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PLoS Pathog ; 17(8): e1009800, 2021 08.
Article in English | MEDLINE | ID: covidwho-1435629


Type I Interferons (IFN-Is) are a family of cytokines which play a major role in inhibiting viral infection. Resultantly, many viruses have evolved mechanisms in which to evade the IFN-I response. Here we tested the impact of expression of 27 different SARS-CoV-2 genes in relation to their effect on IFN production and activity using three independent experimental methods. We identified six gene products; NSP6, ORF6, ORF7b, NSP1, NSP5 and NSP15, which strongly (>10-fold) blocked MAVS-induced (but not TRIF-induced) IFNß production. Expression of the first three of these SARS-CoV-2 genes specifically blocked MAVS-induced IFNß-promoter activity, whereas all six genes induced a collapse in IFNß mRNA levels, corresponding with suppressed IFNß protein secretion. Five of these six genes furthermore suppressed MAVS-induced activation of IFNλs, however with no effect on IFNα or IFNγ production. In sharp contrast, SARS-CoV-2 infected cells remained extremely sensitive to anti-viral activity exerted by added IFN-Is. None of the SARS-CoV-2 genes were able to block IFN-I signaling, as demonstrated by robust activation of Interferon Stimulated Genes (ISGs) by added interferon. This, despite the reduced levels of STAT1 and phospho-STAT1, was likely caused by broad translation inhibition mediated by NSP1. Finally, we found that a truncated ORF7b variant that has arisen from a mutant SARS-CoV-2 strain harboring a 382-nucleotide deletion associating with mild disease (Δ382 strain identified in Singapore & Taiwan in 2020) lost its ability to suppress type I and type III IFN production. In summary, our findings support a multi-gene process in which SARS-CoV-2 blocks IFN-production, with ORF7b as a major player, presumably facilitating evasion of host detection during early infection. However, SARS-CoV-2 fails to suppress IFN-I signaling thus providing an opportunity to exploit IFN-Is as potential therapeutic antiviral drugs.

Interferon-beta/metabolism , SARS-CoV-2/immunology , Viral Proteins/metabolism , Adaptor Proteins, Signal Transducing/metabolism , Adaptor Proteins, Vesicular Transport/metabolism , Animals , Chlorocebus aethiops , Eukaryotic Initiation Factor-2/metabolism , HEK293 Cells , Humans , Interferon-beta/genetics , Interferon-beta/pharmacology , SARS-CoV-2/drug effects , STAT1 Transcription Factor/metabolism , Vero Cells , Viral Proteins/genetics
mSphere ; : e0031321, 2021 Jun 16.
Article in English | MEDLINE | ID: covidwho-1270879


The COVID-19 pandemic has impacted and enforced significant restrictions within our societies, including the attendance of public and professional athletes in gyms. Liquid chalk is a commonly used accessory in gyms and is comprised of magnesium carbonate and alcohol that quickly evaporates on the hands to leave a layer of dry chalk. We investigated whether liquid chalk is an antiseptic against highly pathogenic human viruses, including SARS-CoV-2, influenza virus, and noroviruses. Chalk was applied before or after virus, inoculum and recovery of infectious virus was determined to mimic the use in the gym. We observed that addition of chalk before or after virus contact led to a significant reduction in recovery of infectious SARS-CoV-2 and influenza virus but had little impact on norovirus. These observations suggest that the use and application of liquid chalk can be an effective and suitable antiseptic for major sporting events, such as the Olympic Games. IMPORTANCE To restrict the potential transmission and infectivity of SARS-CoV-2, the use of liquid chalk has been a requirement in an active gym setting. However, its effectiveness has not been scientifically proven. Here, we show that the application of liquid chalk before or after virus inoculum significantly impacts recovery of infectious SARS-CoV-2 and influenza viruses but not noroviruses. Thus, our study has shown that the implementation and application of liquid chalk in communal social gym settings is effective in reducing the infectivity of respiratory viruses, and this supports the use of liquid chalk in major sporting events to restrict the impact of COVID-19 on our communities.

Nat Commun ; 12(1): 3431, 2021 06 08.
Article in English | MEDLINE | ID: covidwho-1262001


The current COVID-19 pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We demonstrate that despite the large size of the viral RNA genome (~30 kb), infectious full-length cDNA is readily assembled in vitro by a circular polymerase extension reaction (CPER) methodology without the need for technically demanding intermediate steps. Overlapping cDNA fragments are generated from viral RNA and assembled together with a linker fragment containing CMV promoter into a circular full-length viral cDNA in a single reaction. Transfection of the circular cDNA into mammalian cells results in the recovery of infectious SARS-CoV-2 virus that exhibits properties comparable to the parental virus in vitro and in vivo. CPER is also used to generate insect-specific Casuarina virus with ~20 kb genome and the human pathogens Ross River virus (Alphavirus) and Norovirus (Calicivirus), with the latter from a clinical sample. Additionally, reporter and mutant viruses are generated and employed to study virus replication and virus-receptor interactions.

Reverse Genetics , SARS-CoV-2/genetics , Amino Acid Sequence , Animals , Base Sequence , Chlorocebus aethiops , Culicidae/virology , Furin/metabolism , Genome, Viral , HEK293 Cells , Humans , Mice , Mutation/genetics , NIH 3T3 Cells , Polymerase Chain Reaction , RAW 264.7 Cells , Receptors, Virus/metabolism , Vero Cells , Viral Proteins/chemistry , Virus Replication