Respiratory allergy, asthma and controlled allergen exposure were associated with significantly reduced gene expression in a protein that the coronavirus uses to infect cells with COVID-19, according to a new study by the University of Wisconsin School of Medicine and Public Health.
The study, published online April 22 in the Journal of Allergy and Clinical Immunology, suggests a possible reason why people with respiratory allergy and asthma do not seem to experience some of the more severe and life-threatening manifestations of the COVID-19 disease. Importantly, previous studies have shown that higher expression of ACE2 is associated with smoking, diabetes, and hypertension — all of which are known risk factors for COVID-19 disease severity.
Viral respiratory infections are the most common trigger of severe asthma exacerbations in children and adults, and it was widely assumed that the novel coronavirus would be no different. Unexpectedly, reports out of China found that asthma and respiratory allergies were not significant risk factors for severe COVID-19 illness in that country. As a result, UW researchers hypothesized that reduced ACE2 gene expression might be one of the contributing reasons why.
“We were surprised to learn that the COVID-19 pandemic in China did not seem to impact people with asthma as severely as we would’ve expected it to,” said Daniel Jackson, MD, lead investigator and associate professor of pediatrics and medicine at UW School of Medicine and Public Health. “Knowing that other risk factors for severe COVID-19 illness like hypertension and obesity lead to increased ACE2 expression, we wanted to determine if patients with allergies and asthma could have reduced ACE2 gene expression as a potential explanation for this unexpected early finding from the outbreak.”