Table 2.

Neutralizing antibody titers for different forms of spike polypeptide-based vaccines against SARS-CoV

Groups	Neutralizing antibody titers (no. of mice)
	<1:20	1:20	1:40	1:80	1:160	1:320	1:640	≥1:1280
1 (S-peptide)	6	0	0	0	0	0	0	0
2 (S-DNA-control)	6	0	0	0	0	0	0	0
3 (tPA-S-DNA)	0	2	0	0	4	0	0	0
4 (tPA-S-DNA boosted with S-peptide)	0	0	0	0	0	0	0	6
5 (CTLA4-S-DNA)	0	4	2	0	0	0	0	0
6 (CTLA4-S-DNA boosted with S-peptide)	0	0	0	0	0	0	0	6
7 (Salmonella-S-DNA-control)	6	0	0	0	0	0	0	0
8 (Salmonella-S-DNA-control boosted with S-peptide)	0	2	0	4	0	0	0	0
9 (Salmonella-tPA-S-DNA)	4	2	0	0	0	0	0	0
10 (Salmonella-tPA-S-DNA boosted with S-peptide)	2	1	2	1	0	0	0	0
11 (Salmonella-CTLA4-S-DNA)	5	1	0	0	0	0	0	0
12 (Salmonella-CTLA4-S-DNA boosted with S-peptide)	2	2	1	0	1	0	0	0