Evasion of type-I interferon by SARS-CoV-2

SUMMARY The coronavirus disease 2019 (COVID-19) is determined by SARS-CoV-2 replication and host immune response, but studies evaluating viral evasion of immune response are lacking. Here we employed unbiased screening to identify SARS-CoV-2 proteins that antagonize type-I interferon (IFN-I) response. Three proteins were found to antagonize IFN-I production via distinct mechanisms: nsp6 binds TBK1 to suppress IRF3 phosphorylation; nsp13 binds and blocks TBK1 phosphorylation; and ORF6 binds importin KPNA2 to inhibit IRF3 nuclear translocation. Two sets of viral proteins were identified to antagonize IFN-I signaling through blocking STAT1/STAT2 phosphorylation or nuclear translocation. Remarkably, SARS-CoV-2 nsp1 and nsp6 suppressed IFN-I signaling more efficiently than SARS-CoV and MERS-CoV. Thus, when treated with IFN-I, a SARS-CoV2 replicon replicated to a higher level than chimeric replicons containing nsp1 or nsp6 from SARS-CoV or MERS-CoV. Altogether, the study has provided insights on SARS-CoV-2 evasion of IFN-I response and its potential impact on viral transmission and pathogenesis.