Fig 2. VACV challenge of IL-15-treated CAST mice.

(A) CAST mice were treated with IL-15 or PBS as in Fig 1 and challenged IP with 460 PFU of VACV expressing FLuc on days 1, 3 and 5 after cessation of IL-15 administration. The progress of infection was measured by injecting luciferin and measuring luminescence. Ventral view images of surviving mice are shown on the indicated day post-infection using the same exposure time and binning factor, which was insufficient to show the low levels of luminescence seen at higher exposure in some mice. Red, blue and purple denote intensity of luminescence from high to low. Days of death or euthanasia (†) are indicated. (B) Total photon flux (photons per second per square centimeter per steradian) of the entire mouse was calculated and shown for each individual. Bars indicate geometric means. Protection of IL-15 treated mice was shown in three independent experiments.