TABLE 2.
Passive transfer of immune serum protects naïve mice from replication of challenge virus in the respiratory tract
| Expt no. and dose of SARS-CoV (TCID50) | Passively transferred seruma | Neutralizing antibody titer in serumb | Mean prechallenge neutralizing anti- body titer in re- cipient mice | Virus replication in challenged mice
|
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|---|---|---|---|---|---|---|---|
| Lungs
|
Nasal turbinates
|
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| No. of mice infected/no. tested | Mean virus titerc ± SE | No. of mice infected/no. tested | Mean virus titer ± SE | ||||
| 1 (103) | Immune | 1:284 | 1:28 | 0/3 | ≤1.5 ± 0d | 2/3 | 3.2 ± 0.72 |
| Nonimmune | ≤1:4 | ≤1:4 | 2/3 | 3.9 ± 1.21 | 2/3 | 2.4 ± 0.32 | |
| 2 (104) | Immune, undiluted | 1:1,024 | 1:231 | 0/3 | ≤1.8 ± 0e* | 1/3 | 2.0 ± 0.17* |
| Immune, 1:10 dilution | 1:274 | 1:22 | 1/3 | 2.0 ± 0.17 | 2/3 | 3.3 ± 0.73 | |
| Nonimmune | ≤1:4 | ≤1:4 | 3/3 | 7.3 ± 0.14 | 3/3 | 5.6 ± 0.55 | |
a
Serum (200 μl) pooled from immunized or uninfected mice was administered to recipient mice by intraperitoneal injection in experiment 1, and 500 μl of the indicated serum preparation was administered to mice in experiment 2.
b
Titer of antibody that neutralized infectivity of 100 TCID50 of SARS-CoV.
c
Virus titers are expressed as log10 TCID50 per gram of tissue. *, P < 0.05 versus nonimmune control.
d
Virus not detected; this value represents the lower limit of detection of infectious virus in a 10% suspension.
e
Virus not detected; this value represents the lower limit of detection of infectious virus in a 5% suspension.