Does type 2 airway inflammation protect against COVID-19?
Allergic airway disease patients appear to be underrepresented among COVID-19 patients. This could be partly attributed to the low ACE2 expression detected in allergic patients, with or without concomitant asthma.46 Furthermore, allergen challenge, which induces T helper (Th)-2 inflammation, has been shown to reduced ACE2 expression in a murine model of asthma, and ACE2 expression was inversely associated with type 2 biomarkers (IL-13, IgE, exhaled nitric oxide fraction).47 These results are in line with previous work showing that decreased ACE expression in the airway epithelium of asthmatic subjects was associated with eosinophilic inflammation.48 Altogether, these data suggest that type 2 airway inflammation may reduce the susceptibility of SARS-CoV-2 infection by reduction of ACE2 expression.