HIF-dependent induction of alveolar miR-147 dampens SARS-CoV-2 immune evasion (preprint)

Acute respiratory distress syndrome (ARDS) causes significant morbidity and mortality during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections1,2. Nevertheless, most patients with coronavirus disease 2019 (COVID-19) recover seamlessly without developing ARDS3, suggesting the existence of endogenous pathways to protect the lungs. Since many microRNAs (miRNAs) serve important roles in endogenous regulatory pathways, we pursued functional roles of miRNAs in COVID-19-ARDS. A screen of miRNAs in human alveolar epithelia or mice infected with SARS-CoV-2 identified miR-147 as a lead candidate. Transcriptional analysis implicated hypoxia-inducible factor 1A (HIF1A) in miR-147 induction during alveolar injury or SARS-CoV-2 infection. Functionally, mice with alveolar epithelial deletion of miR-147 showed increased lung injury in response to SARS-CoV-2 infection. mRNA sequencing and subsequent in silico miR-147-target analysis revealed reduced antiviral responses and identified SARS-CoV-2 ORF8 as a direct miR-147 target. Moreover, mice infected with SARS-CoV-2 and treated with miR-147 packaged in DOPC nanoliposomes showed significant protection with enhanced antiviral responses and improved survival. Finally, proof-of-principle studies in patients with COVID-19 highlighted this pathway in human SARS-CoV-2-associated ARDS. Together, our findings identify a previously unrecognized role of miR-147 in lung protection during viral pneumonia by attenuating immune evasion of SARS-CoV-2.

Biochemical, Biophysical, and Immunological Characterization of Respiratory Secretions in Severe SARS-CoV-2 (COVID-19) Infections (preprint)

Thick, viscous respiratory secretions are a major pathogenic feature of COVID19 disease, but the composition and physical properties of these secretions are poorly understood. We characterized the composition and rheological properties (i.e. resistance to flow) of respiratory secretions collected from intubated COVID19 patients. We find the percent solids and protein content are greatly elevated in COVID19 compared to heathy control samples and closely resemble levels seen in cystic fibrosis, a genetic disease known for thick, tenacious respiratory secretions. DNA and hyaluronan (HA) are major components of respiratory secretions in COVID19 and are likewise abundant in cadaveric lung tissues from these patients. COVID19 secretions exhibit heterogeneous rheological behaviors with thicker samples showing increased sensitivity to DNase and hyaluronidase treatment. In histologic sections from these same patients, we observe increased accumulation of HA and the hyaladherin versican but reduced tumor necrosis factor stimulated gene 6 (TSG6) staining, consistent with the inflammatory nature of these secretions. Finally, we observed diminished type I interferon and enhanced inflammatory cytokines in these secretions. Overall, our studies indicate that increases in HA and DNA in COVID19 respiratory secretion samples correlate with enhanced inflammatory burden and suggest that DNA and HA may be viable therapeutic targets in COVID19 infection.