Figure 3

The production of IFN-γ induced by mutated S366–374. BALB/c mice were immunized by SARS CoV S DNA vaccine and splenocytes were prepared as described previously[7]. Each amino acid residue in S366–374 was replaced by alanine (A), lysine (K), or aspartic acid (D). The 27 distinct S366–374 mutants were used to stimulate splenocytes. (A) After incubation for 14–18 h, the frequency of IFN-γ spot forming unit (SFU) was detected by ELISPOT. (B) After incubation for 72 h, supernatants were collected and levels of IFN-γ were detected by ELISA. “0” represent unstimulated control. KYGVSATKL was a scrambled peptide control. Experiments were performed in duplicate and representative results are shown.