Bioluminescence imaging of live animals was performed with an IVIS Lumina LT series III system (Perkin Elmer, Waltham, MA) as previously described (16 (link)). Infected mice were anesthetized with isoflurane, and Xenolight d-luciferin substrate (Perkin Elmer) was injected i.p. (150 μg/g body weight) 8 to 10 min prior to live imaging. Animals remained under isoflurane sedation for the duration of each imaging session, which occurred at various times postinfection until death or total virus clearance was achieved. Luminescent exposures were collected for 1 to 60 s with small or medium binning factors and various f-stop settings. Living Image Software (Perkin Elmer) was used for acquisition and analysis. For photon flux, a single region of interest was drawn around the entire body, and light emission was measured in photons per second per square centimeter per steradian.