FIG. 7.

CTL activity observed in chimpanzee PBMCs at boost and following challenge. CTL activity is shown at the time of the booster immunization (−2 weeks postchallenge), 1 week later (−1 week), at the time of challenge (0 weeks), and 2 weeks postchallenge. Data were not recorded if the spontaneous lysis of target cells was greater than 30%. Values shown are for effector-to-target cell ratios of 100:1. No lysis of control targets infected with the vaccinia virus β-galactosidase construct over spontaneous levels was observed in these experiments.