Project Summary/Abstract
The acute respiratory distress syndrome (ARDS) was first formally described in 1967, but it has likely been the
predominant cause of death in pandemic viral infections for centuries. Now, the world is at grips with a new
pandemic from SARS-CoV-2, or COVID-19, which has infected over 100 million people worldwide resulting in
>2 million deaths. Central to the immunopathogenesis of ARDS is the role of neutrophils and neutrophil
activation, including the release of neutrophil chromatin into the extracellular space in a process termed
neutrophil extracellular traps, or NETs. Originally described as a form of host defense to inactivate pathogens,
NETs have emerged as a potentially maladaptive response to infections, producing substantial bystander injury
to tissues and serving as a nidus for coagulation. We have shown that NETs are produced in response to both
sterile and pathogen-induced acute lung injury (including Influenza A), and when neutralized, lung injury is
reduced without compromising microbial containment. We have also shown that NETs are increased in the
plasma of patients with ARDS and associate with more severe ARDS and ARDS mortality. Emerging reports
indicate that NETs are also present in the blood and lungs of COVID-19 patients. We are now positioned to
rapidly test the role of NETs in response to SARS-CoV-2 in this application, and to develop novel approaches to
neutralize NETs for therapeutic purposes. In Aim 1, we will challenge neutrophils with SARS-CoV-2 virus or
spike protein to determine the production of NETs and NET-induction molecular pathways. We hypothesize that
secreted neutrophil proteases and NETs themselves will cleave spike protein to prime for enhanced viral
pathogenesis. We will also embark on unbiased studies of neutrophil proteins using mass spectrometry to
determine novel pathways of neutrophil activation resulting from SARS-CoV-2, including from neutrophils
isolated from COVID-19 patients. In Aim 2, we will turn our attention to a mouse model of COVID-19 in which
mouse strains expressing human ACE2 will be challenged with SARS-CoV-2 and lung injury, NETs, and
systemic effects measured. We hypothesize that NETs will be produced and predominantly localize to the
alveolar spaces. We will use mice with gain and loss of function mutations in NET pathways (PAD4-/-, DNase1-
/-, DNase1L3-/-) to test for their pathogenicity in this model. In these studies, we will also test a novel DNase to
neutralize NETs into non-toxic mononucleosomes, which could be rapidly deployed to COVID-19 patients.
Finally, we will test for the role of NET-associated platelet activation, complement activation, and coagulation
responses, and therapeutic strategies to mitigate these systemic effects. In summary, these studies will establish
new knowledge on neutrophil activation and the definitive role of NETs in COVID-19 and identify therapeutic
approaches to target NETs in SARS-CoV-2-induced ARDS.