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1.
Nat Struct Mol Biol ; 28(9): 747-754, 2021 09.
Article in English | MEDLINE | ID: covidwho-1370728

ABSTRACT

Drug discovery campaigns against COVID-19 are beginning to target the SARS-CoV-2 RNA genome. The highly conserved frameshift stimulation element (FSE), required for balanced expression of viral proteins, is a particularly attractive SARS-CoV-2 RNA target. Here we present a 6.9 Å resolution cryo-EM structure of the FSE (88 nucleotides, ~28 kDa), validated through an RNA nanostructure tagging method. The tertiary structure presents a topologically complex fold in which the 5' end is threaded through a ring formed inside a three-stem pseudoknot. Guided by this structure, we develop antisense oligonucleotides that impair FSE function in frameshifting assays and knock down SARS-CoV-2 virus replication in A549-ACE2 cells at 100 nM concentration.


Subject(s)
COVID-19/prevention & control , Cryoelectron Microscopy/methods , Frameshift Mutation/genetics , Oligonucleotides, Antisense/genetics , RNA, Viral/genetics , Response Elements/genetics , SARS-CoV-2/genetics , A549 Cells , Animals , Base Sequence , COVID-19/virology , Cell Line, Tumor , Chlorocebus aethiops , Genome, Viral/genetics , Humans , Models, Molecular , Nucleic Acid Conformation , Oligonucleotides, Antisense/pharmacology , RNA, Viral/chemistry , RNA, Viral/ultrastructure , SARS-CoV-2/physiology , SARS-CoV-2/ultrastructure , Vero Cells , Virus Replication/drug effects , Virus Replication/genetics
2.
Lancet Respir Med ; 9(5): 498-510, 2021 05.
Article in English | MEDLINE | ID: covidwho-1301092

ABSTRACT

BACKGROUND: To date, only monoclonal antibodies have been shown to be effective for outpatients with COVID-19. Interferon lambda-1 is a type III interferon involved in innate antiviral responses with activity against respiratory pathogens. We aimed to investigate the safety and efficacy of peginterferon lambda in the treatment of outpatients with mild-to-moderate COVID-19. METHODS: In this double-blind, placebo-controlled trial, outpatients with laboratory-confirmed COVID-19 were randomly assigned to a single subcutaneous injection of peginterferon lambda 180 µg or placebo within 7 days of symptom onset or first positive swab if asymptomatic. Participants were randomly assigned (1:1) using a computer-generated randomisation list created with a randomisation schedule in blocks of four. At the time of administration, study nurses received a sealed opaque envelope with the treatment allocation number. The primary endpoint was the proportion of patients who were negative for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA on day 7 after the injection, analysed by a χ2 test following an intention-to-treat principle. Prespecified analysis of the primary endpoint, adjusted for baseline viral load, using bivariate logistic regression was done. The trial is now complete. This trial is registered with ClinicalTrials.gov, NCT04354259. FINDINGS: Between May 18, and Sept 4, 2020, we recruited 30 patients per group. The decline in SARS-CoV-2 RNA was greater in those treated with peginterferon lambda than placebo from day 3 onwards, with a difference of 2·42 log copies per mL at day 7 (p=0·0041). By day 7, 24 (80%) participants in the peginterferon lambda group had an undetectable viral load, compared with 19 (63%) in the placebo group (p=0·15). After controlling for baseline viral load, patients in the peginterferon lambda group were more likely to have undetectable virus by day 7 than were those in the placebo group (odds ratio [OR] 4·12 [95% CI 1·15-16·73; p=0·029). Of those with baseline viral load above 106 copies per mL, 15 (79%) of 19 patients in the peginterferon lambda group had undetectable virus on day 7, compared with six (38%) of 16 in the placebo group (OR 6·25 [95% CI 1·49-31·06]; p=0·012). Peginterferon lambda was well tolerated, and adverse events were similar between groups with mild and transient aminotransferase, concentration increases more frequently observed in the peginterferon lambda group. Two individuals met the threshold of grade 3 increase, one in each group, and no other grade 3 or 4 laboratory adverse events were reported. INTERPRETATION: Peginterferon lambda accelerated viral decline in outpatients with COVID-19, increasing the proportion of patients with viral clearance by day 7, particularly in those with high baseline viral load. Peginterferon lambda has potential to prevent clinical deterioration and shorten duration of viral shedding. FUNDING: The Toronto COVID-19 Action Initiative, University of Toronto, and the Ontario First COVID-19 Rapid Research Fund, Toronto General & Western Hospital Foundation.


Subject(s)
Ambulatory Care/methods , COVID-19 , Interleukins , Polyethylene Glycols , SARS-CoV-2 , Viral Load/drug effects , Virus Shedding/drug effects , Antiviral Agents/administration & dosage , Antiviral Agents/adverse effects , COVID-19/diagnosis , COVID-19/drug therapy , COVID-19/immunology , Double-Blind Method , Drug Monitoring/methods , Female , Humans , Intention to Treat Analysis , Interleukins/administration & dosage , Interleukins/adverse effects , Male , Middle Aged , Polyethylene Glycols/administration & dosage , Polyethylene Glycols/adverse effects , RNA, Viral/isolation & purification , SARS-CoV-2/isolation & purification , SARS-CoV-2/physiology , Severity of Illness Index , Treatment Outcome
5.
Nature ; 588(7839): 670-675, 2020 12.
Article in English | MEDLINE | ID: covidwho-943910

ABSTRACT

The distal lung contains terminal bronchioles and alveoli that facilitate gas exchange. Three-dimensional in vitro human distal lung culture systems would strongly facilitate the investigation of pathologies such as interstitial lung disease, cancer and coronavirus disease 2019 (COVID-19) pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here we describe the development of a long-term feeder-free, chemically defined culture system for distal lung progenitors as organoids derived from single adult human alveolar epithelial type II (AT2) or KRT5+ basal cells. AT2 organoids were able to differentiate into AT1 cells, and basal cell organoids developed lumens lined with differentiated club and ciliated cells. Single-cell analysis of KRT5+ cells in basal organoids revealed a distinct population of ITGA6+ITGB4+ mitotic cells, whose offspring further segregated into a TNFRSF12Ahi subfraction that comprised about ten per cent of KRT5+ basal cells. This subpopulation formed clusters within terminal bronchioles and exhibited enriched clonogenic organoid growth activity. We created distal lung organoids with apical-out polarity to present ACE2 on the exposed external surface, facilitating infection of AT2 and basal cultures with SARS-CoV-2 and identifying club cells as a target population. This long-term, feeder-free culture of human distal lung organoids, coupled with single-cell analysis, identifies functional heterogeneity among basal cells and establishes a facile in vitro organoid model of human distal lung infections, including COVID-19-associated pneumonia.


Subject(s)
COVID-19/virology , Lung/cytology , Models, Biological , Organoids/cytology , Organoids/virology , SARS-CoV-2/physiology , Tissue Culture Techniques , Alveolar Epithelial Cells/cytology , Alveolar Epithelial Cells/metabolism , Alveolar Epithelial Cells/virology , COVID-19/metabolism , COVID-19/pathology , Cell Differentiation , Cell Division , Clone Cells/cytology , Clone Cells/metabolism , Clone Cells/virology , Humans , In Vitro Techniques , Influenza A Virus, H1N1 Subtype/growth & development , Influenza A Virus, H1N1 Subtype/physiology , Integrin alpha6/analysis , Integrin beta4/analysis , Keratin-5/analysis , Organoids/metabolism , Pneumonia, Viral/metabolism , Pneumonia, Viral/pathology , Pneumonia, Viral/virology , SARS-CoV-2/growth & development , Single-Cell Analysis , TWEAK Receptor/analysis
6.
Nature ; 586(7830): 560-566, 2020 10.
Article in English | MEDLINE | ID: covidwho-733515

ABSTRACT

Coronaviruses are prone to transmission to new host species, as recently demonstrated by the spread to humans of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic1. Small animal models that recapitulate SARS-CoV-2 disease are needed urgently for rapid evaluation of medical countermeasures2,3. SARS-CoV-2 cannot infect wild-type laboratory mice owing to inefficient interactions between the viral spike protein and the mouse orthologue of the human receptor, angiotensin-converting enzyme 2 (ACE2)4. Here we used reverse genetics5 to remodel the interaction between SARS-CoV-2 spike protein and mouse ACE2 and designed mouse-adapted SARS-CoV-2 (SARS-CoV-2 MA), a recombinant virus that can use mouse ACE2 for entry into cells. SARS-CoV-2 MA was able to replicate in the upper and lower airways of both young adult and aged BALB/c mice. SARS-CoV-2 MA caused more severe disease in aged mice, and exhibited more clinically relevant phenotypes than those seen in Hfh4-ACE2 transgenic mice, which express human ACE2 under the control of the Hfh4 (also known as Foxj1) promoter. We demonstrate the utility of this model using vaccine-challenge studies in immune-competent mice with native expression of mouse ACE2. Finally, we show that the clinical candidate interferon-λ1a (IFN-λ1a) potently inhibits SARS-CoV-2 replication in primary human airway epithelial cells in vitro-both prophylactic and therapeutic administration of IFN-λ1a diminished SARS-CoV-2 replication in mice. In summary, the mouse-adapted SARS-CoV-2 MA model demonstrates age-related disease pathogenesis and supports the clinical use of pegylated IFN-λ1a as a treatment for human COVID-196.


Subject(s)
Betacoronavirus , Coronavirus Infections/drug therapy , Coronavirus Infections/prevention & control , Disease Models, Animal , Interferons/pharmacology , Interferons/therapeutic use , Interleukins/pharmacology , Interleukins/therapeutic use , Pandemics/prevention & control , Pneumonia, Viral/drug therapy , Pneumonia, Viral/prevention & control , Viral Vaccines/immunology , Aging/immunology , Angiotensin-Converting Enzyme 2 , Animals , Betacoronavirus/drug effects , Betacoronavirus/immunology , Betacoronavirus/pathogenicity , COVID-19 , COVID-19 Vaccines , Coronavirus Infections/genetics , Coronavirus Infections/immunology , Female , Forkhead Transcription Factors/genetics , Humans , Interferon-alpha/administration & dosage , Interferon-alpha/pharmacology , Interferon-alpha/therapeutic use , Interferons/administration & dosage , Interleukins/administration & dosage , Male , Mice , Mice, Inbred BALB C , Mice, Transgenic , Models, Molecular , Peptidyl-Dipeptidase A/genetics , Peptidyl-Dipeptidase A/metabolism , Pneumonia, Viral/genetics , Pneumonia, Viral/immunology , Receptors, Virus/genetics , Receptors, Virus/metabolism , SARS-CoV-2
8.
mBio ; 11(3)2020 06 23.
Article in English | MEDLINE | ID: covidwho-612678

ABSTRACT

It is well understood that the adaptive immune response to infectious agents includes a modulating suppressive component as well as an activating component. We now show that the very early innate response also has an immunosuppressive component. Infected cells upregulate the CD47 "don't eat me" signal, which slows the phagocytic uptake of dying and viable cells as well as downstream antigen-presenting cell (APC) functions. A CD47 mimic that acts as an essential virulence factor is encoded by all poxviruses, but CD47 expression on infected cells was found to be upregulated even by pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that encode no mimic. CD47 upregulation was revealed to be a host response induced by the stimulation of both endosomal and cytosolic pathogen recognition receptors (PRRs). Furthermore, proinflammatory cytokines, including those found in the plasma of hepatitis C patients, upregulated CD47 on uninfected dendritic cells, thereby linking innate modulation with downstream adaptive immune responses. Indeed, results from antibody-mediated CD47 blockade experiments as well as CD47 knockout mice revealed an immunosuppressive role for CD47 during infections with lymphocytic choriomeningitis virus and Mycobacterium tuberculosis Since CD47 blockade operates at the level of pattern recognition receptors rather than at a pathogen or antigen-specific level, these findings identify CD47 as a novel potential immunotherapeutic target for the enhancement of immune responses to a broad range of infectious agents.IMPORTANCE Immune responses to infectious agents are initiated when a pathogen or its components bind to pattern recognition receptors (PRRs). PRR binding sets off a cascade of events that activates immune responses. We now show that, in addition to activating immune responses, PRR signaling also initiates an immunosuppressive response, probably to limit inflammation. The importance of the current findings is that blockade of immunomodulatory signaling, which is mediated by the upregulation of the CD47 molecule, can lead to enhanced immune responses to any pathogen that triggers PRR signaling. Since most or all pathogens trigger PRRs, CD47 blockade could be used to speed up and strengthen both innate and adaptive immune responses when medically indicated. Such immunotherapy could be done without a requirement for knowing the HLA type of the individual, the specific antigens of the pathogen, or, in the case of bacterial infections, the antimicrobial resistance profile.


Subject(s)
Betacoronavirus/immunology , CD47 Antigen/metabolism , Immunomodulation/immunology , Receptors, Pattern Recognition/immunology , A549 Cells , Adaptive Immunity/immunology , Animals , CD47 Antigen/genetics , Cell Line, Tumor , Cytokines/immunology , Female , Humans , Immunity, Innate/immunology , Lymphocytic choriomeningitis virus/immunology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mycobacterium tuberculosis/immunology , SARS-CoV-2 , Up-Regulation/immunology
9.
RNA ; 26(8): 937-959, 2020 08.
Article in English | MEDLINE | ID: covidwho-245418

ABSTRACT

As the COVID-19 outbreak spreads, there is a growing need for a compilation of conserved RNA genome regions in the SARS-CoV-2 virus along with their structural propensities to guide development of antivirals and diagnostics. Here we present a first look at RNA sequence conservation and structural propensities in the SARS-CoV-2 genome. Using sequence alignments spanning a range of betacoronaviruses, we rank genomic regions by RNA sequence conservation, identifying 79 regions of length at least 15 nt as exactly conserved over SARS-related complete genome sequences available near the beginning of the COVID-19 outbreak. We then confirm the conservation of the majority of these genome regions across 739 SARS-CoV-2 sequences subsequently reported from the COVID-19 outbreak, and we present a curated list of 30 "SARS-related-conserved" regions. We find that known RNA structured elements curated as Rfam families and in prior literature are enriched in these conserved genome regions, and we predict additional conserved, stable secondary structures across the viral genome. We provide 106 "SARS-CoV-2-conserved-structured" regions as potential targets for antivirals that bind to structured RNA. We further provide detailed secondary structure models for the extended 5' UTR, frameshifting stimulation element, and 3' UTR. Lastly, we predict regions of the SARS-CoV-2 viral genome that have low propensity for RNA secondary structure and are conserved within SARS-CoV-2 strains. These 59 "SARS-CoV-2-conserved-unstructured" genomic regions may be most easily accessible by hybridization in primer-based diagnostic strategies.


Subject(s)
Betacoronavirus/genetics , RNA, Viral/chemistry , RNA, Viral/genetics , Base Sequence , Betacoronavirus/classification , Evolution, Molecular , Genome, Viral , Nucleic Acid Conformation , SARS-CoV-2 , Sequence Alignment , Thermodynamics
10.
J Exp Med ; 217(5)2020 05 04.
Article in English | MEDLINE | ID: covidwho-60343

ABSTRACT

With the first reports on coronavirus disease 2019 (COVID-19), which is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the scientific community working in the field of type III IFNs (IFN-λ) realized that this class of IFNs could play an important role in this and other emerging viral infections. In this Viewpoint, we present our opinion on the benefits and potential limitations of using IFN-λ to prevent, limit, and treat these dangerous viral infections.


Subject(s)
Betacoronavirus/physiology , Coronavirus Infections/metabolism , Interferons/metabolism , Pneumonia, Viral/metabolism , COVID-19 , Humans , Pandemics , SARS-CoV-2 , Virus Internalization
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