Sodium dodecyl sulfate and C31G as microbicidal alternatives to nonoxynol 9: Comparative sensitivity of primary human vaginal keratinocytes

A broad-spectrum vaginal microbicide must be effective against a variety of sexually transmitted disease pathogens and be minimally toxic to the cell types found within the vaginal epithelium, including vaginal keratinocytes. We assessed the sensitivity of primary human vaginal keratinocytes to pote ntial topical vaginal microbicides nonoxynol-9 (N-9), C31G, and sodium dode cyl sulfate (SDS). Direct immunofluorescence and fluorescence-activated cel l sorting analyses demonstrated that primary vaginal keratinocytes expresse d epithelial cell-specific keratin proteins. Experiments that compared vagi nal keratinocyte sensitivity to each agent during a continuous, 48-h exposu re demonstrated that primary vaginal keratinocytes were almost five times m ore sensitive to N-9 than to either C31G or SDS. To evaluate the effect of multiple microbicide exposures on cell viability, primary vaginal keratinoc ytes were exposed to N-9, C31G, or SDS three times during a 78-h period. In these experiments, cells were considerably more sensitive to C31G than to N-9 or SDS at lower concentrations within the range tested. When agent conc entrations were chosen to result in an endpoint of 25% viability after thre e daily exposures, each exposure decreased cell viability at the same const ant rate. When time-dependent sensitivity during a continuous 48-h exposure was examined, exposure to C31G for 18 h resulted in losses in cell viabili ty not caused by either N-9 or SDS until at least 24 to 48 h. Cumulatively, these results reveal important variations in time- and concentration-depen dent sensitivity to N-9, C31G, or SDS within populations of primary human v aginal keratinocytes cultured in vitro. These investigations represent init ial steps toward both in vitro modeling of the vaginal microenvironment and studies of factors that impact the in vivo efficacy of vaginal topical mic robicides.