Microbial biofilms on the surface of intravaginal rings worn in non-human primates

Abstract

Millions of intravaginal rings (IVRs) are used by women worldwide for contraception and for the treatment of vaginal atrophy. These devices also are suitable for local and systemic sustained release drug delivery, notably for antiviral agents in human immunodeficiency virus pre-exposure prophylaxis. Despite the widespread use of IVRs, no studies have examined whether surfaceattached bacterial biofilms develop in vivo, an important consideration when determining the safety of these devices. The present study used scanning electron microscopy, fluorescence in situ hybridization and confocal laser scanning microscopy to study biofilms that formed on the surface of IVRs worn for 28 days by six female pig-tailed macaques, an excellent model organism for the human vaginal microbiome. Four of the IVRs released the nucleotide analogue reverse transcriptase inhibitor tenofovir at a controlled rate and the remaining two were unmedicated. Large areas of the ring surfaces were covered with monolayers of epithelial cells. Two bacterial biofilm phenotypes were found to develop on these monolayers and both had a broad diversity of bacterial cells closely associated with the extracellular material. Phenotype I, the more common of the two, consisted of tightly packed bacterial mats approximately 5 mm in thickness. Phenotype II was much thicker, typically 40 mm, and had an open architecture containing interwoven networks of uniform fibres. There was no significant difference in biofilm thickness and appearance between medicated and unmedicated IVRs. These preliminary results suggest that bacterial biofilms could be common on intravaginal devices worn for extended periods of time.

Pharmacokinetics and Preliminary Safety Study of Pod-Intravaginal Rings Delivering Antiretroviral Combinations for HIV Prophylaxis in a Macaque Model

“…Mucosal levels of the proinflammatory cytokines remained stable throughout the study period in all animals, with no statistically significant changes being observed as a result of the IVRs. This is typical and has been observed previously in pig-tailed macaques with pod-IVRs (15,24).…”

“…The study timeline and biological sample collection points are shown in Fig. 2 and employed published protocols (15,24). Briefly, six sexually mature female pig-tailed macaques (Macaca nemestrina) were used; three received TDF-FTC IVRs (Table 1), and three received TDF-FTC-MVC IVRs.…”

“…The swabs were characterized for the presence of aerobic and anaerobic microorganisms. Details on the methods used to assess vaginal microbiota have been provided elsewhere (24). Histopathological assessments of vaginal biopsy samples (1 biopsy sample each collected proximal and distal to the IVR for each animal at both day 22 and day 31, for a total of 24 samples) preserved in 10% formalin were carried out at Charles River Laboratories (Pathology Associates, Frederick, MD).…”

Pharmacokinetic and Safety Analyses of Tenofovir and Tenofovir-Emtricitabine Vaginal Tablets in Pigtailed Macaques

“…For microflora analysis, vaginal swabs were collected from each macaque, placed into a Port-ACul tube, and transported on ice within 24 h of collection to MageeWomen's Research Institute (Pittsburg, PA) for microbial culture analysis. The presence of anaerobic and aerobic microorganisms was determined as described previously (19).…”

Simian-Human Immunodeficiency Viruses and Their Impact on Non-Human Primate Models for AIDS

“…Safety analyses of macaque-sized elastomeric silicone and polyurethane intravaginal rings (IVRs) loaded with candidate ARV drugs were tested in pig-tailed macaques in four studies ranging in duration from 49 to 73 days with retention of the IVR being 28 days in each study. The presence of IVRs not only made of silicone but other polymers such as, polyurethane in pig-tailed macaques does not cause an alteration longitudinally in the levels of the proinflammatory cytokines locally or systemically and in the vaginal microbiological patterns [225,226]. Efficacy studies in the NHP model with IVRs are just beginning, but preliminary pharmacokinetic studies are very promising [227][228][229][230][231][232][233][234][235].…”