Asthma and COVID-19 pandemic: focus on the eosinophil count and ACE2 expression

Currently, the world is engaged with a coronavirus disease 2019 (COVID-19) caused by acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infection. The Center for Disease Control and Prevention (CDC) has proposed moderate to severe asthma as a risk factor for COVID-19 susceptibility and severity. However, current evidences have not identified asthma in the top 10 comorbidities associated with COVID-19 fatalities. It raises the question that why patients with different type of asthma are not more vulnerable to SARS-CoV-2 infection like other respiratory infection. Increased number of eosinophils and elevated angiotensin-converting enzyme 2 (ACE2) expressions in asthma are supposed as two mechanisms which associated with decreased COVID-19 susceptibility in asthmatics. Some studies have been performed to evaluate two mentioned factors in asthmatic patients compared with healthy individuals. Herein, we address these mechanisms and investigate whether ACE2 and eosinophil could protect asthmatic patients against SARS-CoV-2 infection.