Table 4.

Correlation of antibody titres and protection of mice

(A)	ELISA antibody titre against the S protein (1:x)
	<100	100	400	1600	6,400	25,600	102,400	409,600
Total n of animals	56	7	8	18	28	30	19	2
N of infected animals	47	3	5	3	1	0	0	0
Infected animals (%)	84	43	63	17	4	0	0	0
(B)	Neutralising antibody titre (1:x)a
	<57	58–113	114–227	228–455	456–911	912–1823	1824–3646	>3647
Total n of animals	84	9	12	15	7	22	7	2
N of infected animals	28	1	0	0	0	0	0	0
Infected animals (%)	69	11	0	0	0	0	0	0

In total 168 mice (Balb/C and CD1) were challenged with SARS-CoV. Of the 36 control animals 32, i.e. 89%, became infected.

^aSera that contained no detectable neutralising antibodies are classified according to the detection limit of the respective assay, e.g. a serum with a titer of <1:71 is assigned to the category 114–227; n: number of animals.