Protective capacity of low-dose MVA immunization is lost in the absence of CD8+ T cells. (A) C57BL/6 mice (WT) and mice depleted of CD8+ T cells were challenged with ECTV 2 days after immunization with MVA (105 PFU) or PBS (mock-vaccinated mice) (5 per group). Error bars indicate SEMs, and the numbers of surviving/total animals are given in parentheses. ***, P < 0.001. (B) Virus titers in livers and spleens after lethal ECTV infection. At the time of death or at the end of the experiments (day 21 for wt MVA-vaccinated mice), spleens and livers were removed and homogenized, and the amount of virus was determined by plaque assays (3 to 5 animals per group). Error bars indicate SEMs, and data are representative of at least two independent experiments. n.d., not detectable.