TABLE 1.

Composition and immunogenicity in mice of S. flexneri type 2a O-SP–protein conjugates^a

Polysaccharide and carrier protein	Conjugate composition		Levels (EU/ml of serum) of:
	SA/protein	O-SP/protein (wt/wt)	Anti-LPS		IgG anti-protein
			IgGb	IgM
O-SP–CRM9	None	0.86	0.93 A	1.70	1.50
O-SP–CRM9SA	1:10	1.70	8.27 B	10.1	0.30
O-SP–CRM9SA	1:10	0.39	3.21 C	28.3	2.40
O-SPSA–CRM9	None	1.11	5.24 D	2.63	3.72
O-SPSA–CRM9	None	0.81	2.59 E	6.17	8.51
O-SPSA–CRM9SA	1:10	2.65	6.02	2.53	2.16
O-SPSA–CRM9SA	1:10	1.34	5.45	6.17	2.0
O-SP–rEPA	None	0.86	0.34 F	8.40	724
O-SP–rEPASA	1:5	0.60	0.25 G	16.4	385
O-SPSA–rEPA	None	0.92	0.60 H	5.04	4.95
O-SPSA–rEPASA	1:5	1.16	2.38	7.62	18.6

^aGroups of 10 5-week-old mice were injected subcutaneously with 2.5 μg of O-SP in 0.1 ml of saline on days 0, 14, and 28. Serum samples were taken 7 days after the second and third injections, assayed for IgG and IgM anti-LPS and IgG anti-protein by ELISA (see Materials and Methods), and expressed as geometric mean ELISA units with a standard antiserum arbitrarily assigned a value of 100 EU. Antibody levels only after the third injection are depicted. 

^bB versus A, P = 0.01; B versus F, P = 0.005; B versus G, P = 0.0008; C versus G, P = 0.03; D versus H, P < 0.05; D, E versus H, P < 0.05.