FIG 3.

Effect of oral immunization with attenuated Chlamydia on subsequent challenge infection by wild-type Chlamydia in the genital tract. Female C57BL/6J mice orally inoculated with SPG (controls a and b) (n = 7) or mutant C. muridarum (CMmut at an inoculum dose of 1 × 10⁷ IFUs) (c and d, n = 6) as immunization for 28 days. Both groups of mice were then intravaginally challenged with 2 × 10⁵ IFUs of wild-type C. muridarum (CMwt). All mice were monitored for live chlamydial organisms from both the genital tract (vaginal swabs) (a and c) and gastrointestinal tract (rectal swabs) (b and d) on days 3, 7, and weekly thereafter following the challenge infection. The results were expressed as Log₁₀ IFUs per swab (Y-axis). On day 56, all mice were sacrificed for observing genital tract pathology. Hydrosalpinx was visually evaluated (e 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 image (e1, e2, f1, and f2). Both the hydrosalpinx incidence (along with group sample size) and severity score from each group were listed under the corresponding group images. The same excised genital tract tissues were further processed for monitoring oviduct dilation under microscopy (g and h). After H&E staining, tissue sections of the genital tissues were first examined for the overall appearance of the oviduct tissues under a 4× objective lens. Representative normal oviduct cross-section was labelled with a “$” sign, ovary with “&” and uterine horn tissue with “#” while dilated oviducts were indicated with the white double arrowhead arrows. Both hydrosalpinx (e and f) and oviduct dilation (g and h) were semiquantitatively measured as described the materials and method section. Data were from two independent experiments. Note that mice orally immunized with CMmut were protected from genital tract infection (*, P < 0.05; **, P < 0.01, Wilcoxon for comparing IFUs at different time points; a versus c) and pathology (Wilcoxon for comparing scores while Fisher’s Exact for comparing incidence rates).