Feasibility and safety of cervical biopsy sampling for mucosal immune studies in female sex workers from Nairobi, Kenya

Advances and challenges in studying the tissue-resident T cell compartment in the human female reproductive tract

Tissue-resident memory T cells (TRM ) are considered to be central to maintaining mucosal barrier immunity and tissue homeostasis. Most of this knowledge stems from murine studies, which provide access to all organs. These studies also allow for a thorough assessment of the TRM compartment for each tissue and across tissues with well-defined experimental and environmental variables. Assessing the functional characteristics of the human TRM compartment is substantially more difficult; thus, notably, there is a paucity of studies profiling the TRM compartment in the human female reproductive tract (FRT). The FRT is a mucosal barrier tissue that is naturally exposed to a wide range of commensal and pathogenic microbes, including several sexually transmitted infections of global health significance. We provide an overview of studies describing T cells within the lower FRT tissues and highlight the challenges of studying TRM cells in the FRT: different sampling methods of the FRT greatly affect immune cell recovery, especially of TRM cells. Furthermore, menstrual cycle, menopause, and pregnancy affect FRT immunity, but little is known about changes in the TRM compartment. Finally, we discuss the potential functional plasticity of the TRM compartment during inflammatory episodes in the human FRT to maintain protection and tissue homeostasis, which are required to ensure reproductive fitness.

Women for science and science for women: Gaps, challenges and opportunities towards optimizing pre-exposure prophylaxis for HIV-1 prevention

Preventing new HIV infections remains a global challenge. Young women continue to bear a disproportionate burden of infection. Oral pre-exposure prophylaxis (PrEP), offers a novel women-initiated prevention technology and PrEP trials completed to date underscore the importance of their inclusion early in trials evaluating new HIV PrEP technologies. Data from completed topical and systemic PrEP trials highlight the role of gender specific physiological and social factors that impact PrEP uptake, adherence and efficacy. Here we review the past and current developments of HIV-1 prevention options for women with special focus on PrEP considering the diverse factors that can impact PrEP efficacy. Furthermore, we highlight the importance of inclusion of female scientists, clinicians, and community advocates in scientific efforts to further improve HIV prevention strategies.

OUP accepted manuscript

Background

Mucosa-associated invariant T (MAIT) cells are innate-like T cells with specialized antimicrobial functions. Circulating MAIT cells are depleted in chronic human immunodeficiency virus (HIV) infection, but studies examining this effect in peripheral tissues, such as the female genital tract, are lacking.

Methods

Flow cytometry was used to investigate circulating MAIT cells in a cohort of HIV-seropositive (HIV⁺) and HIV-seronegative (HIV⁻) female sex workers (FSWs), and HIV⁻ lower-risk women (LRW). In situ staining and quantitative polymerase chain reaction were performed to explore the phenotype of MAIT cells residing in paired cervicovaginal tissue. The cervicovaginal microbiome was assessed by means of 16S ribosomal RNA gene sequencing.

Results

MAIT cells in the HIV⁺ FSW group were low in frequency in the circulation but preserved in the ectocervix. MAIT cell T-cell receptor gene segment usage differed between the HIV⁺ and HIV⁻ FSW groups. The TRAV1-2–TRAJ20 transcript was the most highly expressed MAIT TRAJ gene detected in the ectocervix in the HIV⁺ FSW group. MAIT TRAVJ usage was not associated with specific genera in the vaginal microbiome.

Conclusions

MAIT cells residing in the ectocervix are numerically preserved irrespective of HIV infection status and displayed dominant expression of TRAV1-2–TRAJ20. These findings have implications for understanding the role of cervical MAIT cells in health and disease.

HIV-Exposed Seronegative Sex Workers Express Low T-Cell Activation and an Intact Ectocervical Tissue Microenvironment

Immunological correlates of natural resistance to HIV have been identified in HIV-exposed seronegative (HESN) individuals and include a low-inflammatory genital mucosal status. The cervicovaginal epithelium has not been studied for such correlates despite constituting an important barrier against sexual HIV transmission. To fill this gap in knowledge, we collected samples of blood, cervical mononuclear cells, cervicovaginal lavage, and ectocervical tissue from Kenyan HESN sex workers (n = 29) and controls (n = 33). The samples were analyzed by flow cytometry, protein profiling, 16S rRNA gene sequencing, in situ image analysis, and tissue-based RNA sequencing. A significantly higher relative proportion of regulatory T cells in blood (B7⁺CD25^hiFoxP3⁺CD127^loCD4⁺ and B7⁺Helios⁺FoxP3⁺CD4⁺), and a significantly lower proportion of activated cervical T cells (CCR5⁺CD69⁺CD4⁺ and CCR5⁺CD69⁺CD8⁺), were found in the HESN group compared with the controls. In contrast, there were no statistically significant differences between the study groups in cervicovaginal protein and microbiome compositions, ectocervical epithelial thickness, E-cadherin expression, HIV receptor expression, and tissue RNA transcriptional profiles. The identification of an intact ectocervical microenvironment in HESN individuals add new data to current knowledge about natural resistance to sexual transmission of HIV.

The impact of cervical cytobrush sampling on cervico-vaginal immune parameters and microbiota relevant to HIV susceptibility

The immunology and microbiota of the female genital tract (FGT) are key determinants of HIV susceptibility. Cervical cytobrush sampling is a relatively non-invasive method permitting the longitudinal assessment of endocervical immune cells, but effects on FGT immunology are unknown. Blood, cervico-vaginal secretions and cervical cytobrushes were collected from sexually transmitted infection (STI)-free women at baseline and after either 6 hours or 48 hours. Endocervical immune cell subsets were assessed by flow cytometry, and pro-inflammatory cytokines by multiplex ELISA. The density of Lactobacillus species and key bacterial vaginosis-associated bacterial taxa were determined by qPCR. Paired changes were assessed before and after cytobrush sampling. After 6 hours there were significant increases in CD4 + T cell, antigen presenting cell (APC) and neutrophil numbers; APC elevations persisted at 48 hours, while neutrophil and CD4 + T cell numbers returned to baseline. In addition, pro-inflammatory cytokine levels were increased at 6 hours and returned to baseline by 48 hours. No significant changes were observed in the absolute abundance of Lactobacillus species or BV-associated bacteria at either time point. Overall, cytobrush sampling altered genital immune parameters at 6 hours, but only APC number increases persisted at 48 hours. This should be considered in longitudinal analyses of FGT immunology.

Human Immunodeficiency Virus-Infected Women Have High Numbers of CD103-CD8+ T Cells Residing Close to the Basal Membrane of the Ectocervical Epithelium

Background

Genital mucosa is the main portal of entry for various incoming pathogens, including human immunodeficiency virus (HIV), hence it is an important site for host immune defenses. Tissue-resident memory T (TRM) cells defend tissue barriers against infections and are characterized by expression of CD103 and CD69. In this study, we describe the composition of CD8+ TRM cells in the ectocervix of healthy and HIV-infected women.

Methods

Study samples were collected from healthy Swedish and Kenyan HIV-infected and uninfected women. Customized computerized image-based in situ analysis was developed to assess the ectocervical biopsies. Genital mucosa and blood samples were assessed by flow cytometry.

Results

Although the ectocervical epithelium of healthy women was populated with bona fide CD8+ TRM cells (CD103+CD69+), women infected with HIV displayed a high frequency of CD103-CD8+ cells residing close to their epithelial basal membrane. Accumulation of CD103-CD8+ cells was associated with chemokine expression in the ectocervix and HIV viral load. CD103+CD8+ and CD103-CD8+ T cells expressed cytotoxic effector molecules in the ectocervical epithelium of healthy and HIV-infected women. In addition, women infected with HIV had decreased frequencies of circulating CD103+CD8+ T cells.

Conclusions

Our data provide insight into the distribution of CD8+ TRM cells in human genital mucosa, a critically important location for immune defense against pathogens, including HIV.

Minimally invasive monitoring of CD4 T cells at multiple mucosal tissues after intranasal vaccination in rhesus macaques

Studies in nonhuman primates (NHP) for prospective immune cell monitoring subsequent to infection and/or vaccination usually rely on periodic sampling of the blood samples with only occasional collections of biopsies from mucosal tissues because of safety concerns and practical constraints. Here we present evidence in support of cytobrush sampling of oral, rectal, and genital mucosal tissues as a minimally invasive approach for the phenotypic analyses of different T cells subsets de novo as well as prospectively after intranasal immunization in rhesus macaques. Significant percentages of viable lymphocytes were obtained consistently from both naïve and chronically SIV-infected rhesus macaques. The percentages of CD3+ T cells in the blood were significantly higher compared to those in the mucosal tissues analyzed in the naïve animals, while in the SIV+ animals the CD3+ T cells were significantly elevated in the rectal tissues, relative to all other sites analyzed. In the naïve, but not SIV+ macaques, the rectal and vaginal mucosal tissues, compared to oral mucosa and blood, showed higher diversity and percentages of CD4+ T cells expressing the HIV entry co-receptor CCR5 and mucosal specific adhesion (CD103) as well as activation (HLA-DR) and proliferation (Ki67) markers. Sequential daily cytobrush sampling from the oral, rectal, and genital mucosal tissues was performed in SIV+ animals from an ongoing study where they were administered intranasal immunization with adenoviral vectored vaccines incorporating the green fluorescent protein (GFP) reporter gene. We detected a transient increase in GFP+ CD4 T cells in only oral mucosa suggesting limited mucosal trafficking. In general, CD4+ and CD8+ T cells expressing Ki67 transiently increased in all mucosal tissues, but those expressing the CCR5, HLA-DR, and CD103 markers exhibited minor changes. We propose the minimally invasive cytobrush sampling as a practical approach for effective and prospective immune monitoring of the oral-genital mucosal tissues in NHP.

Assessment of Anti-HIV-1 Antibodies in Oral and Nasal Compartments of Volunteers From 3 Different Populations

In this study, we assessed the feasibility of collecting standardized nasal and salivary samples at centers in Nairobi (Kenya), Kigali (Rwanda), and London (United Kingdom) using different collection devices and media (synthetic absorptive matrices versus flocked swabs, and Salimetrics oral swabs versus whole oral fluid collection). We detected anti-Gag (p24) and envelope (gp140) antibodies in both nasal fluid and salivary collections from all HIV-infected individuals, and cross-reactive anti-p24 antibodies were detected in 10% of HIV-uninfected individuals enrolled at one site. Collections from the nasal turbinates were comparable with samples collected deeper in the nasopharyngeal tract, and the yield of anti-p24 IgA in the whole oral fluid samples was higher than in samples collected from the parotid gland. We noted a trend toward reduced levels of anti-HIV antibody in the volunteers receiving anti-retroviral therapy. Levels of antibodies were stable over multiple collection visits. Overall, this study shows that nasal and salivary samples can be collected in a standardized manner over repeated visits in both low- and high-resource settings. These methods may be used in support for future HIV vaccine clinical trials.

HIV-1-negative female sex workers sustain high cervical IFNɛ, low immune activation, and low expression of HIV-1-required host genes

Sex workers practicing in high HIV endemic areas have been extensively targeted to test anti-HIV prophylactic strategies. We hypothesize that in women with high levels of genital exposure to semen changes in cervico-vaginal mucosal and/or systemic immune activation will contribute to a decreased susceptibility to HIV-1 infection. To address this question, we assessed sexual activity and immune activation status (in peripheral blood), as well as cellular infiltrates and gene expression in ectocervical mucosa biopsies in female sex workers (FSWs; n=50), as compared with control women (CG; n=32). FSWs had low-to-absent HIV-1-specific immune responses with significantly lower CD38 expression on circulating CD4(+) or CD8(+) T-cells (both: P<0.001) together with lower cervical gene expression of genes associated with leukocyte homing and chemotaxis. FSWs also had increased levels of interferon-ɛ (IFNɛ) gene and protein expression in the cervical epithelium together with reduced expression of genes associated with HIV-1 integration and replication. A correlative relationship between semen exposure and elevated type-1 IFN expression in FSWs was also established. Overall, our data suggest that long-term condomless sex work can result in multiple changes within the cervico-vaginal compartment that would contribute to sustaining a lower susceptibility for HIV-1 infection in the absence of HIV-specific responses.

Improving Adherence to Post-Cervical Biopsy Sexual Abstinence in Kenyan Female Sex Workers

Problem

Cervical biopsies offer a unique opportunity for studying local immune response. To investigate hormonally induced immune fluctuations in cervical tissues of Kenyan female sex workers, we improved biopsy sampling protocol safety. Here, we report on steps taken to minimize exposure to HIV following two cervical biopsies.

Methods of study

Women were asked to abstain from vaginal intercourse to limit HIV exposure during wound healing with financial compensation. A comprehension tool for informed consent, on‐site detection of prostate‐specific antigens indicating unprotected intercourse within 48 hr, and bi‐weekly text message reminders were implemented.

Results

The implemented methods improved compliance with post‐procedure abstinence by two times (P = 0.013). Fourteen days following a cervical biopsy, no sign of genital inflammation or change in HIV T‐cell target proportion were observed.

Conclusions

This study provides new tools for limiting HIV exposure in studies requiring biopsy sampling among women at risk of acquiring HIV.

Loss of Intra-Epithelial Endocervical Gamma Delta (GD) 1 T Cells in HIV-Infected Women

PROBLEM

Human gamma delta (GD) T cells play a well-documented role in epithelial barrier surveillance and protection. Two subsets of GD T cells, defined by the use of either the Vdelta2 (GD2) or Vdelta1 (GD1) TCR, predominate. We hypothesized that endocervical GD T cells play important role in lower genital tract anti-HIV immune responses.

METHOD OF STUDY

HIV-infected (n = 18) and HIV-uninfected (n = 19) pre-menopausal women participating in the WIHS cohort were recruited. Frequency and phenotype of GD T cells were determined in endocervical cytobrush samples and peripheral blood by multicolor flow cytometry.

RESULTS

We found depletion of GD2 cells in the blood of HIV-infected women as well as significant decrease in the frequency of endocervical GD1 cells compared to uninfected women.

CONCLUSION

We report for the first time, the GD1 cells are a predominant endocervical T-cell subset that is significantly decreased in HIV-infected women.

The first step toward diagnosing female genital schistosomiasis by computer image analysis

Schistosoma haematobium causes female genital schistosomiasis (FGS), which is a poverty-related disease in sub-Saharan Africa. Furthermore, it is co-endemic with human immunodeficiency virus (HIV), and biopsies from genital lesions may expose the individual to increased risk of HIV infection. However, microscopy of urine and hematuria are nonspecific and insensitive predictors of FGS and gynecological investigation requires extensive training. Safe and affordable diagnostic methods are needed. We explore a novel method of diagnosing FGS using computer color analysis of colposcopic images. In a cross-sectional study on young women in an endemic area, we found strong associations between the output from the computer color analysis and both clinical diagnosis (odds ratio [OR] = 5.97, P < 0.001) and urine microscopy for schistosomiasis (OR = 3.52, P = 0.004). Finally, using latent class statistics, we estimate that the computer color analysis yields a sensitivity of 80.5% and a specificity of 66.2% for the diagnosis of FGS.

Colourimetric image analysis as a diagnostic tool in female genital schistosomiasis

Female genital schistosomiasis (FGS) is a highly prevalent waterborne disease in some of the poorest areas of sub-Saharan Africa. Reliable and affordable diagnostics are unavailable. We explored colourimetric image analysis to identify the characteristic, yellow lesions caused by FGS. We found that the method may yield a sensitivity of 83% and a specificity of 73% in colposcopic images. The accuracy was also explored in images of simulated inferior quality, to assess the possibility of implementing such a method in simple, electronic devices. This represents the first step towards developing a safe and affordable aid in clinical diagnosis, allowing for a point-of-care approach.

Collection, isolation, and flow cytometric analysis of human endocervical samples

Despite the public health importance of mucosal pathogens (including HIV), relatively little is known about mucosal immunity, particularly at the female genital tract (FGT). Because heterosexual transmission now represents the dominant mechanism of HIV transmission, and given the continual spread of sexually transmitted infections (STIs), it is critical to understand the interplay between host and pathogen at the genital mucosa. The substantial gaps in knowledge around FGT immunity are partially due to the difficulty in successfully collecting and processing mucosal samples. In order to facilitate studies with sufficient sample size, collection techniques must be minimally invasive and efficient. To this end, a protocol for the collection of cervical cytobrush samples and subsequent isolation of cervical mononuclear cells (CMC) has been optimized. Using ex vivo flow cytometry-based immunophenotyping, it is possible to accurately and reliably quantify CMC lymphocyte/monocyte population frequencies and phenotypes. This technique can be coupled with the collection of cervical-vaginal lavage (CVL), which contains soluble immune mediators including cytokines, chemokines and anti-proteases, all of which can be used to determine the anti- or pro-inflammatory environment in the vagina.

Presence of CD8+ T cells in the ectocervical mucosa correlates with genital viral shedding in HIV-infected women despite a low prevalence of HIV RNA-expressing cells in the tissue

The female genital tract is a portal of entry for sexual HIV transmission and a possible viral reservoir. In this study, the ectocervical CD8+ T cell distribution was explored in situ and was related to expression of CD3 and HLA-DR and presence of HIV RNA. For this purpose, ectocervical tissue samples and genital secretions were collected from HIV-seropositive (HIV+) Kenyan female sex workers (FSWs) (n = 20), HIV-seronegative (HIV-) FSWs (n = 17), and HIV(-) lower-risk women (n = 21). Cell markers were assessed by in situ staining and by quantitative PCR. HIV RNA expression in tissue was analyzed by in situ hybridization, and viral shedding was assessed by quantitative PCR. The HIV+ FSW group had a higher amount of total cells and CD8+, CD3+, and HLA-DR+ cells compared with the HIV(-)FSW group and HIV- lower-risk women. The majority of CD8+ cells were CD3+ T cells, and the numbers of CD8+ cells correlated significantly with plasma and cervical viral load. HIV RNA expression in situ was found in 4 of the 20 HIV+FSW women but did not correlate with cervical or plasma viral load. Thus, the HIV+ women displayed high numbers of CD8+, CD3+, and HLA-DR+ cells, as well as a limited number of HIV RNA+ cells, in their ectocervical mucosa; hence, this localization cannot be neglected as a potential viral reservoir. The elevated levels of CD8+ T cells may play a role in the immunopathogenesis of HIV in the female genital tract.

Optimizing viable leukocyte sampling from the female genital tract for clinical trials: an international multi-site study

Background

Functional analysis of mononuclear leukocytes in the female genital mucosa is essential for understanding the immunologic effects of HIV vaccines and microbicides at the site of HIV exposure. However, the best female genital tract sampling technique is unclear.

Methods and Findings

We enrolled women from four sites in Africa and the US to compare three genital leukocyte sampling methods: cervicovaginal lavages (CVL), endocervical cytobrushes, and ectocervical biopsies. Absolute yields of mononuclear leukocyte subpopulations were determined by flow cytometric bead-based cell counting. Of the non-invasive sampling types, two combined sequential cytobrushes yielded significantly more viable mononuclear leukocytes than a CVL (p<0.0001). In a subsequent comparison, two cytobrushes yielded as many leukocytes (∼10,000) as one biopsy, with macrophages/monocytes being more prominent in cytobrushes and T lymphocytes in biopsies. Sample yields were consistent between sites. In a subgroup analysis, we observed significant reproducibility between replicate same-day biopsies (r = 0.89, p = 0.0123). Visible red blood cells in cytobrushes increased leukocyte yields more than three-fold (p = 0.0078), but did not change their subpopulation profile, indicating that these leukocytes were still largely derived from the mucosa and not peripheral blood. We also confirmed that many CD4⁺ T cells in the female genital tract express the α4β7 integrin, an HIV envelope-binding mucosal homing receptor.

Conclusions

CVL sampling recovered the lowest number of viable mononuclear leukocytes. Two cervical cytobrushes yielded comparable total numbers of viable leukocytes to one biopsy, but cytobrushes and biopsies were biased toward macrophages and T lymphocytes, respectively. Our study also established the feasibility of obtaining consistent flow cytometric analyses of isolated genital cells from four study sites in the US and Africa. These data represent an important step towards implementing mucosal cell sampling in international clinical trials of HIV prevention.