scholarly journals Extracellular 2′-5′ Oligoadenylate Synthetase Stimulates RNase L-Independent Antiviral Activity: a Novel Mechanism of Virus-Induced Innate Immunity

2010 ◽  
Vol 84 (22) ◽  
pp. 11898-11904 ◽  
Author(s):  
Helle Kristiansen ◽  
Christina A. Scherer ◽  
Maralee McVean ◽  
Shawn P. Iadonato ◽  
Susanne Vends ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Antiviral Agent ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Antiviral Compound ◽  
Clinical Prognosis ◽  
Strong Antiviral Activity ◽  
Infected Cells

ABSTRACT The 2′-5′ oligoadenylate synthetase (OAS) proteins are traditionally considered intracellular antiviral proteins. However, several studies demonstrate a correlation between the concentration of freely circulating OAS protein in sera from hepatitis C patients and their clinical prognosis. Here we demonstrate that extracellular OAS1 enters into cells and possesses a strong antiviral activity, both in vitro and in vivo, which is independent of RNase L. The OAS protein directly inhibits viral proliferation and does not require the activation of known antiviral signaling pathways. We propose that OAS produced by cells infected with viruses is released to the extracellular space, where it acts as a paracrine antiviral agent. Thus, the OAS protein represents the first direct antiviral compound released by virus-infected cells.

scholarly journals Filociclovir Is an Active Antiviral Agent against Ocular Adenovirus Isolates In Vitro and in the Ad5/NZW Rabbit Ocular Model

2021 ◽  
Vol 14 (4) ◽  
pp. 294
Author(s):  
Eric G. Romanowski ◽  
Islam T. M. Hussein ◽  
Steven C. Cardinale ◽  
Michelle M. Butler ◽  
Lucas R. Morin ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Topical Treatment ◽  
Antiviral Agent ◽  
Human Adenovirus ◽  
Treatment Groups ◽  
Ocular Infections ◽  
The Mean ◽  
Eye Infection

Presently, there is no FDA- or EMA-approved antiviral for the treatment of human adenovirus (HAdV) ocular infections. This study determined the antiviral activity of filociclovir (FCV) against ocular HAdV isolates in vitro and in the Ad5/NZW rabbit ocular model. The 50% effective concentrations (EC50) of FCV and cidofovir (CDV) were determined for several ocular HAdV types using standard plaque reduction assays. Rabbits were topically inoculated in both eyes with HAdV5. On day 1, the rabbits were divided into four topical treatment groups: (1) 0.5% FCV 4x/day × 10 d; (2) 0.1% FCV 4x/day × 10 d; (3) 0.5% CDV 2x/day × 7 d; (4) vehicle 4x/day × 10 d. Eyes were cultured for virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. The resulting viral eye titers were determined using standard plaque assays. The mean in vitro EC50 for FCV against tested HAdV types ranged from 0.50 to 4.68 µM, whereas those treated with CDV ranged from 0.49 to 30.3 µM. In vivo, compared to vehicle, 0.5% FCV, 0.1% FCV, and 0.5% CDV produced lower eye titers, fewer numbers of positive eye cultures, and shorter durations of eye infection. FCV demonstrated anti-adenovirus activity in vitro and in vivo.

scholarly journals Activation and Antagonism of the OAS–RNase L Pathway

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 14
Author(s):  
Susan R. Weiss
Keyword(s):  
Cell Death ◽  
Antiviral Activity ◽  
Apoptotic Cell ◽  
Early Response ◽  
Apoptotic Cell Death ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Viral Genomes ◽  
L System ◽  
Infected Cells

The oligoadenylate synthetase–ribonuclease L (OAS–RNase L) system is a potent antiviral pathway that severely limits the pathogenesis of many viruses. Upon sensing dsRNA, OASs produce 2′,5′-oligoadenylates (2-5A) that activate RNase L to cleave both host and viral single-stranded RNA, thereby limiting protein production, virus replication and spread, leading to apoptotic cell death. Endogenous host dsRNA, which accumulates in the absence of adenosine deaminase acting on RNA (ADAR)1, can also activate RNase L and lead to apoptotic cell death. RNase L activation and antiviral activity during infections with several types of viruses in human and bat cells is dependent on OAS3 but independent of virus-induced interferon (IFN) and, thus, RNase L can be activated even in the presence of IFN antagonists. Differently from other human viruses examined, Zika virus is resistant to the antiviral activity of RNase L and instead utilizes RNase L to enhance its replication factories to produce more infectious virus. Some betacoronaviruses antagonize RNase L activation by expressing 2′,5′-phosphodiesterases (PDEs) that cleave 2-5A and thereby antagonize activation of RNase L. The best characterized of these PDEs is the murine coronavirus (MHV) NS2 accessory protein. Enzymatically active NS2 is required for replication in myeloid cells and in the liver. Interestingly, while wild type mice clear MHV from the liver by 7–10 days post-infection, RNase L knockout mice fail to effectively clear MHV, probably due to diminished apoptotic death of infected cells. We suggest that RNase L antiviral activity stems from direct cleavage of viral genomes and cessation of protein synthesis as well as through promoting death of infected cells, limiting the spread of virus. Importantly, OASs are pattern recognition receptors and the OAS–RNase L pathway is a primary innate response pathway to viruses, capable of early response, coming into play before IFN is induced or when the virus shuts down IFN signaling.

scholarly journals Astodrimer sodium, dendrimer antiviral, inhibits replication of SARS-CoV-2 in vitro

2020 ◽  
Author(s):  
Jeremy R.A. Paull ◽  
Alex Castellarnau ◽  
Carolyn A. Luscombe ◽  
Jacinth K. Fairley ◽  
Graham P. Heery
Keyword(s):  
Antiviral Activity ◽  
Host Cell ◽  
Cytopathic Effect ◽  
Limit Of Detection ◽  
Antiviral Agent ◽  
Effective Response ◽  
Enveloped Viruses ◽  
Host Cell Interactions

AbstractAn effective response to the ongoing coronavirus disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will require a range of complementary preventive modalities. The current studies were conducted to evaluate the in vitro SARS-CoV-2 antiviral activity of astodrimer sodium, a dendrimer with broad spectrum antimicrobial activity, including against enveloped viruses in in vitro and in vivo models, that is marketed for antiviral and antibacterial applications. We report that astodrimer sodium inhibits replication of SARS-CoV-2 in Vero E6 cells when added to cells 1-hour prior to or 1-hour post infection, with 50% effective concentrations reducing virus-induced cytopathic effect (EC50) ranging from 0.090 to 0.742 μM (0.002 to 0.012 mg/mL). The selectivity index (SI) in these assays was as high as 2197. Astodrimer sodium was also effective in a virucidal evaluation when mixed with virus for 1 hour prior to infection of cells (EC50 1.83 μM [0.030 mg/mL]). Results from a time of addition study, which showed infectious virus was below the lower limit of detection at all time points tested, were consistent with the compound inhibiting early virus entry steps. The data were similar for all investigations and were consistent with the potent antiviral activity of astodrimer sodium being due to inhibition of virus-host cell interactions, as previously demonstrated for other viruses. Further studies will confirm if astodrimer sodium binds to SARS-CoV-2 spike protein and physically blocks initial association of the virus with heparan sulfate proteoglycans on the host cell. Given the in vitro effectiveness and significantly high SI, astodrimer sodium warrants further investigation for potential as a nasally administered or inhaled antiviral agent for SARS-CoV-2 prevention and treatment applications.

scholarly journals Reverse Genetics Reveals a Role of Rotavirus VP3 Phosphodiesterase Activity in Inhibiting RNase L Signaling and Contributing to Intestinal Viral Replication In Vivo

2020 ◽  
Vol 94 (9) ◽  
Author(s):  
Yanhua Song ◽  
Ningguo Feng ◽  
Liliana Sanchez-Tacuba ◽  
Linda L. Yasukawa ◽  
Lili Ren ◽  
...  
Keyword(s):  
Small Intestine ◽  
Viral Replication ◽  
Reverse Genetics ◽  
Innate Immune ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Rotavirus Vaccines

ABSTRACT Our understanding of how rotavirus (RV) subverts host innate immune signaling has greatly increased over the past decade. However, the relative contribution of each virus-encoded innate immune antagonist has not been fully studied in the context of RV infection in vivo. Here, we present both in vitro and in vivo evidence that the host interferon (IFN)-inducible 2′-5′-oligoadenylate synthetase (OAS) and RNase L pathway effectively suppresses the replication of heterologous RV strains. VP3 from homologous RVs relies on its 2′-5′-phosphodiesterase (PDE) domain to counteract RNase L-mediated antiviral signaling. Using an RV reverse-genetics system, we show that compared to the parental strain, VP3 PDE mutant RVs replicated at low levels in the small intestine and were shed less in the feces of wild-type mice, and such defects were rescued in Rnasel−/− suckling mice. Collectively, these findings highlight an important role of VP3 in promoting viral replication and pathogenesis in vivo in addition to its well-characterized function as the viral RNA-capping enzyme. IMPORTANCE Rotaviruses are significant human pathogens that result in diarrhea, dehydration, and deaths in many children around the world. Rotavirus vaccines have suboptimal efficacy in low- to middle-income countries, where the burden of the diseases is the most severe. With the ultimate goal of improving current vaccines, we aim to better understand how rotavirus interacts with the host innate immune system in the small intestine. Here, we demonstrate that interferon-activated RNase L signaling blocks rotavirus replication in a strain-specific manner. In addition, virus-encoded VP3 antagonizes RNase L activity both in vitro and in vivo. These studies highlight an ever-evolving arms race between antiviral factors and viral pathogens and provide a new means of targeted attenuation for next-generation rotavirus vaccine design.

OBR-5-340—A Novel Pyrazolo-Pyrimidine Derivative with Strong Antiviral Activity Against Coxsackievirus B3 In Vitro and In Vivo

2011 ◽  
Vol 90 (2) ◽  
pp. A29 ◽  
Author(s):  
Heike Braun ◽  
Vadim A. Makarov ◽  
Olga B. Riabova ◽  
Elena S. Komarova ◽  
Martina Richter ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Coxsackievirus B3 ◽  
Pyrimidine Derivative ◽  
Strong Antiviral Activity

scholarly journals (−)-Epigallocatechin-3-Gallate Inhibits the Life Cycle of Pseudorabies Virus In Vitro and Protects Mice Against Fatal Infection

2021 ◽  
Vol 10 ◽  
Author(s):  
Changchao Huan ◽  
Weiyin Xu ◽  
Tingting Guo ◽  
Haochun Pan ◽  
Hengyue Zou ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Pseudorabies Virus ◽  
Antiviral Agent ◽  
Economic Cost ◽  
Dependent Manner ◽  
Swine Industry ◽  
Effective Prevention ◽  
Dose Dependent

A newly emerged pseudorabies virus (PRV) variant with enhanced pathogenicity has been identified in many PRV-vaccinated swine in China since 2011. The PRV variant has caused great economic cost to the swine industry, and measures for the effective prevention and treatment of this PRV variant are still lacking. (–)-Epigallocatechin-3-gallate (EGCG) exhibits antiviral activity against diverse viruses and thus in this study, we investigated the anti-PRV activity of EGCG in vitro and in vivo. EGCG significantly inhibited infectivity of PRV Ra and PRV XJ5 strains in PK15 B6 cells and Vero cells. The anti-PRV activity of EGCG was dose-dependent, and 50 μM EGCG could completely block viral infection at different multiplicities of infection. We next revealed that EGCG blocked PRV adsorption and entry to PK15 B6 cells in a dose-dependent manner, but inhibition of PRV entry by EGCG was not as efficient as its inhibition of PRV adsorption. PRV replication was suppressed in PK15 B6 cells treated with EGCG post-infection. However, EGCG did not affect PRV assembly and could promote PRV release. Furthermore, 40 mg/kg EGCG provided 100% protection in BALB/c mice challenged with PRV XJ5, when EGCG was administrated both pre- and post-challenge. These results revealed that EGCG exhibits antiviral activity against PRV mainly by inhibiting virus adsorption, entry and replication in vitro. Meanwhile, EGCG increased the survival of mice challenged with PRV. Therefore, EGCG might be a potential antiviral agent against PRV infection.

scholarly journals In Vitro and In Vivo Antiviral Activity of Nylidrin by Targeting the Hemagglutinin 2-Mediated Membrane Fusion of Influenza A Virus

Viruses ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 581 ◽  
Author(s):  
Yejin Jang ◽  
Jin Soo Shin ◽  
Joo-Youn Lee ◽  
Heegwon Shin ◽  
Sang Jick Kim ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Membrane Fusion ◽  
Influenza A Virus ◽  
Influenza A ◽  
Intracellular Localization ◽  
Pharmacophore Modeling ◽  
Respiratory Pathogens ◽  
Antiviral Compound

Influenza A virus, one of the major human respiratory pathogens, is responsible for annual seasonal endemics and unpredictable periodic pandemics. Despite the clinical availability of vaccines and antivirals, the antigenic diversity and drug resistance of this virus makes it a persistent threat to public health, underlying the need for the development of novel antivirals. In a cell culture-based high-throughput screen, a β2-adrenergic receptor agonist, nylidrin, was identified as an antiviral compound against influenza A virus. The molecule was effective against multiple isolates of subtype H1N1, but had limited activity against subtype H3N2, depending on the strain. By examining the antiviral activity of its chemical analogues, we found that ifenprodil and clenbuterol also had reliable inhibitory effects against A/H1N1 strains. Field-based pharmacophore modeling with comparisons of active and inactive compounds revealed the importance of positive and negative electrostatic patterns of phenyl aminoethanol derivatives. Time-of-addition experiments and visualization of the intracellular localization of nucleoprotein NP demonstrated that an early step of the virus life cycle was suppressed by nylidrin. Ultimately, we discovered that nylidrin targets hemagglutinin 2 (HA2)-mediated membrane fusion by blocking conformational change of HA at acidic pH. In a mouse model, preincubation of a mouse-adapted influenza A virus (H1N1) with nylidrin completely blocked intranasal viral infection. The present study suggests that nylidrin could provide a core chemical skeleton for the development of a direct-acting inhibitor of influenza A virus entry.

scholarly journals RNase L Antiviral Activity Is Not a Critical Component of the Oas1b-Mediated Flavivirus Resistance Phenotype

2019 ◽  
Vol 93 (22) ◽  
Author(s):  
J. C. Madden ◽  
Dan Cui ◽  
M. A. Brinton
Keyword(s):  
Antiviral Activity ◽  
Full Length ◽  
Viral Rna ◽  
Type I ◽  
Mrna Levels ◽  
Rnase L ◽  
Oligoadenylate Synthetase ◽  
Resistant Mouse ◽  
Resistance Phenotype

ABSTRACT In mice, resistance to central nervous system (CNS) disease induced by members of the genus Flavivirus is conferred by an allele of the 2′-5′ oligoadenylate synthetase 1b gene that encodes the inactive full-length protein (Oas1b-FL). The susceptibility allele encodes a C-terminally truncated protein (Oas1b-tr). We show that the efficiency of neuron infection in the brains of resistant and susceptible mice is similar after an intracranial inoculation of two flaviviruses, but amplification of viral proteins and double-stranded RNA (dsRNA) is inhibited in infected neurons in resistant mouse brains at later times. Active OAS proteins detect cytoplasmic dsRNA and synthesize short 2′-5′-linked oligoadenylates (2′-5′A) that interact with the latent endonuclease RNase L, causing it to dimerize and cleave single-stranded RNAs. To evaluate the contribution of RNase L to the resistance phenotype in vivo, we created a line of resistant RNase L−/− mice. Evidence of RNase L activation in infected RNase L+/+ mice was indicated by higher levels of viral RNA in the brains of infected RNase L−/− mice. Activation of type I interferon (IFN) signaling was detected in both resistant and susceptible brains, but Oas1a and Oas1b mRNA levels were lower in RNase L+/+ mice of both types, suggesting that activated RNase L also has a proflaviviral effect. Inhibition of virus replication was robust in resistant RNase L−/− mice, indicating that activated RNase L is not a critical factor in mediating this phenotype. IMPORTANCE The mouse genome encodes a family of Oas proteins that synthesize 2′-5′A in response to dsRNA. 2′-5′A activates the endonuclease RNase L to cleave single-stranded viral and cellular RNAs. The inactive, full-length Oas1b protein confers flavivirus-specific disease resistance. Although similar numbers of neurons were infected in resistant and susceptible brains after an intracranial virus infection, viral components amplified only in susceptible brains at later times. A line of resistant RNase L−/− mice was used to evaluate the contribution of RNase L to the resistance phenotype in vivo. Activation of RNase L antiviral activity by flavivirus infection was indicated by increased viral RNA levels in the brains of RNase L−/− mice. Oas1a and Oas1b mRNA levels were higher in infected RNase L−/− mice, indicating that activated RNase L also have a proflaviviral affect. However, the resistance phenotype was equally robust in RNase L−/− and RNase L+/+ mice.

scholarly journals Vδ2 T-Cells Kill ZIKV-Infected Cells by NKG2D-Mediated Cytotoxicity

2019 ◽  
Vol 7 (9) ◽  
pp. 350 ◽  
Author(s):  
Cimini ◽  
Sacchi ◽  
De Minicis ◽  
Bordoni ◽  
Casetti ◽  
...  
Keyword(s):  
Immune Response ◽  
T Cells ◽  
Antiviral Activity ◽  
A549 Cells ◽  
Protective Immune Response ◽  
Zikv Infection ◽  
Protein Levels ◽  
Infected Cells

An expansion of effector/activated Vδ2 T-cells was recently described in acute Zika virus (ZIKV)-infected patients, but their role in the protective immune response was not clarified. The aim of this study was to define the antiviral activity of Vδ2 T-cells against ZIKV-infected cells. The Vδ2 T-cells expansion and their cytotoxic activity against ZIKV-infected cells were tested in vitro and analyzed by RT-PCR and flow cytometry. We found that ZIKV infection was able to induce Vδ2 T-cells expansion and sensitized A549 cells to Vδ2-mediated killing. Indeed, expanded Vδ2 T-cells killed ZIKV-infected cells through degranulation and perforin release. Moreover, ZIKV infection was able to increase the expression on A549 cells of NKG2D ligands (NKG2DLs), namely MICA, MICB, and ULBP2, at both the mRNA and protein levels, suggesting the possible involvement of these molecules in the recognition by NKG2D-expressing Vδ2 T-cells. Indeed, the killing of ZIKV-infected cells by expanded Vδ2 T-cells was mediated by NKG2D/NKG2DL interaction as NKG2D neutralization abrogated Vδ2 cytotoxicity. Our data showed a strong antiviral activity of Vδ2 T-cells against ZIKV-infected cells, suggesting their involvement in the protective immune response. Other studies are necessary to investigate whether the lack of Vδ2 T-cells expansion in vivo may be associated with disease complications.

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