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

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 Pathogenesis in the Human Female Reproductive Tract

PURPOSE OF REVIEW

Women remain disproportionately affected by the HIV/AIDS pandemic. The primary mechanism for HIV acquisition in women is sexual transmission, yet the immunobiological factors that contribute to HIV susceptibility remain poorly characterized. Here, we review current knowledge on HIV pathogenesis in women, focusing on infection and immune responses in the female reproductive tract (FRT).

RECENT FINDINGS

We describe recent findings on innate immune protection and HIV target cell distribution in the FRT. We also review multiple factors that modify susceptibility to infection, including sex hormones, microbiome, trauma, and how HIV risk changes during women's life cycle. Finally, we review current strategies for HIV prevention and identify barriers for research in HIV infection and pathogenesis in women. A complex network of interrelated biological and sociocultural factors contributes to HIV risk in women and impairs prevention and cure strategies. Understanding how HIV establishes infection in the FRT can provide clues to develop novel interventions to prevent HIV acquisition in women.

Tissue issues: mucosal T-cell responses in HIV-1 infection

PURPOSE OF REVIEW

This review summarizes our current understanding of HIV-1-specific T-cell responses in mucosal tissues, emphasizing recent work and specifically highlighting papers published over the past 18 months.

RECENT FINDINGS

Recent work has improved the standardization of tissue sampling approaches and provided new insights on the abundance, phenotype and distribution of HIV-1-specific T-cell populations in mucosal tissues. In addition, it has recently been established that some lymphocytes exist in tissues as "permanent resident" memory cells that differ from their counterparts in blood.

SUMMARY

HIV-1-specific T-cell responses have been extensively characterized; however, the vast majority of reports have focused on T-cells isolated from peripheral blood. Mucosal tissues of the genitourinary and gastrointestinal tracts serve as the primary sites of HIV-1 transmission, and provide "front line" barrier defenses against HIV-1 and other pathogens. In addition, the gastrointestinal tract remains a significant viral reservoir throughout the chronic phase of infection. Tissue-based immune responses may be critical in fighting infection, and understanding these defenses may lead to improved vaccines and immunotherapeutic strategies.

Resident memory T cells are a cellular reservoir for HIV in the cervical mucosa

HIV viral reservoirs are established very early during infection. Resident memory T cells (T_RM) are present in tissues such as the lower female genital tract, but the contribution of this subset of cells to the pathogenesis and persistence of HIV remains unclear. Here, we show that cervical CD4⁺T_RM display a unique repertoire of clusters of differentiation, with enrichment of several molecules associated with HIV infection susceptibility, longevity and self-renewing capacities. These protein profiles are enriched in a fraction of CD4⁺T_RM expressing CD32. Cervical explant models show that CD4⁺T_RM preferentially support HIV infection and harbor more viral DNA and protein than non-T_RM. Importantly, cervical tissue from ART-suppressed HIV⁺ women contain high levels of viral DNA and RNA, being the T_RM fraction the principal contributor. These results recognize the lower female genital tract as an HIV sanctuary and identify CD4⁺T_RM as primary targets of HIV infection and viral persistence. Thus, strategies towards an HIV cure will need to consider T_RM phenotypes, which are widely distributed in tissues.

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.

Neutrophil extracellular traps (NETs) contribute to pathological changes of ocular graft-vs.-host disease (oGVHD) dry eye: Implications for novel biomarkers and therapeutic strategies

PURPOSE

To investigate the role of neutrophil extracellular traps (NETs) and NET-associated proteins in the pathogenesis of oGVHD and whether dismantling of NETs with heparin reduces those changes.

METHODS

Ocular surface washings from oGVHD patients and healthy subjects were analyzed. Isolated peripheral blood human neutrophils were stimulated to generate NETs and heparinized NETs. We performed in vitro experiments using cell lines (corneal epithelial, conjunctival fibroblast, meibomian gland (MG) epithelial and T cells), and in vivo experiments using murine models, and compared the effects of NETs, heparinized NETs, NET-associated proteins and neutralizing antibodies to NET-associated proteins.

RESULTS

Neutrophils, exfoliated epithelial cells, NETs and NET-associated proteins (extracellular DNA, Neutrophil Elastase, Myeloperoxidase, Oncostatin M (OSM), Neutrophil gelatinase-associated lipocalin (NGAL) and LIGHT/TNFSF14) are present in ocular surface washings (OSW) and mucocellular aggregates (MCA). Eyes with high number of neutrophils in OSW have more severe signs and symptoms of oGVHD. NETs (and OSM) cause epitheliopathy in murine corneas. NETs (and LIGHT/TNFSF14) increase proliferation of T cells. NETs (and NGAL) inhibit proliferation and differentiation of MG epithelial cells. NETs enhance proliferation and myofibroblast transformation of conjunctival fibroblasts. Sub-anticoagulant dose Heparin (100 IU/mL) dismantles NETs and reduces epithelial, fibroblast, T cell and MG cell changes induced by NETs.

CONCLUSION

NETs and NET-associated proteins contribute to the pathological changes of oGVHD (corneal epitheliopathy, conjunctival cicatrization, ocular surface inflammation and meibomian gland disease). Our data points to the potential of NET-associated proteins (OSM or LIGHT/TNFSF14) to serve as biomarkers and NET-dismantling biologics (heparin eye drops) as treatment for oGVHD.

Increased Cervical CD4+CCR5+ T Cells Among Kenyan Sex Working Women Using Depot Medroxyprogesterone Acetate

Depot medroxyprogesterone acetate (DMPA) is the most common hormonal contraceptive used by women in sub-Saharan Africa, however, it has been epidemiologically associated with HIV infections. To assess whether DMPA has an effect on the number and activation of HIV target cells, this study assessed the levels and phenotype of blood- and mucosal-derived HIV target cells among women using DMPA. Thirty-five HIV uninfected women from the Pumwani Sex Worker cohort from Nairobi, Kenya were enrolled in the study (15 using DMPA and 20 not using hormonal contraception). Blood (plasma and peripheral blood mononuclear cells) and cervicovaginal (lavage, cervical cells, and ectocervical biopsies) samples were collected. Cellular phenotype and activation status were determined by flow cytometry, cytokine levels were assessed by bead array and image analysis assessed cell number and phenotype in situ. In blood, the proportion of HIV target cells and activated T cells was lower in DMPA users versus those not using hormonal contraceptives. However, analysis of cervical mononuclear cells showed that DMPA users had elevated levels of activated T cells (CD4⁺CD69⁺) and expressed lower levels of the HIV co-receptor CCR5 on a per cell basis, while tissue samples showed that in the ectocervix, DMPA users had a higher proportion of CD4⁺CCR5⁺ T cells. This study demonstrates that DMPA users had higher levels of activated T cells and HIV target cells in the genital tract. The increased pool of mucosal HIV target cells provides new biological information about the potential impact of DMPA on HIV susceptibility.

Increased degranulation of immune cells is associated with higher cervical viral load in HIV-infected women

OBJECTIVE

The activation of effector immune cells at the cervicovaginal mucosa (CVM) might influence the cervical HIV load and thus the secondary transmission; however, limited information is available about the innate effector cells at CVM during HIV infection. In this study, we quantified and assessed the activation of the effector immune cells at the CVM of HIV-infected women with different disease outcomes: nonprogressive HIV disease (LTNPs) and chronic HIV-infected (CHI) and their relationship with cervical viral shedding.

METHOD

The phenotype and frequency of cytobrush-derived effector immune cells like natural killer cells, T cells, and dendritic cells and their degranulation status (CD107a expression as a surrogate marker of activation) was determined using flow cytometry in age-matched HIV- infected and uninfected women and their association with cervical HIV load was determined.

RESULT

The frequencies of dendritic cells, CD56, CD56 natural killer cell subsets were similar in both the study groups and also within the HIV-infected women with and without progressive disease. The frequencies of CD56CD16 natural killer cells (P = 0.04) and degranulating CD56 natural killer cells were significantly higher among HIV-infected women (P < 0.05). Among HIV-infected women, LTNP women showed reduced degranulation of natural killer and CD8 T cells than seen in the CHI women, which was also associated with lower cervical viral load (P < 0.05).

CONCLUSION

The present study showed that increased degranulation of natural killer and T cells is associated with higher HIV shedding at the CVM of HIV-infected women. Hence reduction of the local immune activation at CVM could be an effective strategy to reduce the cervical viral load.

Innate Invariant NKT Cell Recognition of HIV-1-Infected Dendritic Cells Is an Early Detection Mechanism Targeted by Viral Immune Evasion

Invariant NKT (iNKT) cells are innate-like T cells that respond rapidly with a broad range of effector functions upon recognition of glycolipid Ags presented by CD1d. HIV-1 carries Nef- and Vpu-dependent mechanisms to interfere with CD1d surface expression, indirectly suggesting a role for iNKT cells in control of HIV-1 infection. In this study, we investigated whether iNKT cells can participate in the innate cell-mediated immune response to HIV-1. Infection of dendritic cells (DCs) with Nef- and Vpu-deficient HIV-1 induced upregulation of CD1d in a TLR7-dependent manner. Infection of DCs caused modulation of enzymes in the sphingolipid pathway and enhanced expression of the endogenous glucosylceramide Ag. Importantly, iNKT cells responded specifically to rare DCs productively infected with Nef- and Vpu-defective HIV-1. Transmitted founder viral isolates differed in their CD1d downregulation capacity, suggesting that diverse strains may be differentially successful in inhibiting this pathway. Furthermore, both iNKT cells and DCs expressing CD1d and HIV receptors resided in the female genital mucosa, a site where HIV-1 transmission occurs. Taken together, these findings suggest that innate iNKT cell sensing of HIV-1 infection in DCs is an early immune detection mechanism, which is independent of priming and adaptive recognition of viral Ag, and is actively targeted by Nef- and Vpu-dependent viral immune evasion mechanisms.

Mucosal Blood Group Antigen Expression Profiles and HIV Infections: A Study among Female Sex Workers in Kenya

Background

The ABO blood group antigens are carbohydrate moieties expressed on human red blood cells however; these antigens can also be expressed on some other cells particularly the surface of epithelial cells and may be found in mucosal secretions. In many human populations 80% secrete ABO antigens (termed ‘secretors’) while 20% do not (termed ‘non-secretors’). Furthermore, there are disease conditions that are associated with secretor status.

Objective

To investigate correlations between secretor status and HIV infection among female sex workers in Nairobi, Kenya.

Methodology

This cross-sectional study recruited 280 female sex workers aged 18–65 years from the Pumwani Majengo cohort, Kenya. Blood typing was determined by serological techniques using monoclonal antibodies to the ABO blood group antigens. Secretor phenotyping was determined using anti-H specific lectins specific to salivary, vaginal and cervical blood group H antigen using the agglutination inhibition technique and correlated to individual HIV sero-status. Participants were additionally screened for Bacterial vaginosis, Neisseria gonorrhoea and Trichomonas vaginalis.

Results

Out of the 280 participants, 212 (75.7%) were secretors and 68 (24.3%) were non-secretors. The incidence of all infections: HIV, Bacterial vaginosis, Neisseria gonorrhoea and Trichomonas vaginalis was higher among secretors compared to non-secretors. However, this difference was only statistically significant for HIV infection incidence rates: HIV infected secretors (83.7%) versus HIV un-infected secretors (71.8%) (p = 0.029) Based on ABO phenotype stratification, the incidence of HIV infection was higher among blood group A secretors (26/52 = 50%), in comparison to B (12/39 = 33.3%: p = 0.066), AB (3/9 = 33.3%: p = 0.355), and O secretors (36/112 = 32.1%: p = 0.028).

Conclusion

This is the first report to document the variable expression of the ABH blood group antigens profiling secretor and non-secretor phenotypes in the female genital tract among a high-risk population in a Kenyan population. These findings suggest the non-secretor phenotype may confer a certain degree of protection against HIV infection.

HIV-1 shedding from the female genital tract is associated with increased Th1 cytokines/chemokines that maintain tissue homeostasis and proportions of CD8+FOXP3+ T cells

BACKGROUND

HIV-1 shedding from the female genital tract is associated with increased sexual and perinatal transmission and has been broadly evaluated in cross-sectional studies. However, few longitudinal studies have evaluated how the immune microenvironment effects shedding.

METHODS

Thirty-nine HIV-1-infected women had blood, cervicovaginal lavage, and biopsies of the uterine cervix taken quarterly for up to 5 years. Cytokines/chemokines were quantified by Luminex assay in cervicovaginal lavage, and cellular phenotypes were characterized using immunohistochemistry in cervical biopsies. Comparisons of cytokine/chemokine concentrations and the percent of tissue staining positive for T cells were compared using generalized estimating equations between non-shedding and shedding visits across all women and within a subgroup of women who intermittently shed HIV-1.

RESULTS

Genital HIV-1 shedding was more common when plasma HIV-1 was detected. Cytokines associated with cell growth (interleukin-7), Th1 cells/inflammation (interleukin-12p70), and fractalkine were significantly increased at shedding visits compared with non-shedding visits within intermittent shedders and across all subjects. Within intermittent shedders and across all subjects, FOXP3 T cells were significantly decreased at shedding visits. However, there were significant increases in CD8 cells and proportions of CD8FOXP3 T cells associated with HIV-1 shedding.

CONCLUSIONS

Within intermittent HIV-1 shedders, decreases in FOXP3 T cells at the shedding visit suggests that local HIV-1 replication leads to CD4 T-cell depletion, with increases in the proportion of CD8FOXP3 cells. HIV-1-infected cell loss may promote a cytokine milieu that maintains cellular homeostasis and increases immune suppressor cells in response to HIV-1 replication in the cervical tissues.