FIG. 3.

Rev.1 vaccination by the i.n. route provides protection in the lungs of mice infected with B. melitensis 16 M. Groups of mice were challenged with a retained dose of 4 × 10³ CFU of B. melitensis 16 M. Two groups had previously been immunized with the Rev.1 vaccine by either the s.c. or i.n. route. At 2, 3, or 4 weeks postchallenge, B. melitensis 16 M was recovered from the lungs of nonimmunized, s.c. Rev.1-immunized, and i.n. Rev.1-immunized mice. One-way ANOVA was used to compare bacterial numbers of B. melitensis 16 M in the lungs of nonimmunized mice to the numbers in the lungs of those immunized by the s.c. or i.n. route. Error bars show standard deviations. Statistical significance values for individual immunization routes are as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001.