Background Numerous microbicides that inactivate Chlamydia trachomatis in vitro have failed to prevent transmission of this pathogen in the pigtailed macaque cervical challenge model. Since C trachomatis replicates in endocervical columnar epithelium but not in the squamous vaginal epithelium, we tested whether a cervical barrier would improve protection when used in conjunction with an otherwise non-protective microbicide.

Methods Miniature diaphragm-like cervical barriers were manufactured and provided by ReProtect, Inc. BufferGel, previously found ineffective in this model when used alone, was also provided by ReProtect, Inc. Twenty-four pigtailed macaques were randomly assigned to one of three study arms: cervical barrier device alone; cervical barrier with BufferGel; or no barrier device and no gel (control arm). Eight animals were enrolled in each arm. Each macaque underwent baseline exam, product administration if applicable, cervical challenge with C. trachomatis (E: 5×105 IFU), and weekly follow-up exams for 5 weeks. Chlamydia challenge occurred within 30 min of baseline exams. Cervical barrier devices were removed from all test macaques 18 h after insertion. Each exam included cervicovaginal colposcopy, vaginal pH and cervical swabs for chlamydia detection (culture and NAAT: GenProbe Aptima Combo2). Blood for serum antibody testing was collected at baseline and weeks 2 though five post-inoculation.

Results Detection of chlamydial infection is detailed in the Abstract O4-S2.04 table 1 below. Colposcopic exams were comparable across each of the three test arms of the study, and thus did not detect toxic effects of the gel or the cervical barrier. Baseline vaginal pH was somewhat higher in the No Product arm than in either of the test arms. After chlamydial challenge and throughout the duration of the study, mean vaginal pH remained lowest in the barrier with BufferGel arm, but were similar (within 1 pH unit) in all three study arms.

Conclusions In this pilot study, a cervical barrier used alone provided little or no protection, but the barrier used with BufferGel reduced transmission by 50% (p=0.08). These results should encourage further study of the ability of a cervical barrier combined with a microbicide to provide greater protection against sexually transmitted infections than either used alone.