A convenient cell fusion assay for the study of SARS‐CoV entry and inhibition

SARS‐CoV spike (S) protein‐mediated cell fusion is important for the viral entry mechanism and identification of SARS‐CoV entry inhibitors. In order to avoid the high risks involved in handling SARS‐CoV and to facilitate the study of viral fusion mechanism, we established the cell lines: SR‐COS7 cells that stably express both SARS‐CoV S protein and red fluorescence protein, R‐COS7 cells that stably express red fluorescence protein, and AG‐COS7 cells that stably express both ACE2 and green fluorescence protein, respectively. When SR‐COS7 cells or R‐COS7 cells were cocultured with AG‐COS7 cells, syncytia with yellow fluorescence were conveniently observed after 12 h in SR‐COS7 cells plus AG‐COS7 cells, but not in R‐COS7 cells plus AG‐COS7 cells. The cell‐to‐cell fusion efficiency was simply determined for quantitative analysis based on the number of syncytium detected by flow cytometry. Such new cell‐to‐cell fusion model was further assessed by the potent HR2 peptide inhibitor, which led to the obvious decrease of the cell‐to‐cell fusion efficiency. The successful fusion and inhibition of cell‐based binding assay shows that it can be well used for the study of SARS‐CoV entry and inhibition. iubmb Life, 58: 480 ‐ 486, 2006