Analysis of innate immune sensing of SARS-CoV-2 using recombinant viruses

discovery - The fast pandemic spread of SARS-CoV-2 is fostered by its rather high reproduction number R0 but also by a significant proportion of oligo- or asymptomatic infections that complicate containment. The circumstance that the virus is able to replicate without notable signs of inflammation suggests that the initial innate immune control of viral replication might be deregulated and less effective. Thus, this study aims at characterizing mechanisms that allow SARS-CoV-2 to evade innate immune sensing by the host. Proteins in CoVs that counteract immune sensing include the Endonuclease U (Nsp15) and 2OMethyltransferase (Nsp16), which inhibit the detection of CoV RNA by host RNA sensors upon infection. In addition, mutations in the accessory protein ORF8 have been linked to a reduced replication of SARS-CoV. Here, we will analyze the effects of these immunomodulatory factors in shielding SARS-CoV-2 from innate immunity by generating recombinant viruses lacking the respective functional ORFs. We will test the replication capacity and the ability to avoid detection by innate immunity in vitro and in vivo using transgenic human ACE-2 mice. Making the virus more "visible" to intrinsic immunity will allow the immune system to better control viral replication and clear the virus more efficiently. Identifying viral proteins, which inhibit innate sensing of SARS-CoV-2, will be of high interest to both vaccine development and therapy.