Fig. 4

EGCG inhibits live SARS-CoV-2 and HCoV OC43 infection. a Human lung epithelial cells (Calu-3) were treated with EGCG (50,100 μM) before or after live SARS-CoV-2 (isolate USA-WA1/2020, NR-52281, BEI Resources) infection at MOI = 0.5. Cells were washed 3 times with pre-warmed medium to remove free virus at 1 h post-infection, and then maintained in complete medium containing EGCG for 36 h. Supernatants were collected and plaque assay was carried out using Hela-ACE2 cells. b Cells from (a) were lysed and subjected to western blot to detect SARS-CoV-2 N protein. c HEK293T-hACE2 cells were pre-treated with EGCG (100 μM) for 30 min prior to live SARS-CoV-2 infection at MOI = 0.55 or 0.275. After 1 h virus adsorption in the presence of EGCG, the cells were washed twice with pre-warmed medium, and then maintained in complete medium containing EGCG for 48 h. SARS-CoV-2 RNA copies from culture supernatant were determined at 48 h post-infection by RT-qPCR. d HCT-8 cells (susceptible cells for HCoV OC43) were pre-treated with catechins at indicated dose for 30 min prior to HCoV OC43 infection at MOI = 0.1. After 2 h virus adsorption, the cells were washed twice with pre-warmed medium, and then maintain in complete medium containing EGCG. e HCT-8 cells were treated with EGCG (50,100 μM) before or after live HCoV OC43 infection at MOI = 0.1. After 2 h virus adsorption, the cells were washed twice with pre-warmed medium, and then maintain in complete medium containing EGCG. Intracellular HCoV OC43 RNA were determined at day 4 post-infection by qRT-PCR. Data are shown as mean ± SD, representative of two independent experiments with 3 replicates. *P < 0.05, **P < 0.01, ***P < 0.001