A Study of the Potential of the Pig as a Model for the Vaginal Irritancy of Benzalkonium Chloride in Comparison to the Nonirritant Microbicide PHI-443 and the Spermicide Vanadocene Dithiocarbamate

Abstract

A porcine model was established to test the mucosal toxicity potential of a thiophene thiourea (PHI-443)-based anti-HIV microbicide and a vanadocene-based spermicide, vanadocene dithiocarbamate (VDDTC) in comparison to benzalkonium chloride (BZK). Nine domestic pigs (Duroc) in nonestrus stage received a single intravaginal application of 2% BZK, 2% PHI-443, or 0.1% VDDTC-containing gel. At various times after gel application, cell differentials and levels of inflammatory cytokines (IL-1β, IL-4, IL-6, IL-8, IL-10, IL-18, IFN-γ , and TNF-α) in cervicovaginal lavage (CVL) fluid were monitored by flow cytometry and ELISA, respectively. Eight pigs were exposed intravaginally to a gel with and without BZK or VDDTC for 4 consecutive days and vaginal tissues were scored histologically for inflammation using a new scoring system. Only CVL fluid from pigs exposed to BZK showed a significant increase of IL-1β, IL-8, and also IL-18 production when compared to the controls, PHI-443 or VDDTC-treated groups. Maximum levels of BZK-induced IL-1β (100-fold), IL-8 (2,500-fold), IL-18 (80-fold), and IFN-γ (10-fold) were found at 24 hours. In the in vivo porcine vaginal irritation model, increased levels of vaginal IL-1β, IL-8, and IL-18 were associated with histological changes consistent with vaginal inflammation. These results demonstrate that key cervicovaginal inflammatory cytokines are useful in vivo biomarkers for predicting the mucosal toxicity potential of vaginal products in the physiologically relevant and sensitive porcine model.

Vaginal Chitosan Tablets with Clotrimazole—Design and Evaluation of Mucoadhesive Properties Using Porcine Vaginal Mucosa, Mucin and Gelatine

“…Porcine vaginal mucosa was used for simulation of vaginal mucoadhesion due to similarity of porcine and human vaginas in terms of anatomical structure, pH, vaginal secretion and cervical mucus production. 32) Comparative studies of human and porcine vaginal mucosa revealed similarities in the morphology-both possess a nonkeratinized, stratified and squamous surface epithelium differentiated only in thickness (human: about 150-200 µm, porcine: 116 µm) and demonstrated the striking similarities in barrier composition and permeability. 19) Moreover, experiments with porcine mucosa application allow to replace highly expensive and requiring Bioethics Committee approval in vivo studies.…”

The Effect of β-Glycerophosphate Crosslinking on Chitosan Cytotoxicity and Properties of Hydrogels for Vaginal Application

“…The mechanism of mucoadhesion involves a contact stage between the mucoadhesive and mucosal layer and a subsequently consolidation stage, that comprises several physicochemical interactions (including van der Waals and hydrogen bonds or electrostatic interactions) which strengthen the material-mucin connection, providing intimate and prolonged adhesion [49]. Porcine vaginal mucosa was used for the imitation of vaginal mucoadhesion due to the similarity of porcine and human vaginas in terms of anatomical structure, pH, and vaginal secretion [50]. The effect of CS concentration and β-GP crosslinking on the force of detachment (F max ) and work required to overcome the hydrogel-porcine vaginal mucosa interaction (W ad ) is presented in Figure 5A,B.…”

Mucosal safety of PHI-443 and stampidine as a combination microbicide to prevent genital transmission of HIV-1

“…Rabbits have a simple cuboidal or columnar epithelium that is highly sensitive to mucosal irritants when compared to the stratified squamous epithelium of the human vagina and remains the FDA-approved animal model for testing the acceptability of vaginal microbicides (36). In the rabbit model, repeated intravaginal administration of PHI-443 plus stampidine by a gel formulation at concentrations nearly 2,000 and 10,000 times higher than their respective in vitro anti-HIV IC 50 values did not result in vaginal irritation.…”