Inhibition Of Viral Replication Research Articles

Pulmonary drug delivery: an effective and convenient delivery route to combat COVID-19.

The recent outbreak of coronavirus disease 2019 (COVID-19) in Wuhan, China has spread rapidly around the world, leading to a widespread and urgent effort to develop and use comprehensive approaches in the treatment of COVID-19. While oral therapy is accepted as an effective and simple method, since the primary site of infection and disease progression of COVID-19 is mainly through the lungs, inhaled drug delivery directly to the lungs may be the most appropriate route of administration. To prevent or treat primary SARS-CoV-2 infections, it is essential to target the virus port of entry in the respiratory tract and airway epithelium, which requires rapid and high-intensity inhibition or control of viral entry or replication. To achieve success in this field, inhalation therapy is the most attractive treatment approach due to efficacy/safety profiles. In this review article, pulmonary drug delivery as a unique treatment option in lung diseases will be briefly reviewed. Then, possible inhalation therapies for the treatment of symptoms of COVID-19 will be discussed and the results of clinical trials will be presented. By pulmonary delivery of the currently approved drugs for COVID-19, efficacy of the treatment would be improved along with reducing systemic side effects.Graphical abstract

Discovery and Optimization of Quinoline Analogues as Novel Potent Antivirals against Enterovirus D68.

Enterovirus D68 (EV-D68) is a nonpolio enterovirus that is mainly transmitted through respiratory routes and poses a potential threat for large-scale spread. EV-D68 infections mostly cause moderate to severe respiratory diseases in children and potentially induce neurological diseases. However, there are no specific antiviral drugs or vaccines against EV-D68. Herein, through virtual screening and rational design, a series of novel quinoline analogues as anti-EV-D68 agents targeting VP1 were identified. Particularly, 19 exhibited potent antiviral activity with an EC50 value ranging from 0.05 to 0.10 μM against various EV-D68 strains and showed inhibition of viral replication verified by Western blot, immunofluorescence, and plaque formation assay. Mechanistic studies indicated that the anti-EV-D68 agents work mainly by interacting with VP1. The acceptable bioavailability of 23.9% in rats and significant metabolic stability in human liver microsome (Clint = 10.8 mL/min/kg, t1/2 = 148 min) indicated that compound 19 with a novel scaffold was worth further investigation.

Role of epigenetic modification in interferon treatment of hepatitis B virus infection.

Human hepatitis B virus (HBV) is a small, enveloped DNA virus that causes acute and chronic hepatitis. Chronic hepatitis B (CHB) is associated with hepatocellular carcinoma pathogenesis. Interferons (IFNs) have been used for the treatment of CHB for a long time, with advantages including less treatment duration and sustained virological response. Presently, various evidence suggests that epigenetic modification of the viral covalently closed circular DNA (cccDNA) and the host genome is crucial for the regulation of viral activity. This modification includes histone acetylation, DNA methylation, N6-methyladenosine, and non-coding RNA modification. IFN treatment for CHB can stimulate multiple IFN-stimulated genes for inhibiting virus replication. IFNs can also affect the HBV life cycle through epigenetic modulation. In this review, we summarized the different mechanisms through which IFN-α inhibits HBV replication, including epigenetic regulation. Moreover, the mechanisms underlying IFN activity are discussed, which indicated its potential as a novel treatment for CHB. It is proposed that epigenetic changes such as histone acetylation, DNA methylation, m6A methylation could be the targets of IFN, which may offer a novel approach to HBV treatment.

Elucidation of mechanisms of action of Wei-Sheng-Fang-Yi-Bao-Dan in the treatment of COVID-19 and depression using network pharmacology and molecular docking

Purpose: To investigate the mechanisms of action of Wei-Sheng-Fang-Yi-Bao-Dan (WSFYBD) in the treatment of COVID-19 and depression using network pharmacology and molecular docking.
 Methods: First, the bioactive components and target genes of WSFYBD were retrieved from TCMSP database. The relevant gene targets of depression and COVID-19 were obtained from databases. The core WSFYBD genes for treatment were separately obtained by determining gene intersection. Cytoscape 3.8.0 software was used to draw the visual interactive networks. STRING database was employed to construct protein-protein interaction networks, while Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses were used to determine the function and pathway of target genes via a Bioconductor/R. Finally, AutoDockTools software was employed for molecular docking.
 Results: A total of 105 potential bio-active components and 35 target genes of WSFYBD for COVID-19 therapy were identified. Also, 1905 GO entries (p < 0.05) and 158 related signal pathways (p < 0.05) for COVID-19 were obtained. Similarly, 114 potential bio-active components of WSFYBD and 127 potential therapeutic targets of depression were identified. Moreover, 1948 GO entries (p < 0.05) and 177 related signal pathways for depression were retrieved (p < 0.05). Docking results showed the main bio-active components were closely bound to the core targets.
 Conclusion: The mechanisms for treating COVID-19 show that WSFYBD directly acts on SARS-CoV-2 virus to prevent it from entering the host cell, or inhibits virus replication. Secondly, WSFYBD ameliorates depression by acting on key targets that control over-activated cytokines. Therefore, WSFYBD has potentials for the management of COVID-19 and depression.

Silencing Asian Seabass gab3 Inhibits Nervous Necrosis Virus Replication.

The nervous necrosis virus (NNV) causes the viral nervous necrosis (VNN) disease in aquatic animals and has been a major threat in aquaculture. Thus, it is essential for the development of a prevention method to minimize economic losses caused by NNV such as the identification of NNV resistance genes and application of these genes in molecular breeding to increase disease resistance. gab3 is an important NNV resistance gene in Asian seabass. However, the mechanism of gab3 in NNV resistance has not been elucidated. In this study, knockdown of gab3 in NNV-infected Asian seabass cells resulted in a significant decrease in viral RNA and virus titers. Knockout of gab3 in zebrafish led to an increased survival rate and resistant time after NNV infection. Cellular localization of the GAB3 and NNV by immunofluorescence staining showed that the GAB3 was translocated from the nucleus to the cytoplasm, and finally reached the cell membrane of SB cells after 48h post NNV infection. Our study suggests that gab3 plays an important role in NNV replication and silencing gab3 can inhibit virus replication.

Interaction of GC376, a SARS-COV-2 MPRO inhibitor, with model lipid membranes

Partitioning and effect of antiviral GC376, a potential SARS-CoV-2 inhibitor, on model lipid membranes was studied using dynamic light scattering (DLS), UV–VIS spectrometry, Excimer fluorescence, Differential scanning calorimetry (DSC) and Small- and Wide-angle X-ray scattering (SAXS/WAXS). Partition coefficient of GC376 between lipid and water phase was found to be low, reaching KP = 46.8 ± 18.2. Results suggest that GC376 partitions into lipid bilayers at the level of lipid head-groups, close to the polar/hydrophobic interface. Changes in structural and thermodynamic properties strongly depend on the GC376/lipid mole ratio. Already at lowest mole ratios GC376 induces increase of lateral pressures, mainly in the interfacial region of the bilayer. Hereby, the pre- and main-transition temperature of the lipid system increases, what is attributed to tighter packing of acyl chains induced by GC376. At GC376/DPPC ≥ 0.03 mol/mol we detected formation of domains with different GC376 content resulting in the lateral phase separation and changes in both, main transition temperature and enthalpy. The observed changes are attributed to the response of the system on the increased lateral stresses induced by partitioning of GC376. Obtained results are discussed in context of liposome-based drug delivery systems for GC376 and in context of indirect mechanism of virus replication inhibition.

Pharmacophore model-aided virtual screening combined with comparative molecular docking and molecular dynamics for identification of marine natural products as SARS-CoV-2 papain-like protease inhibitors

Targeting SARS-CoV-2 papain-like protease using inhibitors is a suitable approach for inhibition of virus replication and dysregulation of host anti-viral immunity. Engaging all five binding sites far from the catalytic site of PLpro is essential for developing a potent inhibitor. We developed and validated a structure-based pharmacophore model with 9 features of a potent PLpro inhibitor. The pharmacophore model-aided virtual screening of the comprehensive marine natural product database predicted 66 initial hits. This hit library was downsized by filtration through a molecular weight filter of ≤ 500 g/mol. The 50 resultant hits were screened by comparative molecular docking using AutoDock and AutoDock Vina. Comparative molecular docking enables benchmarking docking and relieves the disparities in the search and scoring functions of docking engines. Both docking engines retrieved 3 same compounds at different positions in the top 1 % rank, hence consensus scoring was applied, through which CMNPD28766, aspergillipeptide F emerged as the best PLpro inhibitor. Aspergillipeptide F topped the 50-hit library with a pharmacophore-fit score of 75.916. Favorable binding interactions were predicted between aspergillipeptide F and PLpro similar to the native ligand XR8-24. Aspergillipeptide F was able to engage all the 5 binding sites including the newly discovered BL2 groove, site V. Molecular dynamics for quantification of Cα-atom movements of PLpro after ligand binding indicated that it exhibits highly correlated domain movements contributing to the low free energy of binding and a stable conformation. Thus, aspergillipeptide F is a promising candidate for pharmaceutical and clinical development as a potent SARS-CoV-2 PLpro inhibitor.

A Candidate Therapeutic Monoclonal Antibody Inhibits Both HRSV and HMPV Replication in Mice.

Human metapneumovirus (HMPV) and human respiratory virus (HRSV) are two leading causes of acute respiratory tract infection in young children. While there is no licensed drug against HMPV, the monoclonal antibody (mAb) Palivizumab is approved against HRSV for prophylaxis use only. Novel therapeutics against both viruses are therefore needed. Here, we describe the identification of human mAbs targeting these viruses by using flow cytometry-based cell sorting. One hundred and two antibodies were initially identified from flow cytometry-based cell sorting as binding to the fusion protein from HRSV, HMPV or both. Of those, 95 were successfully produced in plants, purified and characterized for binding activity by ELISA and neutralization assays as well as by inhibition of virus replication in mice. Twenty-two highly reactive mAbs targeting either HRSV or HMPV were isolated. Of these, three mAbs inhibited replication in vivo of a single virus while one mAb could reduce both HRSV and HMPV titers in the lung. Overall, this study identifies several human mAbs with virus-specific therapeutic potential and a unique mAb with inhibitory activities against both HRSV and HMPV.

Tea as a natural gift for discovering antiviral candidates

Coronavirus disease (COVID-19) remains rampant worldwide and poses a serious threat to human health. Tea is a medicinal and edible homologous plant that exhibits potential anti-SARS-CoV-2 properties via the prevention of virus entry into host cells, inhibition of virus replication, and enhancement of the innate and cellular immune responses. In this review, the properties of six major types of tea were systematically summarized, including green tea, yellow tea, white tea, oolong tea, black tea, and dark tea. We focused on the primary components of tea exhibiting antiviral pharmacological activities, which included (–)-epigallocatechin-3-gallate, (–)-gallocatechin gallate, tannic acid, oolonghomobisflavan A, theaflavins, and white-tip silver needle flavonoids. Among them, (–)-epigallocatechin-3-gallate is proposed to be an antiviral compound that interferes with the entire life cycle of SARS-CoV-2 by balancing inflammation and immunity. Thus, this compound can serve as a promising lead structure for the development of SARS-CoV-2 inhibitors.

Critical roles of Parkin and PINK1 in antiviral immunity and protection from cell death in Enterovirus-induced viral myocarditis

Abstract Background Myocarditis is an inflammatory disease of the heart muscle often resulting in cardiac dysfunction and death. One of the most common causes is a cardiac infection with viruses, especially with enteroviruses of the Coxsackievirus B (CVB) family. CVB3-induced viral myocarditis is a well-established model to elucidate viral myocarditis in mice. It is assumed that mitochondrial damage control and mitochondria-associated innate immunity is essential for defence against viral infection of the heart muscle. And Parkinson's disease genes Parkin and PINK1 are well known for their critical function in mitochondrial homeostasis and damage control. We investigated the roles of Parkin and PINK1 in CVB3-induced viral myocarditis mouse model. Material and methods Male C57BL/6J WT, Parkin KO and PINK1 KO mice were used in an age of 8 to 12 weeks. The animals were injected intraperitoneally with 1x104 plaque forming units of CVB3 diluted in phosphate-buffered saline. Control and survived virus-infected mice were sacrificed for tissue sampling at day 7 to investigate imaging and molecular workup. Result After virus inoculation, the Parkin KO and PINK1 KO groups showed a significantly lower 28-day survival rate compared with the WT group (p<0.001 in Parkin KO; p<0.001 in PINK1 KO). Evans-Blue Dye (EBD) staining image of day 7 after virus-infection showed that the hearts of Parkin KO and PINK1 KO mice were more severely damaged than the hearts of WT mice (3.2-fold, p<0.01 in Parkin KO; 2.6-fold, p<0.05 in PINK1 KO). H&E staining showed that severe inflammatory reaction occurred in the hearts of WT mice, although the inflammatory reaction was much lower compared to WT in the hearts of Parkin KO and PINK1 KO mice (p<0.001 in Parkin KO; p<0.001 in PINK1 KO). In immunohistochemistry, EBD staining positive area colocalized well with CVB3 in Parkin KO and PINK1 KO mice hearts, although EBD staining positive area was rare and didn't colocalized well CVB3 in WT mice hearts. mRNA levels of cell markers (CD3, natural cytotoxicity receptors, F4/80), inflammatory cytokines (IL-1β, IL-6, TNF-α), type II interferon, macrophage-derived protective factors, and CXCL10 family cytokines were lower in virus-infected Parkin/PINK1 KO mice than WT mice. Western blots showed that phospho-p65 increased less than WT in the heart of Parkin KO (0.7-fold, p<0.05) and PINK1 KO mice (0.58-fold, p<0.05). Conclusion The Parkin KO and PINK1 KO mice showed a higher mortality rate and more severe cardiomyocyte damage than the WT mice in the viral myocarditis mouse model. Parkin and PINK1 is critical to the type II IFN pathway that inhibits virus replication. And Parkin and PINK1 play an important role in the recruitment of IFN-γ-producing lymphocytes through NF-κB pathway and CXCL10 family chemokines. Funding Acknowledgement Type of funding sources: None.

Cromileptes altivelis microRNA Transcriptome Analysis upon Nervous Necrosis Virus (NNV) Infection and the Effect of cal-miR-155 on Cells Apoptosis and Virus Replication.

MicroRNAs (miRNAs) could regulate various biological processes. Nervous necrosis virus (NNV) is one of the primary germs of the Humpback grouper (Cromileptes altivelis), a commercial fish of great importance for Asian aquaculture. However, there is limited available information on the host-virus interactions of C. altivelis. miRNAs have been shown to play key roles in the host response to infection by a variety of pathogens. To better understand the regulatory mechanism of miRNAs, we constructed miRNA transcriptomes and identified immune-related miRNAs of C. altivelis spleen in response to NNV infection. Reads from the three libraries were mapped onto the Danio rerio reference genome. As a result, a total of 942 mature miRNAs were determined, with 266 known miRNAs and 676 novel miRNAs. Among them, thirty-two differentially expressed miRNAs (DEmiRs) were identified compared to the PBS control. These DEmiRs were targeted on 895 genes, respectively, by using miRanda v3.3a. Then, 14 DEmiRs were validated by qRT-PCR and showed consistency with those obtained from high-throughput sequencing. In order to study the relationship between viral infection and host miRNA, a cell line from C. altivelis brain (CAB) was used to examine the expressions of five known DEmiRs (miR-132-3p, miR-194a, miR-155, miR-203b-5p, and miR-146) during NNV infection. The results showed that one miRNA, cal-miRNA-155, displayed significantly increased expression in response to the virus infection. Subsequently, it was proved that overexpression of cal-miR-155 enhanced cell apoptosis with or without NNV infection and inhibited virus replication in CAB cells. Oppositely, the cal-miRNA-155 inhibitor markedly suppressed apoptosis in CAB cells. The results of the apoptosis-related genes mRNA expression also showed the regulation of cal-miR-155 on the apoptosis process in CAB cells. These findings verify that miR-155 might exert a function as a pro-apoptotic factor in reply to NNV stimulation in CAB cells and help us further study the molecular mechanisms of the pathogenesis of NNV in C. altivelis.

Altı Tıbbi Bitkinin Sitotoksik Etkileri ve SARS-CoV-2'ye Karşı Antiviral Etkinliğinin Araştırılması

Aim: Today, the COVID-19 pandemic, which causes deaths in 224 countries around the world, continues to show its effect all over the world. However, unfortunately, there are few studies that determine the effect of natural products derived from plants on COVID-19. However, as it is known, the source of most drugs is plants and medicinal aromatic plants have been used frequently for therapeutic purposes since the existence of humanity. The aim of this study is to investigate the cytotoxic effects of six medicinal plants such as Licorice (Glycyrrhiza glabra), Saffron (Crocus sativus L.), Black Cumin (Nigella sativa L.), Laurel (Lauris nobilis), Buckwheat (Lavandula stoechas) and Zahter (Thymbra spicata L. var. spicata) and their antiviral activities against SARS-CoV-2 in vitro conditions.
 Material and Method: This study was carried out in two stages. In the first stage, plants were collected and extracts were obtained. At the beginning of the second stage, cytotoxic effects on vero cells at non-cytotoxic broad-spectrum concentrations against SARS-CoV-2 in cell culture of six medicinal plants were investigated. In this step, the concentration of six ethnobotanically important medicinal plants that were not cytotoxic to SARS-CoV-2 was determined. In the continuation of the second stage, the plants were evaluated for the determination of viral replication inhibition and their antiviral effectiveness against SARS-CoV-2. In this step, in vitro antiviral effects of plants against SARS-CoV-2 were determined at a concentration that did not show cytotoxic effects.. 
 Results: The concentration of six plants used in the study without cytotoxic effects was determined.. Among the plants examined, it was determined that the only plant that was effective against SARS-CoV-2 in vitro conditions was the licorice plant (Glycyrrhiza glabra). The licorice plant was found to inhibit SARS-CoV-2 in vitro at the 2nd dilution (1:4) after the initial concentration.
 Conclusion: According to the findings obtained from our study, it was determined that the licorice plant was effective against the SARS-CoV-2 in vitro conditions. Supported by further studies, it can be thought that our findings may contribute to the fight against the COVID-19 pandemic.
 Keywords: SARS-CoV-2, Antiviral Efficacy, Plant Extract, Licorice (Glycyrrhiza glabra), Saffron (Crocus sativus L.), Black Cumin (Nigella sativa L.), Laurel (Lauris nobilis), Buckwheat (Lavandula stoechas), Zahter (Thymbra spicata L. var. spicata).

Stability characterization of a fractional-order viral system with the non-cytolytic immune assumption

This article deals with a Caputo fractional-order viral model that incorporates the non-cytolytic immune hypothesis and the mechanism of viral replication inhibition. Firstly, we establish the existence, uniqueness, non-negativity, and boundedness of the solutions of the proposed viral model. Then, we point out that our model has the following three equilibrium points: equilibrium point without virus, equilibrium state without immune system, and equilibrium point activated by immunity with humoral feedback. By presenting two critical quantities, the asymptotic stability of all said steady points is examined. Finally, we examine the finesse of our results by highlighting the impact of fractional derivatives on the stability of the corresponding steady points.

Regulation of innate immune responses by rabies virus.

Rabies virus (RABV) is an infectious and neurotropic pathogen that causes rabies and infects humans and almost all warm‐blooded animals, posing a great threat to people and public safety. It is well known that innate immunity is the critical first line of host defense against viral infection. It monitors the invading pathogens by recognizing the pathogen‐associated molecular patterns and danger‐associated molecular patterns through pattern‐recognition receptors, leading to the production of type I interferons (IFNα/β), inflammatory cytokines, and chemokines, or the activation of autophagy or apoptosis to inhibit virus replication. In the case of RABV, the innate immune response is usually triggered when the skin or muscle is bitten or scratched. However, RABV has evolved many ways to escape or even hijack innate immune response to complete its own replication and eventually invades the central nervous system (CNS). Once RABV reaches the CNS, it cannot be wiped out by the immune system or any drugs. Therefore, a better understanding of the interplay between RABV and innate immunity is necessary to develop effective strategies to combat its infection. Here, we review the innate immune responses induced by RABV and illustrate the antagonism mechanisms of RABV to provide new insights for the control of rabies.

The First 5'-Phosphorylated 1,2,3-Triazolyl Nucleoside Analogues with Uracil and Quinazoline-2,4-Dione Moieties: A Synthesis and Antiviral Evaluation.

A series of 5′-phosphorylated (dialkyl phosphates, diaryl phosphates, phosphoramidates, H-phosphonates, phosphates) 1,2,3-triazolyl nucleoside analogues in which the 1,2,3-triazole-4-yl-β-D-ribofuranose fragment is attached via a methylene group or a butylene chain to the N-1 atom of the heterocycle moiety (uracil or quinazoline-2,4-dione) was synthesized. All compounds were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1). Antiviral assays revealed three compounds, 13b, 14b, and 17a, which showed moderate activity against influenza virus A (H1N1) with IC50 values of 17.9 μM, 51 μM, and 25 μM, respectively. In the first two compounds, the quinazoline-2,4-dione moiety is attached via a methylene or a butylene linker, respectively, to the 1,2,3-triazole-4-yl-β-D-ribofuranosyl fragment possessing a 5′-diphenyl phosphate substituent. In compound 17a, the uracil moiety is attached via the methylene unit to the 1,2,3-triazole-4-yl-β-D-ribofuranosyl fragment possessing a 5′-(phenyl methoxy-L-alaninyl)phosphate substituent. The remaining compounds appeared to be inactive against influenza virus A/PR/8/34/(H1N1). The results of molecular docking simulations indirectly confirmed the literature data that the inhibition of viral replication is carried out not by nucleoside analogues themselves, but by their 5′-triphosphate derivatives.

Effects and mechanism of Aβ1−42 on EV-A71 replication

Backgroundβ-Amyloid (Aβ) protein is a pivotal pathogenetic factor in Alzheimer’s disease (AD). However, increasing evidence suggests that the brain has to continuously produce excessive Aβ to efficaciously prevent pathogenic micro-organism infections, which induces and accelerates the disease process of AD. Meanwhile, Aβ exhibits activity against herpes simplex virus type 1 (HSV-1) and influenza A virus (IAV) replication, but not against other neurotropic viruses. Enterovirus A71 (EV-A71) is the most important neurotropic enterovirus in the post-polio era. Given the limitation of existing research on the relationship between Aβ and other virus infections, this study aimed to investigate the potent activity of Aβ on EV-A71 infection and extended the potential function of Aβ in other unenveloped viruses may be linked to Alzheimer's disease or infectious neurological diseases.MethodsAβ peptides 1–42 are a major pathological factor of senile plaques in Alzheimer’s disease (AD). Thus, we utilized Aβ1–42 as a test subject to perform our study. The production of monomer Aβ1–42 and their high-molecular oligomer accumulations in neural cells were detected by immunofluorescence assay, ELISA, or Western blot assay. The inhibitory activity of Aβ1–42 peptides against EV-A71 in vitro was detected by Western blot analysis or qRT-PCR. The mechanism of Aβ1–42 against EV-A71 replication was analyzed by time-of-addition assay, attachment inhibition assay, pre-attachment inhibition analysis, viral-penetration inhibition assay, TEM analysis of virus agglutination, and pull-down assay.ResultsWe found that EV-A71 infection induced Aβ production and accumulation in SH-SY5Y cells. We also revealed for the first time that Aβ1–42 efficiently inhibited the RNA level of EV-A71 VP1, and the protein levels of VP1, VP2, and nonstructural protein 3AB in SH-SY5Y, Vero, and human rhabdomyosarcoma (RD) cells. Mechanistically, we demonstrated that Aβ1–42 primarily targeted the early stage of EV-A71 entry to inhibit virus replication by binding virus capsid protein VP1 or scavenger receptor class B member 2. Moreover, Aβ1–42 formed non-enveloped EV-A71 particle aggregates within a certain period and bound to the capsid protein VP1, which partially caused Aβ1–42 to prevent viruses from infecting cells.ConclusionsOur findings unveiled that Aβ1–42 effectively inhibited nonenveloped EV-A71 by targeting the early phase of an EV-A71 life cycle, thereby extending the potential function of Aβ in other non-envelope viruses linked to infectious neurological diseases.

Heparin Protects Human Neural Progenitor Cells from Zika Virus-Induced Cell Death While Preserving Their Differentiation into Mature Neuroglial Cells.

ABSTRACTZika virus (ZIKV) is an arbovirus member of the Flaviviridae family that causes severe congenital brain anomalies in infected fetuses. The key target cells of ZIKV infection, human neural progenitor cells (hNPCs), are highly permissive to infection that causes the inhibition of cell proliferation and induces cell death. We have previously shown that pharmaceutical-grade heparin inhibits virus-induced cell death with negligible effects on in vitro virus replication in ZIKV-infected hNPCs at the “high” multiplicity of infection (MOI) of 1. Here, we show that heparin inhibits formation of ZIKV-induced intracellular vacuoles, a signature of paraptosis, and inhibits necrosis and apoptosis of hNPCs grown as neurospheres (NS). To test whether heparin preserved the differentiation of ZIKV-infected hNPCs into neuroglial cells, hNPCs were infected at the MOI of 0.001. In this experimental condition, heparin inhibited ZIKV replication by ca. 2 log10, mostly interfering with virion attachment, while maintaining its protective effect against ZIKV-induced cytopathicity. Heparin preserved differentiation into neuroglial cells of hNPCs that were obtained from either human-induced pluripotent stem cells (hiPSC) or by fetal tissue. Quite surprisingly, multiple additions of heparin to hNPCs enabled prolonged virus replication while preventing virus-induced cytopathicity. Collectively, these results highlight the potential neuroprotective effect of heparin that could serve as a lead compound to develop novel agents for preventing the damage of ZIKV infection on the developing brain.IMPORTANCE ZIKV is a neurotropic virus that invades neural progenitor cells (NPCs), causing inhibition of their proliferation and maturation into neurons and glial cells. We have shown previously that heparin, an anticoagulant also used widely during pregnancy, prevents ZIKV-induced cell death with negligible inhibition of virus replication. Here, we demonstrate that heparin also exerts antiviral activity against ZIKV replication using a much lower infectious inoculum. Moreover, heparin interferes with different modalities of virus-induced cell death. Finally, heparin-induced prevention of virus-induced NPC death allows their differentiation into neuroglial cells despite the intracellular accumulation of virions. These results highlight the potential use of heparin, or pharmacological agents derived from it, in pregnant women to prevent the devastating effects of ZIKV infection on the developing brain of their fetuses.

Unveiling Mycoviromes Using Fungal Transcriptomes.

Viruses infecting fungi are referred to as mycoviruses. Here, we carried out in silico mycovirome studies using public fungal transcriptomes mostly derived from mRNA libraries. We identified 468 virus-associated contigs assigned to 5 orders, 21 families, 26 genera, and 88 species. We assembled 120 viral genomes with diverse RNA and DNA genomes. The phylogenetic tree and genome organization unveiled the possible host origin of mycovirus species and diversity of their genome structures. Most identified mycoviruses originated from fungi; however, some mycoviruses had strong phylogenetic relationships with those from insects and plants. The viral abundance and mutation frequency of mycoviruses were very low; however, the compositions and populations of mycoviruses were very complex. Although coinfection of diverse mycoviruses in the fungi was common in our study, most mycoviromes had a dominant virus species. The compositions and populations of mycoviruses were more complex than we expected. Viromes of Monilinia species revealed that there were strong deviations in the composition of viruses and viral abundance among samples. Viromes of Gigaspora species showed that the chemical strigolactone might promote virus replication and mutations, while symbiosis with endobacteria might suppress virus replication and mutations. This study revealed the diversity and host distribution of mycoviruses.

Structural Basis for the Inhibition of Coronaviral Main Proteases by a Benzothiazole-Based Inhibitor.

The ongoing spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused hundreds of millions of cases and millions of victims worldwide with serious consequences to global health and economies. Although many vaccines protecting against SARS-CoV-2 are currently available, constantly emerging new variants necessitate the development of alternative strategies for prevention and treatment of COVID-19. Inhibitors that target the main protease (Mpro) of SARS-CoV-2, an essential enzyme that promotes viral maturation, represent a key class of antivirals. Here, we showed that a peptidomimetic compound with benzothiazolyl ketone as warhead, YH-53, is an effective inhibitor of SARS-CoV-2, SARS-CoV, and MERS-CoV Mpros. Crystal structures of Mpros from SARS-CoV-2, SARS-CoV, and MERS-CoV bound to the inhibitor YH-53 revealed a unique ligand-binding site, which provides new insights into the mechanism of inhibition of viral replication. A detailed analysis of these crystal structures defined the key molecular determinants required for inhibition and illustrate the binding mode of Mpros from other coronaviruses. In consideration of the important role of Mpro in developing antivirals against coronaviruses, insights derived from this study should add to the design of pan-coronaviral Mpro inhibitors that are safer and more effective.

Myricetin inhibits pseudorabies virus infection through direct inactivation and activating host antiviral defense.

Myricetin, a polyhydroxyflavone compound, is one of the main ingredients of various human foods and therefore also known as dietary flavonoids. Due to the continuous emergence of resistant strains of herpesviruses, novel control measures are required. In the present study, myricetin exhibited potent antiviral activity against pseudorabies virus (PRV), a model organism of herpesvirus. The suppression rate could reach up to 96.4% at a concentration of 500 μM in cells, and the 50% inhibitory concentration (IC50) was 42.69 μM. Moreover, the inhibitory activity was not attenuated by the increased amount of infective dose, and a significant reduction of intracellular PRV virions was observed by indirect immunofluorescence. A mode of action study indicated that myricetin could directly inactivate the virus in vitro, leading to inhibition of viral adsorption, penetration and replication in cells. In addition to direct killing effect, myricetin could also activate host antiviral defense through regulation of apoptosis-related gene expressions (Bcl-2, Bcl-xl, Bax), NF-κB and MAPK signaling pathways and cytokine gene expressions (IL-1α, IL-1β, IL-6, c-Jun, STAT1, c-Fos, and c-Myc). In PRV-infected mouse model, myricetin could enhance the survival rate by 40% at 5 days post infection, and viral loads in kidney, liver, lung, spleen, and brain were significantly decreased. The pathological changes caused by PRV infection were improved by myricetin treatment. The gene expressions of inflammatory factors (MCP-1, G-CSF, IL-1α, IL-1β, and IL-6) and apoptotic factors (Bcl-xl, Bcl-2, and Bax) were regulated by myricetin in PRV-infected mice. The present findings suggest that myricetin can effectively inhibit PRV infection and become a candidate for development of new anti-herpesvirus drugs.