OAS1 and COVID-19: Finally, in individuals with moderate SARS-CoV-2 infection, 2’-5’-Oligoadenylate Synthetase 1 (OAS1), OAS2, OAS3, and T cell Immunoreceptor with Ig and ITIM domains (TIGIT) were elevated, but these levels significantly decreased with increased COVID-19 severity (Fig 4B).