FIG. 3.

Prime-boost vaccination with live Y. pestis generates T cells that limit bacterial growth in vivo. CD4 and CD8 T cells (5 × 10⁶) were copurified from prime-boost-vaccinated mice, as well as naïve control mice, and transferred intravenously to naïve mice as described for Fig. 2. On the following day, all recipient mice were challenged intranasally with a lethal dose of KIM5 (2 × 10⁵ CFU). At 1, 3, and 5 days later, cohorts of mice were euthanatized and bacterial CFU in the lung (A), blood (B), spleen (C), and liver (D) were measured. Where indicated (*), significantly reduced bacterial CFU were observed in mice that received primed T cells compared with those that received naïve T cells (P < 0.0001; n = 5 mice/condition/time point except for the naïve T cells on day 5, where bacterial CFU were measured in the three mice that survived to that time). Error bars indicate standard deviations.