Table 1.

Antibody responses of antisera obtained two weeks after 3 doses of different formulation of rlipoA-RBD in the mouse, rabbit and hamster immunogenicity studies

Immunogenicity studies			Anti-A-rRBDIgG titer of pooled sera	Neutralization titer of pooled sera againsta
				TcdA	TcdB
Mouse	A-rRBD (μg)	0	<100	<4	<4
		3	3.5 × 103	32	<4
		10	2.7 × 104	256	<4
		30	5.3 × 104	128	<4
	rlipoA-RBD (μg)	0.3	2.3 × 105	512	<4
		3	2.3 × 105	512	<4
		10	3.3 × 105	512	4
		30	2.5 × 105	1024	4
	TcdA toxoidb (μg)	10	7.7 × 104	256	<4
Rabbit	A-rRBD (μg)	10	2.3 × 105	128	<4
	rlipoA-RBD (μg)	10	7.7 × 105	512	<4
	TcdA toxoidb (μg)	10	7.7 × 104	2048	<4
Hamster	A-rRBD (μg)	10	3.7 × 104	128	<4
	B-rRBD (μg)	10	2 × 103	8	64
	rlipoA-RBD (μg)	10	5.7 × 105	512	8
	A-rRBD (μg) + B-rRBDc (μg)	10	2.7 × 104	32	16
	rlipoA-RBD (μg) + B-rRBD (μg)	10	7.7 × 105	512	64
	A-rRBD (μg) + B-rRBD (μg) + alumc	10	4.3 × 105	64	64
	A-rRBD (μg) + B-rRBD (μg) + Pam3CSK4d	10	1.7 × 105	32	8

^aNeutralization titer of pooled sera against toxins was defined as the highest diluted sample which could protect against 50 % cell rounding induced by toxins

^bMouse antibody responses to 3 doses of 10 μg of TcdA toxoid. The immunogenicity studies were performed and described in previous report [30]

^cHamster antibody responses to 3 doses of 10 μg of each A-rRBD (μg) and B-rRBD formulated with 300 μg of alum

^dHamster antibody responses to 3 doses of 10 μg of each A-rRBD (μg) and B-rRBD formulated with 10 μg of Pam3CSK4