Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) preferentially infects airway epithelial cells. This infection is mediated by the binding of SARS-CoV-2 spike (S) protein to ACE2 expressed on target cells. Patients with allergic (type-2) asthma have been reported to be less susceptible to coronavirus disease 2019 (COVID-19), but these effects are controversial and mechanistically unclear. We previously showed lower expression of ACE2 mRNA in airway epithelial cells from type-2 asthmatics compared to healthy donors. Moreover, we and others demonstrated that the type-2 cytokine interleukin 13 (IL-13) suppresses ACE2 expression and SARS-CoV-2 infection in human epithelial cells. To better understand the relationship between type-2 inflammation, ACE2 expression, and SARS-CoV-2 infection, we investigated the effects of IL-13 on critical steps of epithelial cell infection by SARS-CoV-2: S protein-mediated binding to ACE2 on epithelial cells, and ACE2-mediated SARS-CoV-2 entry into these cells. Recombinant IL-13 significantly inhibited both these processes. This inhibition appeared to be mediated by IL-13-induced suppression of ACE2 transcription because IL-13 failed to affect S protein-mediated viral entry into cells that express ACE2 under the control of an IL-13 unresponsive heterologous promoter. We propose that IL-13 protects epithelial cells from SARS-CoV-2 infection largely by inhibiting ACE2 expression and ACE2-mediated downstream events that allow the virus to access its cellular targets.