Pathogenic effect of Trichomonas vaginalis on various cell lines in vitro.
Trichomoniasis has been linked to pelvic inflammatory disease, cervical cancer, increased HIV transmission, infertility as well as co-infections with other STIs. In 2002, an association was found with Trichomonas vaginalis and PID in HIV positive women. Therefore, the question arose whether T. vaginalis is able to invade the upper genital tract of HIV infected women. A prerequisite for invasion of the upper genital tract is the capability of the organism to adhere to the cells of the organs involved. This study therefore investigated the interaction between T. vaginalis and vaginal, cervical and endometrial cells. In comparing adhesion and cytotoxicity of T. vaginalis to cells of the upper and lower genital tract at different pH, immortalized vaginal (VK2), cervical (ME 180) and endometrial (KLE) cells were exposed to a standardized inoculum of trichomonads at pH 4.5 to 7.0. Adhesion was measured microscopically after acridine orange staining and cytotoxicity was established by measuring LDH release using a commercial kit. Adhesion of the ME-180 and VK2 cell lines was found to be pH dependent. However, the KLE cell line was not. As the pH increased, adherence to the vaginal and cervical cells decreased. Adhesion to endometrial cells was minimal at neutral pH but marked adhesion was found at lower pH. For the vaginal cell line, cytotoxicity was minimal at pH 4.5 but substantial (30 to 60%) at higher pH. In contrast, cytotoxicity on cervical and endometrial cells was highest at lower pH. The pronounced toxicity of vaginal epithelial cells at pH 5 and pH 5.5 is in keeping with the pH range found in patients with vaginitis. The observations on the cervical epithelium suggest toxic effect on the ecto-cervical epithelium immediate after acquisition of the infection. Adhesion of trichomonads to the endometrial cell line suggests that T. vaginalis is capable of colonization of the upper genital tract. At pH values applicable to the in vivo situation, toxicity was very low.