Microbicide excipients can greatly increase susceptibility to genital herpes transmission in the mouse

Abstract

BackgroundSeveral active ingredients proposed as vaginal microbicides have been shown paradoxically to increase susceptibility to infection in mouse genital herpes (HSV-2) vaginal susceptibility models and in clinical trials. In addition, "inactive ingredients" (or excipients) used in topical products to formulate and deliver the active ingredient might also cause epithelial toxicities that increase viral susceptibility. However, excipients have not previously been tested in susceptibility models.MethodsExcipients commonly used in topical products were formulated in a non-toxic vehicle (the "HEC universal placebo"), or other formulations as specified. Twelve hours after exposure to the excipient or a control treatment, mice were challenged with a vaginal dose of HSV-2, and three days later were assessed for infection by vaginal lavage culture to assess susceptibility.ResultsThe following excipients markedly increased susceptibility to HSV-2 after a single exposure: 5% glycerol monolaurate (GML) formulated in K-Y® Warming Jelly, 5% GML as a colloidal suspension in phosphate buffered saline, K-Y Warming Jelly alone, and both of its humectant/solvent ingredients (neat propylene glycol and neat PEG-8). For excipients formulated in the HEC vehicle, 30% glycerin significantly increased susceptibility, and a trend toward increased HSV-2 susceptibility was observed after 10% glycerin, and 0.1% disodium EDTA, but not after 0.0186% disodium EDTA. The following excipients did not increase susceptibility: 10% propylene glycol, 0.18%, methylparaben plus 0.02% propylparaben, and 1% benzyl alcohol.ConclusionsAs reported with other surfactants, the surfactant/emulsifier GML markedly increased susceptibility to HSV-2. Glycerin at 30% significantly increased susceptibility, and, undiluted propylene glycol and PEG-8 greatly increased susceptibility.

Electrospun Solid Dispersions of Maraviroc for Rapid Intravaginal Preexposure Prophylaxis of HIV

“…It is possible that much lower concentrations could be used to preserve the beneficial effects of Tween on drug release rates while minimizing concerns about toxicity. Our in vitro testing of surfactant cytotoxicity shows that Tween 20 and Tween 80 are tolerated 10 times better than glycerol monolaurate (shown to be safe in macaques [36] but potentially harmful in mice [37]) and 50 times better than nonoxynol-9 by TZM-bL cells, with an LD 50 for Tween 20 of 0.24% (wt/vol) in cell culture medium. The in vivo toxicity of electrospun fibers containing small amounts of Tween 20 remains to be evaluated.…”

The Effect of Commonly Used Excipients on the Epithelial Integrity of Human Cervicovaginal Tissue

“…Previously, Grammen et al and Moench et al evaluated the effect of excipients on cervicovaginal tissue by using in vitro cell lines and a mouse model. 19,20 However, the baseline thickness of the epithelial layers, the types of epithelial cells present in the tissue, as well as the type and abundance of tight junction proteins are quite different between intact human cervicovaginal tissue and these preclinical models. 34,35 These differences affect the interpretation of previous findings, and they limit their applicability toward optimizing clinically applied vaginal PrEP products.…”

“…8,28,29 Although identified as generally-regarded-as-safe excipients by the Food and Drug Administration (FDA), several of these excipients were reported to affect the epithelial barrier in human cell culture or animal models. [18][19][20][21] Excipients chosen for evaluation represent a variety of functional categories and diverse chemical structures. The excipient concentration used in this study (Table 2) was determined based on the following considerations: Disodium EDTA is widely reported to decrease the integrity of intestinal cell monolayer (Caco-2) 30 and excised intestinal epithelium, 31 so three concentrations (0.05%, 0.1%, and 1%) were chosen to cover the relevant levels of use.…”

“…18 Several other tissue explant and mouse studies reported that treatment with excipients that are frequently used in vaginal products could alter the cervicovaginal tissue integrity and even increase the rate of vaginal herpes simplex virus 2 (HSV-2) transmission. [19][20][21] McClelland et al evaluated the effect of vaginal washing on the incidence of HIV-1 infection in 1,270 African women between 1993 and 2003. They found that women who partake in vaginal washing, by vaginal douching or washing with water and soap, had higher HIV acquisition risk as compared with women who did not perform vaginal washing.…”

“…These excipients are commonly used in vaginal formulations, and some of them are reported to affect certain aspects of the epithelial barrier. 19,20 The effect on epithelial integrity was evaluated by analyzing the transepithelial electrical resistance (TEER), tissue morphology (hematoxylin & eosin [H&E] staining), paracellular permeability (mannitol flux), and cell viability ([1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan] (MTT) assay), with or without excipients. Finally, the effect of excipients on tissue susceptibility to HIV-1 infection was tested in an explant model by using an ex vivo cultured human ectocervix.…”