Antagonism of stress granules key for SARS-CoV-2 infection and pathogenesis.

Viruses must subvert host responses to facilitate successful infection. While most antiviral responses are associated with interferons, stress granules (SG) are another barrier to viral infection by inducing translation arrest. To combat SG activity, viruses have evolved mechanisms to disrupt formation and disassemble these complexes. Our prior studies identified residues in SARS-CoV-2 NSP3 (Y138/F145) and nucleocapsid (F17) that independently antagonize SG activity. Disrupting these key residues in NSP3 or nucleocapsid attenuated viral replication, but only modestly impacted in vivo pathogenesis suggesting overlap in SG antagonism partially compensate for the individual losses. In this study, we evaluated a SARS-CoV-2 mutant (YF/F17A) that combines the NSP3 and N mutations. We find that loss of both SG antagonizing functions attenuates SARS-CoV-2 replication in vitro. While no changes are seen in type I IFN sensitivity, attenuation corresponds to increased induction of SGs. Importantly, the SARS-CoV-2 YF/F17A mutant has significant attenuation in vivo with reduced viral replication, less weight loss, and limited immune pathology. Notably, infection with the YF/F17A mutant stimulated less interferon and inflammation. Despite these muted host responses, the YF/F17A mutant stimulated robust protection against subsequent challenge with WT SARS-CoV-2. Overall, the study highlights the importance of SG control for SARS-CoV-2 infection and offers a novel, interferon independent target for vaccination and therapeutic treatment going forward.