FIG 5.
V3526S protects aged mice from lethal SARS-CoV disease. (A to C) Percent weight loss (A) and survival curve (B) of aged mice immunized with S protein-based vaccines from V3000S (black; n = 10), V3526S (blue; n = 12), V3014S (gray; n = 6), or control (VRP HA; dashed; n = 7) challenge with 105 PFU of SARS-CoV MA15. (C) Lung virus titers at 2 days postinfection and 4 days postinfection, determined by plaque assay on Vero cells. V3000S (black; n = 6 [day 2], 3 [day 4]), V3526S (blue; n = 5 [day 2], 3 [day 4]), V3014S (gray, n = 3), and control (VRP HA; white; n = 4 [day 2], 3 [day 4]) are shown. Error bars indicate SEM. *, P < 0.05; ***, P < 0.001 (Student's t test). (D) Representative H&E-stained lung sections harvested 4 days postinfection from the indicated vaccine groups showing lungs, alveoli, and airway vasculature at lower (40×) and higher (400×) magnification. Note clean airways in V3526S and V3000S groups, as indicated by green arrows, and denuded airways in V3014S (green arrow). Note the massive inflammatory infiltrates (yellow arrows) in V3014S and VRP-HA groups, which are reduced in V3526S and V3000S groups.