Revised Title: Yerkes National Primate Research Center Role of type-I IFN in regulating COVID-19 induced inflammation and pathogenesis Revised Abstract: This is an administrative supplement from the Yerkes National Primate Research Center (YNPRC). The goal of the supplement is to conduct a study with a total of 30 rhesus macaques in which 15 CoV-infected “control” animals are compared to 15 CoV-infected macaques treated with type I IFN antagonist to increase disease severity. Recent studies suggest that a defective type-I IFN response may cause severe and life-threatening COVID-19 outcomes due to uncontrolled viral spread and excessive inflammation. SARS-CoV-2-infected rhesus macaques develop mild to moderate COVID, and the aim of the experimental treatment is to induce more severe disease in this NHP model to test potential therapeutics. An adaptive trial design is proposed to provide statistical power will using the fewest number of animals. A wide range of viral, molecular, cellular, immunological, and clinical endpoints will be collected from the animals at serial timepoints and several tissues/organs will also be sampled in serial necropsies in subsets of animals (terminal necropsies in all remaining animals). Many of these samples will be investigated histologically and/or via molecular and other approaches by two different labs to test and develop NPRC COVID-19 SOPs and assess reproducibility. Samples will also be bio-banked as resources for future use by other researchers. The investigative team and environment are considered excellent. The project is considered high priority due to its importance for understanding the inflammatory sequalae of COVID, developing a rhesus model of severe disease, and working across NPRCs and accessing relevant expertise to advance standardized SOPs. This work should provide an in depth understanding of pathogenesis and inflammatory pathways, which will be critical to testing candidate therapeutics and second/third generation vaccines.