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1.
Cell ; 185(19): 3588-3602.e21, 2022 Sep 15.
Article in English | MEDLINE | ID: covidwho-2027949

ABSTRACT

The current dogma of RNA-mediated innate immunity is that sensing of immunostimulatory RNA ligands is sufficient for the activation of intracellular sensors and induction of interferon (IFN) responses. Here, we report that actin cytoskeleton disturbance primes RIG-I-like receptor (RLR) activation. Actin cytoskeleton rearrangement induced by virus infection or commonly used reagents to intracellularly deliver RNA triggers the relocalization of PPP1R12C, a regulatory subunit of the protein phosphatase-1 (PP1), from filamentous actin to cytoplasmic RLRs. This allows dephosphorylation-mediated RLR priming and, together with the RNA agonist, induces effective RLR downstream signaling. Genetic ablation of PPP1R12C impairs antiviral responses and enhances susceptibility to infection with several RNA viruses including SARS-CoV-2, influenza virus, picornavirus, and vesicular stomatitis virus. Our work identifies actin cytoskeleton disturbance as a priming signal for RLR-mediated innate immunity, which may open avenues for antiviral or adjuvant design.


Subject(s)
Actins , COVID-19 , Actin Cytoskeleton , Antiviral Agents , Humans , Interferons , Ligands , Protein Phosphatase 1 , RNA , RNA Helicases , Receptors, Retinoic Acid/metabolism , SARS-CoV-2
2.
Cell Host Microbe ; 30(9): 1255-1268.e5, 2022 09 14.
Article in English | MEDLINE | ID: covidwho-1936160

ABSTRACT

SARS-CoV-2 Omicron rapidly outcompeted other variants and currently dominates the COVID-19 pandemic. Its enhanced transmission and immune evasion are thought to be driven by numerous mutations in the Omicron Spike protein. Here, we systematically introduced BA.1 and/or BA.2 Omicron Spike mutations into the ancestral Spike protein and examined the impacts on Spike function, processing, and susceptibility to neutralization. Individual mutations of S371F/L, S375F, and T376A in the ACE2-receptor-binding domain as well as Q954H and N969K in the hinge region 1 impaired infectivity, while changes to G339D, D614G, N764K, and L981F moderately enhanced it. Most mutations in the N-terminal region and receptor-binding domain reduced the sensitivity of the Spike protein to neutralization by sera from individuals vaccinated with the BNT162b2 vaccine and by therapeutic antibodies. Our results represent a systematic functional analysis of Omicron Spike adaptations that have allowed this SARS-CoV-2 variant to dominate the current pandemic.


Subject(s)
COVID-19 , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/chemistry , Angiotensin-Converting Enzyme 2 , Antibodies, Neutralizing , Antibodies, Viral , BNT162 Vaccine , Humans , Pandemics , SARS-CoV-2/genetics , SARS-CoV-2/pathogenicity , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/metabolism , Viral Envelope Proteins
3.
J Virol ; 96(11): e0059422, 2022 06 08.
Article in English | MEDLINE | ID: covidwho-1840553

ABSTRACT

It has recently been shown that an early SARS-CoV-2 isolate (NL-02-2020) hijacks interferon-induced transmembrane proteins (IFITMs) for efficient replication in human lung cells, cardiomyocytes, and gut organoids. To date, several "variants of concern" (VOCs) showing increased infectivity and resistance to neutralization have emerged and globally replaced the early viral strains. Here, we determined whether the five current SARS-CoV-2 VOCs (Alpha, Beta, Gamma, Delta, and Omicron) maintained the dependency on IFITM proteins for efficient replication. We found that depletion of IFITM2 strongly reduces viral RNA production by all VOCs in the human epithelial lung cancer cell line Calu-3. Silencing of IFITM1 had modest effects, while knockdown of IFITM3 resulted in an intermediate phenotype. Strikingly, depletion of IFITM2 generally reduced infectious virus production by more than 4 orders of magnitude. In addition, an antibody directed against the N terminus of IFITM2 inhibited SARS-CoV-2 VOC replication in induced pluripotent stem cell (iPSC)-derived alveolar epithelial type II cells, thought to represent major viral target cells in the lung. In conclusion, endogenously expressed IFITM proteins (especially IFITM2) are critical cofactors for efficient replication of genuine SARS-CoV-2 VOCs, including the currently dominant Omicron variant. IMPORTANCE Recent data indicate that SARS-CoV-2 requires endogenously expressed IFITM proteins for efficient infection. However, the results were obtained with an early SARS-CoV-2 isolate. Thus, it remained to be determined whether IFITMs are also important cofactors for infection of emerging SARS-CoV-2 VOCs that outcompeted the original strains in the meantime. This includes the Omicron VOC, which currently dominates the pandemic. Here, we show that depletion of endogenous IFITM2 expression almost entirely prevents productive infection of Alpha, Beta, Gamma, Delta, and Omicron SARS-CoV-2 VOCs in human lung cells. In addition, an antibody targeting the N terminus of IFITM2 inhibited SARS-CoV-2 VOC replication in iPSC-derived alveolar epithelial type II cells. Our results show that SARS-CoV-2 VOCs, including the currently dominant Omicron variant, are strongly dependent on IFITM2 for efficient replication, suggesting a key proviral role of IFITMs in viral transmission and pathogenicity.


Subject(s)
Lung , Membrane Proteins , SARS-CoV-2 , Virus Replication , COVID-19/virology , Cell Line, Tumor , Humans , Lung/virology , Membrane Proteins/genetics , Membrane Proteins/metabolism , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/physiology , Virus Internalization
4.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-333018

ABSTRACT

The SARS-CoV-2 Omicron variant rapidly outcompeted other variants and currently dominates the COVID-19 pandemic. Its enhanced transmission, immune evasion and pathogenicity is thought to be driven by numerous mutations in the Omicron Spike protein. Here, we examined the impact of amino acid changes that are characteristic for the BA.1 and/or BA.2 Omicron lineages on Spike function, processing and susceptibility to neutralization. Individual mutations of S371F/L, S375F and T376A in the ACE2 receptor-binding domain as well as Q954H and N969K in the hinge region 1 impaired infectivity, while changes of G339D, D614G, N764K and L981F moderately enhanced it. Most mutations in the N-terminal region and the receptor binding domain reduced sensitivity of the Spike protein to neutralization by sera from individuals vaccinated with the BNT162b2 vaccine or therapeutic antibodies. Our results represent a systematic functional analysis of Omicron Spike adaptations that allowed this SARS-CoV-2 variant to overtake the current pandemic.

5.
Med Microbiol Immunol ; 2022 Apr 02.
Article in English | MEDLINE | ID: covidwho-1772912

ABSTRACT

The innate immune system is a powerful barrier against invading pathogens. Interferons (IFNs) are a major part of the cytokine-mediated anti-viral innate immune response. After recognition of a pathogen by immune sensors, signaling cascades are activated that culminate in the release of IFNs. These activate cells in an autocrine or paracrine fashion eventually setting cells in an anti-viral state via upregulation of hundreds of interferon-stimulated genes (ISGs). To evade the anti-viral effect of the IFN system, successful viruses like the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolved strategies to counteract both IFN induction and signaling. In fact, more than half of the about 30 proteins encoded by SARS-CoV-2 target the IFN system at multiple levels to escape IFN-mediated restriction. Here, we review recent insights into the molecular mechanisms used by SARS-CoV-2 proteins to suppress IFN production and the establishment of an anti-viral state.

6.
J Virol ; 96(6): e0207721, 2022 03 23.
Article in English | MEDLINE | ID: covidwho-1714342

ABSTRACT

Emerging strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic, that show increased transmission fitness and/or immune evasion are classified as "variants of concern" (VOCs). Recently, a SARS-CoV-2 variant first identified in November 2021 in South Africa has been recognized as a fifth VOC, termed "Omicron." What makes this VOC so alarming is the high number of changes, especially in the viral Spike protein, and accumulating evidence for increased transmission efficiency and escape from neutralizing antibodies. In an amazingly short time, the Omicron VOC has outcompeted the previously dominating Delta VOC. However, it seems that the Omicron VOC is overall less pathogenic than other SARS-CoV-2 VOCs. Here, we provide an overview of the mutations in the Omicron genome and the resulting changes in viral proteins compared to other SARS-CoV-2 strains and discuss their potential functional consequences.


Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19/immunology , COVID-19/virology , Genome, Viral , Humans , Immune Evasion , Mutation , SARS-CoV-2/genetics , SARS-CoV-2/immunology , SARS-CoV-2/pathogenicity , Spike Glycoprotein, Coronavirus/metabolism
7.
Nat Commun ; 12(1): 6855, 2021 11 25.
Article in English | MEDLINE | ID: covidwho-1537312

ABSTRACT

The bat sarbecovirus RaTG13 is a close relative of SARS-CoV-2, the cause of the COVID-19 pandemic. However, this bat virus was most likely unable to directly infect humans since its Spike (S) protein does not interact efficiently with the human ACE2 receptor. Here, we show that a single T403R mutation increases binding of RaTG13 S to human ACE2 and allows VSV pseudoparticle infection of human lung cells and intestinal organoids. Conversely, mutation of R403T in the SARS-CoV-2 S reduces pseudoparticle infection and viral replication. The T403R RaTG13 S is neutralized by sera from individuals vaccinated against COVID-19 indicating that vaccination might protect against future zoonoses. Our data suggest that a positively charged amino acid at position 403 in the S protein is critical for efficient utilization of human ACE2 by S proteins of bat coronaviruses. This finding could help to better predict the zoonotic potential of animal coronaviruses.


Subject(s)
Angiotensin-Converting Enzyme 2/chemistry , Protein Binding , SARS-CoV-2/genetics , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Animals , COVID-19/virology , COVID-19 Vaccines , Caco-2 Cells , Cloning, Molecular , HEK293 Cells , Humans , Molecular Dynamics Simulation , Mutation , Replicon , Species Specificity , Stem Cells , Zoonoses
8.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-293046

ABSTRACT

We have recently shown that a SARS-CoV-2 strain isolated in the Netherlands in February 2020 (NL-02-2020) hijacks interferon-induced transmembrane proteins, especially IFITM2, as entry cofactors for efficient infection. Here, we examined whether SARS-CoV-2 'variants of concern' (VOCs), including the currently dominating delta variant, maintained the dependency on IFITMs for efficient replication. Depletion of IFITM2 reduced viral RNA production from 31- (B.1.1.7) to 755-fold (P.1). In comparison, silencing of IFITM1 had little effect, while knock-down of IFITM3 resulted in an intermediate phenotype. Strikingly, silencing of IFITM2 generally reduced infectious virus production in Calu-3 cells to near background levels. An antibody directed against the N-terminus of IFITM2 inhibited SARS-CoV-2 VOC replication in iPSC-derived alveolar epithelial type II cells. In conclusion, endogenously expressed IFITM proteins (especially IFITM2) are important cofactors for replication of genuine SARS-CoV-2 VOCs, including the Delta variant.

9.
Nat Commun ; 12(1): 4584, 2021 07 28.
Article in English | MEDLINE | ID: covidwho-1387354

ABSTRACT

Interferon-induced transmembrane proteins (IFITMs 1, 2 and 3) can restrict viral pathogens, but pro- and anti-viral activities have been reported for coronaviruses. Here, we show that artificial overexpression of IFITMs blocks SARS-CoV-2 infection. However, endogenous IFITM expression supports efficient infection of SARS-CoV-2 in human lung cells. Our results indicate that the SARS-CoV-2 Spike protein interacts with IFITMs and hijacks them for efficient viral infection. IFITM proteins were expressed and further induced by interferons in human lung, gut, heart and brain cells. IFITM-derived peptides and targeting antibodies inhibit SARS-CoV-2 entry and replication in human lung cells, cardiomyocytes and gut organoids. Our results show that IFITM proteins are cofactors for efficient SARS-CoV-2 infection of human cell types representing in vivo targets for viral transmission, dissemination and pathogenesis and are potential targets for therapeutic approaches.


Subject(s)
Angiotensin-Converting Enzyme 2/genetics , Antigens, Differentiation/genetics , Membrane Proteins/genetics , RNA-Binding Proteins/genetics , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics , Amino Acid Sequence , Angiotensin-Converting Enzyme 2/antagonists & inhibitors , Angiotensin-Converting Enzyme 2/metabolism , Antibodies, Neutralizing/pharmacology , Antigens, Differentiation/metabolism , Binding Sites , COVID-19/virology , Gene Expression Regulation , Host-Pathogen Interactions/drug effects , Host-Pathogen Interactions/genetics , Humans , Interferon-beta/pharmacology , Membrane Proteins/antagonists & inhibitors , Membrane Proteins/metabolism , Protein Binding , Protein Interaction Domains and Motifs , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , RNA-Binding Proteins/antagonists & inhibitors , RNA-Binding Proteins/metabolism , SARS-CoV-2/drug effects , SARS-CoV-2/metabolism , Sequence Alignment , Sequence Homology, Amino Acid , Spike Glycoprotein, Coronavirus/metabolism , Virus Attachment/drug effects
10.
Nat Commun ; 12(1): 1726, 2021 03 19.
Article in English | MEDLINE | ID: covidwho-1142436

ABSTRACT

SARS-CoV-2 is a respiratory pathogen and primarily infects the airway epithelium. As our knowledge about innate immune factors of the respiratory tract against SARS-CoV-2 is limited, we generated and screened a peptide/protein library derived from bronchoalveolar lavage for inhibitors of SARS-CoV-2 spike-driven entry. Analysis of antiviral fractions revealed the presence of α1-antitrypsin (α1AT), a highly abundant circulating serine protease inhibitor. Here, we report that α1AT inhibits SARS-CoV-2 entry at physiological concentrations and suppresses viral replication in cell lines and primary cells including human airway epithelial cultures. We further demonstrate that α1AT binds and inactivates the serine protease TMPRSS2, which enzymatically primes the SARS-CoV-2 spike protein for membrane fusion. Thus, the acute phase protein α1AT is an inhibitor of TMPRSS2 and SARS-CoV-2 entry, and may play an important role in the innate immune defense against the novel coronavirus. Our findings suggest that repurposing of α1AT-containing drugs has prospects for the therapy of COVID-19.


Subject(s)
COVID-19/drug therapy , SARS-CoV-2/drug effects , Serine Endopeptidases/metabolism , Serine Proteinase Inhibitors/pharmacology , alpha 1-Antitrypsin/pharmacology , Antibodies, Viral/blood , Antiviral Agents/pharmacology , COVID-19/blood , Caco-2 Cells , Humans , Immunoglobulin G/blood , Molecular Docking Simulation , Spike Glycoprotein, Coronavirus/metabolism , Virus Internalization/drug effects , Virus Replication/drug effects
11.
Nat Metab ; 3(2): 149-165, 2021 02.
Article in English | MEDLINE | ID: covidwho-1065968

ABSTRACT

Infection-related diabetes can arise as a result of virus-associated ß-cell destruction. Clinical data suggest that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing the coronavirus disease 2019 (COVID-19), impairs glucose homoeostasis, but experimental evidence that SARS-CoV-2 can infect pancreatic tissue has been lacking. In the present study, we show that SARS-CoV-2 infects cells of the human exocrine and endocrine pancreas ex vivo and in vivo. We demonstrate that human ß-cells express viral entry proteins, and SARS-CoV-2 infects and replicates in cultured human islets. Infection is associated with morphological, transcriptional and functional changes, including reduced numbers of insulin-secretory granules in ß-cells and impaired glucose-stimulated insulin secretion. In COVID-19 full-body postmortem examinations, we detected SARS-CoV-2 nucleocapsid protein in pancreatic exocrine cells, and in cells that stain positive for the ß-cell marker NKX6.1 and are in close proximity to the islets of Langerhans in all four patients investigated. Our data identify the human pancreas as a target of SARS-CoV-2 infection and suggest that ß-cell infection could contribute to the metabolic dysregulation observed in patients with COVID-19.


Subject(s)
Islets of Langerhans/virology , SARS-CoV-2/growth & development , Aged , Aged, 80 and over , Angiotensin-Converting Enzyme 2/biosynthesis , Angiotensin-Converting Enzyme 2/genetics , COVID-19/physiopathology , Cells, Cultured , Diabetes Mellitus , Female , Humans , Islets of Langerhans/cytology , Islets of Langerhans/physiopathology , Male , Pancreas, Exocrine/cytology , Pancreas, Exocrine/physiopathology , Pancreas, Exocrine/virology , Pancreatic Diseases/etiology , Pancreatic Diseases/virology , Serine Endopeptidases/biosynthesis , Serine Endopeptidases/genetics , Virus Internalization , Virus Replication
12.
Cell Mol Gastroenterol Hepatol ; 11(4): 935-948, 2021.
Article in English | MEDLINE | ID: covidwho-917333

ABSTRACT

BACKGROUND AND AIMS: The COVID-19 pandemic has spread worldwide and poses a severe health risk. While most patients present mild symptoms, descending pneumonia can lead to severe respiratory insufficiency. Up to 50% of patients show gastrointestinal symptoms like diarrhea or nausea, intriguingly associating with prolonged symptoms and increased severity. Thus, models to understand and validate drug efficiency in the gut of COVID-19 patients are of urgent need. METHODS: Human intestinal organoids derived from pluripotent stem cells (PSC-HIOs) have led, due to their complexity in mimicking human intestinal architecture, to an unprecedented number of successful disease models including gastrointestinal infections. Here, we employed PSC-HIOs to dissect SARS-CoV-2 pathogenesis and its inhibition by remdesivir, one of the leading drugs investigated for treatment of COVID-19. RESULTS: Immunostaining for viral entry receptor ACE2 and SARS-CoV-2 spike protein priming protease TMPRSS2 showed broad expression in the gastrointestinal tract with highest levels in the intestine, the latter faithfully recapitulated by PSC-HIOs. Organoids could be readily infected with SARS-CoV-2 followed by viral spread across entire PSC-HIOs, subsequently leading to organoid deterioration. However, SARS-CoV-2 spared goblet cells lacking ACE2 expression. Importantly, we challenged PSC-HIOs for drug testing capacity. Specifically, remdesivir effectively inhibited SARS-CoV-2 infection dose-dependently at low micromolar concentration and rescued PSC-HIO morphology. CONCLUSIONS: Thus, PSC-HIOs are a valuable tool to study SARS-CoV-2 infection and to identify and validate drugs especially with potential action in the gut.


Subject(s)
Adenosine Monophosphate/analogs & derivatives , Alanine/analogs & derivatives , COVID-19/drug therapy , COVID-19/metabolism , Human Embryonic Stem Cells , Intestinal Mucosa , Organoids , SARS-CoV-2/physiology , Virus Replication/drug effects , Adenosine Monophosphate/pharmacology , Alanine/pharmacology , Caco-2 Cells , Human Embryonic Stem Cells/metabolism , Human Embryonic Stem Cells/pathology , Human Embryonic Stem Cells/virology , Humans , Intestinal Mucosa/metabolism , Intestinal Mucosa/pathology , Intestinal Mucosa/virology , Organoids/metabolism , Organoids/pathology , Organoids/virology
13.
mBio ; 11(5)2020 10 16.
Article in English | MEDLINE | ID: covidwho-873466

ABSTRACT

Recent evidence shows that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is sensitive to interferons (IFNs). However, the most effective types of IFNs and the underlying antiviral effectors remain to be defined. Here, we show that zinc finger antiviral protein (ZAP), which preferentially targets CpG dinucleotides in viral RNA sequences, restricts SARS-CoV-2. We further demonstrate that ZAP and its cofactors KHNYN and TRIM25 are expressed in human lung cells. Type I, II, and III IFNs all strongly inhibited SARS-CoV-2 and further induced ZAP expression. Comprehensive sequence analyses revealed that SARS-CoV-2 and its closest relatives from horseshoe bats showed the strongest CpG suppression among all known human and bat coronaviruses, respectively. Nevertheless, endogenous ZAP expression restricted SARS-CoV-2 replication in human lung cells, particularly upon treatment with IFN-α or IFN-γ. Both the long and the short isoforms of human ZAP reduced SARS-CoV-2 RNA expression levels, but the former did so with greater efficiency. Finally, we show that the ability to restrict SARS-CoV-2 is conserved in ZAP orthologues of the reservoir bat and potential intermediate pangolin hosts of human coronaviruses. Altogether, our results show that ZAP is an important effector of the innate response against SARS-CoV-2, although this pandemic pathogen emerged from zoonosis of a coronavirus that was preadapted to the low-CpG environment in humans.IMPORTANCE Although interferons inhibit SARS-CoV-2 and have been evaluated for treatment of coronavirus disease 2019 (COVID-19), the most effective types and antiviral effectors remain to be defined. Here, we show that IFN-γ is particularly potent in restricting SARS-CoV-2 and in inducing expression of the antiviral factor ZAP in human lung cells. Knockdown experiments revealed that endogenous ZAP significantly restricts SARS-CoV-2. We further show that CpG dinucleotides which are specifically targeted by ZAP are strongly suppressed in the SARS-CoV-2 genome and that the two closest horseshoe bat relatives of SARS-CoV-2 show the lowest genomic CpG content of all coronavirus sequences available from this reservoir host. Nonetheless, both the short and long isoforms of human ZAP reduced SARS-CoV-2 RNA levels, and this activity was conserved in horseshoe bat and pangolin ZAP orthologues. Our findings indicating that type II interferon is particularly efficient against SARS-CoV-2 and that ZAP restricts this pandemic viral pathogen might promote the development of effective immune therapies against COVID-19.


Subject(s)
Betacoronavirus/physiology , Coronavirus Infections/virology , CpG Islands , Pneumonia, Viral/virology , RNA-Binding Proteins/metabolism , Animals , Betacoronavirus/classification , Betacoronavirus/genetics , Betacoronavirus/metabolism , COVID-19 , Cell Line , Coronavirus/classification , Coronavirus/genetics , Coronavirus/physiology , Gene Expression/drug effects , Genome, Viral , Humans , Interferons/pharmacology , Pandemics , Phylogeny , Protein Isoforms , RNA, Viral/genetics , RNA, Viral/metabolism , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/genetics , SARS-CoV-2 , Virus Replication/drug effects
14.
Nucleic Acids Res ; 48(19): 10890-10908, 2020 11 04.
Article in English | MEDLINE | ID: covidwho-817440

ABSTRACT

Although endogenous retroviruses (ERVs) are known to harbor cis-regulatory elements, their role in modulating cellular immune responses remains poorly understood. Using an RNA-seq approach, we show that several members of the ERV9 lineage, particularly LTR12C elements, are activated upon HIV-1 infection of primary CD4+ T cells. Intriguingly, HIV-1-induced ERVs harboring transcription start sites are primarily found in the vicinity of immunity genes. For example, HIV-1 infection activates LTR12C elements upstream of the interferon-inducible genes GBP2 and GBP5 that encode for broad-spectrum antiviral factors. Reporter assays demonstrated that these LTR12C elements drive gene expression in primary CD4+ T cells. In line with this, HIV-1 infection triggered the expression of a unique GBP2 transcript variant by activating a cryptic transcription start site within LTR12C. Furthermore, stimulation with HIV-1-induced cytokines increased GBP2 and GBP5 expression in human cells, but not in macaque cells that naturally lack the GBP5 gene and the LTR12C element upstream of GBP2. Finally, our findings suggest that GBP2 and GBP5 have already been active against ancient viral pathogens as they suppress the maturation of the extinct retrovirus HERV-K (HML-2). In summary, our findings uncover how human cells can exploit remnants of once-infectious retroviruses to regulate antiviral gene expression.


Subject(s)
CD4-Positive T-Lymphocytes/immunology , Endogenous Retroviruses/genetics , Gene Expression Regulation/immunology , HIV Infections/genetics , Promoter Regions, Genetic , T-Lymphocyte Subsets/immunology , Animals , CD4-Positive T-Lymphocytes/cytology , GTP-Binding Proteins/genetics , GTP-Binding Proteins/immunology , HEK293 Cells , HIV Infections/immunology , HIV-1 , Humans , Macaca mulatta , T-Lymphocyte Subsets/cytology
15.
Antiviral Res ; 181: 104882, 2020 09.
Article in English | MEDLINE | ID: covidwho-684270

ABSTRACT

SARS-CoV-2 is a novel pandemic coronavirus that caused a global health and economic crisis. The development of efficient drugs and vaccines against COVID-19 requires detailed knowledge about SARS-CoV-2 biology. Several techniques to detect SARS-CoV-2 infection have been established, mainly based on counting infected cells by staining plaques or foci, or by quantifying the viral genome by PCR. These methods are laborious, time-consuming and expensive and therefore not suitable for a high sample throughput or rapid diagnostics. We here report a novel enzyme-based immunodetection assay that directly quantifies the amount of de novo synthesized viral spike protein within fixed and permeabilized cells. This in-cell ELISA enables a rapid and quantitative detection of SARS-CoV-2 infection in microtiter format, regardless of the virus isolate or target cell culture. It follows the established method of performing ELISA assays and does not require expensive instrumentation. Utilization of the in-cell ELISA allows to e.g. determine TCID50 of virus stocks, antiviral efficiencies (IC50 values) of drugs or neutralizing activity of sera. Thus, the in-cell spike ELISA represents a promising alternative to study SARS-CoV-2 infection and inhibition and may facilitate future research.


Subject(s)
Antibodies, Viral/immunology , Betacoronavirus/immunology , Coronavirus Infections/virology , Enzyme-Linked Immunosorbent Assay/methods , Pneumonia, Viral/virology , Severe Acute Respiratory Syndrome/virology , Spike Glycoprotein, Coronavirus/immunology , Animals , Betacoronavirus/isolation & purification , COVID-19 , Chlorocebus aethiops , Coronavirus Infections/diagnosis , Humans , Pandemics , Pneumonia, Viral/diagnosis , SARS-CoV-2 , Severe Acute Respiratory Syndrome/diagnosis , Spike Glycoprotein, Coronavirus/genetics , Vero Cells , Viral Plaque Assay
16.
Science ; 369(6508): 1249-1255, 2020 09 04.
Article in English | MEDLINE | ID: covidwho-654484

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the current coronavirus disease 2019 (COVID-19) pandemic. A major virulence factor of SARS-CoVs is the nonstructural protein 1 (Nsp1), which suppresses host gene expression by ribosome association. Here, we show that Nsp1 from SARS-CoV-2 binds to the 40S ribosomal subunit, resulting in shutdown of messenger RNA (mRNA) translation both in vitro and in cells. Structural analysis by cryo-electron microscopy of in vitro-reconstituted Nsp1-40S and various native Nsp1-40S and -80S complexes revealed that the Nsp1 C terminus binds to and obstructs the mRNA entry tunnel. Thereby, Nsp1 effectively blocks retinoic acid-inducible gene I-dependent innate immune responses that would otherwise facilitate clearance of the infection. Thus, the structural characterization of the inhibitory mechanism of Nsp1 may aid structure-based drug design against SARS-CoV-2.


Subject(s)
Betacoronavirus/chemistry , Immune Evasion , Immunity, Innate , Protein Biosynthesis , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/metabolism , Betacoronavirus/immunology , Betacoronavirus/metabolism , Betacoronavirus/physiology , Binding Sites , COVID-19 , Coronavirus Infections/immunology , Coronavirus Infections/virology , Cryoelectron Microscopy , DEAD Box Protein 58/genetics , DEAD Box Protein 58/metabolism , Humans , Interferon-beta/genetics , Interferon-beta/metabolism , Models, Molecular , Pandemics , Pneumonia, Viral/immunology , Pneumonia, Viral/virology , Protein Binding , Protein Domains , Protein Interaction Domains and Motifs , Protein Structure, Secondary , RNA, Messenger/metabolism , Receptors, Immunologic , Ribosome Subunits, Small, Eukaryotic/chemistry , Ribosome Subunits, Small, Eukaryotic/metabolism , SARS-CoV-2
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