Structure of the NS3 helicase from Zika virus Jain, Rinku; Coloma, Javier; García-Sastre, Adolfo ...
Nature structural & molecular biology,
08/2016, Letnik:
23, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Zika virus has emerged as a pathogen of major health concern. Here, we present a high-resolution (1.62-Å) crystal structure of the RNA helicase from the French Polynesia strain. The structure is ...similar to that of the RNA helicase from Dengue virus, with variability in the conformations of loops typically involved in binding ATP and RNA. We identify druggable 'hotspots' that are well suited for in silico and/or fragment-based high-throughput drug discovery.
Significance Vaccination is the most effective means of attaining protection against influenza viruses. However, the constantly evolving nature of influenza viruses enables them to escape preexisting ...immune surveillance, and thus thwarts public health efforts to control influenza annual epidemics and occasional pandemics. One solution is to elicit antibodies directed against highly conserved epitopes, such as those within the stem region of influenza HA, the principal target of virus-neutralizing antibody responses. This study shows that annual influenza vaccines induce antibody responses that are largely directed against the highly variable HA head region. In contrast, heterologous immunization with HA derived from influenza strains that are currently not circulating in humans (e.g. H5N1) can substantially increase HA stem-specific responses.
Transcription of viral mRNA in cells infected with influenza viruses involves capturing and cleaving the first 10–20 nucleotides of 5′ capped host mRNAs to be used as primers in viral RNA synthesis. ...A newly developed inhibitor of the viral endonuclease responsible for this cap-snatching shows therapeutic efficacy for the treatment of influenza. To view this Bench to Bedside, open or download the PDF.
Transcription of viral mRNA in cells infected with influenza viruses involves capturing and cleaving the first 10–20 nucleotides of 5′ capped host mRNAs to be used as primers in viral RNA synthesis. A newly developed inhibitor of the viral endonuclease responsible for this cap-snatching shows therapeutic efficacy for the treatment of influenza. To view this Bench to Bedside, open or download the PDF.
Repurposing drugs as treatments for COVID-19, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has drawn much attention. Beginning with sigma receptor ligands and ...expanding to other drugs from screening in the field, we became concerned that phospholipidosis was a shared mechanism underlying the antiviral activity of many repurposed drugs. For all of the 23 cationic amphiphilic drugs we tested, including hydroxychloroquine, azithromycin, amiodarone, and four others already in clinical trials, phospholipidosis was monotonically correlated with antiviral efficacy. Conversely, drugs active against the same targets that did not induce phospholipidosis were not antiviral. Phospholipidosis depends on the physicochemical properties of drugs and does not reflect specific target-based activities-rather, it may be considered a toxic confound in early drug discovery. Early detection of phospholipidosis could eliminate these artifacts, enabling a focus on molecules with therapeutic potential.
Influenza viruses cause seasonal epidemics as well as pandemics and are a significant concern for human health. Current influenza virus vaccines show efficacy when they are antigenically well matched ...to circulating strains. Seasonal influenza viruses undergo antigenic drift at a high rate and, therefore, current vaccines have to be reformulated and readministered on an annual basis. Mismatches between vaccine strains and circulating strains frequently occur, significantly decreasing vaccine efficacy. In addition, current seasonal influenza virus vaccines have limited efficacy against newly emerging pandemic viruses. A universal influenza virus vaccine that induces long-term protection against all influenza virus strains would abolish the need for annual readministration of seasonal influenza virus vaccines and would significantly enhance our pandemic preparedness. Here we discuss the characteristics of universal influenza virus vaccines, their potential target antigens, and critical aspects to consider on the path to successfully developing such vaccines.
Abstract During the immune response, striking the right balance between positive and negative regulation is critical to effectively mount an anti-microbial defense while preventing detrimental ...effects from exacerbated immune activation. Intra-cellular immune signaling is tightly regulated by various post-translational modifications, which allow for this dynamic response. One of the post-translational modifiers critical for immune control is ubiquitin, which can be covalently conjugated to lysines in target molecules, thereby altering their functional properties. This is achieved in a process involving E3 ligases which determine ubiquitination target specificity. One of the most prominent E3 ligase families is that of the tripartite motif (TRIM) proteins, which counts over 70 members in humans. Over the last years, various studies have contributed to the notion that many members of this protein family are important immune regulators. Recent studies into the mechanisms by which some of the TRIMs regulate the innate immune system have uncovered important immune regulatory roles of both covalently attached, as well as unanchored poly-ubiquitin chains. This review highlights TRIM evolution, recent findings in TRIM-mediated immune regulation, and provides an outlook to current research hurdles and future directions.
The mammalian interferon (IFN) signaling pathway is a primary component of the innate antiviral response, and viral pathogens have evolved multiple mechanisms to antagonize this pathway and to ...facilitate infection. Bluetongue virus (BTV), an orbivirus of the Reoviridae family, is transmitted by midges to ruminants and causes a disease that produces important economic losses and restriction to animal trade and is of compulsory notification to the World Organization for Animal Health (OIE). Here, we show that BTV interferes with IFN‐I and IFN‐II responses in two ways, by blocking STAT1 phosphorylation and by degrading STAT2. BTV‐NS3 protein, which is involved in virion egress, interacts with STAT2, and induces its degradation by an autophagy‐dependent mechanism. This STAT2 degradative process requires the recruitment of an E3‐Ub‐ligase to NS3 as well as NS3 K63 polyubiquitination. Taken together, our study identifies a new mechanism by which a virus degrades STAT2 for IFN signaling blockade, highlighting the diversity of mechanisms employed by viruses to subvert the IFN response.
Synopsis
The arbovirus bluetongue virus (BTV) utilizes its non‐structural protein 3 (NS3), involved in virion egress, to interfere with IFN signaling by impairing STAT1 phosphorylation and mediating autophagic STAT2 degradation. This autophagic STAT2 degradative process requires the recruitment of an E3‐Ub‐ligase to NS3 as well as NS3 K63 poly‐ubiquitination.
BTV‐NS3 interferes with IFN signaling by inhibiting STAT1 phosphorylation and mediating STAT2 autophagic degradation.
BTV‐NS3 is polyubiquitinated through K63 chains.
BTV‐NS3‐mediated autophagic STAT2 degradation is dependent on NS3 K63 poly‐ubiquitination and the recruitment of an E3‐Ub‐ligase to NS3.
Bluetongue virus interferes with IFN signaling by impairing STAT1 phosphorylation and by mediating autophagic degradation of STAT2. K63‐linked ubiquitylation of the non‐structural protein NS3 is required for autophagic degradation of STAT2.
Summary
Host organisms have developed sophisticated antiviral responses in order to defeat emerging influenza A viruses (IAVs). At the same time IAVs have evolved immune evasion strategies. The ...immune system of mammals provides several lines of defence to neutralize invading pathogens or limit their replication. Here, we summarize the mammalian innate and adaptive immune mechanisms involved in host defence against viral infection and review strategies by which IAVs avoid, circumvent or subvert these mechanisms. We highlight well‐characterized, as well as recently described features of this intriguing virus‐host molecular battle.
Influenza A virus is being extensively studied because of its major impact on human and animal health. However, the dynamics of influenza virus infection and the cell types infected in vivo are ...poorly understood. These characteristics are challenging to determine, partly because there is no efficient replication-competent virus expressing an easily traceable reporter gene. Here, we report the generation of a recombinant influenza virus carrying a GFP reporter gene in the NS segment (NS1-GFP virus). Although attenuated when compared with wild-type virus, the NS1-GFP virus replicates efficiently in murine lungs and shows pathogenicity in mice. Using whole-organ imaging and flow cytometry, we have tracked the dynamics of influenza virus infection progression in mice. Imaging of murine lungs shows that infection starts in the respiratory tract in areas close to large conducting airways and later spreads to deeper sections of the lungs. In addition to epithelial cells, we found GFP-positive antigen-presenting cells, such as CD11b⁺CD11c⁻, CD11b⁻CD11c⁺, and CD11b⁺CD11c⁺, as early as 24 h after intranasal infection. In addition, a significant proportion of NK and B cells were GFP positive, suggesting active infection of these cells. We next tested the effects of the influenza virus inhibitors oseltamivir and amantadine on the kinetics of in vivo infection progression. Treatment with oseltamivir dramatically reduced influenza infection in all cell types, whereas, surprisingly, amantadine treatment more efficiently blocked infection in B and NK cells. Our results demonstrate high levels of immune cells harboring influenza virus antigen during viral infection and cell-type—specific effects upon treatment with antiviral agents, opening additional avenues of research in the influenza virus field.
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