ACE2 and COVID-19: To discern the physiological relevance of this finding to the development of COVID-19, we transfected U-251 MG cells with an increasing dose of ACE2 (0.1, 0.125, 0.25, 0.5, 1, and 2 μg) or a negative control vector for 24 h, then stimulated the cells with poly (I:C), or IFNα for an additional 10 h.