Figure 6. Protective efficacy of L2R immunized mice against C. trachomatis serovar D challenge.

Thirty sham (O) and 30 L2R immunized mice (●) were intravaginally challenged with 4.3×10⁴ IFU/mouse (10 ID₅₀) of serovar D. We chose serovar D as the challenge strain because it is one of the most prevalent serovars associated with human urogenital infection and it is antigenically related to L2. (A) Vaginal swabs from serovar D challenged mice were cultured for recoverable IFU on 3, 7, 10, 14 and 28 dpi. Forty-six days after mice cleared their primary D infection they were re-challenged a second time with serovar D. Each symbol represents the mean number of recoverable IFUs ± SEM. Note that L2R immunized mice were not protected from serovar D colonization. There was a significant difference between L2R and sham immunized mice in the burden of D shedding at days 3 and 7 post-challenge (p<0.0001). However, the burden and duration of infection did not differ between the groups at day 14-28. Interestingly, sham immunized mice that had been infected and then re-challenge with serovar D exhibited near sterilizing immunity. In contrast, L2R immunized and serovar D challenged mice were less protected. All mice in this group were infected following challenge. The numbers of culture positive mice for each group of re-challenged mice are shown in (B) serovar D primary challenge, and (C) serovar D secondary challenge.