In the new coronavirus, it is well known that ACE2 is the main receptor. The results of a detailed investigation of the expression status of ACE2 in human have been reported.
https://www.nature.com/articles/s41467-020-19145-6
Ace2 is said to be expressed in the nasopharynx, lungs, small intestine, kidneys, and testes by gene expression analysis, but immunostaining using ACE2 antibodies shows that ACE2 is relatively less expressed in the lungs than in other organs. In addition, ACE2 seems to be expressed in a fairly locally expressed in motile cilia on epithelial cells of the Upper respiratory tract.
On the other hand, it was also found that the expression level of ACE2 was little correlated with age, gender, and smoking. The administration of drugs such as Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARBs) used in the treatment of hypertension, which is a concern for SARS-CoV-2 infections, was also found to have no effect on ACE2 expression.
Therefore, as for the prevention and severity of the new coronavirus (COVID-19), the followings are pointed out as a conclusion.
(1) SARS-CoV-2 inhibitors in the oral nasal cavity are effective in preventing infection,
(2) The expression level of ACE2 itself has nothing to do with the severity of COVID-19.