ABSTRACT
Background: Systemic and local inflammation following SARS-CoV-2 infection has been widely described and predictive of disease severity and death. However, the exact immune mediators driving inflammation contributing to SARS-CoV-2 host defense vs. those driving immune-mediated pathology in humans have not been fully elucidated. Deficiencies in type-I interferon (IFN-I) responses, including inborn errors to genes in the IFN-I pathway, neutralizing auto-antibodies against all subtypes of IFN-I, or the lack of production of IFN-I, are associated with severe COVID-19 in otherwise healthy individuals. Conversely, sustained IFN-I responses have been shown to contribute to severe COVID-19 by exacerbating inflammation, and prolonged IFN-I signaling has been shown to interfere with lung repair following viral infection and to increase susceptibility to bacterial infections. Thus, it is critical to understand the roles of IFN-I signaling in COVID-19 to design therapeutic strategies. Methods: Here, we modulated IFN-I signaling in rhesus macaques (Macaca mulatta;RMs) from day-1 through day 2 post SARS-CoV-2 infection (dpi) using an IFN-I antagonist (IFNant). Eighteen RMs (9 control and 9 IFNant treated) were infected with SARS-CoV-2 on day 0, with 6 RMs sacrificed at 2, 4, and 7dpi. Nasal and throat swabs were collected for viral load;blood and bronchoalveolar lavage fluid (BAL) for flow cytometry and RNAseq. Results: IFNant treatment prior to infection resulted in a highly significant and consistent reduction in SARS-CoV-2 viral load in the lower airways (>3-log difference;2dpi BAL) and upper airways (nasal and throat swabs). Treatment with IFNant initiated also potently reduced: (i) soluble markers of inflammation in BAL, (ii) expansion of inflammatory monocytes (CD14+CD16+), and (iii) pathogenesis in the lung. Furthermore, Siglec-1 expression, which has been shown to enhance SARS-CoV-2 infection, was rapidly downregulated in the lung and in monocytes of IFNant-treated RMs. Remarkably, RNAseq analysis showed a robust reduction in pathways associated with inflammation and decreased levels of interferon-stimulated genes post-infection in treated RMs. Thus, IFNant treatment prior to infection resulted in limited viral replication, inflammation, and pathogenesis in SARS-CoV-2-infected RMs. Conclusion: These data indicate a vital, early role of IFN-I in regulating COVID-19 progression and emphasize the importance of understanding IFN-I pathways in COVID-19 for the development of targeted therapeutic strategies.
ABSTRACT
Background: The emergence of SARS-CoV-2 and COVID-19 pandemic has placed an excessive burden on public and private healthcare systems with over 1,400,000 deaths worldwide. Thus, therapeutics aimed at mitigating disease severity are urgently needed. Immunological features of COVID-19 progression include an influx of innate and adaptive immune cells to the lung, with severe cases having elevated levels of pro-inflammatory cytokines and chemokines. Baricitinib is an oral, selective inhibitor of JAK 1/2 with potent antiinflammatory activity approved for patients with moderate to severe active rheumatoid arthritis and predicted to have anti-SARS-CoV-2 effects based on in silico modeling. Methods: 8 rhesus macaques (RMs) were infected with 1.1x10 6 PFU SARSCoV- 2;at 2 days post infection (dpi), 4 of the 8 RMs began daily baricitinib treatment (4 mg/day). Nasal and throat swabs were collected daily for viral load;longitudinal blood and bronchoalveolar lavage (BAL) samples were collected for viral load, flow cytometry, cytokines and RNAseq analysis and at 10/11 dpi all RMs were euthanized for pathological analyses. Results: Baricitinib was found in plasma and in the lungs of all treated RMs and was safe and well tolerated. Viral replication dynamics measured from nasal and throat swabs, BAL and lung at necropsy were not reduced with baricitinib. Innate Type-I IFN antiviral responses and adaptive SARS-CoV-2- specific T-cell responses remained similar between the two groups. RMs treated with baricitinib showed reduced inflammation (ferritin, CRP, histology), T cell immune activation and proliferation, neutrophil NETosis activity, and lung pathology, with decreased type 2 pneumocyte hyperplasia, peribronchiolar hyperplasia, and inflammatory cell infiltration. Importantly, baricitinib treated RMs had a rapid and remarkably potent suppression of alveolar macrophage production of cytokines (IL-6, TNFa, IL-10, IL-1b and IFNb1) and chemokines (CCL4L1, CXCL10, CXCL3 and CXCL8) responsible for a pro-inflammatory environment and for the recruitment of neutrophil and pro-inflammatory monocytes. Additionally, we identified that a population of MARCOmacrophages are the primary producers of pro-inflammatory cytokines and are reduced in the lungs of baricitinib treated animals. Conclusion: These data provide rationale and mechanistic insight for the use of baricitinib as a frontline therapeutic to reduce systemic inflammation induced following SARS-CoV-2 infection.