Resolution of genital C. muridarum challenge after intranasal CPAF-plus-IL-12 immunization. HLA-DR4 tg, C57BL/6, and MHC-IIΔ/Δ animals (five mice/group) were treated i.n. with CPAF plus IL-12 or PBS (mock) on days 0, 14, and 28, rested for 1 month, and then challenged i.vag with 1,500 IFU of C. muridarum. Vaginal chlamydial shedding was monitored at 3-day intervals. (A) Numbers of chlamydial IFU recovered from vaginal swabs at the indicated days after genital challenge. Each bar represents the mean ± SD for the animal group. *, significant difference between indicated groups (P < 0.01, Kruskal-Wallis test); ♣, significant difference in chlamydial recovery from CPAF-plus-IL-12-vaccinated or mock-immunized (PBS) MHC-IIΔ/Δ animals and all other groups (P < 0.01, Kruskal-Wallis test). (B) Percentage of animals shedding Chlamydia after genital challenge. Significant differences were detected in the time required for resolution of infection between challenged CPAF-plus-IL-12-vaccinated HLA-DR4 tg or C57BL/6 mice and all other experimental groups (P < 0.001, Kaplan-Meier test). Results are representative of two independent experiments.