Chlamydia trachomatis, for which no vaccine is available, is the most common bacterial sexually transmitted disease. The study showed before that in TLR-4-based C. trachomatis serovar E (Ser E), the grade of phosphate substitution in an aluminium hydroxide adjuvant formulation had an impact on elicited antibody titers and IFN-α levels. Here, they have included these observations to the assessment of the influence on the bacterial challenge utilising outbreed CD-1 Mouse immunes from C. trachomatis Ser E rMOMP formulations.

The results indicated the highest neutralising antibody titers in the rMOMP vaccination with the most phosphate substitution, whereas a formula with the lowest phosphate substitution produced the highest IFN-β. Mice with formulations of the least substituted phosphate adjuvant have been shown to provide the most robust protection, as demonstrated by the numbers of mice with positive vaginal cultures, positive cultures, and number of recuperated C. trachomatis cells. This is the first report that immunisation of an outbred strain of rMOMP causes protection against C. trachomatis vaginal disorder.