Expression of SARS-CoV-2 entry receptors in the respiratory tract of healthy individuals, smokers and asthmatics

SARS-CoV-2 is causing a pandemic with currently > 29 million confirmed cases and > 900,000 deaths worldwide. The locations and mechanisms of virus entry into the human respiratory tract are incompletely characterized. We analyzed publicly available RNA microarray datasets for SARS-CoV-2 entry receptors and cofactorsACE2,TMPRSS2,BSG (CD147)andFURIN. We found thatACE2andTMPRSS2are upregulated in the airways of smokers. In asthmatics,ACE2tended to be downregulated in nasal epithelium, andTMPRSS2was upregulated in the bronchi. Furthermore, respiratory epithelia were negative for ACE-2 and TMPRSS2 protein expression while positive for BSG and furin, suggesting a possible alternative entry route for SARS-CoV-2.