Immunological microenvironments in the human vagina and cervix: mediators of cellular immunity are concentrated in the cervical transformation zone

Dendritic cells and macrophages in the genitourinary tract

Dendritic cells (DCs) and macrophages are antigen-presenting cells (APCs) that are important in innate immune defense as well as in the generation and regulation of adaptive immunity against a wide array of pathogens. The genitourinary (GU) tract, which serves an important reproductive function, is constantly exposed to numerous agents of sexually transmitted infections (STIs). To combat these STIs, several subsets of DCs and macrophages are strategically localized within the GU tract. In the female genital mucosa, recruitment and function of these APCs are uniquely governed by sex hormones. This review summarizes the latest advances in our understanding of DCs and macrophages in the GU tract with respect to their subsets, lineage, and function. In addition, we discuss the divergent roles of these cells in immune defense against STIs as well as in maternal tolerance to the fetus.

Role of cervical dendritic cell subsets, co-stimulatory molecules, cytokine secretion profile and beta-estradiol in development of sequalae to Chlamydia trachomatis infection

BACKGROUND

Chlamydia trachomatis infection of the female genital tract can lead to serious sequelae resulting in fertility related disorders. Little is known about the mechanism leading to Chlamydia induced pathology and factors responsible for it. As only some of the women develops reproductive disorders while majority of the women clears infection without any severe sequalae, mucosal immune response in women with or without fertility disorders was studied to identify factors which may lead to final clinical outcome of chlamydial infection.

METHODS

Myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) populations in cervical mucosa and peripheral blood were analyzed in controls and Chlamydia positive women with or without fertility disorders with multicoloured flow cytometric analysis. Cervical cytokines (IL-6, IL-8, IL-10, IL-12, TNF-alpha and IFN-gamma), C-reactive protein levels and sex hormone levels in serum were quantified by ELISA.

RESULTS

In cervix of Chlamydia positive women with fertility disorders, significantly high (P < 0.05) numbers of pDCs were present with increased CD80 expression. pDCs correlated significantly with C-reactive protein levels, IL-6 and IFN-gamma levels in women with fertility disorders. In contrast, mDCs showed significant upregulation of CD1a during chlamydial infection and correlated significantly with IL-12 levels in Chlamydia positive fertile women. beta-estradiol levels were significantly higher in women having fertility disorders as compared to fertile women and have significant correlations (r = 0.65; P < 0.05) with pDCs numbers, CD80 expression, IL-6 levels and IFN-gamma levels in these women.

CONCLUSION

These results suggest that development of sequalae in some women can be a result of interplay of many factors including type of dendritic cell, co stimulatory molecule expression, cytokine secretion pattern and hormone levels.

Biomedical interventions to prevent HIV infection: evidence, challenges, and way forward

Intensive research efforts for more than two decades have not yet resulted in an HIV vaccine of even moderate effectiveness. However, some progress has been made with other biomedical interventions, albeit on the basis of inconsistent levels of evidence. The male condom, if used correctly and consistently, has been proven in observational studies to be very effective in blocking HIV transmission during sexual intercourse; and, in three randomised trials, male circumcision was protective against HIV acquisition among men. Treatment of sexually transmitted infections, a public health intervention in its own right, has had mixed results, depending in part on the epidemic context in which the approach was assessed. Finally, oral and topical antiretroviral compounds are being assessed for their role in reduction of HIV transmission during sexual intercourse. Research on biomedical interventions poses formidable challenges. Difficulties with product adherence and the possibility of sexual disinhibition are important concerns. Biomedical interventions will need to be part of an integrative package that includes biomedical, behavioural, and structural interventions. Assessment of such multicomponent approaches with moderate effects is difficult. Issues to be considered include the nature of control groups and the effect of adherence on the true effectiveness of the intervention.

Innate Immunity in the Female Reproductive Tract: Role of Sex Hormones in Regulating Uterine Epithelial Cell Protection Against Pathogens

The mucosal immune system in the upper female reproductive tract is uniquely prepared to maintain a balance between the presence of commensal bacteria, sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and an immunologically distinct fetus. At the center of this dynamic system are the epithelial cells that line the Fallopian tubes, uterus, cervix and vagina. Epithelial cells provide a first line of defense that confers continuous protection, by providing a physical barrier as well as secretions containing bactericidal and virucidal agents. In addition to maintaining a state of ongoing protection, these cells have evolved to respond to pathogens, in part through Toll-like receptors (TLRs), to enhance innate immune protection and, when necessary, to contribute to the initiation of an adaptive immune response. Against this backdrop, epithelial cell innate and adaptive immune function is modulated to meet the constraints of procreation. The overall goal of this review is to focus on the dynamic role of epithelial cells in the upper reproductive tract, with special emphasis on the uterus, to define the unique properties of these cells as they maintain homeostasis in preparation for successful fertilization and pregnancy while at the same time confer protection against sexually transmitted infections, which threaten to compromise women's reproductive health and survival. By understanding the nature of this protection and the ways in which innate and adaptive immunity are regulated by sex hormones, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

Chlamydia trachomatis infection: host immune responses and potential vaccines

Chlamydia trachomatis causes genital tract infections that affect men, women, and children on a global scale. This review focuses on innate and adaptive immune responses in the female reproductive tract (FRT) to genital tract infections with C. trachomatis. It covers C. trachomatis infections and highlights our current knowledge of genital tract infections, serovar distribution, infectious load, and clinical manifestations of these infections in women. The unique features of the immune system of the FRT will be discussed and will include a review of our current knowledge of innate and adaptive immunity to chlamydial infections at this mucosal site. The use of animal models to study the pathogenesis of, and immunity to, Chlamydia infection of the female genital tract will also be discussed and a review of recent immunization and challenge experiments in the murine model of chlamydial FRT infection will be presented.

A Phase I study of the functional performance, safety and acceptability of the BufferGel Duet

BACKGROUND

The purpose of this study was to assess the functional performance of the BufferGel Duet, a buffering microbicide and spermicide gel applied to the cervix and vagina by a novel applicator that also serves as a mechanical barrier.

STUDY DESIGN

This was a noncomparative Phase I safety trial in 30 healthy couples, aged 20-50 years, at low risk for sexually transmitted infections, who agreed to use the gel-device combination twice in 1 week and respond to detailed questionnaires about their experience. The female participants were examined with colposcopy before and 6-18 h after using the second device.

RESULTS

Based on written instructions alone, 25 women successfully placed and 28 women successfully removed the device. Three women reported feeling the device dislodge around the time of intercourse. The product was equally acceptable to both men and women. Most users concluded that intercourse was the same or better with the device than with no product. About 73% would choose Duet over male condoms, and no one preferred the standard diaphragm. Colposcopic findings were noted in 79% of women with external genital findings (9) or cervicovaginal peeling (18) predominating. Only one finding breached the epithelium. Most product-related adverse events were mild (10/11) and confined to the genitourinary tract.

CONCLUSIONS

The successful placements and acceptability suggest that further product development is warranted and could target over-the-counter use. During increased duration of use or more frequent dosing, cervicovaginal monitoring is advised based on the extent of peeling and external colposcopic findings in this short-term study.

A randomized controlled safety trial of the diaphragm and cellulose sulfate microbicide gel in sexually active women in Zimbabwe

BACKGROUND

Cellulose sulfate (CS) is an antimicrobial and contraceptive agent. We assessed its safety when used alone or with the diaphragm in Harare, Zimbabwe.

STUDY DESIGN

This was a randomized controlled safety trial with three arms: diaphragm with 6% CS gel vs. diaphragm with KY gel vs. CS gel alone. Participants were instructed to use their study products before every sex act for a period of 6 months. Safety end points were assessed monthly by questionnaires and urinanalysis and bimonthly by clinical examinations, colposcopy, wet mounts and gram stains.

RESULTS

One hundred nineteen monogamous women were enrolled (28% HIV+) and 105 (88%) completed the study. No urinary tract infections were diagnosed during the study; 81.4% women had symptoms and/or signs of genital irritation considered at least possibly related to the gel or device, and 41.5% had changes in vaginal flora. There were no statistically significant differences between treatment groups in safety end points. All six women with deep epithelial disruption were diaphragm users, and all such findings were on the external genitalia. Of those, 4 had herpetic ulcers which were unrelated to products use.

CONCLUSIONS

Cellulose sulfate appeared safe when used for 6 months alone or with a diaphragm.

Diaphragm and lubricant gel for prevention of HIV acquisition in southern African women: a randomised controlled trial

BACKGROUND

Female-controlled methods of HIV prevention are urgently needed. We assessed the effect of provision of latex diaphragm, lubricant gel, and condoms (intervention), compared with condoms alone (control) on HIV seroincidence in women in South Africa and Zimbabwe.

METHODS

We did an open-label, randomised controlled trial in HIV-negative, sexually active women recruited from clinics and community-based organisations, who were followed up quarterly for 12-24 months (median 21 months). All participants received an HIV prevention package consisting of pre-test and post-test counselling about HIV and sexually transmitted infections, testing, treatment of curable sexually transmitted infections, and intensive risk-reduction counselling. The primary outcome was incident HIV infection. This study is registered with ClinicalTrials.gov, number NCT00121459.

FINDINGS

Overall HIV incidence was 4.0% per 100 woman-years: 4.1% in the intervention group (n=2472) and 3.9% in the control group (n=2476), corresponding to a relative hazard of 1.05 (95% CI 0.84-1.32, intention-to-treat analysis). The proportion of women using condoms was significantly lower in the intervention than in the control group (54%vs 85% of visits, p<0.0001). The proportions of participants who reported adverse events (60% [1523] vs 61% [1529]) and serious adverse events (5% [130] vs 4% [101]) were similar between the two groups.

INTERPRETATION

We observed no added protective benefit against HIV infection when the diaphragm and lubricant gel were provided in addition to condoms and a comprehensive HIV prevention package. Our observation that lower condom use in women provided with diaphragms did not result in increased infection merits further research. Although the intervention seemed safe, our findings do not support addition of the diaphragm to current HIV prevention strategies.

Mucosal immune responses in the genital tract of HIV-1-exposed uninfected women

The development of HIV-1 vaccines and microbicides remains hindered by our limited understanding of correlates of immune protection to infection. Evidence indicating that resistance to HIV-1 infection is indeed possible comes from HIV-1-exposed yet uninfected individuals, including cohorts of commercial sex workers and discordant couples. Despite their uninfected status some of these individuals have mucosal and systemic HIV-1-specific humoral and cellular immune responses in addition to their innate immune response. The combined contribution of innate and adaptive immunity as well as genetic factors is most likely of great importance for this protection against infection. Here we review data on the antibody responses and secreted immune molecules of the innate immune system in the female genital tract with emphasis on individuals who seem to resist HIV-1-infection despite repeated exposure to the virus.

Mucosal dendritic cells

The internal surfaces of the human body are covered by distinct types of epithelial cells and mucus-secreting cells. The mucosal surfaces serve many vital functions, such as respiration (nasal passage and lung), absorption (gastrointestinal tract), excretion (lung, urinary tract, large intestine), and reproduction (reproductive tract). In performing these functions, the host is inevitably exposed to environmental antigens, food particles, commensal flora, and pathogens. Mucosal surfaces contain specialized dendritic cells (DCs) capable of sensing these external stimuli and mounting appropriate local responses depending on the nature of the elements they encounter. In the absence of pathogens, mucosal DCs either ignore the antigen or induce regulatory responses. Upon recognition of microorganisms that invade the mucosal barrier, mucosal DCs mount robust protective immunity. This review highlights progress in our understanding of how mucosal DCs process external information and direct appropriate responses by mobilizing various cells of the innate and adaptive immune systems to achieve homeostasis and protection.

Vaginal mucosal vaccine for recurrent urinary tract infections in women: results of a phase 2 clinical trial

PURPOSE

We assessed the clinical efficacy of vaginal mucosal immunization with a multivalent bacterial vaccine in women with recurrent urinary tract infections.

MATERIALS AND METHODS

A total of 75 patients in a double-blind study were randomly assigned to receive placebo only, primary immunization without boosters, or primary immunization plus boosters using vaginal suppositories containing placebo or vaccine. Vaccine suppositories contained 10 strains of heat-killed uropathogenic bacteria and placebo suppositories had no vaccine organisms. All women were monitored for 6 months to record the number of infections and adverse events.

RESULTS

Analysis of data on urinary tract infections caused by any bacteria showed the greatest difference in infection rates between patients in the vaccine plus boosters protocol compared to those receiving placebo only (p = 0.100). When only E. coli urinary tract infections were considered in the analysis, urinary tract infection recurrence rates were significantly less in women given booster immunizations compared to placebo (p = 0.0015). Furthermore, women who received vaccine with boosters and who were sexually active, less than 52 years old, or had not undergone hysterectomy had E. coli urinary tract infections at a much lower rate than women given placebo only (p = 0.0002, 0.002 and 0.003, respectively). No significant adverse events were associated with vaccine treatment.

CONCLUSIONS

This study demonstrated the efficacy of vaginal mucosal immunization with a multivalent vaccine in reducing recurrence of E. coli urinary tract infections. The results suggest that the vaccine may provide the most benefit to sexually active women in the 20 to 50-year-old age group.

The genital tract immune milieu: an important determinant of HIV susceptibility and secondary transmission

HIV is generally sexually acquired across the genital or rectal mucosa after exposure to the genital secretions of an HIV-infected partner. Most exposures to HIV do not result in infection, likely due to protection afforded by an intact mucosal epithelium, as well as by innate and adaptive mucosal immune factors present in the genital tract. Another important mucosal determinant of transmission may be the number and activation status of potential HIV target cells, including CCR5/CD4+ T cells and DC-SIGN+ dendritic cells. The simultaneous presence of other genital infections, including classical sexually transmitted infections (STIs), can enhance HIV susceptibility either by breaching the epithelial barrier, recruiting HIV target cells to the genital tract, or by generating a pro-inflammatory local immune milieu. In HIV-infected individuals, genital co-infections increase HIV levels in the genital secretions, thereby increasing secondary sexual transmission. Co-infections that act as important HIV cofactors include human cytomegalovirus (CMV), Herpes simplex virus type 2 (HSV2), Neisseria gonorrhoeae and many others. Strategies focused on genital co-infections, such as vaccines, microbicides and suppressive therapy, are feasible in the short term and have the potential to curb the pandemic.

Comprehensive Proteomic Analysis of Human Cervical−Vaginal Fluid

Cervical-vaginal fluid (CVF) is a potential rich source of biomarkers for enhancing our understanding of human parturition and pathologic conditions affecting pregnancy. In this study, we performed a comprehensive survey of the CVF proteome in pregnancy utilizing multidimensional liquid chromatography (2D-LC) coupled with mass spectrometry and gel-electrophoresis-based protein separation and identification. In total, 150 unique proteins were identified using multiple protein identification algorithms. Metabolism (32%) and immune response-related (22%) proteins are the major functional categories represented in the CVF proteome. A comparison of the CVF, serum, and amniotic fluid proteomes showed that 77 proteins are unique to CVF, while 56 and 17 CVF proteins also occur in serum and amniotic fluid, respectively. This data set provides a foundation for evaluation of these proteins as potential CVF biomarkers for noninvasive diagnosis of pregnancy-related disorders.

T-Lymphocyte Profile and Total and Virus-Specific Immunoglobulin Concentrations in the Cervix of HIV-1-Infected Women

BACKGROUND

The mucosal lymphocyte population is the largest in the body, and the gastrointestinal compartment has been well characterized in HIV infection. Much less is known about the effects of HIV on the genital tract.

OBJECTIVE

: To examine the T-lymphocyte phenotype and receptor repertoire as well as total and virus-specific immunoglobulin concentrations in the endocervix of HIV-infected women at different stages of infection as compared with uninfected women.

PATIENTS AND METHODS

Participants were 12 seronegative women, 10 HIV-infected "slow progressors" not taking antiretroviral therapy, and 9 HIV-infected women whose antiretroviral therapy was failing. We used multiparameter flow cytometry to enumerate T-cell populations on cytobrush-obtained cervical specimens, the immunoscope technique to determine the T-cell receptor (TCR) repertoire, and quantitative enzyme-linked immunosorbent assays for antibody determinations on cervical secretions absorbed onto ophthalmic sponges. Nonparametric statistical analyses were performed.

RESULTS

We found marked depletion of leukocytes and CD4 T lymphocytes in the endocervix of HIV-infected women as compared with uninfected women; this was significant at more advanced disease stages. Naive T cells were rare in the endocervix of all groups. Activation marker expression was higher in endocervical T lymphocytes than in peripheral blood among control and slow-progressing HIV-infected women but not in women failing therapy. Endocervical T lymphocytes showed highly restricted utilization of Vbeta TCR families. Unlike other mucosal sites, the cervix contained IgG as the predominant immunoglobulin isotype. HIV-IgG was detected in the cervix of most HIV-infected women and in blood of all infected women.

CONCLUSIONS

HIV infection induces substantial changes in the immune profile of the female genital tract. Further study of the implications of these findings for HIV acquisition and transmission is needed.

Natural mucosal antibodies reactive with first extracellular loop of CCR5 inhibit HIV-1 transport across human epithelial cells

OBJECTIVE

The genital mucosa represents the major site for initial host-HIV-1 contact. HIV-1-protective mucosal immunity has been identified either in subjects who despite repeated sexual exposure, remain seronegative (ESN) or in long-term non-progressor HIV-1-seropositive individuals (LTNP). As a subset of ESN and LTNP produce anti-CCR5 antibodies both at systemic and mucosal level, we studied the role of anti-CCR5 antibodies in blocking HIV transfer through human epithelial cells.

DESIGN AND METHODS

To evaluate HIV-1-inhibitory activity by anti-CCR5 antibodies, a two-chambers system was established to model HIV-1 infection across the human mucosal epithelium. Moreover, peripheral blood mononuclear cells (PBMC) and a CCR5 transfected cell line were also used in a classical HIV-infectivity assay. CCR5-specific IgG and IgA were used to inhibit HIV replication.

RESULTS

Either serum or mucosal IgA to CCR5 were able to specifically block transcytosis of CCR5- but not CXCR4-HIV strains across a tight epithelial cell layer by interacting with the first extracellular loop of the receptor (amino acids YAAAQWDFGNTMCQ). Monoclonal antibodies against other regions of CCR5 had no effect on HIV transcytosis. Moreover, mucosal CCR5-specific IgA neutralized CCR5-tropic strains and SOS-JRFL pseudovirus replication in PBMC and CCR5 transfected cell lines respectively, with a mechanism different than that observed for transcytosis.

CONCLUSIONS

Anti-CCR5 Abs shed light on the immunological mechanisms involved in the control of HIV-1 infection in a model that can be considered an experimentum naturae for resistance to HIV. They could be useful in the design of new strategies against HIV infection at mucosal sites.

Distribution of simian immunodeficiency virus target cells in vaginal tissues of normal rhesus macaques: implications for virus transmission

Most new cases of HIV-1 infection occur as the result of vaginal transmission. Identifying the phenotype and distribution of potential viral target cells in the vagina is important for understanding events in viral transmission and for developing effective prevention strategies. For example, compounds that prevent CD4 or CCR5 binding have been demonstrated recently to prevent vaginal transmission in rhesus macaques, but the expression and distribution of CCR5 has not been examined in the macaque vagina. The objective of this study was to examine the distribution and phenotype of cells and molecules in the vagina of rhesus macaques that may be involved in HIV transmission, including CCR5, CD3, CD4, CD8, CD1a, CD28, CD95, CD123 and HLA-DR. Normal juvenile and adult female rhesus macaques were examined by multicolor immunohistochemistry and flow cytometry. Although both CD4 and CCR5 were observed in the lamina propria, essentially no CD4 or CCR5 expression was detected within the squamous or keratinized layers of the vaginal epithelium. CCR5 expression was higher in the vaginal lamina propria of mature macaques compared to 1-3-year-old juveniles. The vast majority of CD4(+)CCR5(+) lymphocytes in the vagina had a central memory (CD95(+)CD28(+)) phenotype. Numerous CCR5-expressing dendritic cells (CD123(+)) or macrophages (CD68(+)) were observed in the lamina propria, but no CCR5, CD4 or DC-SIGN expression was detectable in the epithelium. Thus, the multiple layers of squamous epithelium normally covering the vaginal mucosa may provide an effective barrier against vaginal HIV-1 transmission. Microbicides that block CD4 or CCR5 expression may act within the deeper layers of the vaginal epithelium rather than on the epithelial surface.

Selective transmission of CCR5-utilizing HIV-1: the 'gatekeeper' problem resolved?

Understanding the mechanisms of HIV-1 transmission is crucial for the development of effective preventive microbicides and vaccine strategies, and remains one of the main goals of HIV research. Over the past decade, many studies have focused on trying to identify the 'gatekeeping' mechanism that restricts the transmission of CXCR4-utilizing HIV-1 more efficiently than CCR5-utilizing HIV-1. However, to date, no study has explained the almost perfect negative selection of the former in vivo. Here, we propose that there is no single gatekeeper and that, instead, the selective transmission of R5 HIV-1 depends on the superimposition of multiple imperfect gatekeepers.