Fig. 4.

Survival rate and lung virus titer of mice intranasally (IN) immunized with SARS S protein vaccine or SARS VLP vaccine after SARS-CoV lethal challenge. Mice were immunized (IN) with vehicle, 0.8 μg or 4 μg of SARS S protein or SARS VLPs, without adjuvant, on day 0 and 21 (n = 14 or 15). Mice were challenged with 2 LD₅₀ of SARS-CoV strain v2163 on day 42. Five mice per group were sacrificed on day 45. Lung tissues were collected and assayed for virus titer. The remaining mice were monitored for survival and body weight from day 42 to day 63. (A) Survival percentage curve; (B) survival table with the mean day of death; (C) animal weight change for 21 days after challenge; (D) lung SARS-CoV titer at day 45, 3 days post challenge. Virus titer was calculated as log₁₀ CCID₅₀/gram lung tissue. Results were expressed as mean titer ± SEM. Statistical significance between the vehicle and vaccine groups was determined by the student t test. ***p < 0.001.