

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 [...].

Insertion of an Amphipathic Linker in a Tetrapodal Tryptophan Derivative Leads to a Novel and Highly Potent Entry Inhibitor of Enterovirus A71 Clinical Isolates

AL-471, the leading exponent of a class of potent HIV and enterovirus A71 (EV-A71) entry inhibitors discovered in our research group, contains four l-tryptophan (Trp) units bearing an aromatic isophthalic acid directly attached to the C2 position of each indole ring. Starting from AL-471, we (i) replaced l-Trp with d-Trp, (ii) inserted a flexible linker between C2 and the isophthalic acid, and (iii) substituted a nonaromatic carboxylic acid for the terminal isophthalic acid. Truncated analogues lacking the Trp motif were also synthesized. Our findings indicate that the antiviral activity seems to be largely independent of the stereochemistry (l- or d-) of the Trp fragment and also that both the Trp unit and the distal isophthalic moiety are essential for antiviral activity. The most potent derivative, 23 (AL-534), with the C2 shortest alkyl urea linkage (three methylenes), showed subnanomolar potency against different EV-71 clinical isolates. This finding was only observed before with the early dendrimer prototype AL-385 (12 l-Trp units) but remained unprecedented for the reduced-size prototype AL-471. Molecular modeling showed the feasibility of high-affinity binding of the novel l-Trp-decorated branches of 23 (AL-534) to an alternative site on the VP1 protein that harbors significant sequence variation among EV-71 strains.

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.

Identification of a novel binding inhibitor that blocks the interaction between hSCARB2 and VP1 of enterovirus 71

Enterovirus 71 (EV-A71) infection causes severe hand-foot-and-mouth disease that leads to cardiopulmonary complications and death in young children under 5 years of age. Although there are available vaccines for EV-A71 C4, however, there are no efficient drugs for severe cases. Thus, there is an urgent need to find new direct-antiviral agents (DAAs) to control EV-A71 infection. In this study, we report our discovery of the EV-A71 capsid inhibitor PTC-209HBr, a small-molecule Bmi-1 inhibitor and an anticancer agent, and its derivatives that inhibit multiple enteroviruses with an EC50 at a submicromolar efficacy. The mechanism of action of PTC-209HBr was confirmed by time-of-addition, resistance selection and reverse genetics experiments, microscale thermophoresis (MST), viral binding and entry assays, coimmunoprecipitation (Co-IP) and immunofluorescence experiments (IF). Mechanistic studies indicated that PTC-209HBr inhibited EV-A71 infection by impeding the binding between VP1 and the receptor hSCARB2 during the early stage of EV-A71 infection through hindering viral entry into host cells. Collectively, these findings indicated that PCT-209HBr is a novel inhibitor of enteroviruses with a confirmed mechanism of action that can be further developed into EV-A71 DAAs.

3,4-Dicaffeoylquinic Acid from the Medicinal Plant Ilex kaushue Disrupts the Interaction Between the Five-Fold Axis of Enterovirus A-71 and the Heparan Sulfate Receptor

While infections by enterovirus A71 (EV-A71) are generally self-limiting, they can occasionally lead to serious neurological complications and death. No licensed therapies against EV-A71 currently exist. Using anti-virus-induced cytopathic effect assays, 3,4-dicaffeoylquinic acid (3,4-DCQA) from Ilex kaushue extracts was found to exert significant anti-EV-A71 activity, with a broad inhibitory spectrum against different EV-A71 genotypes. Time-of-drug-addition assays revealed that 3,4-DCQA affects the initial phase (entry step) of EV-A71 infection by directly targeting viral particles and disrupting viral attachment to host cells. Using resistant virus selection experiments, we found that 3,4-DCQA targets the glutamic acid residue at position 98 (E98) and the proline residue at position 246 (P246) in the 5-fold axis located within the VP1 structural protein. Recombinant viruses harboring the two mutations were resistant to 3,4-DCQA-elicited inhibition of virus attachment and penetration into human rhabdomyosarcoma (RD) cells. Finally, we showed that 3,4-DCQA specifically inhibited the attachment of EV-A71 to the host receptor heparan sulfate (HS), but not to the scavenger receptor class B member 2 (SCARB2) and P-selectin glycoprotein ligand-1 (PSGL1). Molecular docking analysis confirmed that 3,4-DCQA targets the 5-fold axis to form a stable structure with the E98 and P246 residues through noncovalent and van der Waals interactions. The targeting of E98 and P246 by 3,4-DCQA was found to be specific; accordingly, HS binding of viruses carrying the K242A or K244A mutations in the 5-fold axis was successfully inhibited by 3,4-DCQA.The clinical utility of 3,4-DCQA in the prevention or treatment of EV-A71 infections warrants further scrutiny. IMPORTANCE The canyon region and the 5-fold axis of the EV-A71 viral particle located within the VP1 protein mediate the interaction of the virus with host surface receptors. The three most extensively investigated cellular receptors for EV-A71 include SCARB2, PSGL1, and cell surface heparan sulfate. In the current study, a RD cell-based anti-cytopathic effect assay was used to investigate the potential broad spectrum inhibitory activity of 3,4-DCQA against different EV-A71 strains. Mechanistically, we demonstrate that 3,4-DCQA disrupts the interaction between the 5-fold axis of EV-A71 and its heparan sulfate receptor; however, no effect was seen on the SCARB2 or PSGL1 receptors. Taken together, our findings show that this natural product may pave the way to novel anti-EV-A71 therapeutic strategies.

Assessing In Vitro Resistance Development in Enterovirus A71 in the Context of Combination Antiviral Treatment

There are currently no antivirals available to treat infection with enterovirus A71 (EV-A71) or any other enterovirus. The extensively studied capsid binders rapidly select for drug-resistant variants. We here explore whether the combination of two direct-acting enterovirus inhibitors with a different mechanism of action may delay or prevent resistance development to the capsid binders. To that end, the in vitro dynamics of resistance development to the capsid binder pirodavir was studied either alone or in combination with a viral 2C-targeting compound (SMSK_0213), a viral 3C-protease inhibitor (rupintrivir) or a viral RNA-dependent RNA polymerase inhibitor (7DMA). We demonstrate that combining pirodavir with either rupintrivir or 7DMA delays the development of resistance to pirodavir and that no resistance to the protease or polymerase inhibitor develops. The combination of pirodavir with the 2C inhibitor results in a double-resistant virus population, where only the minority carries the resistant mutation.

Functional Insights into Silymarin as an Antiviral Agent against Enterovirus A71 (EV-A71)

Enterovirus A71 (EV-A71) is a major neurovirulent agent capable of causing severe hand, foot and mouth disease (HFMD) associated with neurological complications and death. Currently, no FDA-approved antiviral is available for the treatment of EV-A71 infections. The flavonoid silymarin was shown to exert virucidal effects, but the binding site on the capsid was unknown. In this study, the ligand interacting site of silymarin was determined in silico and validated in vitro. Moreover, the potential of EV-A71 to develop resistance against silymarin was further evaluated. Molecular docking of silymarin with the capsid of EV-A71 indicated that silymarin binds to viral protein 1 (VP1) of EV-A71, specifically at the GH loop of VP1. The in vitro binding of silymarin with VP1 of EV-A71 was validated using recombinant VP1 through ELISA competitive binding assay. Continuous passaging of EV-A71 in the presence of silymarin resulted in the emergence of a mutant carrying a substitution of isoleucine by threonine (I97T) at position 97 of the BC loop of EV-A71. The mutation was speculated to overcome the inhibitory effects of silymarin. This study provides functional insights into the underlying mechanism of EV-A71 inhibition by silymarin, but warrants further in vivo evaluation before being developed as a potential therapeutic agent.

Double Arylation of the Indole Side Chain of Tri- and Tetrapodal Tryptophan Derivatives Renders Highly Potent HIV-1 and EV-A71 Entry Inhibitors†

We have recently described a new generation of potent human immunodeficiency virus (HIV) and EV-A71 entry inhibitors. The prototypes contain three or four tryptophan (Trp) residues bearing an isophthalic acid moiety at the C2 position of each side-chain indole ring. This work is now extended by both shifting the position of the isophthalic acid to C7 and synthesizing doubly arylated C2/C7 derivatives. The most potent derivative (50% effective concentration (EC₅₀) HIV-1, 6 nM; EC₅₀ EV-A71, 40 nM), 33 (AL-518), is a C2/C7 doubly arylated tetrapodal compound. Its superior anti-HIV potency with respect to the previous C2-arylated prototype is in consonance with its higher affinity for the viral gp120. 33 (AL-518) showed comparable antiviral activities against X4 and R5 HIV-1 strains and seems to interact with the tip and base of the gp120 V3 loop. Taken together, these findings support the interest in 33 (AL-518) as a useful new prototype for anti-HIV/EV71 drug development.

Multivalent Tryptophan- and Tyrosine-Containing [60]Fullerene Hexa-Adducts as Dual HIV and Enterovirus A71 Entry Inhibitors

Unprecedented 3D hexa‐adducts of [60]fullerene peripherally decorated with twelve tryptophan (Trp) or tyrosine (Tyr) residues have been synthesized. Studies on the antiviral activity of these novel compounds against HIV and EV71 reveal that they are much more potent against HIV and equally active against EV71 than the previously described dendrimer prototypes AL‐385 and AL‐463, which possess the same number of Trp/Tyr residues on the periphery but attached to a smaller and more flexible pentaerythritol core. These results demonstrate the relevance of the globular 3D presentation of the peripheral groups (Trp/Tyr) as well as the length of the spacer connecting them to the central core to interact with the viral envelopes, particularly in the case of HIV, and support the hypothesis that [60]fullerene can be an alternative and attractive biocompatible carbon‐based scaffold for this type of highly symmetrical dendrimers. In addition, the functionalized fullerenes here described, which display twelve peripheral negatively charged indole moieties on their globular surface, define a new and versatile class of compounds with a promising potential in biomedical applications.

Novel capsid binder and PI4KIIIbeta inhibitors for EV-A71 replication inhibition

The Hand, Foot and Mouth Disease (HFMD) is a highly contagious viral illness generally manifests as a mild disease in young children and immunocompromised adults. It has however emerged as a significant public health threat in recent years as outbreaks have been occurring regularly, especially in the Asia–Pacific. The disease can result from infections by a wide variety of human enteroviruses, particularly, Enterovirus A71 (EV-A71) has garnered more attention due to its association with severe disease in infected patients. Despite the potential to result severe neurological complications or even fatality, there is currently no effective antiviral for treatment of EV-A71 infections and the only vaccines available are restricted to distribution in China. In this study, we report the in vitro and in vivo evaluation of two candidate antiviral compounds active against EV-A71, a viral capsid inhibitor (G197) and a novel host-targeting phosphatidylinositol 4-kinase III beta inhibitor (N373) which, especially when used in combination, can significantly improve the survival and pathology of infected mice.

Antivirals blocking entry of enteroviruses and therapeutic potential

Viruses from the genus Enterovirus (EV) of the Picornaviridae family are known to cause diseases such as hand foot and mouth disease (HFMD), respiratory diseases, encephalitis and myocarditis. The capsid of EV is an attractive target for the development of direct-acting small molecules that can interfere with viral entry. Some of the capsid binders have been evaluated in clinical trials but the majority have failed due to insufficient efficacy or unacceptable off-target effects. Furthermore, most of the capsid binders exhibited a low barrier to resistance. Alternatively, host-targeting inhibitors such as peptides derived from the capsid of EV that can recognize cellular receptors have been identified. However, the majority of these peptides displayed low anti-EV potency (µM range) as compared to the potency of small molecule compounds (nM range). Nonetheless, the development of anti-EV peptides is warranted as they may complement the small-molecules in a drug combination strategy to treat EVs. Lastly, structure-based approach to design antiviral peptides should be utilized to unearth potent anti-EV peptides.

Spike glycoproteins: Their significance for corona viruses and receptor binding activities for pathogenesis and viral survival

The recent outbreak of Covid-19 is posing a severe threat to public health globally. Coronaviruses (CoVs) are the largest known group of positive-sense RNA viruses surviving on an extensive number of natural hosts. CoVs are enveloped and non-segmented viruses with a size between 80 and 120 nm. CoV attachment to the surface receptor and its subsequent entrance into cells is mediated by Spike glycoprotein (S). For enhanced CoV entry and successful pathogenesis of CoV, proteolytic processing and receptor-binding act synergistically for induction of large-scale S conformational changes. The shape, size and orientation of receptor-binding domains in viral attachment proteins are well conserved among viruses of different classes that utilize the same receptor. Therefore, investigations unraveling the distribution of cellular receptors with respect to CoV entry, structural aspects of glycoproteins and related conformational changes are highly significant for understanding virus invasion and infection spread. We present the characteristic features of CoV S-Proteins, their significance for CoVs and related receptor binding activities for pathogenesis and viral survival. We are analyzing the novel role of S-protein of CoVs along with their interactive receptors for improving host immunity and decreasing infection spread. This is hoped that presented information will open new ways in tackling coronavirus, especially for the ongoing epidemic.

Rosmarinic acid exhibits broad anti-enterovirus A71 activity by inhibiting the interaction between the five-fold axis of capsid VP1 and cognate sulfated receptors

Enterovirus A71 (EV-A71), a positive-stranded RNA virus of the Picornaviridae family, may cause neurological complications or fatality in children. We examined specific factors responsible for this virulence using a chemical genetics approach. Known compounds from an anti-EV-A71 herbal medicine, Salvia miltiorrhiza (Danshen), were screened for anti-EV-A71. We identified a natural product, rosmarinic acid (RA), as a potential inhibitor of EV-A71 by cell-based antiviral assay and in vivo mouse model. Results also show that RA may affect the early stage of viral infection and may target viral particles directly, thereby interfering with virus-P-selectin glycoprotein ligand-1 (PSGL1) and virus-heparan sulfate interactions without abolishing the interaction between the virus and scavenger receptor B2 (SCARB2). Sequencing of the plaque-purified RA-resistant viruses revealed a N104K mutation in the five-fold axis of the structural protein VP1, which contains positively charged amino acids reportedly associated with virus-PSGL1 and virus-heparan sulfate interactions via electrostatic attraction. The plasmid-derived recombinant virus harbouring this mutation was confirmed to be refractory to RA inhibition. Receptor pull-down showed that this non-positively charged VP1-N104 is critical for virus binding to heparan sulfate. As the VP1-N104 residue is conserved among different EV-A71 strains, RA may be useful for inhibiting EV-A71 infection, even for emergent virus variants. Our study provides insight into the molecular mechanism of virus-host interactions and identifies a promising new class of inhibitors based on its antiviral activity and broad spectrum effects against a range of EV-A71.

Rational design of highly potent broad-spectrum enterovirus inhibitors targeting the nonstructural protein 2C

There is a great need for antiviral drugs to treat enterovirus (EV) and rhinovirus (RV) infections, which can be severe and occasionally life-threatening. The conserved nonstructural protein 2C, which is an AAA+ ATPase, is a promising target for drug development. Here, we present a structure-activity relationship study of a previously identified compound that targets the 2C protein of EV-A71 and several EV-B species members, but not poliovirus (PV) (EV-C species). This compound is structurally related to the Food and Drug Administration (FDA)-approved drug fluoxetine—which also targets 2C—but has favorable chemical properties. We identified several compounds with increased antiviral potency and broadened activity. Four compounds showed broad-spectrum EV and RV activity and inhibited contemporary strains of emerging EVs of public health concern, including EV-A71, coxsackievirus (CV)-A24v, and EV-D68. Importantly, unlike (S)-fluoxetine, these compounds are no longer neuroactive. By raising resistant EV-A71, CV-B3, and EV-D68 variants against one of these inhibitors, we identified novel 2C resistance mutations. Reverse engineering of these mutations revealed a conserved mechanism of resistance development. Resistant viruses first acquired a mutation in, or adjacent to, the α2 helix of 2C. This mutation disrupted compound binding and provided drug resistance, but this was at the cost of viral fitness. Additional mutations at distantly localized 2C residues were then acquired to increase resistance and/or to compensate for the loss of fitness. Using computational methods to identify solvent accessible tunnels near the α2 helix in the EV-A71 and PV 2C crystal structures, a conserved binding pocket of the inhibitors is proposed.

There is a great need for antiviral drugs to treat enterovirus and rhinovirus infections, which can be severe and occasionally life-threatening. This study describes novel small molecule inhibitors that target a broad spectrum of clinically relevant enterovirus species; a common mechanism of resistance development revealed the target to be a highly conserved binding pocket in the viral helicase 2C.

Serotype specific epitopes identified by neutralizing antibodies underpin immunogenic differences in Enterovirus B

Echovirus 30 (E30), a serotype of Enterovirus B (EV-B), recently emerged as a major causative agent of aseptic meningitis worldwide. E30 is particularly devastating in the neonatal population and currently no vaccine or antiviral therapy is available. Here we characterize two highly potent E30-specific monoclonal antibodies, 6C5 and 4B10, which efficiently block binding of the virus to its attachment receptor CD55 and uncoating receptor FcRn. Combinations of 6C5 and 4B10 augment the sum of their individual anti-viral activities. High-resolution structures of E30-6C5-Fab and E30-4B10-Fab define the location and nature of epitopes targeted by the antibodies. 6C5 and 4B10 engage the capsid loci at the north rim of the canyon and in-canyon, respectively. Notably, these regions exhibit antigenic variability across EV-Bs, highlighting challenges in development of broad-spectrum antibodies. Our structures of these neutralizing antibodies of E30 are instructive for development of vaccines and therapeutics against EV-B infections.

So far no vaccine or antiviral therapy is available for Echovirus 30 (E30) that causes aseptic meningitis. Here, the authors generate and characterise two E30-specific monoclonal antibodies that block binding of the virus to its attachment receptor CD55 and uncoating receptor FcRn, and determine the cryo-EM structures of E30 with the bound neutralizing antibodies.

Scaffold Simplification Strategy Leads to a Novel Generation of Dual Human Immunodeficiency Virus and Enterovirus-A71 Entry Inhibitors

Currently, there are only three FDA-approved drugs that inhibit human immunodeficiency virus (HIV) entry-fusion into host cells. The situation is even worse for enterovirus EV71 infection for which no antiviral therapies are available. We describe here the discovery of potent entry dual inhibitors of HIV and EV71. These compounds contain in their structure three or four tryptophan (Trp) residues linked to a central scaffold. Critical for anti-HIV/EV71 activity is the presence of extra phenyl rings, bearing one or two carboxylates, at the C2 position of the indole ring of each Trp residue. The most potent derivatives, 22 and 30, inhibit early steps of the replicative cycles of HIV-1 and EV-A71 by interacting with their respective viral surfaces (glycoprotein gp120 of HIV and the fivefold axis of the EV-A71 capsid). The high potency, low toxicity, facile chemical synthesis, and great opportunities for chemical optimization make them useful prototypes for future medicinal chemistry studies.

2019 meeting of the global virus network

The Global Virus Network (GVN) was established in 2011 to strengthen research and responses to emerging viral causes of human disease and to prepare against new viral pandemics. There are now 52 GVN Centers of Excellence and 9 Affiliate laboratories in 32 countries. The 11th International GVN meeting was held from June 9-11, 2019 in Barcelona, Spain and was jointly organized with the Spanish Society of Virology. A common theme throughout the meeting was globalization and climate change. This report highlights the recent accomplishments of GVN researchers in several important areas of medical virology, including severe virus epidemics, anticipation and preparedness for changing disease dynamics, host-pathogen interactions, zoonotic virus infections, ethical preparedness for epidemics and pandemics, one health and antivirals.

Targeting viral entry as a strategy for broad-spectrum antivirals

The process of entry into a host cell is a key step in the life cycle of most viruses. In recent years, there has been a significant increase in our understanding of the routes and mechanisms of entry for a number of these viruses. This has led to the development of novel broad-spectrum antiviral approaches that target host cell proteins and pathways, in addition to strategies focused on individual viruses or virus families. Here we consider a number of these approaches and their broad-spectrum potential.

Modifications in the branched arms of a class of dual inhibitors of HIV and EV71 replication expand their antiviral spectrum

We have previously reported a new class of dendrimers with tryptophan (Trp) residues on the surface that show dual antiviral activities against HIV and enterovirus EV71. The prototype compound of this family is a derivative of pentaerythritol with 12 peripheral Trp groups and trivalent spacer arms. Here a novel series of dendrimers with divalent and tetravalent branched arms, instead of the trivalent ones present on the prototype, has been synthesized and its activity against HIV, EV71 and a panel of 16 different viruses and other pathogens has been determined. Convergent or divergent approaches have been used for the synthesis of these compounds. Our findings demonstrate that only compounds with tetravalent branched arms showed the same anti-HIV and anti-EV71 activity of the prototype (low micromolar) and even gain significant antiviral activity against new pathogens such as HSV-2, adenovirus-2, human corona virus and respiratory syncytial virus, being the first members of the Trp dendrimer family that showed activity against those viruses. As the prototype, these compounds also showed low-nanomolar activity against a representative EV71 clinical isolate. Experimental work carried on to determine the mode of action of the most potent IIa, containing tetravalent branched arms, demonstrated that it interacts with the viral envelopes of HIV, EV71 and HSV-2 and thus may prevent virus attachment to the host cell. These results support the interest of this new series of Trp dendrimers and qualify them as useful prototypes for the development of novel inhibitors of viral entry with broad antiviral spectrum.

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Tryptophan (Trp) dendrimers with divalent and tetravalent branched arms have been synthesized.

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Only dendrimers with tetravalent branched arms (IIa-IId) showed (sub)micromolar inhibitory activity against HIV and EV71.

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IIa-IId inhibit a representative EV71 clinical isolate in the low-nanomolar range.

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IIa-IId are the first members of the Trp dendrimer family that showed activity against new viruses such as HSV-2.