Elucidation of HSV-1 and HSV-2 mucosal behavior in a new human genital organ culture for a better understanding and control of genital herpes

Abstract

Human genital herpes is worldwide one of the most prevalent causes of genital ulcer disease and with a prevalence reaching up to 80% (developing countries), one of the most important sexually transmitted diseases (STD’s). The principal causative agent is herpes simplex virus type 2 (HSV-2); however, the frequency of primary genital herpes infections caused by herpes simplex virus type 1 (HSV-1) is on the increase. No efficacious HSV-vaccine is present on the market, and the likelihood of one coming to market soon is low. In order to find novel antiviral strategies and vaccines, it is necessary to first get a fundamental image on how the virus breaches through the mucosal barrier. Therefore, we developed a human genital mucosa explant model (endocervix and ectocervix/vagina) to mimic HSV dissemination in genital mucosa. Firstly, special emphasis was put on maintenance of tissue morphology as well as tissue viability during in vitro culture up to 96h: (i) epithelial thickness, lamina reticularis thickness and connective tissue composition were evaluated using light microscopy; (ii) epithelial integrity and basement membrane continuity were examined on conservation by means of transmission electron microscopy; (iii) occurrence of apoptosis was monitored by TUNEL-assay. Next, an assessment on the susceptibility of these human genital mucosa explants to a herpes simplex virus infection was performed. We successfully visualized the evolution of HSV-1 and HSV-2 mucosal spread in genital mucosa at 0h, 12h, 24h, 48h and 72h pi in ectocervical and endocervical tissues. HSV clearly exhibited a plaquewise mucosal spread and induced prominent epithelial syncytia. Replication was found to be less prone in endocervical epithelium and to be hampered in intact ectocervical/vaginal epithelium. Starting from 48h pi, few epithelial viral plaques crossed the BM proving that the virus is able to breach a critical barrier, the basement membrane, and infiltrate the host.