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.

Comparison of the immune response to Ars-BGG in germfree or conventional piglets

Neonatal germfree (GF) colostrum-deprived and conventional (CV) colostrum-fed piglets were immunized IP with p-azo-phenyl-arsonate-bovine gamma globulin (Ars-BGG) in Freund's adjuvant to study the development of the immune response in the absence or presence of maternal antibodies and environmental antigens. Overall, the immune response varied greatly within each group but did not differ in GF from CV piglets statistically. Affinity immunoblot analysis suggested that anti-Ars antibody was more restricted in GF than CV piglets and clonotype shifts occurred more in GF than CV piglets after each antigenic stimulation. In contrast, the clonotype pattern of the anti-BGG antibody was similarly heterogeneous in the two groups. Based on the affinity immunoblot data the antibodies generated to the Ars-haptenic group in CV piglets are more heterogeneous than GF piglets and suggest that clonotype generation is influenced by maternal antibodies and environmental antigens.

Intestinal absorption of immunologically intact macromolecules in germfree colostrum-deprived piglets maintained on total parenteral nutrition

We have compared the neonatal absorption of anti-bovine gamma-globulin (BGG) antibody supplied in colostrum or saline in three groups of piglets born and maintained under different environmental conditions to determine the effect of these conditions on the cessation of intestinal absorption of macromolecules (anti-BGG antibody), termed "closure." An enzyme-linked immunosorbent assay was used to estimate the concentration of anti-BGG antibody in sera from each group of piglets. Three stages of macromolecular absorption through the piglet's intestine could be detected. The first stage is a nonselective massive absorption of macromolecules (in milligram levels) that lasts up to 3 days in germfree (GF) colostrum-deprived or conventional colostrum-fed piglets but up to 5 days in GF piglets maintained on total parenteral nutrition. In this stage, absorption was significantly (r = .05) higher in piglets fed anti-BGG serum with colostrum than in piglets fed anti-BGG serum without colostrum on GF day 0 (31.28% vs 15.59%) and GF-total parenteral nutrition day 3 (3.08% vs 0.11%). Thus, whenever there was the ability to absorb a massive amount of macromolecules, the sow colostrum had an enhancing affect. Although there was a minor effect of environmental or orally received stimuli in delaying closure, absorption of macromolecules decreased in all piglets maintained either parenterally or enterally after day 3. Thus, intestinal closure to massive absorption of macromolecules in piglets is primarily time (age)-dependent. The second stage is a selective absorption of immunoglobulins in much smaller quantities (microgram levels), inasmuch as absorption of 0.02% to 0.1% was determined in all 5-day-old piglets.(ABSTRACT TRUNCATED AT 250 WORDS)

Total parenteral nutrition in germfree colostrum-deprived neonatal miniature piglets: a unique model to study the ontogeny of the immune system

In order to investigate the regulatory role of the immune system on gastrointestinal macromolecular permeability in neonates, and ontogeny of the neonatal immune system, we have developed a total parenteral nutrition (TPN) program capable of maintaining immunologically "virgin" germfree (GF) neonatal piglets. GF colostrum-deprived piglets obtained by aseptic hysterectomy 3-5 days prior to term were denied any oral feeding and maintained on central venous hyperalimentation in the GF isolators. GF piglets were anesthetized and 20-gauge silicone tubing was inserted into the external jugular vein and advanced to the level of right auricle of the heart. The distal end of the cannula was subcutaneously tunneled out between the shoulders and attached to a light jacket, tether, and swivel assembly that allowed the piglet to move freely inside the cage in a germfree unit. The TPN formula provided 60 Cal/kg/day for the first day and gradually increased up to 165 Cal/kg/day for day-7 and older piglets. The GF piglets were maintained on the TPN formula for 21 days and weight gain of the GF-TPN piglets averaged 23 g/day. The hematologic and serum biochemical parameters of GF-TPN piglets were within the normal range of gnotobiotic animals of their age group. The serum levels of total protein and albumin in the GF-TPN piglets were significantly less than those of colostrum-fed piglets, who absorbed a large quantity of the colostral macromolecules through their gastrointestinal tract into the blood stream.(ABSTRACT TRUNCATED AT 250 WORDS)