Prevention of HIV transmission using a tenofovir disoproxil fumarate (TDF)-eluting intravaginal ring (IVR) is a complex and poorly understood interplay between transport of drug and virus throughout and within the tissues of the female reproductive tract (FRT). Sufficiently high drug levels must be achieved both throughout and within the tissues of the entire FRT to prevent viral infection. This work demonstrates that not only is virus capable of infecting the ovaries, but that an IVR is also sometimes capable of achieving low drug concentrations there as well, highlighting the complexity of transport within the FRT and the need for further experiments and modeling.
Three pigtail macaques were treated with TDF-IVRs for 28 days, and vaginally challenged with a high dose of a replicative SIVmac239 virus and a single round non-replicative SIV-based vector expressing Luciferase and mCherry reporter genes. In order to identify infection events the isolated FRT was treated with luciferin to detect Luciferase activity using IVIS. TFV and TFV-DP concentrations in tissue were quantified using LC-MS/MS, with 13C-labeled TFV used as an internal standard.
Infection events were detected in both ovaries in two animals and in one ovary of the third macaque using IVIS. TFV levels were found to be variable throughout the FRT, with the highest concentrations found in the upper vagina/lower cervical area, near the site of the ring. The concentration of TFV in the FRT of the macaques were in the range of 40-28,000 fmol/mg of tissue and the concentration of TFV-DP in the FRT of the macaques were in the range of 3-6000 fmol/mg of tissue.
Infection events were seen in the ovaries of all three macaques, possibly reflecting the variability of ovarian drug levels (range of 7-30 fmol TFV-DP/mg of tissue) and virus transport.