ACE2 and infection: We infected human lung epithelial cell line Calu-3 and HeLa cells expressing ACE2 (HeLa-ACE2) with SARS-CoV-2, and then examined the phosphorylation of STING at Ser366 (phospho-STINGSer366), a hallmark of STING activation.26 At 8 h post infection, phospho-STINGSer366 was barely detected in Calu-3 and HeLa-ACE2 cells, while after infection for 16 h, both cell lines showed robust STINGSer366 phosphorylation (Fig. 1a, b).