Fig 2.

Immunization with the YopE_69-77 peptide mediates protection against lethal Y. pseudotuberculosis challenge. Groups of C57BL/6 mice were immunized with YopE_69-77 peptide plus CT or with CT alone, as described in the legend of Fig. 1. (A, B) Seventeen days after the last immunization, the mice received 5 × 10⁹ CFU of 32777 (10 LD₅₀s) i.g. (A) At 5 days postchallenge, cohorts of mice were euthanized, and the percentages of YopE_69-77-specific CD8 T cells among total CD8 T cell populations in the indicated organs from either CT- or peptide-plus-CT-immunized mice were determined by flow cytometry and tetramer staining. (B) Bacterial colonization levels in the indicated organs were determined by CFU assay (number of log₁₀ CFU/organ) at 5 days postchallenge. Each symbol represents the value obtained from one mouse. The limit of detection was log₁₀ CFU of 1.7. The data shown are the summary of two independent experiments with cohorts of 2 to 3 mice. By Mann-Whitney test, “*” indicated P values of less than 0.05, while “**” indicates P values of less than 0.01 compared to CT-immunized mice. (C) Survival of immunized mice that were challenged was followed for 28 days. Numbers in parentheses indicate the number of mice in the treatment group. The data shown are from one experiment. The P value obtained by log rank test is indicated.