SRA

Inflammation following SARS-CoV-2 infection is a hallmark of COVID-19 and predictive of morbidity and death. However, the inflammatory pathways contributing to host-defense vs immune-mediated pathology have not been fully elucidated. This duality is clearly seen with type-I interferons (IFN-I) which are critical mediators of innate control of viral infections, but also drive recruitment of inflammatory cells to site of infection, a key feature of severe COVID-19. Here, we modulated IFN-I signaling in rhesus macaques (Macaca mulatta) prior to and during acute SARS-CoV-2 infection (day -1 through day 2 post infection) using a mutated IFNa2 (IFN-modulator; IFNmod) which blocks binding to IFNAR2 and signaling of endogenous IFN-I. IFNmod treatment resulted in a highly significant and consistent reduction in SARS-CoV-2 viral load in BAL, lung, and hilar LN (>3-log difference) and upper airways (nasal swabs). IFNmod also potently reduced inflammatory cytokines and chemokines in BAL, expansion of inflammatory monocytes (CD14+CD16+), and lung pathogenesis. Furthermore, Siglec-1 expression, which has been shown to enhance SARS-CoV-2 infection, was rapidly downregulated in the lung and on monocytes of IFNmod-treated SARS-CoV-2 infected RMs. Notably, while RNAseq analysis showed that IFNmod induced a modest upregulation of antiviral IFN-stimulated genes (ISGs) in uninfected RMs, it resulted in a robust reduction in pathways associated with both antiviral and inflammatory ISGs in SARS-CoV-2-infected RMs. In conclusion, IFNmod treatment provides sufficient levels of type I IFN signaling that inhibit viral replication while also limiting hyperinflammation. IFN-I plays a vital role in regulating SARS-CoV-2 replication, but uncontrolled IFN signaling has a detrimental impact on inflammation and pathogenesis. A better understanding of the role of IFN-I pathways is essential for designing therapies targeting these pathways and aimed at limiting COVID-19 pathogenesis. Overall design: Uninfected Rhesus Macaque Study (n=4): Four uninfected rhesus macaques (RMs) were treated with a four-day course of IFNmod (1mg/day, intramuscularly) to assess the effects of IFNmod in the absence of experimental infection. Brochoalveolar lavage (BAL) fluid was collected prior to treatment initiation (pre-treatment baseline (BL)), 1 day post treatment initiation, and 3 days post treatment initiation. Blood was collected at BL and at days 1, 2, and 3 post treatment initiation.; SARS-CoV-2-infected Rhesus Macaque Study (n=18). 18 RMs were infected with SARS-CoV-2 (USA-WA/2020 strain) intratracheally and intranasally. To investigate the role of type I IFN in SARS-CoV-2 pathogenesis, 9 of these RMs received a four-day course of IFNmod (1mg/day, intramuscularly) beginning 1 day prior to infection (day-1) and ending on day 2 post infection while the remaining 9 control animals were untreated. Animals were necropsied at 2 days post infection (dpi), 4dpi, or 7dpi. Brochoalveolar lavage (BAL) fluid was collected before treatment was initiated and animals were infected (baseline (BL)), 2 days post infection (dpi), and, depending on necropsy date, at 4dpi and 7dpi. Blood was collected at BL and at days 1, 2, 4, 5 and 7dpi also depending on necropsy date.