Dr Su Ling Loo

Background: The mechanisms underlying altered susceptibility and propensity to severe Coronavirus disease 2019 (COVID-19) disease in at-risk groups such as patients with chronic obstructive pulmonary disease (COPD) are poorly understood. Inhaled corticosteroids (ICSs) are widely used in COPD, but the extent to which these therapies protect or expose patients to risk of severe COVID-19 is unknown. Objective: The aim of this study was to evaluate the effect of ICSs following pulmonary expression of the SARS-CoV-2 viral entry receptor angiotensin-converting enzyme-2 (ACE2). Methods: We evaluated the effect of ICS administration on pulmonary ACE2 expression in vitro in human airway epithelial cell cultures and in vivo in mouse models of ICS administration. Mice deficient in the type I IFN-a/ß receptor (Ifnar1-/-) and administration of exogenous IFN-ß were used to study the functional role of type-I interferon signaling in ACE2 expression. We compared sputum ACE2 expression in patients with COPD stratified according to use or nonuse of ICS. Results: ICS administration attenuated ACE2 expression in mice, an effect that was reversed by exogenous IFN-ß administration, and Ifnar1-/- mice had reduced ACE2 expression, indicating that type I interferon contributes mechanistically to this effect. ICS administration attenuated expression of ACE2 in airway epithelial cell cultures from patients with COPD and in mice with elastase-induced COPD-like changes. Compared with ICS nonusers, patients with COPD who were taking ICSs also had reduced sputum expression of ACE2. Conclusion: ICS therapies in COPD reduce expression of the SARS-CoV-2 entry receptor ACE2. This effect may thus contribute to altered susceptibility to COVID-19 in patients with COPD.

The recurrent emergence of novel, pathogenic coronaviruses (CoVs) severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1; 2002), Middle East respiratory syndrome (MERS)-CoV (2012), and most recently SARS-CoV-2 (2019) has highlighted the need for physiologically informative airway epithelial cell infection models for studying immunity to CoVs and development of antiviral therapies. To address this, we developed an in vitro infection model for two human coronaviruses; alphacoronavirus 229E-CoV (229E) and betacoronavirus OC43-CoV (OC43) in differentiated primary human bronchial epithelial cells (pBECs). Primary BECs from healthy subjects were grown at air-liquid interface (ALI) and infected with 229E or OC43, and replication kinetics and time-course expression of innate immune mediators were assessed. OC43 and 229E-CoVs replicated in differentiated pBECs but displayed distinct replication kinetics: 229E replicated rapidly with viral load peaking at 24 h postinfection, while OC43 replication was slower peaking at 96 h after infection. This was associated with diverse antiviral response profiles defined by increased expression of type I/III interferons and interferon-stimulated genes (ISGs) by 229E compared with no innate immune activation with OC43 infection. Understanding the host-virus interaction for previously established coronaviruses will give insight into pathogenic mechanisms underpinning SARS-CoV-2-induced respiratory disease and other future coronaviruses that may arise from zoonotic sources.

Patients with frequent exacerbations represent a chronic obstructive pulmonary disease (COPD) subgroup requiring better treatment options. The aim of this study was to determine the innate immune mechanisms that underlie susceptibility to frequent exacerbations in COPD. We measured sputum expression of immune mediators and bacterial loads in samples from patients with COPD at stable state and during virusassociated exacerbations. In vitro immune responses to rhinovirus infection in differentiated primary bronchial epithelial cells (BECs) sampled from patients with COPD were additionally evaluated. Patients were stratified as frequent exacerbators (=2 exacerbations in the preceding year) or infrequent exacerbators (<2 exacerbations in the preceding year) with comparisons made between these groups. Frequent exacerbators had reduced sputum cell mRNA expression of the antiviral immune mediators type I and III interferons and reduced interferon-stimulated gene (ISG) expression when clinically stable and during virus-associated exacerbation. A role for epithelial cellintrinsic innate immune dysregulation was identified: induction of interferons and ISGs during in vitro rhinovirus (RV) infection was also impaired in differentiated BECs from frequent exacerbators. Frequent exacerbators additionally had increased sputum bacterial loads at 2 wk following virus-associated exacerbation onset. These data implicate deficient airway innate immunity involving epithelial cells in the increased propensity to exacerbations observed in some patients with COPD. Therapeutic approaches to boost innate antimicrobial immunity in the lung could be a viable strategy for prevention and treatment of frequent exacerbations.