In a study published on April 22, 2020 in JACI, data from ITN’s CATEEC clinical trial was used to investigate the connection between asthma and allergic disease and the novel coronavirus, SARS-CoV2 (COVID-19). The virus that leads to COVID-19, which has caused a global pandemic, uses the cell receptor angiotensin-converting enzyme-1 (ACE2) to enter human cells and cause infection. Interestingly, while several underlying respiratory conditions have been identified as risk factors for developing COVID-19 illness, asthma and allergy has been unexpectedly underrepresented in early epidemiologic studies of severe COVID-19 illnesses. The authors of this manuscript utilized three recent allergy and asthma studies to determine whether ACE2 expression differs in those with allergy and asthma.
The ITN’s CATEEC study was designed to directly compare allergic responses to cat allergen delivered by environmental exposure chamber (EEC) or nasal allergen challenge (NAC) in order to better understand and employ these methods as allergy evaluation tools. Nasal epithelial cells were collected pre and post-allergen challenge as part of the study and were used in conjunction with airway epithelial cells from two other recent allergy and asthma clinical studies to investigate whether allergy and asthma are associated with reduced ACE2 expression.
The CATEEC samples demonstrated a significant reduction in ACE2 expression following allergen challenge by both NAC and EEC. Similarly, in the Urban Environment and Childhood Asthma (URECA) study, participants who were more sensitive to allergen had lower ACE2 expression in nasal epithelial cells. The third study included adults with mild asthma who had significantly reduced ACE2 expression following allergen exposure in bronchial epithelial cells.
This work demonstrates that allergy and allergen exposure both reduce expression of ACE2, which might reduce the risk of severe COVID-19 disease. Additional research investigating how allergic inflammation may regulate COVID-19 pathogenesis could identify new prevention and treatment approaches to more effectively control the COVID-19 pandemic.