Rectal use of a 1% tenofovir (TFV) gel is currently being evaluated for HIV prevention. While careful assessment of mucosal safety of candidate microbicides is a primary concern, tools to assess mucosal toxicity are limited. Mass spectrometry-based proteomics is a sensitive and high throughput technique that can provide in-depth information on inflammation processes in biological systems. Here we utilized a proteomics approach to characterize mucosal responses in study participants involved in a phase 1 clinical trial of a rectal TFV-based gel. Project Gel was a phase 1 randomized (1:1), double-blind, multi-site, placebo-controlled trial in which 24 participants received rectal TFV or a universal placebo (HEC) over a course of 8 daily doses. Rectal mucosal swabs were collected after 0, 1 and 8 doses and were analyzed by label-free tandem mass spectrometry. Differential protein expression was evaluated using a combination of paired (time-effects), unpaired (across study arm) t-tests, and multivariate (LASSO) modelling. Within the TFV arm, 7% (17/249, p<0.05) and 10% (25/249, p<0.05) of total proteins changed after 1 and 8 daily applications of TFV gel, respectively, compared to 3% (7/249, p<0.05) and 6% (16/249, p<0.05) in the HEC arm. Biofunctional analysis associated TFV use with a decrease in epidermal barrier proteins (adj. p=1.21x10-10). Multivariate modelling identified 13 proteins that confidently separated TFV gel users (100% calibration and 96% cross-validation accuracy), including the epithelial integrity factors (FLMNB, CRNN, CALM), serpins (SPB13, SPB5) and cytoskeletal proteins (VILI, VIME, WRD1). This study suggested that daily rectal applications of a 1% TFV gel may be associated with mucosal proteome changes involving epidermal development. Further assessment of more extended use of TFV-gel usage is recommended to validate these initial associations.
Rectal 1% tenofovir gel use associates with altered epidermal protein expression.