Fig. 3.

(a) The locations of four synthetic peptides on SARS-CoV spike protein sharing sequence homology with human proteins are indicated. (b) Binding ability of SARS patient sera to spike peptides. SARS patient sera (from a pool of five patients) or healthy control sera (from a pool of five healthy controls) were 1 : 20 diluted and added to the wells coated with spike protein S2 domain, D02, D03, D07, or D08 peptides. ELISA was performed for the detection of the binding activity of patient or healthy control sera to these peptides. Experiments were carried out in duplicate, and the averages are shown. (c) Blockage of A549 cell binding ability by spike peptides. SARS patient sera or healthy control sera were preabsorbed with 10 µg S2, D02, D03, D07, or D08 peptides overnight at 4 °C before incubated with A549 cells. The binding activity of patient or healthy control sera to A549 cells was determined by flow cytometry. Experiments were carried out in duplicate, and the averages are shown. *P < 0·05, **P < 0·01, ***P < 0·001.