Immune responses to HIV in the female reproductive tract, immunologic parallels with the gastrointestinal tract, and research implications

Common and Divergent Features of T Cells from Blood, Gut, and Genital Tract of Antiretroviral Therapy-Treated HIV+ Women

T cells residing in mucosal tissues play important roles in homeostasis and defense against microbial pathogens. The gut and female reproductive tract (FRT) are both tolerogenic environments, but they differ in the kinds of foreign Ags they need to tolerate. How these different environments influence the properties of their T cells is poorly understood, but important for understanding women's health. We recruited antiretroviral therapy-suppressed women living with HIV who donated, within one visit, blood and tissue samples from the ileum, colon, rectosigmoid, endometrium, endocervix, and ectocervix. With these samples, we conducted 36-parameter cytometry by time of flight phenotyping of T cells. Although gut and FRT T cells shared features discriminating them from their blood counterparts, they also harbored features distinguishing them from one another. These included increased proportions of CD69+ T resident memory cells of the T effector memory phenotype, as well as preferential coexpression of CD69 and CD103, on the gut-derived cells. In contrast, CD69+CD103+ T resident memory CD8+ T cells from FRT, but not those from gut, preferentially expressed PD1. We further determined that a recently described population of CXCR4+ T inflammatory mucosal cells differentially expressed multiple other chemokine receptors relative to their blood counterparts. Our findings suggest that T cells resident in different tolerogenic mucosal sites take on distinct properties.

Ex Vivo Evaluation of Mucosal Responses to Vaccination with ALVAC and AIDSVAX of Non-Human Primates

Non-human primates (NHPs) remain the most relevant challenge model for the evaluation of HIV vaccine candidates; however, discrepancies with clinical trial results have emphasized the need to further refine the NHP model. Furthermore, classical evaluation of vaccine candidates is based on endpoints measured systemically. We assessed the mucosal responses elicited upon vaccination with ALVAC and AIDSVAX using ex vivo Rhesus macaque mucosal tissue explant models. Following booster immunization with ALVAC/AIDSVAX, anti-gp120 HIV-1CM244-specific IgG and IgA were detected in culture supernatant cervicovaginal and colorectal tissue explants, as well as systemically. Despite protection from ex vivo viral challenge, no neutralization was observed with tissue explant culture supernatants. Priming with ALVAC induced distinct cytokine profiles in cervical and rectal tissue. However, ALVAC/AIDSVAX boosts resulted in similar modulations in both mucosal tissues with a statistically significant decrease in cytokines linked to inflammatory responses and lymphocyte differentiation. With ALVAC/AIDSVAX boosts, significant correlations were observed between cytokine levels and specific IgA in cervical explants and specific IgG and IgA in rectal tissue. The cytokine secretome revealed differences between vaccination with ALVAC and ALVAC/AIDSVAX not previously observed in mucosal tissues and distinct from the systemic response, which could represent a biosignature of the vaccine combination.

HIV-1 Sanctuary Sites-the Role of Membrane-Associated Drug Transporters and Drug Metabolic Enzymes

Despite significant advances in the treatment of human immunodeficiency virus-1 (HIV) infection with highly active antiretroviral drug therapy, the persistence of the virus in cellular and anatomic reservoirs is a major obstacle preventing total HIV eradication. Viral persistence could result from a variety of contributing factors including, but not limited to, non-adherence to treatment and adverse drug reactions, latently infected cells carrying replication-competent virus, drug-drug interactions, and inadequate antiretroviral drug (ARV) concentrations reached in several anatomic sites such as the brain, testis, and gut-associated lymphoid tissues. The distribution of ARVs at specific sites of infection is primarily dependent on drug physicochemical properties and drug plasma protein binding, as well as drug efflux, influx, and metabolic processes. A thorough understanding of the functional roles of drug transporters and metabolic enzymes in the disposition of ARVs in immune cell types and tissues that are characterized as HIV reservoirs and sanctuaries is critical to overcome the challenge of suboptimal drug distribution at sites of persistent HIV infection. This review summarizes the current knowledge related to the expression and function of drug transporters and metabolic enzymes in HIV cellular and anatomic reservoirs, and their potential contribution to drug-drug interactions and insufficient drug concentration at these sites.

Parallel studies of mucosal immunity in the reproductive and gastrointestinal mucosa of HIV-infected women

PROBLEM

The effects of HIV on the gastrointestinal tract (GIT), including CD4 depletion, epithelial disruption, and collagen deposition, are well documented and only partially reversed by combination antiretroviral therapy (cART). However, the effects of HIV on the female reproductive tract (FRT) are poorly understood, and most studies have focused on ectocervix and vagina without assessing the upper tract. Here, we investigated CD4⁺ T-cell frequency, phenotype, and HIV-specific T-cell responses in the endocervix and endometrium of HIV-infected women, comparing these tissues to the GIT.

METHOD OF STUDY

Mucosal samples and blood were obtained from 18 women: four who were HIV-positive and not on cART for at least 3 years prior to sampling, including two natural controllers (viral load [VL] undetectable and CD4 >350); nine women on cART with low to undetectable VL; and five HIV-uninfected women. Mucosal samples included terminal ileum, sigmoid colon, endocervical cytobrush, endocervical curettage, and endometrial biopsy. T-cell frequency, phenotypes, and HIV-specific T-cell responses were analyzed by multiparameter flow cytometry.

RESULTS

T-cell activation, measured by CD38/HLA-DR co-expression, remained significantly elevated in endometrium following cART, but was lower in gastrointestinal tissues. HIV-specific CD8⁺ T-cell responses were detected in ileum, colon, and endometrial tissues of women both on and off cART, and were of higher magnitude on those not on cART.

CONCLUSION

Our findings reveal differences in CD4⁺ T-cell frequencies, immune activation, and HIV-specific T-cell responses between the gastrointestinal and reproductive tracts, and highlight differences between HIV controllers and women on cART.

The menstrual cycle may not be limited to the endometrium but also may impact gut permeability

OBJECTIVE

To examine associations between IgA responses to Gram-negative gut commensal bacteria and peri-menstrual symptoms and sex hormone levels during the menstrual cycle in women with and without premenstrual symptoms.

METHODS

Forty women aged 18-45 years completed the Daily Record of Severity of Problems (DRSP) during all 28 consecutive days of the menstrual cycle. We assayed, in plasma, IgA responses to six Gram-negative bacteria, that is, Hafnei alvei, Pseudomonas aeruginosa, Morganella morganii, Klebsiella pneumoniae, Pseudomonas putida and Citobacter koseri, progesterone and oestradiol at days 7, 14, 21 and 28 of the menstrual cycle.

RESULTS

Significant changes in Δ (actual - 1 week earlier) IgA to lipopolysaccharides (LPS) of the six Gram-negative bacteria during the menstrual cycle were observed with peak IgA levels at T4 (day 28) and lows at T1 or T2 (day 7 or 14). The ΔIgA changes in H. alvei, M. Morganii, P. putida during the menstrual cycle were significantly and positively associated with changes in the total DRSP score, and severity of physio-somatic, anxiety and breast-craving, but not depressive, symptoms. The changes in IgA responses to LPS were largely predicted by changes in progesterone and steady-state levels of progesterone averaged over the luteal phase.

DISCUSSION

Menstrual cycle-associated changes in IgA directed against LPS and by inference bacterial translocation may be driven by the effects of progesterone on transcellular, paracellular and vascular pathways (leaky gut) thereby contributing to the severity of physio-somatic and anxiety symptoms as well as fatigue, breast swelling and food cravings.

Effects of the levonorgestrel-containing intrauterine device, copper intrauterine device, and levonorgestrel-containing oral contraceptive on susceptibility of immune cells from cervix, endometrium and blood to HIV-1 fusion measured ex vivo

Globally, HIV/AIDS is a leading cause of morbidity worldwide among reproductive-aged cisgender women, highlighting the importance of understanding effects of contraceptives on HIV-1 risk. Some observational studies suggest there may be an increased risk of HIV-1 acquisition among women using the long-acting injectable progestin contraceptive, depo-medroxyprogesterone acetate. The potential mechanism of this susceptibility is unclear. There are few data on the role of the upper female reproductive tract in HIV-1 transmission, and the mechanisms of HIV-1 infection are likely to differ in the upper compared to the lower reproductive tract due to differences in tissue composition and variable effects of sex steroids on mucosal immune cell distribution and activity. In this study, we measured the susceptibility of mucosal immune cells from the upper female reproductive tract to HIV-1 entry using the virion-based HIV-1 fusion assay in samples from healthy female volunteers. We studied 37 infectious molecular clones for their ability to fuse to cells from endometrial biopsies in three participants and found that subtype (B or C) and origin of the virus (transmitted founder or chronic control) had little influence on HIV-1 fusion susceptibility. We studied the effect of contraceptives on HIV-1 susceptibility of immune cells from the cervix, endometrium and peripheral blood by comparing fusion susceptibility in four groups: users of the copper intrauterine device (IUD), levonorgestrel-containing oral contraceptive, levonorgestrel-containing IUD and unexposed controls (n = 58 participants). None of the contraceptives was associated with higher rates of HIV-1 entry into female reproductive tract cells compared to control samples from the mid-luteal phase.

Incidence of sexually transmitted infections during pregnancy

Prevalence of sexually transmitted infections (STI) is high among pregnant women in certain settings. We estimated STI incidence and compared STI risk in pregnant and non-pregnant women. Data came from the Methods for Improving Reproductive Health in Africa (MIRA) study conducted in South Africa and Zimbabwe 2003-2006. Women aged 18-50 years with at least one follow-up visit within 6 months of enrollment were included. Follow-up visits included laboratory testing for pregnancy, chlamydia, gonorrhea, trichomoniasis, and HIV, as well as self-report of hormonal contraceptive (HC) use, sexual behaviors and intravaginal practices. All visits were classified according to pregnancy status. Incidence of each STI was calculated using follow-up time. Cox proportional hazards models were fitted using pregnancy as a time-varying exposure and sexual behaviors and intravaginal practices as time-varying covariates. Among 4,549 women, 766 (16.8%) had a positive pregnancy test. Median follow-up time was 18 months [IQR: 12-24]. The overall incidence rate of chlamydia was 6.7 per 100 person years (py) and 9.9/100py during pregnancy; gonorrhea incidence was 2.7/100py and 4.9/100py during pregnancy; trichomoniasis incidence was 7.1/100py overall and 9.2/100py during pregnancy. Overall HIV incidence was 3.9/100py and 3.8/100py during pregnancy. In crude models, pregnancy increased risk for chlamydia (hazard ratio (HR) 1.5, 95%CI: 1.1-1.2), however there was no increased risk of any measured STI in adjusted models. STI Incidence was high during pregnancy however pregnancy did not increase STI risk after adjustment for sexual behaviors. Greater efforts are needed to help pregnant women avoid STIs.

Progestin-Containing Contraceptives Alter Expression of Host Defense-Related Genes of the Endometrium and Cervix

Epidemiological studies indicate that progestin-containing contraceptives increase susceptibility to HIV, although the underlying mechanisms involving the upper female reproductive tract are undefined. To determine the effects of depot medroxyprogesterone acetate (DMPA) and the levonorgestrel intrauterine system (LNG-IUS) on gene expression and physiology of human endometrial and cervical transformation zone (TZ), microarray analyses were performed on whole tissue biopsies. In endometrium, activated pathways included leukocyte chemotaxis, attachment, and inflammation in DMPA and LNG-IUS users, and individual genes included pattern recognition receptors, complement components, and other immune mediators. In cervical TZ, progestin treatment altered expression of tissue remodeling and viability but not immune function genes. Together, these results indicate that progestins influence expression of immune-related genes in endometrium relevant to local recruitment of HIV target cells with potential to increase susceptibility and underscore the importance of the upper reproductive tract when assessing the safety of contraceptive products.

Interactions between HIV-1 and mucosal cells in the female reproductive tract

Worldwide, the heterosexual route is the prevalent mode of HIV-1 transmission, and the female reproductive tract accounts for approximately 40% of all HIV-1 transmissions. HIV-1 infection in the female reproductive tract involves three major events: entry through the mucosal epithelium, productive infection in subepithelial mononuclear cells, and delivery to lymph nodes to initiate systemic infection. Here, we provide a focused review of the interaction between HIV-1 and mucosal epithelial cells, lymphocytes, macrophages, and dendritic cells in female genital mucosa. Increased understanding of these interactions could illuminate new approaches for interdicting HIV-1 heterosexual transmission.

Sex hormones selectively impact the endocervical mucosal microenvironment: implications for HIV transmission

Several studies suggest that progesterone and estrogens may affect HIV transmission in different, possibly opposing ways. Nonetheless, a direct comparison of their effects on the mucosal immune system has never been done. We hypothesize that sex hormones might impact the availability of cells and immune factors important in early stages of mucosal transmission, and, in doing so influence the risk of HIV acquisition. To test this hypothesis, we employed 15 ovarectomized rhesus macaques: 5 were treated with Depot Medroxy Progesterone Acetate (DMPA), 6 with 17-β estradiol (E2) and 4 were left untreated. All animals were euthanized 5 weeks after the initiation of hormone treatment, a time post-DMPA injection associated with high susceptibility to SIV infection. We found that DMPA-treated macaques exhibited higher expression of integrin α4β7 (α4β7) on CD4+ T cells, the gut homing receptor and a marker of cells highly susceptible to HIV, in the endocervix than did the E2-treated animals. In contrast, the frequency of CCR5+ CD4+ T cells in DMPA-treated macaques was higher than in the E2-treated group in vaginal tissue, but lower in endocervix. α4β7 expression on dendritic cells (DCs) was higher in the DMPA-treated group in the endocervical tissue, but lower in vaginal tissue and on blood DCs compared with the E2-treated animals. Soluble MAdCAM-1, the α4β7 ligand, was present in the vaginal fluids of the control and E2-treated groups, but absent in the fluids from DMPA-treated animals. Both hormones modulated the expression and release of inflammatory factors and modified the distribution of sialomucins in the endocervix. In summary, we found that sex hormones profoundly impact mucosal immune factors that are directly implicated in HIV transmission. The effect is particularly significant in the endocervix. This may increase our understanding of the potential hormone-driven modulation of HIV susceptibility and potentially guide contraceptive policies in high-risk settings.

Mycoplasma genitalium promotes epithelial crossing and peripheral blood mononuclear cell infection by HIV-1

BACKGROUND

Mycoplasma genitalium co-infection in HIV-infected individuals has been reported to increase the shedding of HIV in the urogenital region of females. To better understand this relationship, we investigated the influence of M. genitalium on the transmission and replication of HIV using an in vitro model.

METHODS

The Transwell co-culture system was employed to assess the crossing of an endocervical cell barrier by HIV-1. Immunocytochemistry and confocal microscopy were used to assess the distribution of the nectin-1 molecule on M. genitalium-infected epithelial cells of the End1/E6E7 endocervical cell line, grown as monolayers in the insert wells. Peripheral blood mononuclear cells (PBMC) were cultured in the bottom wells to assess the effects of M. genitalium, passing through the semipermeable culturing membrane, on subsequent HIV infection of susceptible target cells.

RESULTS

Infection of the endocervical cells with the adhesion-positive M. genitalium G37 strain (wild-type) significantly elevated the passage of HIV across the epithelial cell barrier relative to HIV transfer across endocervical cells infected with the adhesion-negative M. genitalium JB1 strain. Immunostaining of the M. genitalium-G37-infected epithelial cells disclosed capping and internalization of the junctional regulatory protein nectin-1, in association with reduced transepithelial resistance (TER) in the cell monolayer. When PBMC were cultured beneath insert wells containing M. genitalium-G37-infected epithelial cell monolayers, we observed significantly enhanced infectivity and replication of HIV added afterward to the cultures.

CONCLUSIONS

M. genitalium influences events on both sides of a cultured mucosal epithelial monolayer: (1) by infecting the epithelial cells and reducing the integrity of the barrier itself, and (2) by activating HIV target cells below it, thereby promoting HIV infection and progeny virus production.

Distribution of immune cells in the human cervix and implications for HIV transmission

PROBLEM

Knowledge of the mucosal immune cell composition of the human female genital tract is important for understanding susceptibility to HIV-1.

METHOD OF STUDY

We developed an optimized procedure for multicolor flow cytometry analysis of immune cells from human cervix to characterize all major immune cell subsets in the endocervix and ectocervix.

RESULTS

Half of tissue hematopoietic cells were CD14(+) , many of which were macrophages and about a third were CD11c(+) , most of which were CD103(-) CD11b(+) CX3CR1(+) DC-SIGN(+) dendritic cells (DCs). The other dominant population were T cells, with more CD8 than CD4 cells. T cells (both CD8 and CD4) and B cells were more abundant in the ectocervix than endocervix of pre-menopausal women; however, CD8(+) T cell and B cell numbers declined in the ectocervix after menopause, while CD4 T cell counts remained higher. B, NK and conventional myeloid and plasmocytoid DCs each were a few percent of tissue hematopoietic cells. Although the ectocervix had more HIV-susceptible CD4(+) T cells, polarized endocervical explants supported HIV replication significantly better.

CONCLUSION

Due to their abundance in the genital tract, CX3CR1(+) DC-SIGN(+) DCs might be important in HIV transmission. Our data also suggest that the columnar epithelium of the upper genital tract might be a preferential site for HIV transmission.

Insights into B cells and HIV-specific B-cell responses in HIV-infected individuals

Human immunodeficiency virus (HIV) disease is associated with dysregulation and dysfunction involving all major lymphocyte populations, including B cells. Such perturbations occur early in the course of infection and are driven in large part by immune activation resulting from ongoing HIV replication leading to bystander effects on B cells. While most of the knowledge regarding immune cell abnormalities in HIV-infected individuals has been gained from studies conducted on the peripheral blood, it is clear that the virus is most active and most damaging in lymphoid tissues. Here, we discuss B-cell perturbations in HIV-infected individuals, focusing on the skewing of B-cell subsets that circulate in the peripheral blood and their counterparts that reside in lymphoid tissues. This review also highlights recent advances in evaluating HIV-specific B-cell responses both in the memory B-cell compartment, as well as in circulating antibody-secreting plasmablasts and the more differentiated plasma cells residing in tissues. Finally, we consider how knowledge gained by investigating B cells in HIV-infected individuals may help inform the development of an effective antibody-based HIV vaccine.

Animal models for microbicide safety and efficacy testing

PURPOSE OF REVIEW

Early studies have cast doubt on the utility of animal models for predicting success or failure of HIV-prevention strategies, but results of multiple human phase 3 microbicide trials, and interrogations into the discrepancies between human and animal model trials, indicate that animal models were, and are, predictive of safety and efficacy of microbicide candidates.

RECENT FINDINGS

Recent studies have shown that topically applied vaginal gels, and oral prophylaxis using single or combination antiretrovirals are indeed effective in preventing sexual HIV transmission in humans, and all of these successes were predicted in animal models. Further, prior discrepancies between animal and human results are finally being deciphered as inadequacies in study design in the model, or quite often, noncompliance in human trials, the latter being increasingly recognized as a major problem in human microbicide trials.

SUMMARY

Successful microbicide studies in humans have validated results in animal models, and several ongoing studies are further investigating questions of tissue distribution, duration of efficacy, and continued safety with repeated application of these, and other promising microbicide candidates in both murine and nonhuman primate models. Now that we finally have positive correlations with prevention strategies and protection from HIV transmission, we can retrospectively validate animal models for their ability to predict these results, and more importantly, prospectively use these models to select and advance even safer, more effective, and importantly, more durable microbicide candidates into human trials.

Phenotype and functionality of CD4+ and CD8+ T cells in the upper reproductive tract of healthy premenopausal women

PROBLEM

The goal of this study was to investigate the phenotype and functional responsiveness of CD4(+) and CD8(+) T-cells in the upper reproductive tract of healthy premenopausal women. The lower reproductive tract is frequently studied as a site of sexually transmitted infections; however, the upper reproductive tract may also be a portal of entry and dissemination for pathogens, including HIV-1.

METHOD OF STUDY

Endometrial biopsy, endocervical curettage, cytobrush, and blood were collected during mid-luteal phase from 23 healthy women. T-cells were isolated and analyzed by flow cytometry.

RESULTS

As compared with their counterparts in blood, endometrial and endocervical T-cells had enhanced CCR5 expression, and were enriched for activated, effector memory cells. Endometrial T-cells were more responsive to polyclonal stimuli, producing a broad range of cytokines and chemokines.

CONCLUSION

These findings underscore the responsiveness of endometrial T-cells to stimulation, and reveal their activated phenotype. These findings also suggest susceptibility of the upper reproductive tract to HIV-1 infection.

Unbiased proteomics analysis demonstrates significant variability in mucosal immune factor expression depending on the site and method of collection

Female genital tract secretions are commonly sampled by lavage of the ectocervix and vaginal vault or via a sponge inserted into the endocervix for evaluating inflammation status and immune factors critical for HIV microbicide and vaccine studies. This study uses a proteomics approach to comprehensively compare the efficacy of these methods, which sample from different compartments of the female genital tract, for the collection of immune factors. Matching sponge and lavage samples were collected from 10 healthy women and were analyzed by tandem mass spectrometry. Data was analyzed by a combination of differential protein expression analysis, hierarchical clustering and pathway analysis. Of the 385 proteins identified, endocervical sponge samples collected nearly twice as many unique proteins as cervicovaginal lavage (111 vs. 61) with 55% of proteins common to both (213). Each method/site identified 73 unique proteins that have roles in host immunity according to their gene ontology. Sponge samples enriched for specific inflammation pathways including acute phase response proteins (p = 3.37×10⁻²⁴) and LXR/RXR immune activation pathways (p = 8.82×10⁻²²) while the role IL-17A in psoriasis pathway (p = 5.98×10⁻⁴) and the complement system pathway (p = 3.91×10⁻³) were enriched in lavage samples. Many host defense factors were differentially enriched (p<0.05) between sites including known/potential antimicrobial factors (n = 21), S100 proteins (n = 9), and immune regulatory factors such as serpins (n = 7). Immunoglobulins (n = 6) were collected at comparable levels in abundance in each site although 25% of those identified were unique to sponge samples. This study demonstrates significant differences in types and quantities of immune factors and inflammation pathways collected by each sampling technique. Therefore, clinical studies that measure mucosal immune activation or factors assessing HIV transmission should utilize both collection methods to obtain the greatest representation of immune factors secreted into the female genital tract.

Innate and adaptive anti-HIV immune responses in the female reproductive tract

The mucosal surface of the female reproductive tract (FRT) is the primary site of transmission for a plethora of sexually transmitted infections, including human immunodeficiency virus (HIV), that represent a significant burden upon womens' health worldwide. However, fundamental aspects of innate and adaptive immune protection against HIV infection in the FRT are poorly understood. The FRT immune system is regulated by the cyclical changes of the sex hormones estradiol and progesterone across the menstrual cycle, which as we have hypothesized, leads to the creation of a window of vulnerability during the secretory stage of the menstrual cycle, when the risk of HIV transmission is increased. The goal of this review is to summarize the multiple levels of protection against HIV infection in the FRT, the contribution of different cell types including epithelial cells, macrophages, T cells, and dendritic cells to this, and their regulation by estradiol and progesterone. Understanding the unique immune environment in the FRT will allow for the potential development of novel therapeutic interventions such as vaccines and microbicides that may reduce or prevent HIV transmission in women.