The antifungal isavuconazole inhibits the entry of lassa virus by targeting the stable signal peptide-GP2 subunit interface of lassa virus glycoprotein

Architectural organization and in situ fusion protein structure of lymphocytic choriomeningitis virus

Arenaviruses exist globally and can cause hemorrhagic fever and neurological diseases, exemplified by the zoonotic pathogen lymphocytic choriomeningitis virus (LCMV). The structures of individual LCMV proteins or their fragments have been reported, but the architectural organization and the nucleocapsid assembly mechanism remain elusive. Importantly, the in situ structure of the arenavirus fusion protein complex (glycoprotein complex, GPC) as present on the virion prior to fusion, particularly with its integral stable signal peptide (SSP), has not been shown, hindering efforts such as structure-based vaccine design. Here, we have determined the in situ structure of LCMV proteins and their architectural organization in the virion by cryogenic electron tomography. The tomograms reveal the global distribution of GPC, matrix protein Z, and the contact points between the viral envelope and nucleocapsid. Subtomogram averaging yielded the in situ structure of the mature GPC with its transmembrane domain intact, revealing the GP2-SSP interface and the endodomain of GP2. The number of RNA-dependent RNA polymerase L molecules packaged within each virion varies, adding new perspectives to the infection mechanism. Together, these results delineate the structural organization of LCMV and offer new insights into its mechanism of LCMV maturation, egress, and cell entry.

IMPORTANCE

The impact of COVID-19 on public health has highlighted the importance of understanding zoonotic pathogens. Lymphocytic choriomeningitis virus (LCMV) is a rodent-borne human pathogen that causes hemorrhagic fever. Herein, we describe the in situ structure of LCMV proteins and their architectural organization on the viral envelope and around the nucleocapsid. The virion structure reveals the distribution of the surface glycoprotein complex (GPC) and the contact points between the viral envelope and the underlying matrix protein, as well as the association with the nucleocapsid. The morphology and sizes of virions, as well as the number of RNA polymerase L inside each virion vary greatly, highlighting the fast-changing nature of LCMV. A comparison between the in situ GPC trimeric structure and prior ectodomain structures identifies the transmembrane and endo domains of GPC and key interactions among its subunits. The work provides new insights into LCMV assembly and informs future structure-guided vaccine design.

Hexestrol, an estrogen receptor agonist, inhibits Lassa virus entry

Lassa virus (LASV) is the causative agent of human Lassa fever which in severe cases manifests as hemorrhagic fever leading to thousands of deaths annually. However, no approved vaccines or antiviral drugs are currently available. Recently, we screened approximately 2,500 compounds using a recombinant vesicular stomatitis virus (VSV) expressing LASV glycoprotein GP (VSV-LASVGP) and identified a P-glycoprotein inhibitor as a potential LASV entry inhibitor. Here, we show that another identified candidate, hexestrol (HES), an estrogen receptor agonist, is also a LASV entry inhibitor. HES inhibited VSV-LASVGP replication with a 50% inhibitory concentration (IC50) of 0.63 µM. Importantly, HES also inhibited authentic LASV replication with IC50 values of 0.31 µM-0.61 µM. Time-of-addition and cell-based membrane fusion assays suggested that HES inhibits the membrane fusion step during virus entry. Alternative estrogen receptor agonists did not inhibit VSV-LASVGP replication, suggesting that the estrogen receptor itself is unlikely to be involved in the antiviral activity of HES. Generation of a HES-resistant mutant revealed that the phenylalanine at amino acid position 446 (F446) of LASVGP, which is located in the transmembrane region, conferred resistance to HES. Although mutation of F446 enhanced the membrane fusion activity of LASVGP, it exhibited reduced VSV-LASVGP replication, most likely due to the instability of the pre-fusion state of LASVGP. Collectively, our results demonstrated that HES is a promising anti-LASV drug that acts by inhibiting the membrane fusion step of LASV entry. This study also highlights the importance of the LASVGP transmembrane region as a target for anti-LASV drugs.IMPORTANCELassa virus (LASV), the causative agent of Lassa fever, is the most devastating mammarenavirus with respect to its impact on public health in West Africa. However, no approved antiviral drugs or vaccines are currently available. Here, we identified hexestrol (HES), an estrogen receptor agonist, as the potential antiviral candidate drug. We showed that the estrogen receptor itself is not involved in the antiviral activity. HES directly bound to LASVGP and blocked membrane fusion, thereby inhibiting LASV infection. Through the generation of a HES-resistant virus, we found that phenylalanine at position 446 (F446) within the LASVGP transmembrane region plays a crucial role in the antiviral activity of HES. The mutation at F446 caused reduced virus replication, likely due to the instability of the pre-fusion state of LASVGP. These findings highlight the potential of HES as a promising candidate for the development of antiviral compounds targeting LASV.

Treatment of highly virulent mammarenavirus infections-status quo and future directions

INTRODUCTION

Mammarenaviruses are negative-sense bisegmented enveloped RNA viruses that are endemic in Africa, the Americas, and Europe. Several are highly virulent, causing acute human diseases associated with high case fatality rates, and are considered to be significant with respect to public health impact or bioterrorism threat.

AREAS COVERED

This review summarizes the status quo of treatment development, starting with drugs that are in advanced stages of evaluation in early clinical trials, followed by promising candidate medical countermeasures emerging from bench analyses and investigational animal research.

EXPERT OPINION

Specific therapeutic treatments for diseases caused by mammarenaviruses remain limited to the off-label use of ribavirin and transfusion of convalescent sera. Progress in identifying novel candidate medical countermeasures against mammarenavirus infection has been slow in part because of the biosafety and biosecurity requirements. However, novel methodologies and tools have enabled increasingly efficient high-throughput molecular screens of regulatory-agency-approved small-molecule drugs and led to the identification of several compounds that could be repurposed for the treatment of infection with several mammarenaviruses. Unfortunately, most of them have not yet been evaluated in vivo. The most promising treatment under development is a monoclonal antibody cocktail that is protective against multiple lineages of the Lassa virus in nonhuman primate disease models.

Entry inhibitors as arenavirus antivirals

Arenaviruses belonging to the Arenaviridae family, genus mammarenavirus, are enveloped, single-stranded RNA viruses primarily found in rodent species, that cause severe hemorrhagic fever in humans. With high mortality rates and limited treatment options, the search for effective antivirals is imperative. Current treatments, notably ribavirin and other nucleoside inhibitors, are only partially effective and have significant side effects. The high lethality and lack of treatment, coupled with the absence of vaccines for all but Junín virus, has led to the classification of these viruses as Category A pathogens by the Centers for Disease Control (CDC). This review focuses on entry inhibitors as potential therapeutics against mammarenaviruses, which include both New World and Old World arenaviruses. Various entry inhibition strategies, including small molecule inhibitors and neutralizing antibodies, have been explored through high throughput screening, genome-wide studies, and drug repurposing. Notable progress has been made in identifying molecules that target receptor binding, internalization, or fusion steps. Despite promising preclinical results, the translation of entry inhibitors to approved human therapeutics has faced challenges. Many have only been tested in in vitro or animal models, and a number of candidates showed efficacy only against specific arenaviruses, limiting their broader applicability. The widespread existence of arenaviruses in various rodent species and their potential for their zoonotic transmission also underscores the need for rapid development and deployment of successful pan-arenavirus therapeutics. The diverse pool of candidate molecules in the pipeline provides hope for the eventual discovery of a broadly effective arenavirus antiviral.

Structural and molecular biology of Sabiá virus

Brazilian mammarenavirus, or Sabiá virus (SABV), is a New World (NW) arenavirus associated with fulminant hemorrhagic disease in humans and the sole biosafety level 4 microorganism ever isolated in Brazil. Since the isolation of SABV in the 1990s, studies on viral biology have been scarce, with no available countermeasures against SABV infection or disease. Here we provide a comprehensive review of SABV biology, including key aspects of SABV replication, and comparisons with related Old World and NW arenaviruses. SABV is most likely a rodent-borne virus, transmitted to humans, through exposure to urine and feces in peri-urban areas. Using protein structure prediction methods and alignments, we analyzed shared and unique features of SABV proteins (GPC, NP, Z, and L) that could be explored in search of therapeutic strategies, including repurposing intended application against arenaviruses. Highly conserved catalytic activities present in L protein could be targeted for broad-acting antiviral activity among arenaviruses, while protein-protein interactions, such as those between L and the matrix protein Z, have evolved in NW arenaviruses and should be specific to SABV. The nucleoprotein (NP) also shares targetable interaction interfaces with L and Z and exhibits exonuclease activity in the C-terminal domain, which may be involved in multiple aspects of SABV replication. Envelope glycoproteins GP1 and GP2 have been explored in the development of promising cross-reactive neutralizing antibodies and vaccines, some of which could be repurposed for SABV. GP1 remains a challenging target in SABV as evolutive pressures render it the most variable viral protein in terms of both sequence and structure, while antiviral strategies targeting the Z protein remain to be validated. In conclusion, the prediction and analysis of protein structures should revolutionize research on viruses such as SABV by facilitating the rational design of countermeasures while reducing dependence on sophisticated laboratory infrastructure for experimental validation.

Design, Synthesis, and Biological Evaluation of Benzimidazole Derivatives as Potential Lassa Virus Inhibitors

The Lassa virus (LASV) causes Lassa fever, a highly infectious and lethal agent of acute viral hemorrhagic fever. At present, there are still no effective treatments available, creating an urgent need to develop novel therapeutics. Some benzimidazole compounds targeting the arenavirus envelope glycoprotein complex (GPC) are promising inhibitors of LASV. In this study, we synthesized two series of LASV inhibitors based on the benzimidazole structure. Lentiviral pseudotypes bearing the LASV GPC were established to identify virus entry inhibitors. Surface plasmon resonance (SPR) was further used to verify the binding activities of the potential compounds. Compounds 7d-Z, 7h-Z, 13c, 13d, and 13f showed relatively excellent antiviral activities with IC₅₀ values ranging from 7.58 to 15.46 nM and their SI values above 1251. These five representative compounds exhibited stronger binding affinity with low equilibrium dissociation constants (K_D < 8.25 × 10^-7 M) in SPR study. The compound 7h-Z displayed the most potent antiviral activity (IC₅₀ = 7.58 nM) with a relatively high SI value (2496), which could be further studied as a lead compound. The structure-activity relationship indicated that the compounds with lipophilic and spatially larger substituents might possess higher antiviral activity and a much larger safety margin. This study will provide some good guidance for the development of highly active compounds with a novel skeleton against LASV.

Pseudotyped Viruses for Mammarenavirus

Mammarenaviruses are classified into New World arenaviruses (NW) and Old World arenaviruses (OW). The OW arenaviruses include the first discovered mammarenavirus-lymphocytic choriomeningitis virus (LCMV) and the highly lethal Lassa virus (LASV). Mammarenaviruses are transmitted to human by rodents, resulting in severe acute infections and hemorrhagic fever. Pseudotyped viruses have been widely used as a tool in the study of mammarenaviruses. HIV-1, SIV, FIV-based lentiviral vectors, VSV-based vectors, MLV-based vectors, and reverse genetic approaches have been applied in the construction of pseudotyped mammarenaviruses. Pseudotyped mammarenaviruses are commonly used in receptor research, neutralizing antibody detection, inhibitor screening, viral virulence studies, functional analysis of N-linked glycans, and studies of viral infection, endocytosis, and fusion mechanisms.

Application of Pseudotyped Viruses

Highly pathogenic emerging and reemerging viruses have serious public health and socioeconomic implications. Although conventional live virus research methods can more reliably investigate disease pathogenicity and evaluate antiviral products, they usually depend on high-level biosafety laboratories and skilled researchers; these requirements hinder in vitro assessments of efficacy, as well as efforts to test vaccines and antibody drugs. In contrast, pseudotyped viruses (i.e., single-round infectious viruses that mimic the membrane structures of various live viruses) are widely used in studies of highly pathogenic viruses because they can be handled in biosafety level 2 facilities. This chapter provides a concise overview of various aspects of pseudotyped virus technologies, including (1) exploration of the mechanisms of viral infection; (2) evaluation of the efficacies of vaccines and monoclonal antibodies based on pseudovirion-based neutralization assay; (3) assessment of antiviral agents (i.e., antibody-based drugs and inhibitors); (4) establishment of animal models of pseudotyped virus infection in vivo; (5) investigation of the evolution, infectivity, and antigenicity of viral variants and viral glycosylation; and (6) prediction of antibody-dependent cell-mediated cytotoxic activity.

Purification and characterization of the Lassa virus transmembrane domain

Lassa virus (LASV) is the most prevalent arenavirus afflicting humans and has high potential to become a threat to global public health. The transmembrane domain (TM) of the LASV glycoprotein complex forms critical interactions with the LASV stable signal peptide that are important for the maturation and fusion activity of the virus. A further study of the structure-based molecular mechanisms is required to understand the role of the TM in the lifecycle of LASV in greater detail. However, it is challenging to obtain the TM in high quantity and purity due to its hydrophobic nature which results in solubility issues that makes it prone to aggregation in typical buffer systems. Here, we designed a purification and detergent screen protocol for the highly insoluble TM to enhance the yield and purity for structural studies. Based on the detergents tested, the TM had the highest incorporation in LMPG. Circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy were utilized to confirm the best detergent system for structural studies. Through CD spectroscopy, we were able to characterize the secondary structure of the TM as largely alpha-helical, while NMR spectroscopy showed a well-structured and stable TM in LMPG. From these results, LMPG was determined to be the optimal detergent for further structural studies.

Lassa Virus Infection: a Summary for Clinicians

OBJECTIVES

This summary on Lassa virus (LASV) infection and Lassa fever disease (LF) was developed from a clinical perspective to provide clinicians a condensed, accessible understanding of the current literature. The information provided highlights pathogenesis, clinical features, and diagnostics with an emphasis on therapies and vaccines that have demonstrated potential value for use in clinical or research environments.

METHODS

An integrative literature review was conducted on the clinical and pathological features, vaccines, and treatments for LASV infection, with a focus on recent studies and in vivo evidence from humans and/or non-human primates (NHPs), when available.

RESULTS

Two antiviral medications with potential benefit for the treatment of LASV infection and one for post-exposure prophylaxis were identified, although a larger number of potential candidates are currently being evaluated. Multiple vaccine platforms are in pre-clinical development for LASV prevention, but data from human clinical trials are not yet available.

CONCLUSION

We provide succinct summaries of medical countermeasures against LASV to give the busy clinician a rapid reference. Although there are no approved drugs or vaccines for LF, we provide condensed information from a literature review for measures that can be taken when faced with a suspected infection, including investigational treatment options and hospital engineering controls.

Contemporary and emerging pharmacotherapeutic agents for the treatment of Lassa viral haemorrhagic fever disease

This review was designed to discuss the emerging and current pharmacotherapeutic agents for the treatment of Lassa viral haemorrhagic fever disease (LVHFD), also known as Lassa fever (LF). Original peer-reviewed articles that investigated LF were identified using the Medline Entrez-PubMed search. Information was also sourced from printed textbooks and reports by recognized health professional bodies such as the WHO, CDC, the Nigerian Federal Ministry of Health and the United Nations Children's Fund (UNICEF). A total of 103 articles were reviewed and 78 were found to contain information relevant to the study. LF remains an endemic disease of public health concern in the West Africa region, and in the rest of the world as cases have been imported into non-endemic regions as well. Currently, there are no approved vaccines or therapeutics for the treatment of Lassa mammarenavirus (LASV) infection. There are, however, off-label therapeutics being used (ribavirin and convalescent plasma) whose efficacy is suboptimal. Research is still ongoing on possible therapeutic options and drug repurposing of therapeutic agents currently in use for other clinical conditions. Considered therapeutic options include favipiravir, taribavirin, Arevirumab-3 and experimental drugs such as losmapimod, adamantyl diphenyl piperazine 3.3, Arbidol (umifenovir) and decanoyl-RRLL-chloromethyl ketone (dec-RRLL-CMK). Current treatments for LF are limited, hence the institution of mitigating measures to prevent infection is of utmost importance and should be prioritized, especially in endemic regions. Heightened searches for other therapeutic options with greater efficacy and lower toxicity are still ongoing, as well as for vaccines as the absence of these classifies the disease as a priority disease of high public health impact.

Lassa virus glycoprotein complex review: insights into its unique fusion machinery

Lassa virus (LASV), an arenavirus endemic to West Africa, causes Lassa fever-a lethal hemorrhagic fever. Entry of LASV into the host cell is mediated by the glycoprotein complex (GPC), which is the only protein located on the viral surface and comprises three subunits: glycoprotein 1 (GP1), glycoprotein 2 (GP2), and a stable signal peptide (SSP). The LASV GPC is a class one viral fusion protein, akin to those found in viruses such as human immunodeficiency virus (HIV), influenza, Ebola virus (EBOV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These viruses are enveloped and utilize membrane fusion to deliver their genetic material to the host cell. Like other class one fusion proteins, LASV-mediated membrane fusion occurs through an orchestrated sequence of conformational changes in its GPC. The receptor-binding subunit, GP1, first engages with a host cell receptor then undergoes a unique receptor switch upon delivery to the late endosome. The acidic pH and change in receptor result in the dissociation of GP1, exposing the fusion subunit, GP2, such that fusion can occur. These events ultimately lead to the formation of a fusion pore so that the LASV genetic material is released into the host cell. Interestingly, the mature GPC retains its SSP as a third subunit-a feature that is unique to arenaviruses. Additionally, the fusion domain contains two separate fusion peptides, instead of a standard singular fusion peptide. Here, we give a comprehensive review of the LASV GPC components and their unusual features.

Target specificity of selective bioactive compounds in blocking α-dystroglycan receptor to suppress Lassa virus infection: an in silico approach

Lassa hemorrhagic fever, caused by Lassa mammarenavirus (LASV) infection, accumulates up to 5000 deaths every year. Currently, there is no vaccine available to combat this disease. In this study, a library of 200 bioactive compounds was virtually screened to study their drug-likeness with the capacity to block the α-dystroglycan (α-DG) receptor and prevent LASV influx. Following rigorous absorption, distribution, metabolism, and excretion (ADME) and quantitative structure-activity relationship (QSAR) profiling, molecular docking was conducted with the top ligands against the α-DG receptor. The compounds chrysin, reticuline, and 3-caffeoylshikimic acid emerged as the top three ligands in terms of binding affinity. Post-docking analysis revealed that interactions with Arg76, Asn224, Ser259, and Lys302 amino acid residues of the receptor protein were important for the optimum binding affinity of ligands. Molecular dynamics simulation was performed comprehensively to study the stability of the protein-ligand complexes. In-depth assessment of root-mean-square deviation (RMSD), root mean square fluctuation (RMSF), polar surface area (PSA), B-Factor, radius of gyration (Rg), solvent accessible surface area (SASA), and molecular surface area (MolSA) values of the protein-ligand complexes affirmed that the candidates with the best binding affinity formed the most stable protein-ligand complexes. To authenticate the potentialities of the ligands as target-specific drugs, an in vivo study is underway in real time as the continuation of the research.

CP100356 Hydrochloride, a P-Glycoprotein Inhibitor, Inhibits Lassa Virus Entry: Implication of a Candidate Pan-Mammarenavirus Entry Inhibitor

Lassa virus (LASV)—a member of the family Arenaviridae—causes Lassa fever in humans and is endemic in West Africa. Currently, no approved drugs are available. We screened 2480 small compounds for their potential antiviral activity using pseudotyped vesicular stomatitis virus harboring the LASV glycoprotein (VSV-LASVGP) and a related prototypic arenavirus, lymphocytic choriomeningitis virus (LCMV). Follow-up studies confirmed that CP100356 hydrochloride (CP100356), a specific P-glycoprotein (P-gp) inhibitor, suppressed VSV-LASVGP, LCMV, and LASV infection with half maximal inhibitory concentrations of 0.52, 0.54, and 0.062 μM, respectively, without significant cytotoxicity. Although CP100356 did not block receptor binding at the cell surface, it inhibited low-pH-dependent membrane fusion mediated by arenavirus glycoproteins. P-gp downregulation did not cause a significant reduction in either VSV-LASVGP or LCMV infection, suggesting that P-gp itself is unlikely to be involved in arenavirus entry. Finally, our data also indicate that CP100356 inhibits the infection by other mammarenaviruses. Thus, our findings suggest that CP100356 can be considered as an effective virus entry inhibitor for LASV and other highly pathogenic mammarenaviruses.

Potent antifungal agents and use of nanocarriers to improve delivery to the infected site: A systematic review

There are four major classes of antifungals with the predominant mechanism of action being targeting of cell wall or cell membrane. As in other drugs, low solubility of these compounds has led to low bioavailability in target tissues. Enhanced drug dosages have effects such as toxicity, drug-drug interactions, and increased drug resistance by fungi. This article reviews the current state-of-the-art of antifungals, structure, mechanism of action, other usages, and toxic side effects. The emergence of nanoformulations to transport and uniformly release cargo at the target site is a boon in antifungal treatment. The article details research that lead to the development of nanoformulations of antifungals and potential advantages and avoidance of the lacunae characterizing conventional drugs. A range of nanoformulations based on liposomes, polymers are in various stages of research and their potential advantages have been brought out. It could be observed that under similar dosages, test models, and duration, nanoformulations provided enhanced activity, reduced toxicity, higher uptake and higher immunostimulatory effects. In most instances, the mechanism of antifungal activity of nanoformulations was similar to that of regular antifungal. There are possibilities of coupling multiple antifungals on the same nano-platform. Increased activity coupled with multiple mechanisms of action presents for nanoformulations a tremendous opportunity to overcome antifungal resistance. In the years to come, robust methods for the preparation of nanoformulations taking into account the repeatability and reproducibility in action, furthering the studies on nanoformulation toxicity and studies of human models are required before extensive use of nanoformulations as a prescribed drug.

Screening and Identification of Lujo Virus Inhibitors Using a Recombinant Reporter Virus Platform

Lujo virus (LUJV), a highly pathogenic arenavirus, was first identified in 2008 in Zambia. To aid the identification of effective therapeutics for LUJV, we developed a recombinant reporter virus system, confirming reporter LUJV comparability with wild-type virus and its utility in high-throughput antiviral screening assays. Using this system, we evaluated compounds with known and unknown efficacy against related arenaviruses, with the aim of identifying LUJV-specific and potential new pan-arenavirus antivirals. We identified six compounds demonstrating robust anti-LUJV activity, including several compounds with previously reported activity against other arenaviruses. These data provide critical evidence for developing broad-spectrum antivirals against high-consequence arenaviruses.

Progress in Anti-Mammarenavirus Drug Development

Mammarenaviruses are prevalent pathogens distributed worldwide, and several strains cause severe cases of human infections with high morbidity and significant mortality. Currently, there is no FDA-approved antiviral drugs and vaccines against mammarenavirus and the potential treatment option is limited to an off-label use of ribavirin that shows only partial protective effect and associates with side effects. For the past few decades, extensive research has reported potential anti-mammarenaviral drugs and their mechanisms of action in host as well as vaccine candidates. This review describes current knowledge about mammarenavirus virology, progress of antiviral drug development, and technical strategies of drug screening.

High-Throughput Screening of an FDA-Approved Drug Library Identifies Inhibitors against Arenaviruses and SARS-CoV-2

Arenaviruses are a large family of enveloped negative-strand RNA viruses that include several causative agents of severe hemorrhagic fevers. Currently, there are no FDA-licensed drugs to treat arenavirus infection except for the off-labeled use of ribavirin. Here, we performed antiviral drug screening against the Old World arenavirus lymphocytic choriomeningitis virus (LCMV) using an FDA-approved drug library. Five drug candidates were identified, including mycophenolic acid, benidipine hydrochloride, clofazimine, dabrafenib, and apatinib, for having strong anti-LCMV effects. Further analysis indicated that benidipine hydrochloride inhibited LCMV membrane fusion, and an adaptive mutation on the LCMV glycoprotein D414 site was found to antagonize the anti-LCMV activity of benidipine hydrochloride. Mycophenolic acid inhibited LCMV replication by depleting GTP production. We also found mycophenolic acid, clofazimine, dabrafenib, and apatinib can inhibit the newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Owing to their FDA-approved status, these drug candidates can potentially be used rapidly in the clinical treatment of arenavirus and SARS-CoV-2 infection.

Management of Lassa Fever: A Current Update

Lassa fever (LF) is on the top-priority infections list of both the Food and Drug Administration (FDA) and World Health Organization (WHO). This review explores the different treatment approaches found in the literature within the last 20 years. Even though ribavirin stands out among medication options, only one clinical trial was done to assess its efficacy in humans, which necessitated that we look in-depth about the latest updates in managing LF infection. For that matter, we used a Medical Subject Headings (MeSH) search on PubMed. Inclusion criteria included papers written in the English language and human subjects. Intravenous (IV) ribavirin is the most effective treatment for an acute infection. Post-exposure prophylaxis with oral ribavirin is recommended. There is not sufficient evidence to recommended convalescent plasma for the treatment of Lassa fever. LF continues to be left in the shade from global and scientific attention despite experts expecting a rise in current and future infections due to the Lassa fever virus (LFV).

The antifungal drug isavuconazole inhibits the replication of human cytomegalovirus (HCMV) and acts synergistically with anti-HCMV drugs

We recently reported that some clinically approved antifungal drugs are potent inhibitors of human cytomegalovirus (HCMV). Here, we report the broad-spectrum activity against HCMV of isavuconazole (ICZ), a new extended-spectrum triazolic antifungal drug. ICZ inhibited the replication of clinical isolates of HCMV as well as strains resistant to the currently available DNA polymerase inhibitors. The antiviral activity of ICZ against HCMV could be linked to the inhibition of human cytochrome P450 51 (hCYP51), an enzyme whose activity we previously demonstrated to be required for productive HCMV infection. Moreover, time-of-addition studies indicated that ICZ might have additional inhibitory effects during the first phase of HCMV replication. Importantly, ICZ showed synergistic antiviral activity in vitro when administered in combination with different approved anti-HCMV drugs at clinically relevant doses. Together, these results pave the way to possible future clinical studies aimed at evaluating the repurposing potential of ICZ in the treatment of HCMV-associated diseases.

Drugs, host proteins and viral proteins: how their promiscuities shape antiviral design

The reciprocal nature of drug specificity and target specificity implies that the same is true for their respective promiscuities. Protein promiscuity has two broadly different types of footprint in drug design. The first is relaxed specificity of binding sites for substrates, inhibitors, effectors or cofactors. The second involves protein-protein interactions of regulatory processes such as signal transduction and transcription, and here protein intrinsic disorder plays an important role. Both viruses and host cells exploit intrinsic disorder for their survival, as do the design and discovery programs for antivirals. Drug action, strictly speaking, always relies upon promiscuous activity, with drug promiscuity enlarging its scope. Drug repurposing searches for additional promiscuity on the part of both the drug and the target in the host. Understanding the subtle nuances of these promiscuities is critical in the design of novel and more effective antivirals.