Antiviral Effect of Lithium Chloride on Replication of Marek’s Disease Virus in Chicken Embryonic Fibroblasts

To investigate the antiviral effect of lithium chloride (LiCl) on the replication of Marek’s disease virus (MDV) in chicken embryonic fibroblast (CEF) cells, real-time PCR, Western blotting, plaque counting, and indirect immunofluorescence experiments were performed at different time points of LiCl treated CEF cells with virus infection. The results demonstrated that LiCl could affect multiple steps of virus replication and inhibit viral gene expression and protein synthesis in a dose- and time-dependent manner. Moreover, LiCl could directly affect viral infectivity as well. In addition, LiCl significantly affected the gene expression of IFN-β related genes in virus-infected cells. These results indicate that LiCl significantly inhibits MDV replication and proliferation in CEF cells and it has the potential to be used as an antiviral agent against MDV.     

Antiviral Activity of Baicalein and Quercetin against the Japanese Encephalitis Virus

Japanese encephalitis (JE), a mosquito-borne viral disease, is endemic to the entire east and southeast Asia, and some other parts of the world. Currently, there is no effective therapeutic available for JE; therefore, finding the effective antiviral agent against JEV replication is crucial. In the present study, the in vitro antiviral activity of baicalein and quercetin, two purportedly antiviral bioflavonoids, was evaluated against Japanese encephalitis virus (JEV) replication in Vero cells. Anti-JEV activities of these compounds were examined on different stages of JEV replication cycle. The effects of the compounds on virus replication were determined by foci forming unit reduction assay (FFURA) and quantitative RT-PCR. Baicalein showed potent antiviral activity with IC₅₀ = 14.28 μg/mL when it was introduced to the Vero cells after adsorption of JEV. Quercetin exhibited weak anti-JEV effects with IC₅₀ = 212.1 μg/mL when the JEV infected cells were treated with the compound after virus adsorption. However, baicalein exhibited significant effect against JEV adsorption with IC₅₀ = 7.27 μg/mL while quercetin did not show any anti-adsorption activity. Baicalein also exhibited direct extracellular virucidal activity on JEV with IC₅₀ = 3.44 μg/mL. However, results of quantitative RT-PCR experiments confirmed the findings from FFURA. This study demonstrated that baicalein should be considered as an appropriate candidate for further investigations, such as the study of molecular and cellular mechanism(s) of action and in vivo evaluation for the development of an effective antiviral compound against Japanese encephalitis virus.     

Enhanced Antiviral Function of Magnesium Chloride-Modified Heparin on a Broad Spectrum of Viruses

Previous studies reported on the broad-spectrum antiviral function of heparin. Here we investigated the antiviral function of magnesium-modified heparin and found that modified heparin displayed a significantly enhanced antiviral function against human adenovirus (HAdV) in immortalized and primary cells. Nuclear magnetic resonance analyses revealed a conformational change of heparin when complexed with magnesium. To broadly explore this discovery, we tested the antiviral function of modified heparin against herpes simplex virus type 1 (HSV-1) and found that the replication of HSV-1 was even further decreased compared to aciclovir. Moreover, we investigated the antiviral effect against the new severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and measured a 55-fold decreased viral load in the supernatant of infected cells associated with a 38-fold decrease in virus growth. The advantage of our modified heparin is an increased antiviral effect compared to regular heparin.     

Exploring the Effect of Structure-Based Scaffold Hopping on the Inhibition of Coxsackievirus A24v Transduction by Pentavalent N-Acetylneuraminic Acid Conjugates

Coxsackievirus A24 variant (CVA24v) is the primary causative agent of the highly contagious eye infection designated acute hemorrhagic conjunctivitis (AHC). It is solely responsible for two pandemics and several recurring outbreaks of the disease over the last decades, thus affecting millions of individuals throughout the world. To date, no antiviral agents or vaccines are available for combating this disease, and treatment is mainly supportive. CVA24v utilizes Neu5Ac-containing glycans as attachment receptors facilitating entry into host cells. We have previously reported that pentavalent Neu5Ac conjugates based on a glucose-scaffold inhibit CVA24v infection of human corneal epithelial cells. In this study, we report on the design and synthesis of scaffold-replaced pentavalent Neu5Ac conjugates and their effect on CVA24v cell transduction and the use of cryogenic electron microscopy (cryo-EM) to study the binding of these multivalent conjugates to CVA24v. The results presented here provide insights into the development of Neu5Ac-based inhibitors of CVA24v and, most significantly, the first application of cryo-EM to study the binding of a multivalent ligand to a lectin.     

Sialyl-LacNAc-PNA⋅DNA Concatamers by Rolling-Circle Amplification as Multivalent Inhibitors of Influenza A Virus Particles

The surfaces of influenza A virus (IAV) particles are packed with hundreds of homo-trimeric hemagglutinins (HAs). Monovalent sugars have low affinity for HA, but distance-optimized bivalent sialyl-LacNAc (SLN) conjugates bind it with 10³-fold enhanced potency. Herein, we describe the oligomerization of distance-optimized bivalent binders by branched and linear hybridization on long repetitive DNA templates. The most effective complexes fully inhibited IAVs at a DNA template concentration of 10⁻⁹ m . Although a 10⁻² m concentration of free trisaccharide ligand is required for full inhibition of the virus, DNA templating enables a 10⁴-fold reduction in the amount of sugar required. Notably, hybridization-induced rigidification of the DNA templates increased the serospecificity. Cryo-TEM analysis revealed that both spaghetti-type linear forms and cotton-ball-like clusters are able to bridge several adjacent HA molecules on the IAV surface. Programmed self-assembly of ligand–nucleic acid conjugates on long DNA templates might provide generic access to target-specific, high-affinity binders of proteins on globular objects such as cells and viruses.     

Identification of a βCD-Based Hyper-Branched Negatively Charged Polymer as HSV-2 and RSV Inhibitor

Cyclodextrins and cyclodextrin derivatives were demonstrated to improve the antiviral potency of numerous drugs, but also to be endowed with intrinsic antiviral action. They are suitable building blocks for the synthesis of functionalized polymer structures with potential antiviral activity. Accordingly, four water-soluble hyper-branched beta cyclodextrin (βCD)-based anionic polymers were screened against herpes simplex virus (HSV-2), respiratory syncytial virus (RSV), rotavirus (HRoV), and influenza virus (FluVA). They were characterized by FTIR-ATR, TGA, elemental analyses, zeta-potential measurements, and potentiometric titrations, while the antiviral activity was investigated with specific in vitro assays. The polymer with the highest negative charge, pyromellitic dianhydride-linked polymer (P_PMDA), showed significant antiviral action against RSV and HSV-2, by inactivating RSV free particles and by altering HSV-2 binding to the cell. The polymer fraction with the highest molecular weight showed the strongest antiviral activity and both P_PMDA and its active fractions were not toxic for cells. Our results suggest that the polymer virucidal activity against RSV can be exploited to produce new antiviral materials to counteract the virus dissemination through the air or direct contact. Additionally, the strong HSV-2 binding inhibition along with the water solubility of P_PMDA and the acyclovir complexation potential of βCD are attractive features for developing new therapeutic topical options against genital HSV-2 infection.     

Synthesis and structure-activity relationship studies of HIV-1 virion infectivity factor (Vif) inhibitors that block viral replication

The human immunodeficiency virus 1 (HIV-1) virion infectivity factor (Vif) protein, essential for in vivo viral replication, protects the virus from innate antiviral cellular factor apolipoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3G (APOBEC3G; A3G) and is an attractive target for the development of novel antiviral therapeutics. We have evaluated the structure-activity relationships of N-(2-methoxyphenyl)-2-((4-nitrophenyl)thio)benzamide (RN-18), a small molecule recently identified as an inhibitor of Vif function that blocks viral replication only in nonpermissive cells expressing A3G, by inhibiting Vif-A3G interactions. Microwave-assisted cross-coupling reactions were developed to prepare a series of RN18 analogues with diverse linkages and substitutions on the phenyl rings. A dual cell-based assay system was used to assess antiviral activity against wild-type HIV-1 in both nonpermissive (H9) and permissive (MT4) cells that also allowed evaluation of specificity. In general, variations of phenyl substitutions were detrimental to antiviral potency and specificity, but isosteric replacements of amide and ether linkages were relatively well tolerated. These structure-activity relationship data define structural requirements for Vif-specific activity, identify new compounds with improved antiviral potency and specificity, and provide leads for further exploration to develop new antiviral therapeutics.     

Entrectinib—A SARS-CoV-2 Inhibitor in Human Lung Tissue (HLT) Cells

Since the start of the COVID-19 outbreak, pharmaceutical companies and research groups have focused on the development of vaccines and antiviral drugs against SARS-CoV-2. Here, we apply a drug repurposing strategy to identify drug candidates that are able to block the entrance of the virus into human cells. By combining virtual screening with in vitro pseudovirus assays and antiviral assays in Human Lung Tissue (HLT) cells, we identify entrectinib as a potential antiviral drug.     

Antiviral activity of silver nanoparticle/chitosan composites against H1N1 influenza A virus

Silver nanoparticle (Ag NP)/chitosan (Ch) composites with antiviral activity against H1N1 influenza A virus were prepared. The Ag NP/Ch composites were obtained as yellow or brown floc-like powders following reaction at room temperature in aqueous medium. Ag NPs (3.5, 6.5, and 12.9 nm average diameters) were embedded into the chitosan matrix without aggregation or size alternation. The antiviral activity of the Ag NP/Ch composites was evaluated by comparing the TCID₅₀ ratio of viral suspensions treated with the composites to untreated suspensions. For all sizes of Ag NPs tested, antiviral activity against H1N1 influenza A virus increased as the concentration of Ag NPs increased; chitosan alone exhibited no antiviral activity. Size dependence of the Ag NPs on antiviral activity was also observed: antiviral activity was generally stronger with smaller Ag NPs in the composites. These results indicate that Ag NP/Ch composites interacting with viruses exhibit antiviral activity.     

The Peptide A-3302-B Isolated from a Marine Bacterium Micromonospora sp. Inhibits HSV-2 Infection by Preventing the Viral Egress from Host Cells

Herpesviruses are highly prevalent in the human population, and frequent reactivations occur throughout life. Despite antiviral drugs against herpetic infections, the increasing appearance of drug-resistant viral strains and their adverse effects prompt the research of novel antiherpetic drugs for treating lesions. Peptides obtained from natural sources have recently become of particular interest for antiviral therapy applications. In this work, we investigated the antiviral activity of the peptide A-3302-B, isolated from a marine bacterium, Micromonospora sp., strain MAG 9-7, against herpes simplex virus type 1, type 2, and human cytomegalovirus. Results showed that the peptide exerted a specific inhibitory activity against HSV-2 with an EC₅₀ value of 14 μM. Specific antiviral assays were performed to investigate the mechanism of action of A-3302-B. We demonstrated that the peptide did not affect the expression of viral proteins, but it inhibited the late events of the HSV-2 replicative cycle. In detail, it reduced the cell-to-cell virus spread and the transmission of the extracellular free virus by preventing the egress of HSV-2 progeny from the infected cells. The dual antiviral and previously reported anti-inflammatory activities of A-3302-B, and its effect against an acyclovir-resistant HSV-2 strain are attractive features for developing a therapeutic to reduce the transmission of HSV-2 infections.     

Comparison of Cell Fusions Induced by Influenza Virus and SARS-CoV-2

Virus–cell fusion is the key step for viral infection in host cells. Studies on virus binding and fusion with host cells are important for understanding the virus–host interaction and viral pathogenesis for the discovery of antiviral drugs. In this review, we focus on the virus–cell fusions induced by the two major pandemic viruses, including the influenza virus and SARS-CoV-2. We further compare the cell fusions induced by the influenza virus and SARS-CoV-2, especially the pH-dependent fusion of the influenza virus and the fusion of SARS-CoV-2 in the type-II transmembrane serine protease 2 negative (TMPRSS2^-) cells with syncytia formation. Finally, we present the development of drugs used against SARA-CoV-2 and the influenza virus through the discovery of anti-fusion drugs and the prevention of pandemic respiratory viruses.     

Sulfonated and Carboxymethylated β-Glucan Derivatives with Inhibitory Activity against Herpes and Dengue Viruses

The infection of mammalian cells by enveloped viruses is triggered by the interaction of viral envelope glycoproteins with the glycosaminoglycan, heparan sulfate. By mimicking this carbohydrate, some anionic polysaccharides can block this interaction and inhibit viral entry and infection. As heparan sulfate carries both carboxyl and sulfate groups, this work focused on the derivatization of a (1→3)(1→6)-β-D-glucan, botryosphaeran, with these negatively-charged groups in an attempt to improve its antiviral activity. Carboxyl and sulfonate groups were introduced by carboxymethylation and sulfonylation reactions, respectively. Three derivatives with the same degree of carboxymethylation (0.9) and different degrees of sulfonation (0.1; 0.2; 0.4) were obtained. All derivatives were chemically characterized and evaluated for their antiviral activity against herpes (HSV-1, strains KOS and AR) and dengue (DENV-2) viruses. Carboxymethylated botryosphaeran did not inhibit the viruses, while all sulfonated-carboxymethylated derivatives were able to inhibit HSV-1. DENV-2 was inhibited only by one of these derivatives with an intermediate degree of sulfonation (0.2), demonstrating that the dengue virus is more resistant to anionic β-D-glucans than the Herpes simplex virus. By comparison with a previous study on the antiviral activity of sulfonated botryosphaerans, we conclude that the presence of carboxymethyl groups might have a detrimental effect on antiviral activity.     

干扰素诱导的MxA蛋白及其抗丙型肝炎病毒感染作用的研究进展

干扰素α(Interferon α,IFNα)是目前公认的可有效抗丙型肝炎病毒(Hepatitis C virus,HCV)的药物,其主要通过诱导细胞产生抗病毒蛋白而发挥作用。抗黏病毒蛋白A(Mixovirus resistance protein A,MxA)是由I型IFN诱导产生的相对分子质量为78000的抗病毒蛋白,主要分布于细胞质中,具有识别HCV核糖核蛋白复合物(Virus ribonucleoprotein complexes,vRNPs)的功能,通过MxA的GTP酶活性水解HCV核衣壳,使病毒核酸释放并被胞浆中的核酸内切酶降解。本文主要对IFN的分类、MxA的结构和作用机制及近年来MxA抗HCV感染作用的研究进展作一综述。     

Synthesis of Antiviral Perfluoroalkyl Derivatives of Teicoplanin and Vancomycin

The limited scope of antiviral drugs and increasing problem of antiviral drug resistance represent a global health threat. Glycopeptide antibiotics and their lipophilic derivatives have emerged as relevant inhibitors of diverse viruses. Herein, we describe a new strategy for the synthesis of dual hydrophobic and lipophobic derivatives of glycopeptides to produce selective antiviral agents without membrane-disrupting activity. Perfluorobutyl and perfluorooctyl moieties were attached through linkers of different length to azido derivatives of vancomycin aglycone and teicoplanin pseudoaglycone, and the new derivatives were evaluated against a diverse panel of viruses. The teicoplanin derivatives displayed strong anti-influenza virus activity at nontoxic concentrations. Some of the perfluoroalkylated glycopeptides were also active against a few other viruses such as herpes simplex virus or coronavirus. These data encourage further exploration of glycopeptide analogues for broad antiviral application.     

Role of CD4+ T Cells in the Control of Viral Infections: Recent Advances and Open Questions

CD4+ T cells orchestrate adaptive immune responses through their capacity to recruit and provide help to multiple immune effectors, in addition to exerting direct effector functions. CD4+ T cells are increasingly recognized as playing an essential role in the control of chronic viral infections. In this review, we present recent advances in understanding the nature of CD4+ T cell help provided to antiviral effectors. Drawing from our studies of natural human immunodeficiency virus (HIV) control, we then focus on the role of high-affinity T cell receptor (TCR) clonotypes in mediating antiviral CD4+ T cell responses. Last, we discuss the role of TCR affinity in determining CD4+ T cell differentiation, reviewing the at times divergent studies associating TCR signal strength to the choice of a T helper 1 (Th1) or a T follicular helper (Tfh) cell fate.     

Synthesis and Anti‐herpetic Activity of Phosphoramidate ProTides

Among the many prodrug approaches aimed at delivering nucleoside monophosphates into cells, the phosphoramidate ProTide approach is one that has shown success, which has made it possible for some of the phosphoramidates to enter into clinical trials. Herein, we report the synthesis and antiviral activity of a series of phosphoramidate ProTides designed to bypass the thymidine kinase (TK) dependence of the parent nucleoside analogues. Phosphoramidate derivatives of (E)‐5‐(2‐bromovinyl)‐2′‐deoxyuridine (BVDU) that contain L ‐alanine or pivaloyloxymethyl iminodiacetate (IDA‐POM) exhibit anti‐HSV‐1 and anti‐VZV activity in cell cultures, but they largely lost antiviral potency against TK‐deficient virus strains. Among deazapurine nucleosides and their phosphoramidate derivatives, the 7‐deazaadenine containing nucleosides and their phosphoramidate triester derivatives showed weak antiviral activity against VZV. Apparently, intracellular nucleotide delivery with these phosphoramidates is partly successful. However, none of the compound prodrugs showed superior activity to their parent drugs.     

Antiviral metal complexes

The initial events (virus adsorption and fusion with the cells) in the replicative cycle of human immunodeficiency virus (HIV) can serve as targets for the antiviral action of metal-binding compounds such as polyanionic compounds (polysulfates, polysulfonates, polycarboxylates, polyoxometalates, and sulfonated or carboxylated metalloporphyrins), bicyclams and G-octet-forming oligonucleotides. The adsorption and fusion of HIV with its target cells depends on the interaction of the viral envelope glycoproteins (gp 120) with the receptors (CD4, CXCR4) at the outer cell membrane. We are currently investigating how the aforementioned compounds interfere with these viral glycoproteins and/or cell receptor.     

Understanding Viral Infection Mechanisms and Patient Symptoms for the Development of COVID-19 Therapeutics

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, has become a worldwide pandemic. Symptoms range from mild fever to cough, fatigue, severe pneumonia, acute respiratory distress syndrome (ARDS), and organ failure, with a mortality rate of 2.2%. However, there are no licensed drugs or definitive treatment strategies for patients with severe COVID-19. Only antiviral or anti-inflammatory drugs are used as symptomatic treatments based on clinician experience. Basic medical researchers are also trying to develop COVID-19 therapeutics. However, there is limited systematic information about the pathogenesis of COVID-19 symptoms that cause tissue damage or death and the mechanisms by which the virus infects and replicates in cells. Here, we introduce recent knowledge of time course changes in viral titers, delayed virus clearance, and persistent systemic inflammation in patients with severe COVID-19. Based on the concept of drug reposition, we review which antiviral or anti-inflammatory drugs can effectively treat COVID-19 patients based on progressive symptoms and the mechanisms inhibiting virus infection and replication.     

The Role of Chemokines in Hepatitis C Virus-Mediated Liver Disease

The hepatitis C virus (HCV) is a global health problem affecting more than 170 million people. A chronic HCV infection is associated with liver fibrosis, liver cirrhosis and hepatocellular carcinoma. To enable viral persistence, HCV has developed mechanisms to modulate both innate and adaptive immunity. The recruitment of antiviral immune cells in the liver is mainly dependent on the release of specific chemokines. Thus, the modulation of their expression could represent an efficient viral escape mechanism to hamper specific immune cell migration to the liver during the acute phase of the infection. HCV-mediated changes in hepatic immune cell chemotaxis during the chronic phase of the infection are significantly affecting antiviral immunity and tissue damage and thus influence survival of both the host and the virus. This review summarizes our current understanding of the HCV-mediated modulation of chemokine expression and of its impact on the development of liver disease. A profound knowledge of the strategies used by HCV to interfere with the host’s immune response and the pro-fibrotic and pro-carcinogenic activities of HCV is essential to be able to design effective immunotherapies against HCV and HCV-mediated liver diseases.