Table 3.

Protection from virus replication in the mouse respiratory tract after transfer of the anti-SARS-CoV antibody S3.1

Passive transfer antibody	Virus replication in challenged mice
	Lungs		Nasal turbinates
	No. infected/no. tested	Mean (±s.e.m.) virus titer	No. infected/no. tested	Mean (±s.e.m.) virus titer
S3.1 sup	0/4	≤1.5 ± 0	4/4	4.8 ± 0.32
S3.1, 800 μg	0/4	≤1.5 ± 0	2/4	2.5 ± 0.47
S3.1, 200 μg	0/4	≤1.5 ± 0	4/4	3.4 ± 0.41
S3.1, 50 μg	2/4	3.2 ± 1.36	4/4	4.8 ± 0.75
M12, 800 μg	4/4	7.5 ± 0.1	4/4	6.4 ± 0.41

The indicated amounts of purified antibody (in 500 μl) or S3.1 culture supernatant (sup; 2 ml, 10 μg/ml) were administered to recipient mice by intraperitoneal injection 24 h before intranasal challenge with 10⁴ TCID₅₀ SARS-CoV. Monoclonal antibody M12 (human IgG1,κ) was injected as a negative control. Virus titers measured after 2 d are expressed as log₁₀ TCID₅₀ per gram of tissue. The lower limit of detection of infectious virus in a 10% w/v suspension of lung homogenate was 1.5 log₁₀TCID₅₀ per g and in 5% w/v suspension of nasal turbinates was 1.8 log₁₀TCID₅₀ per g. Comparisons that were statistically significantly different (P < 0.05) in a Student's t-test were: in lungs, 800 μg S3.1 versus 800 μg M12, 200 μg S3.1 versus 800 μg M12, and 50 μg S3.1 versus 800 μg M12; in nasal turbinates, 800 μg S3.1 versus 800 μg M12 and 200 μg S3.1 versus 800 μg M12.