FIG 1.
Effect of intravaginal immunization with an attenuated Chlamydia on subsequent challenge infection by wild-type Chlamydia. Groups of female C57BL/6J mice were intravaginally inoculated with SPG buffer (Ctrl, n = 8) (a); or a mutant C. muridarum (CMmut at an inoculum dose of 2 × 105 inclusion forming units or IFUs, n = 8) (d) as immunization for 56 days. Subsequently, both groups of mice were intravaginally challenged with wild-type C. muridarum (CMwt at an inoculum dose of 2 × 105 IFUs) (b and e). All mice were monitored for live Chlamydia burdens in the genital tract by taking vaginal swabs on days 3, 7, and weekly thereafter (X-axis) following the immunization (Panels a and d) and challenge infection (b and e), respectively. The number of live organisms recovered from each vaginal swab was expressed as log10IFUs (Y-axis). Then, 56 days after the challenge infection, all mice were sacrificed for observing hydrosalpinx (c and f). Only one representative image of the entire genital tract was shown for each group. Oviducts positive for hydrosalpinx were marked with white arrows. The magnified images of oviduct/ovary regions (with hydrosalpinx scores indicated in white numbers) were shown on the right of the overall genital tract image. Both the hydrosalpinx incidence (along with group sample size) and severity score from each group were listed next to the corresponding group images. *, P < 0.05; **, P < 0.01 (Fisher’s exact for comparing incidences while Wilcoxon for scores or IFUs). Data were from two or three independent experiments. Note that intravaginal immunization with CMmut induced significant protection against both infection and pathogenicity of CMwt.