Coronavirus disease 2019 and asthma, allergic rhinitis: molecular mechanisms and host–environmental interactions

Abstract

Purpose of review Coronavirus disease 2019 (COVID-19), a respiratory infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 virus), is a pandemic in over 120 countries worldwide. Risk factors for severe COVID-19 include older age, ethnicity, sex, comorbidities, and living conditions. Although asthmatics and those with allergies are susceptible to more severe outcomes to viral infections, interestingly, asthma has not been reported to be a major comorbidity of COVID-19. However, there are some conflicting reports on the impact of asthma on COVID-19. The underlying immunological and molecular mechanisms may explain at least in part these observations. Furthermore, environmental factors like air pollution that have detrimental effects on asthma and respiratory illnesses also have an impact on COVID-19. Recent findings Angiotensin-converting enzyme 2 (ACE2) is the receptor for the attachment and entry of SARS-CoV-2 into the host cells that is upregulated by Th1-mediated responses. In asthmatics, ACE2 gene expression is generally reduced and recent studies have shown a negative correlation between the levels of Th2 cytokines including IL-4, IL-5, and IL-13 in airway epithelial cells and other type 2 biomarkers with ACE2 expression. This may explain in part the potential protective role of asthma on COVID-19. Here, we review the relation of respiratory viral illnesses and asthma, the immune-molecular mechanisms of SARS-CoV-2 infection, the impact of asthma on COVID-19 and that of SARS-CoV-2 on asthma and allergic rhinitis, and the impact of environmental factors like air pollution on COVID-19. Summary Expression of ACE2 in airway epithelial cells in SARS-COV-2 is influenced by inflammatory profile. Respiratory allergic diseases like asthma appear to have a protective effect against SARS-COV-2 infection. However, the clinical association between asthma and SARS-COV-2 is not fully established and the underlying immune-molecular mechanisms may explain these observations.

Impact of the State of Emergency during the COVID-19 Pandemic in 2020 on Asthma Exacerbations among Children in Kobe City, Japan

“…Another interesting finding is that the number of patients with AE showed the usual increase in fall. COVID-19 itself has been reported to be related to AE [68,69]. However, in 2020, only a few COVID-19 cases in patients under 20 years of age were reported in Kobe (<10 years old, n = 3 (Apr), n = 7 (Jul), n = 20 (Aug), n = 7 (Sep), n = 6 (Oct), n = 12 (Nov), and n = 34 (Dec); ≥10 to <20 years old, n = 1 (Mar), n = 6 (Apr), n = 7 (Jul), n = 26 (Aug), n = 28 (Sep), n = 14 (Oct), n = 61 (Nov), and n = 71 (Dec)) (https:// www.city.kobe.lg.jp/a73576/kenko/health/infection/protection/covid_19.html; accessed on 14 August 2020).…”

The Impact of Coronavirus Disease 2019 on Pediatric Asthma in the United States

“… 7 Interestingly, these patients also tended to have higher known risk factors for COVID-19 including hypertension, lymphopenia, and male gender. 7 , 8 This suggest that T2-low phenotype is likely associated with higher risk for COVID-19. Another study of cohort of children with asthma, the urban environment and childhood asthma cohort (URECA), revealed that allergic sensitization in children (positive IgE tests for allergens either skin or serum testing) with asthma was associated with decreased ACE2 expression in children.…”

The study of COVID-19 infection following vaccination in patients with multiple sclerosis

“…Another study among pediatric population could not find any relation between history of allergic reactions and the risk of worse outcome COVID-19 ( Du et al, 2021 ). In a review, Wakabayashi and colleagues suggested that respiratory allergic diseases could inhibit severe inflammatory responses in COVID-19 ( Wakabayashi et al, 2021 ). On the other hand, in line with our study, a Korean cohort study found asthma and allergic rhinitis associated with severe COVID-19 ( Yang et al, 2020 ).…”