Replication of SARS-CoV Urbani (A) and GD03 (B) in the NT and lungs of mock-immunized hamsters and hamsters immunized with rSARS-CoV-ΔE or rSARS-CoV on days 2 and 5 postchallenge. Virus titers represent the mean from four hamsters per day. Error bars indicate standard errors. *, P < 0.05 (Kruskal-Wallis, Mann-Whitney U test). The lower limit of detection is 10^1.5 TCID₅₀/g tissue.

Hamster activity wheel use. (A) Activity of hamsters recorded on indicated days before (squares) and after intranasal immunization (arrow) for hamsters immunized with rSARS-CoV or rSARS-CoV-ΔE. n = 4 per group. Error bars indicate standard errors. The difference in the activity of hamsters that received rSARS-CoV-ΔE and the preimmunization activity of all hamsters was not significant (P = 0.32). The difference in the activity of hamsters that received rSARS-CoV and the preimmunization activity of all hamsters was significant (P < 0.005). (B) Activity of hamsters immunized with rSARS-CoV, rSARS-CoV-ΔE, or medium alone (L15; mock) recorded on indicated days before (squares) and after intranasal challenge with SARS-CoV Urbani (arrow). n = 4 per group. Error bars indicate standard error. The difference in the activity of hamsters that received rSARS-CoV-ΔE and the prechallenge activity of all hamsters was not significant (P = 0.23). The difference in the activity of hamsters that received rSARS-CoV and the prechallenge activity of all hamsters was significant (P < 0.005). The difference in the activity of hamsters that were mock immunized and the prechallenge activity of all hamsters was significant (P < 0.005).

Lung histopathology of normal (uninfected) (A), rSARS-CoV-immunized (B), rSARS-CoV-ΔE-immunized (C), and mock-immunized (D) hamsters 5 days after challenge with SARS-CoV Urbani. Hematoxylin and eosin staining. Magnification, ×20.