Virulence and viral growth of SARS-CoV-∆E after serial passage in mice.

<p>16-week-old BALB/c mice were intranasally inoculated with 100,000 pfu of wt, ΔE and ∆E-8a-dup viruses. (A) Weight loss and survival were monitored for 10 days. Data represent two independent experiments with 5 mice per group. (B) Viral titer in lungs was determined at 2 and 4 days post infection (n = 3, each day). Error bars represent standard deviations. Statistically significant data are indicated with one asterisk (<i>P</i> < 0.05). (C) Lung tissue sections from mice infected with the different recombinant viruses were prepared and stained with hematoxylin and eosin at 2 and 4 dpi. Three independent mice per group were analyzed. Original magnification was 20x and representative images are shown. (D) 16-week-old BALB/c mice were intranasally inoculated with 100,000 pfu of wt or ΔE-8a-dup viruses and were monitored daily for weight loss and survival.