Pulmonary inflammation is a prominent manifestation of ARDS, and neutrophils in BALF correlate with the disease severity.22,23 We found a markedly elevated number of neutrophils around airway and perivascular sites, infiltrating to the pulmonary parenchyma and to the alveolar with increased MPO activities on 3 dpi, especially in treated hACE2 mice (Fig. 2a, c, d). Here, MPO is linked to acute respiratory distress syndrome.