Sensitive methods to detect epithelial disruption: tests for microhemorrhage in cervicovaginal lavages.

The toxic effects of topical microbicides might include epithelial disruption, and if sufficiently severe, may cause visible bleeding. We have developed two sensitive methods to detect hemorrhage far below the visual detection threshold: an enzyme-linked immunosorbent assay for human hemoglobin and a method for staining and enumerating red blood cells by fluorescent microscopy. We have applied these methods to cervicovaginal and introital lavages, and found them to be sensitive and quantitative over a broad range. Comparing the new techniques with a standard heme-detection assay (Hemastix) we found them to be more sensitive, more objective, more fully quantitative, and more likely to be indicative of recent events. In pilot studies we found that the red blood cell and hemoglobin concentrations in samples taken in the luteal phase of the menstrual cycle are low, but still within the detection range of the new assays, providing a quantifiable baseline from which increases in blood from epithelial disruption can be detected and quantified. We propose that these new methods may be used for the safety assessment of microbicides by detecting and quantifying microhemorrhage in cervicovaginal secretions before and after exposure to microbicide.

Growth of Neisseria gonorrhoeae in the female mouse genital tract does not require the gonococcal transferrin or hemoglobin receptors and may be enhanced by commensal lactobacilli.

Neisseria gonorrhoeae is capable of utilizing a variety of iron sources in vitro, including human transferrin, human lactoferrin, hemoglobin, hemoglobin-haptoglobin complexes, heme, and heterologous siderophores. Transferrin has been implicated as a critical iron store for N. gonorrhoeae in the human male urethra. The demonstration that gonococci can infect the lower genital tracts of estradiol-treated BALB/c mice in the absence of human transferrin, however, suggests that other usable iron sources are present in the murine genital tract. Here we demonstrate that gonococcal transferrin and hemoglobin receptor mutants are not attenuated in mice, thereby ruling out transferrin and hemoglobin as essential for murine infection. An increased frequency of phase variants with the hemoglobin receptor "on" (Hg(+)) occurred in ca. 50% of infected mice; this increase was temporally associated with an influx of neutrophils and detectable levels of hemoglobin in the vagina, suggesting that the presence of hemoglobin in inflammatory exudates selects for Hg(+) phase variants during infection. We also demonstrate that commensal lactobacilli support the growth of N. gonorrhoeae in vitro unless an iron chelator is added to the medium. We hypothesize that commensal lactobacilli may enhance growth of gonococci in vivo by promoting the solubilization of iron on mucosal surfaces through the production of metabolic intermediates. Finally, transferrin-binding lipoprotein (TbpB) was detected on gonococci in vaginal smears, suggesting that although gonococci replicate within the genital tracts of mice, they may be sufficiently iron-stressed to express iron-repressible proteins. In summary, these studies support the potential role of nontransferrin, nonhemoglobin iron sources during gonococcal infection of the female genital tract.

Vaginal transmission of cell-associated HIV-1 in the mouse is blocked by a topical, membrane-modifying agent.

Because both HIV-1 virions and HIV-infected cells are present in the semen and cervical mucus of infected individuals, HIV-1 prevention strategies must consider both cell-free and cell-associated virus. Antibodies that target HIV-1 virions have been shown to prevent vaginal transmission of cell-free virus in macaques, but since cell-associated transmission has not been reliably demonstrated in this model system, no strategies to prevent such transmission have been tested. We have employed a mouse model in which SCID mice carry human peripheral blood leukocytes (HuPBLs). In these mice, vaginal transmission of cell-associated, but not cell-free, HIV-1 transmission occurs, mediated by transepithelial migration of HIV-infected cells. Topical application of beta-cyclodextrin (beta-CD), a cholesterol-sequestering agent that interferes with cell migration and budding of virus from lipid rafts, blocks transmission of cell-associated HIV-1. The HuPBL-SCID model of vaginal HIV-1 transmission should prove useful for investigating cell-associated HIV-1 transmucosal HIV-1 transmission, as well as for screening reagents for their potential efficacy in preventing sexual HIV-1 transmission.