Table 1.

Summary of postchallenge analyses of normal control rabbits and rabbits immunized with either the T. pallidum Gpd or the pET-3a vector

ImmunizationNo. of rabbitsLesion typeTime of lesion appearance (days)No. of lesions ulceratingMaximum lesion diameter (mm) (mean ± SD)bNo. of dark-field-microscopy-positive aspirates VDRL titer (5 weeks postchallenge)No. of dark-field-microscopy-positive rabbits in tissue transfer assay
RangeMean ± SDPer rabbitPer lesionRangeMean
None (control)5Typical12–1614 ± 0.824/3015.0 ± 1.64/421/244–3216NDe
Gpd5Atypical7–97.1 ± 0.5a0/30a8.8 ± 2.5a0/3c0/18a2–84d3/3
pET-3a vector4Typical14–1515.4 ± 3.77/2414.1 ± 2.03/411/244–85.6d3/3c
  • a P < 0.0001 compared with either normal or vector-immunized control animals (statistical analyses performed using the Student t test for the time of lesion appearance and analysis of variance with repeated measures for the number of lesions ulcerating and the lesion aspirate dark-field-microscopy analysis).

  • b Further postchallenge analyses were performed only on the four rabbits contained within the second protection experiment.

  • c One rabbit from each of the Gpd- and vector control-immunized groups was euthanized during the course of the experiment.

  • d P < 0.02 compared with normal control animals (statistical analysis performed using the Student t test).

  • e ND, not determined.