CD127 and CD25 expression defines CD4+ T cell subsets that are differentially depleted during HIV infection

T Cell Homeostasis Disturbances in a Cohort of Long-Term Elite Controllers of HIV Infection

Elite controllers (ECs) are people living with HIV (PLWH) able to control HIV replication without antiretroviral therapy and have been proposed as a model of a functional HIV cure. Much evidence suggests that this spontaneous control of HIV has a cost in terms of T cell homeostasis alterations. We performed a deep phenotypic study to obtain insight into T cell homeostasis disturbances in ECs maintaining long-term virologic and immunologic control of HIV (long-term elite controllers; LTECs). Forty-seven PLWH were included: 22 LTECs, 15 non-controllers under successful antiretroviral therapy (onART), and 10 non-controllers not receiving ART (offART). Twenty uninfected participants (UCs) were included as a reference. T cell homeostasis was analyzed by spectral flow cytometry and data were analyzed using dimensionality reduction and clustering using R software v3.3.2. Dimensionality reduction and clustering yielded 57 and 54 different CD4 and CD8 T cell clusters, respectively. The offART group showed the highest perturbation of T cell homeostasis, with 18 CD4 clusters and 15 CD8 clusters significantly different from those of UCs. Most of these alterations were reverted in the onART group. Interestingly, LTECs presented several disturbances of T cell homeostasis with 15 CD4 clusters and 13 CD8 clusters different from UC. Moreover, there was a specific profile of T cell homeostasis alterations associated with LTECs, characterized by increases in clusters of naïve T cells, increases in clusters of non-senescent effector CD8 cells, and increases in clusters of central memory CD4 cells. These results demonstrate that, compared to ART-mediated control of HIV, the spontaneous control of HIV is associated with several disturbances in CD4 and CD8 T cell homeostasis. These alterations could be related to the existence of a potent and efficient virus-specific T cell response, and to the ability to halt disease progression by maintaining an adequate pool of CD4 T cells.

T follicular helper cell profiles differ by malaria antigen and for children compared to adults

Background

Circulating T-follicular helper (cT FH ) cells have the potential to provide an additional correlate of protection against Plasmodium falciparum ( Pf) as they are essential to promote B cell production of long-lasting antibodies. Assessing the specificity of cT FH subsets to individual malaria antigens is vital to understanding the variation observed in antibody responses and identifying promising malaria vaccine candidates.

Methods

Using spectral flow cytometry and unbiased clustering analysis we assessed antigen-specific cT FH cell recall responses in vitro to malaria vaccine candidates Pf SEA-1A and Pf GARP within a cross-section of children and adults living in a malaria holoendemic region of western Kenya.

Findings

In children, a broad array of cT FH subsets (defined by cytokine and transcription factor expression) were reactive to both malaria antigens, Pf SEA-1A and Pf GARP, while adults had a narrow profile centering on cT FH 17- and cT FH 1/17-like subsets following stimulation with Pf GARP only.

Interpretation

Because T FH 17 cells are involved in the maintenance of memory antibody responses within the context of parasitic infections, our results suggest that Pf GARP might generate longer lived antibody responses compared to Pf SEA-1A. These findings have intriguing implications for evaluating malaria vaccine candidates as they highlight the importance of including cT FH profiles when assessing interdependent correlates of protective immunity.

Immune regulation and therapeutic application of T regulatory cells in liver diseases

CD4+ CD25+ FOXP3+ T regulatory cells (Tregs) are a subset of the immunomodulatory cell population that can inhibit both innate and adaptive immunity by various regulatory mechanisms. In hepatic microenvironment, proliferation, plasticity, migration, and function of Tregs are interrelated to the remaining immune cells and their secreted cytokines and chemokines. In normal conditions, Tregs protect the liver from inflammatory and auto-immune responses, while disruption of this crosstalk between Tregs and other immune cells may result in the progression of chronic liver diseases and the development of hepatic malignancy. In this review, we analyze the deviance of this protective nature of Tregs in response to chronic inflammation and its involvement in inducing liver fibrosis, cirrhosis, and hepatocellular carcinoma. We will also provide a detailed emphasis on the relevance of Tregs as an effective immunotherapeutic option for autoimmune diseases, liver transplantation, and chronic liver diseases including liver cancer.

Immune resilience despite inflammatory stress promotes longevity and favorable health outcomes including resistance to infection

Some people remain healthier throughout life than others but the underlying reasons are poorly understood. Here we hypothesize this advantage is attributable in part to optimal immune resilience (IR), defined as the capacity to preserve and/or rapidly restore immune functions that promote disease resistance (immunocompetence) and control inflammation in infectious diseases as well as other causes of inflammatory stress. We gauge IR levels with two distinct peripheral blood metrics that quantify the balance between (i) CD8+ and CD4+ T-cell levels and (ii) gene expression signatures tracking longevity-associated immunocompetence and mortality-associated inflammation. Profiles of IR metrics in ~48,500 individuals collectively indicate that some persons resist degradation of IR both during aging and when challenged with varied inflammatory stressors. With this resistance, preservation of optimal IR tracked (i) a lower risk of HIV acquisition, AIDS development, symptomatic influenza infection, and recurrent skin cancer; (ii) survival during COVID-19 and sepsis; and (iii) longevity. IR degradation is potentially reversible by decreasing inflammatory stress. Overall, we show that optimal IR is a trait observed across the age spectrum, more common in females, and aligned with a specific immunocompetence-inflammation balance linked to favorable immunity-dependent health outcomes. IR metrics and mechanisms have utility both as biomarkers for measuring immune health and for improving health outcomes.

Subsets of Tissue CD4 T Cells Display Different Susceptibilities to HIV Infection and Death: Analysis by CyTOF and Single Cell RNA-seq

CD4 T lymphocytes belong to diverse cellular subsets whose sensitivity or resistance to HIV-associated killing remains to be defined. Working with lymphoid cells from human tonsils, we characterized the HIV-associated depletion of various CD4 T cell subsets using mass cytometry and single-cell RNA-seq. CD4 T cell subsets preferentially killed by HIV are phenotypically distinct from those resistant to HIV-associated cell death, in a manner not fully accounted for by their susceptibility to productive infection. Preferentially-killed subsets express CXCR5 and CXCR4 while preferentially-infected subsets exhibit an activated and exhausted effector memory cell phenotype. Single-cell RNA-seq analysis reveals that the subsets of preferentially-killed cells express genes favoring abortive infection and pyroptosis. These studies emphasize a complex interplay between HIV and distinct tissue-based CD4 T cell subsets, and the important contribution of abortive infection and inflammatory programmed cell death to the overall depletion of CD4 T cells that accompanies untreated HIV infection.

Increased frequency of Th17 cells and IL-17 levels are associated with low bone mineral density in postmenopausal women

Osteoporosis is one of the chronic and often neglected bone diseases in aging postmenopausal women that affect the quality of life. Studies on ovariectomized mice models indicated the reciprocal role of Th17 cells and Treg cells in the aetiology of osteoporosis. While Th17 cells promote osteoclastogenesis, Treg cells exhibit anti-osteoclastogenic activity. This exploratory study aimed to determine the difference in the frequency of these T-cell subtypes in pre-and postmenopausal women and to examine their association with BMD. In our study, the frequency of Treg cells, analyzed by flow cytometry, did not differ between pre-and postmenopausal women. However, plasma levels of IL-10 along with IL-10+CD4+T cells were higher in post- compared to premenopausal women. The frequency of Th17 cells was higher in postmenopausal women irrespective of their BMD, however, only postmenopausal women with low BMD had elevated IL-17 levels and their T-scores were associated with Th17 frequency. Collectively, the results suggest that estrogen insufficiency in postmenopausal women may lead to increased Th17 cell frequency and elevated IL-17 levels which are associated with low BMD. This study highlights, Th17 cells and IL-17 as key players in the pathogenesis of osteoporosis and they can be the potential targets for immunotherapy in the treatment of osteoporosis.

Imbalance of circulating CTLA4+ follicular helper and follicular regulatory T cells in obstetric antiphospholipid syndrome

Obstetric antiphospholipid syndrome (OAPS) is a systemic autoimmune disease that is characterized clinically by a variety of obstetric manifestations (fetal death and recurrent abortions) and serologically by the presence of antiphospholipid antibodies (aPLs). Whether dysregulation of Follicular helper T (Tfh) and Follicular regulatory T (Tfr) cells contribute to the immunopathogenesis in OAPS is still unknown. We analyzed phenotypic characterizations of circulating Tfh cells and Tfr cells in OAPS patients and healthy individuals. CTLA4(Cytotoxic T lymphocyte antigen 4)⁺ Tfh cells and CTLA4⁺ Tfr cells were declined and CTLA4⁺ Tfr/Tfh ratio and IL-21 were increased in OAPS patients compared with healthy controls. Percentages of CTLA4⁺ Tfh cells and CTLA4⁺ Tfr cells were the lowest in OAPS patients whose antiphospholipid antibodies (aPL) were triple positive. Increased CTLA4⁺ Tfr/Tfh ratio was positively correlated with anti-β2 glycoprotein I (anti-β2GPI) IgM, Complement 4(C4) or IL-21 in OAPS. Increased Th17 subtype and decreased Th1, Th2 subtypes in Tfh cells and Tfr cells, increased effector memory subtype and decreased central memory subtype of Tfh cells and Tfr cells were also observed in OAPS compared with healthy individuals. Our data demonstrated that an imbalance of circulating CTLA4⁺ Tfh cells, and Tfr cells correlates with the immunopathogenesis of OAPS.

Human Adipose Tissue-Derived Mesenchymal Stromal Cells Inhibit CD4+ T Cell Proliferation and Induce Regulatory T Cells as Well as CD127 Expression on CD4+CD25+ T Cells

Mesenchymal stromal cells (MSC) exert their immunomodulatory potential on several cell types of the immune system, affecting and influencing the immune response. MSC efficiently inhibit T cell proliferation, reduce the secretion of pro-inflammatory cytokines, limit the differentiation of pro-inflammatory Th subtypes and promote the induction of regulatory T cells (Treg). In this study, we analyzed the immunomodulatory potential of human adipose tissue-derived MSC (ASC), on CD4+ T cells, addressing potential cell-contact dependency in relation to T cell receptor stimulation of whole human peripheral blood mononuclear cells (PBMC). ASC were cultured with not stimulated or anti-CD3/CD28-stimulated PBMC in direct and transwell cocultures; PBMC alone were used as controls. After 7 days, cocultures were harvested and we analyzed: (1) the inhibitory potential of ASC on CD4+ cell proliferation and (2) phenotypic changes in CD4+ cells in respect of Treg marker (CD25, CD127 and FoxP3) expression. We confirmed the inhibitory potential of ASC on CD4+ cell proliferation, which occurs upon PBMC stimulation and is mediated by indoleamine 2,3-dioxygenase. Importantly, ASC reduce both pro- and anti-inflammatory cytokine secretion, without indications on specific Th differentiation. We found that stimulation induces CD25 expression on CD4+ cells and that, despite inhibiting overall CD4+ cell proliferation, ASC can specifically induce the proliferation of CD4+CD25+ cells. We observed that ASC induce Treg (CD4+CD25+CD127−FoxP3+) only in not stimulated cocultures and that ASC increase the ratio of CD4+CD25+CD127+FoxP3− cells at the expense of CD4+CD25+CD127−FoxP3− cells. Our study provides new insights on the interplay between ASC and CD4+ T cells, proposing that ASC-dependent induction of Treg depends on PBMC activation which affects the balance between the different subpopulations of CD4+CD25+ cells expressing CD127 and/or FoxP3.

High CD45 expression of CD8+ and CD4+ T cells correlates with the size of HIV-1 reservoir in blood

Using mass cytometry, we investigated the expression of 28 markers on CD8+ and CD4+ T cells from HIV-1 infected patients with a variable size of HIV-1 reservoir defined as high (HR) and low (LR) reservoir; we aimed at identifying phenotypic associations of T cells with size of HIV-1 reservoir. We showed that the frequency of CD45+ CD8+ and CD4+ T cells was directly proportional to the size of HIV-1 reservoir; HR patients had a significantly larger frequency of blood CD45^high T cells and higher CD45 expression on both CD8+ and CD4+ T cells. CD45 is a receptor-type protein tyrosine phosphatase essential in TCR signaling. Functional and phenotypical analysis of CD45^high cells revealed that they express activation and proliferation markers (CD38 + HLA-DR + and Ki-67) and produce cytokines upon in vitro activation. CD45^high T cells also expressed high levels of immune check-point PD-1. Our results link CD45 expression on T cells to HIV-1 reservoir; PD-1 expression on CD45^high T cells may contribute to their exhaustion.

The replication-competent HIV-1 latent reservoir is primarily established near the time of therapy initiation

Although antiretroviral therapy (ART) is highly effective at suppressing HIV-1 replication, the virus persists as a latent reservoir in resting CD4⁺ T cells during therapy. This reservoir forms even when ART is initiated early after infection, but the dynamics of its formation are largely unknown. The viral reservoirs of individuals who initiate ART during chronic infection are generally larger and genetically more diverse than those of individuals who initiate therapy during acute infection, consistent with the hypothesis that the reservoir is formed continuously throughout untreated infection. To determine when viruses enter the latent reservoir, we compared sequences of replication-competent viruses from resting peripheral CD4⁺ T cells from nine HIV-positive women on therapy to viral sequences circulating in blood collected longitudinally before therapy. We found that, on average, 71% of the unique viruses induced from the post-therapy latent reservoir were most genetically similar to viruses replicating just before ART initiation. This proportion is far greater than would be expected if the reservoir formed continuously and was always long lived. We conclude that ART alters the host environment in a way that allows the formation or stabilization of most of the long-lived latent HIV-1 reservoir, which points to new strategies targeted at limiting the formation of the reservoir around the time of therapy initiation.

Loss of BAP1 expression is associated with an immunosuppressive microenvironment in uveal melanoma, with implications for immunotherapy development

Immunotherapy using immune checkpoint inhibitors (ICIs) induces durable responses in many metastatic cancers. Metastatic uveal melanoma (mUM), typically occurring in the liver, is one of the most refractory tumours to ICIs and has dismal outcomes. Monosomy 3 (M3), polysomy 8q, and BAP1 loss in primary uveal melanoma (pUM) are associated with poor prognoses. The presence of tumour-infiltrating lymphocytes (TILs) within pUM and surrounding mUM - and some evidence of clinical responses to adoptive TIL transfer - strongly suggests that UMs are indeed immunogenic despite their low mutational burden. The mechanisms that suppress TILs in pUM and mUM are unknown. We show that BAP1 loss is correlated with upregulation of several genes associated with suppressive immune responses, some of which build an immune suppressive axis, including HLA-DR, CD38, and CD74. Further, single-cell analysis of pUM by mass cytometry confirmed the expression of these and other markers revealing important functions of infiltrating immune cells in UM, most being regulatory CD8+ T lymphocytes and tumour-associated macrophages (TAMs). Transcriptomic analysis of hepatic mUM revealed similar immune profiles to pUM with BAP1 loss, including the expression of IDO1. At the protein level, we observed TAMs and TILs entrapped within peritumoural fibrotic areas surrounding mUM, with increased expression of IDO1, PD-L1, and β-catenin (CTNNB1), suggesting tumour-driven immune exclusion and hence the immunotherapy resistance. These findings aid the understanding of how the immune response is organised in BAP1 - mUM, which will further enable functional validation of detected biomarkers and the development of focused immunotherapeutic approaches. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Selected commensal bacteria change profiles of Helicobacter pylori-induced T cells via dendritic cell modulation

BACKGROUND

The mechanisms of downregulation of protective immunity against Helicobacter pylori (Hp) infection strongly depend on dendritic cell (DC)-induced T-lymphocyte differentiation pattern. Lactic acid bacteria (LAB) strains can modulate Hp-induced immunoresponse by changes in DC activation profiles. Here, we want to find out if the LAB-pulsed DCs will change Hp-induced T-cell responsiveness patterns.

MATERIALS AND METHODS

The naive peripheral CD4⁺ T cells were co-cultured with Hp CagA + pulsed monocyte-derived DCs (DC/CD4⁺ T cell) in the presence/absence of the feces-derived probiotics: antagonistic or non-antagonistic to Hp (Lactobacillus rhamnosus 900, Lr, Lactobacillus paracasei 915, Lp, respectively), as assessed by the agar slab method. The regulatory T-cell (Treg) population was assessed by flow cytometry, and IFN-γ, IL-12p70, IL-10, and IL-17A levels were evaluated by ELISA method.

RESULTS

The Hp-pulsed DC/CD4⁺ T-cell co-cultures were characterized by high IL-10, decreased IL-12p70 and IFN-γ levels, and elevated Treg population. In contrast, Lr-pulsed DC/CD4⁺ T-cell co-cultures expressed low IL-10, high IL-12p70 and IFN-γ levels and declined Treg population; this responsiveness pattern was not changed by Hp. The responsiveness pattern of the Lp/Hp-pulsed DC/CD4⁺ T-cell co-cultures did not differ from those pulsed with Hp alone.

CONCLUSION

In contrast to Lp, Lr probiotic strain overcomes Hp-mediated immune profile in the DC/T-cell co-cultures toward Th1 pattern and limited generation of Tregs in vitro. Lr may therefore be used as a component of anti-Hp treatment.

T cell functionality in HIV-1, HIV-2 and dually infected individuals: correlates of disease progression and immune restoration

The role of suppressive anti-retroviral therapy (ART) in eliciting restoration of dysregulated immune function remains unclear in HIV-1 infection. Also, due to tailoring of therapeutic regimens towards HIV-1, this possible impairment of therapy may be even more pronounced in HIV-2 and dual (HIV-D) infection. Thus, we evaluated the impact of ART on immune restoration by assessing T cell functions, including HIV specific responses in HIV-1-, HIV-2- and HIV-D-infected individuals. Both ART-treated and naive infected subjects showed persistently altered frequency of CD4+ T cell subsets [regulatory T cells (Treg ), naive/central memory, effector memory], increased immune activation, cytoxicity and decreased frequency of natural killer T (NKT)- like cells and T helper type 17 (Th17)/Treg ratio with elevated microbial translocation. Further, HIV-specific responses were dominated by gag-specific CD4+ T cells in virologically suppressed HIV-D individuals, suggesting retention of T cell memory for both viruses. Increased antigen-specific responses, including dual-functional interleukin (IL)-2/interferon (IFN)-γ CD4+ T cells, were detected in therapy receiving HIV-2-infected individuals indicative of a greater and more functionally diverse T cell memory repertoire. We delineated immune signatures specific to therapy-naive single HIV infection, as well as a unique signature associated with HIV-2 disease progression and immune restoration. Circulating Treg frequency, T cell activation and microbial translocation levels correlated with disease progression and immune restoration among all types of HIV infection. Also, memory responses negatively correlated, irrespective of type of infection, in ART receiving infected individuals, with CD4 rebound and decreased pan T cell activation. Our data highlight the need for adjunct immunomodulatory therapeutic strategies to achieve optimal immune restoration in HIV infection.

Blocking Formation of the Stable HIV Reservoir: A New Perspective for HIV-1 Cure

Recent studies demonstrate that the stable HIV-1 reservoir in resting CD4+ T cells is mostly formed from viruses circulating when combination antiretroviral therapy (ART) is initiated. Here we explore the immunological basis for these observations. Untreated HIV-1 infection is characterized by a progressive depletion of memory CD4+ T cells which mostly express CD127, the α chain of the IL-7 receptor (IL-7R). Depletion results from both direct infection and bystander loss of memory CD4+ T cells in part attributed to dysregulated IL-7/IL-7R signaling. While IL-7/IL7R signaling is not essential for the generation of effector CD4+ T cells from naïve cells, it is essential for the further transition of effectors to memory CD4+ T cells and their subsequent homeostatic maintenance. HIV-1 infection therefore limits the transition of CD4+ T cells from an effector to long-lived memory state. With the onset of ART, virus load (VL) levels rapidly decrease and the frequency of CD127+ CD4+ memory T cells increases, indicating restoration of effector to memory transition in CD4+ T cells. Collectively these data suggest that following ART initiation, HIV-1 infected effector CD4+ T cells transition to long-lived, CD127+ CD4+ T cells forming the majority of the stable HIV-1 reservoir. We propose that combining ART initiation with inhibition of IL-7/IL-7R signaling to block CD4+ T cell memory formation will limit the generation of long-lived HIV-infected CD4+ T cells and reduce the overall size of the stable HIV-1 reservoir.

Simian Immunodeficiency Virus Infects Functionally Polarized Memory CD4 T Cells Equivalently In Vivo

Among the numerous immunological abnormalities observed in chronically human immunodeficiency virus (HIV)-infected individuals, perturbations in memory CD4 T cells are thought to contribute specifically to disease pathogenesis. Among these, functional imbalances in the frequencies of T regulatory cells (Tregs) and interleukin 17 (IL-17)/IL-22-producing Th cells (Th17/Th22) from mucosal sites and T follicular helper (Tfh) cells in lymph nodes are thought to facilitate specific aspects of disease pathogenesis. However, while preferential infection of Tfh cells is widely thought to create an important viral reservoir in an immunologically privileged site in vivo, whether immunological perturbations among memory CD4 T cell populations are attributable to their relative infectivity by the virus in vivo is unclear. Here we studied peripheral blood and lymphoid tissues from antiretroviral (ARV)-treated and ARV-naive Asian macaques and isolated functionally defined populations of memory CD4 T cells. We then assessed the degree to which these populations were infected by simian immunodeficiency virus (SIV) in vivo, to determine whether particular functionally identified populations of memory CD4 T cells were preferentially infected by the virus. We found that SIV did not preferentially infect Th17 cells, compared to Th1 cells, Th2 cells, or Tregs. Moreover, Th17 cells contributed proportionately to the total pool of infected cells. Taken together, our data suggest that, although Tfh cells are more prone to harbor viral DNA, other functionally polarized cells are equally infected by the virus in vivo and Th17 cells are not preferentially infected.IMPORTANCE Functional perturbations of memory CD4 T cells have been suggested to underlie important aspects of HIV disease progression. However, the mechanisms underlying these perturbations remain unclear. Using a nonhuman primate model of HIV, we show that SIV infects functionally defined populations of memory CD4 T cells equally in different anatomic sites. Thus, preferential infection by the virus is unlikely to cause functional perturbations.

Increased Regulatory T-Cell Activity and Enhanced T-Cell Homeostatic Signaling in Slow Progressing HIV-infected Children

Pediatric slow progressors (PSP) are rare ART-naïve, HIV-infected children who maintain high CD4 T-cell counts and low immune activation despite persistently high viral loads. Using a well-defined cohort of PSP, we investigated the role of regulatory T-cells (TREG) and of IL-7 homeostatic signaling in maintaining normal-for-age CD4 counts in these individuals. Compared to children with progressive disease, PSP had greater absolute numbers of TREG, skewed toward functionally suppressive phenotypes. As with immune activation, overall T-cell proliferation was lower in PSP, but was uniquely higher in central memory TREG (CM TREG), indicating active engagement of this subset. Furthermore, PSP secreted higher levels of the immunosuppressive cytokine IL-10 than children who progressed. The frequency of suppressive TREG, CM TREG proliferation, and IL-10 production were all lower in PSP who go on to progress at a later time-point, supporting the importance of an active TREG response in preventing disease progression. In addition, we find that IL-7 homeostatic signaling is enhanced in PSP, both through preserved surface IL-7receptor (CD127) expression on central memory T-cells and increased plasma levels of soluble IL-7receptor, which enhances the bioactivity of IL-7. Combined analysis, using a LASSO modeling approach, indicates that both TREG activity and homeostatic T-cell signaling make independent contributions to the preservation of CD4 T-cells in HIV-infected children. Together, these data demonstrate that maintenance of normal-for-age CD4 counts in PSP is an active process, which requires both suppression of immune activation through functional TREG, and enhanced T-cell homeostatic signaling.

Immune signatures for HIV-1 and HIV-2 induced CD4+T cell dysregulation in an Indian cohort

Background

HIV-2 infection is characterised by a longer asymptomatic phase and slower AIDS progression than HIV-1 infection. Identifying unique immune signatures associated with HIV-2 pathogenesis may thus provide therapeutically useful insight into the management of HIV infection. This study examined the dynamics of the CD4⁺T cell compartment, critical in disease progression, focussing on chronic HIV-2 and HIV-1 infected individuals at various stages of disease progression.

Methods

A total of 111 participants including untreated and treated HIV infected individuals and seronegative individuals were enrolled in this study. The relative proportion of CD4⁺T cell subsets, expressing CD25 (IL-2Rα) and CD127 (IL-7R), in HIV infected individuals and seronegative controls were assessed by multiparametric flow cytometry. Additionally, levels of immune activation and cytotoxic T lymphocytes in both the CD4⁺T and CD8⁺T cell compartments was evaluated.

Results

Both treated and untreated, HIV-1 and HIV-2 infected individuals showed apparent dysregulation in CD4⁺ T cell subset frequency that was associated with disease progression. Furthermore, longitudinal sampling from a group of HIV-1 infected individuals on virologically effective ART showed no significant change in dysregulated CD4⁺T cell subset frequency. For both ART naïve and receiving groups associations with disease progression were strongest and significant with CD4⁺ T cell subset frequency compared to per cell expression of IL-2Rα and IL-7Rα. In untreated HIV-2 infected individuals, T cell activation was lower compared to ART naïve HIV-1 infected individuals and higher than seronegative individuals. Also, the level of Granzyme-B expressing circulating T cells was higher in both ART-naïve HIV-1 and HIV-2 infected individuals compared to seronegative controls.

Conclusion

Dysregulation of IL-2 and IL-7 homeostasis persists in CD4⁺T cell subsets irrespective of presence or absence of viremia or antiretroviral therapy in HIV infection. Furthermore, we report for the first time on levels of circulating Granzyme-B expressing CD4⁺T and CD8⁺T cells in chronic HIV-2 infection. Lower immune activation in these individuals indicates that persistent immune activation driven CD4⁺T cell depletion, as observed in untreated HIV-1 infected individuals, may not be as severe and provides evidence for a disparate pathogenesis mechanism. Our work also supports novel immunomodulatory therapeutic strategies for both HIV-1 and HIV-2 infection.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3743-7) contains supplementary material, which is available to authorized users.

Adult T-cell leukemia/lymphoma and acquired immunodeficiency syndrome - CD4+ T-cell malignancy in CD4+ T-cell deficient status: A paradox

CD4 counts along with viral loads are important parameters in the monitoring of human immunodeficiency virus (HIV) infection. Human T-cell lymphotropic virus type I (HTLV-I) is known to be an etiological agent for adult T-cell leukemia/lymphoma (ATLL). Coinfection of HTLV-I and HIV is well known in regions with high seroprevalence, and there is no published data in the Indian scenario. We present an interesting case of occurrence of CD4+ T-cell proliferation in a known beta thalassemia major with acquired HIV seropositivity accompanied by simultaneously increasing CD4+ counts and viral loads. Further workup revealed ATLL with an underlying HTLV infection.

Downregulation of IL-7 and IL-7R Reduces Membrane-Type Matrix Metalloproteinase 14 in Granular Corneal Dystrophy Type 2 Keratocyte

Purpose

Granular corneal dystrophy type 2 (GCD2) is caused by a point mutation (R124H) in the TGF-β-induced gene (TGFBI). However, the mechanisms underlying the accumulation of TGF-β-induced protein (TGFBIp) are poorly understood. Therefore, we evaluated the signaling cascade affecting the expression of TGFBIp using patient-derived cells.

Methods

Keratocyte primary cultures were prepared from corneas from the eye bank or from heterozygous or homozygous patients with GCD2 after penetrating or lamellar keratoplasty. GCD2 diagnoses were based on the results of a DNA analysis for the R124H TGFβI mutation. Keratocytes were treated with various cytokines and then analyzed using quantitative PCR (qPCR) array, qPCR, flow cytometry, ELISA, and Western blotting.

Results

TGFBI expression was counterregulated by IL-7 in corneal fibroblasts. IL-7 expression was significantly reduced in corneal fibroblasts from patients with GCD2. TGF-β and TGFBI expression were reduced on IL-7 treatment in corneal fibroblasts. Interestingly, the interplay between TGF-β and IL-7 was regulated by the RANKL/RANK signaling cascade. Also, IL-7 regulates the expression of a membrane-type matrix metalloproteinase (MT-MMP), which plays a crucial role in migration and neovascularization in the cornea.

Conclusions

These studies demonstrate that impaired IL-7 expression in patients with GCD2 affects disease pathogenesis via a failure to control TGF-β expression. The RANKL/RANK axis regulates TGF-β and TGFBI expression via IL-7-mediated MT-MMP regulation in corneal fibroblasts. These findings improve our understanding of the pathogenesis of GCD2.

The role of Treg population in pathogenesis of Crimean Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a severe human infection caused by CCHF virus (CCHFV). Today, although the literature on CCHF pathogenesis is still limited, it is thought to be associated with immunosuppression in the early phase of infection followed by pro-inflammatory immune response that may lead to fatal outcomes. The aim of this study is to investigate the role of regulatory T-cells (T_reg cells) in the pathogenesis of CCHFV. Peripheral blood mononuclear cell samples collected from 14 acute CCHF patients with mild disease course and 13 healthy subjects were included in this study. T_reg expression and functional levels were analyzed by flow cytometry. T_reg cells were identified as CD4+CD25 + CD127dim cells, and their functional levels were compared by measuring their ability to suppress CD69 and CD154 expression by activated T-cells. The flow cytometry analysis revealed that total T-cell and helper T-cell levels did not vary between the two groups. In contrast, CCHF patients displayed higher T_reg cell levels but lower T_reg suppressive activities when compared with control subjects. This is the first study on the involvement of T_reg cells in CCHF pathogenesis. Our results indicate that even though T_reg cell levels are elevated during acute phase of CCHF infection, not all generated T_reg cells has immunosuppressive capacity, and therefore may not represent 'true' T_reg cell population. Future studies on the intrinsic mechanisms responsible for the reduced T_reg inhibitory activities are required for further enlightening the CCHF pathogenesis, especially in the acute phase of the disease.

Regulatory T Cells Contribute to HIV-1 Reservoir Persistence in CD4+ T Cells Through Cyclic Adenosine Monophosphate-Dependent Mechanisms in Humanized Mice In Vivo

Background

Regulatory T cells (Tregs) suppress T-cell immune activation and human immunodeficiency virus type 1 (HIV-1) replication, but the role of Tregs in HIV-1 reservoir persistence is poorly defined.

Methods

Tregs were depleted by denileukin diftitox in humanized mice with chronic HIV-1 infection. Viral replication in lineage cells was determined by p24 expression. Levels of HIV-1 RNA and DNA in human cells, as well as replication-competent-virus-producing cells, were measured to quantified viral replication and reservoirs.

Results

Treg depletion resulted in a blip of HIV-1 replication in T cells but not in myeloid cells. The major activated reservoir cells were memory CD4+ T cells in vivo. Interestingly, the transient activation of viral replication led to HIV-1 reservoir reduction after viremia resuppression, as indicated by the quantity of HIV-1 DNA and replication-competent-virus-producing cells. Furthermore, we demonstrated that Tregs use cyclic adenosine monophosphate (cAMP)-dependent protein kinase A pathway to inhibit HIV-1 activation and replication in resting conventional T cells in vitro.

Conclusion

Tregs suppress HIV-1 replication in T cells and contribute to HIV-1 reservoir persistence. cAMP produced in Tregs is involved in their suppression of viral gene activation and expression. Treg depletion combined with combination antiretroviral therapy provides a novel strategy for HIV-1 cure.

Differentiating Immune Cell Targets in Gut-Associated Lymphoid Tissue for HIV Cure

The single greatest challenge to an HIV cure is the persistence of latently infected cells containing inducible, replication-competent proviral genomes, which constitute only a small fraction of total or infected cells in the body. Although resting CD4+ T cells in the blood are a well-known source of viral rebound, more than 90% of the body's lymphocytes reside elsewhere. Many are in gut tissue, where HIV DNA levels per million CD4+ T cells are considerably higher than in the blood. Despite the significant contribution of gut tissue to viral replication and persistence, little is known about the cell types that support persistence of HIV in the gut; importantly, T cells in the gut have phenotypic, functional, and survival properties that are distinct from T cells in other tissues. The mechanisms by which latency is established and maintained will likely depend on the location and cytokine milieu surrounding the latently infected cells in each compartment. Therefore, successful HIV cure strategies require identification and characterization of the exact cell types that support viral persistence, particularly in the gut. In this review, we describe the seeding of the latent HIV reservoir in the gut mucosa; highlight the evidence for compartmentalization and depletion of T cells; summarize the immunologic consequences of HIV infection within the gut milieu; propose how the damaged gut environment may promote the latent HIV reservoir; and explore several immune cell targets in the gut and their place on the path toward HIV cure.

Dysregulation of Circulating Tfr/Tfh Ratio in Primary biliary cholangitis

Follicular helper T (Tfh) cells and follicular regulatory T (Tfr) cells are critical for the development and maintenance of germinal centre (GC) and humoral immune responses. Accumulating evidence has demonstrated that the dysregulation of either Tfh cells or Tfr cells contributes to the pathogenesis of autoimmune diseases. We aim to investigate the roles of circulating Tfh cells and circulating Tfr cells in the pathogenesis of primary biliary cholangitis (PBC). A total of 34 patients with PBC and 27 health individuals were enrolled in this study. Flow cytometry revealed that circulating Tfh (CD4⁺ CXCR5⁺ CD127^hi CD25^lo ) cells were increased, but Tfr (CD4⁺ CXCR5⁺ CD127^lo CD25^hi ) cells and ratio of Tfr/Tfh were dramatically decreased in PBC patients compared with healthy controls. The Tfr/Tfh ratio was negatively correlated with level of serum IgM. Meanwhile, we also observed effector memory (CCR7^lo PD-1^hi ) Tfh cells and Tfr cells were dramatically increased, but central memory (CCR7^hi PD-1^lo ) Tfh cells and Tfr cells were decreased in PBC patients compared with healthy controls. Effector memory Tfr cells were positively correlated with level of serum ALP. These results indicate that an imbalance of circulating Tfr cells and Tfh cells may be involved in the immunopathogenesis of PBC and may provide novel insight for the development of PBC therapies.

Assessment of the HIV-1 reservoir in CD4+ regulatory T cells by a Droplet Digital PCR based approach

The relative contribution of regulatory T cells (Treg) as reservoir of HIV-1 in patients on chronic antiretroviral therapy is unclear to date. The aim of the current study was to assess the total HIV DNA burden and replication competent viral reservoir in Treg in comparison to central and effector memory cells (Tcm and Tem). Peripheral blood mononuclear cells were obtained from 10 HIV patients treated with antiretroviral therapy. Droplet Digital PCR (ddPCR) was used to quantify total HIV DNA loads in FACS-sorted CD4+ Treg (CD25+CD127lo) as compared to Tcm (CD45RO+CCR7+) and Tem (CD45RO+CCR7-). In contrast to earlier reports, no significant difference was found in total HIV DNA burden associated with Treg when compared to Tem and Tcm cells. In a subset of patients, quantitative viral outgrowth assays were also performed, using novel ddPCR based readout to quantify frequencies of Treg harboring replication competent virus.

Microvesicles released by apoptotic human neutrophils suppress proliferation and IL-2/IL-2 receptor expression of resting T helper cells

Membrane-coated microvesicles (MVs) have been identified as important mediators in intercellular communication. During the process of apoptosis, dying cells dynamically release MVs. Neutrophils are the most abundant type of leukocytes in the circulation. Due to their very short lifespan, it is likely that they are the source of large amounts of apoptotic cell-derived MVs. Here, we show that MVs released by apoptotic human polymorphonuclear neutrophils (apoPMN-MVs), but not the apoptotic neutrophils themselves, selectively suppress the proliferation of CD25 (IL-2Rα)^neg CD127 (IL-7Rα)^pos Th cells in a dose-dependent manner. In contrast, the proliferation of total T cells is not affected by MVs. Importantly, apoPMN-MVs suppress the secretion of IL-2 as well as the expression of and signaling via the IL-2 receptor (IL-2R) by CD25^neg CD127^pos Th cells. Addition of IL-7 strongly reduced the suppression of T-cell proliferation by MVs and the addition of IL-2 completely abrogated the suppressive effect. Thus, apoPMN-MVs suppressed a subset of Th cells by downregulating IL-2 and IL-2R expression and signaling. This may represent an important mechanism to prevent the activation and expansion of resting T cells in the absence of sufficient cytokine stimulation, and thereby maintaining immune tolerance.

Presence of HLA-DR Molecules and HLA-DRB1 mRNA in Circulating CD4(+) T Cells

The human major histocompatibility complex class II isotype HLA-DR is currently used as an activation marker for T cells. However, whether an endogenous protein expression or a molecular acquisition accounts for the presence of HLA-DR on T cells remains undetermined and still controversial. To further characterize this phenomenon, we compared several aspects of the presence of the HLA-DR protein to the presence of associated mRNA (HLA-DRB1), focusing on human T cells from peripheral blood of healthy individuals. Using a flow cytometric approach, we determined that the HLA-DR observed on CD4(+) T cells was almost exclusively cell surface-associated, while for autologous CD19(+) B cells, the protein could be located in the plasma membrane as well as in the cytoplasm. Moreover, negligible expression levels of HLA-DRB1 were found in CD4(+) T cells, using an HLA-DRB1 allele-specific qPCR assay. Finally, the presence of HLA-DR was not confined to activated CD4(+) and CD8(+) T cells, as evaluated by the co-expression of CD25. The functional role of the HLA-DR molecule on T cells remains enigmatic; however, this study presents evidence of fundamental differences for the presence of HLA-DR on T cells from HLA-DR in the context of antigen-presenting cells, which is a well-known phenomenon. Although an inducible endogenous protein expression cannot be excluded for the T cells, our findings suggest that a re-evaluation of the HLA-DR as a T cells activation marker is warranted.

Naive and Memory CD4⁺ T Cells Are Differentially Affected in Indonesian HIV Patients Responding to ART

While most HIV patients beginning antiretroviral therapy (ART) with advanced immunodeficiency recover CD4(+) T cell numbers, the profiles and functions of the newly acquired CD4(+) T cells have not been monitored in a resource-limiting setting. In this study, HIV patients (n = 31) from Jakarta, Indonesia, were studied 9 months after commencing ART with nadir CD4(+) T cell counts <200 cells/μL. All patients were hepatitis C virus (HCV) seropositive, but asymptomatic. Twelve healthy age-matched controls from the same community were included. CD4(+) T cell subsets, immune activation (HLA-DR), and expression of the interleukin (IL)-7 receptor α chain (CD127) were quantitated by flow cytometry. Proliferation (expression of Ki67) was measured following in vitro stimulation (5 days) with anti-CD3 antibody or IL-7. Fifty-two percent of patients recovered CD4(+) T cell counts >200 cells/μL over 12 months. At 9 months, patients had fewer naive and CD31(+)-naive CD4(+) T cells, more effector memory (EM) CD4(+) T cells, and higher HLA-DR expression on CD4(+) T cells than controls. CD127 expression was low on all CD4(+) T cell subsets except for naive cells, where it was similar to controls. Similarly, after anti-CD3 antibody or IL-7 stimulation, patients had lower Ki67 expression than controls in all subsets, except naive CD4(+) T cells where it was normal or elevated. Overall in the first year of ART, patients had fewer naive and more EM CD4(+) T cells. Ongoing immune activation and, antigen-driven stimulation and differentiation of naive T cells may reduce the naive T cell pool, while driving the maturation and accumulation of memory cells with proliferative defects.

Prognostic value of circulating regulatory T cell subsets in untreated non-small cell lung cancer patients

The role of the different circulating regulatory T-cells (Treg) subsets, as well as their correlation with clinical outcome of non-small cell lung cancer (NSCLC) patients is poorly understood. Peripheral blood from 156 stage III/IV chemotherapy-naive NSCLC patients and 31 healthy donors (HD) was analyzed with flow cytometry for the presence and functionality of CD4⁺ Treg subsets (naive, effector and terminal effector). Their frequencies were correlated with the clinical outcome. All CD4⁺ Treg subsets exhibited highly suppressive activity by TGF-β and IL-10 production. The percentages of naive Treg were found elevated in NSCLC patients compared to HD and were associated with poor clinical outcome, whereas the percentage of terminal effector Treg was lower compared to HD and higher levels were correlated with improved clinical response. At baseline, normal levels of naive and effector Treg were associated with longer overall survival (OS) compared to high levels, while the high frequency of the terminal effector Treg was correlated with longer Progression-Free Survival and OS. It is demonstrated, for first time, that particular CD4⁺ Treg subtypes are elevated in NSCLC patients and their levels are associated to the clinical outcome. The blocking of their migration to the tumor site may be an effective therapeutic strategy.

CD4+ T Follicular Helper and IgA+ B Cell Numbers in Gut Biopsies from HIV-Infected Subjects on Antiretroviral Therapy Are Similar to HIV-Uninfected Individuals

Background

Disruption of gastrointestinal tract epithelial and immune barriers contribute to microbial translocation, systemic inflammation, and progression of HIV-1 infection. Antiretroviral therapy (ART) may lead to reconstitution of CD4⁺ T cells in gut-associated lymphoid tissue (GALT), but its impact on humoral immunity within GALT is unclear. Therefore, we studied CD4⁺ subsets, including T follicular helper cells (Tfh), as well as resident B cells that have switched to IgA production, in gut biopsies, from HIV⁺ subjects on suppressive ART compared to HIV-negative controls (HNC).

Methods

Twenty-three HIV⁺ subjects on ART and 22 HNC undergoing colonoscopy were recruited to the study. Single-cell suspensions were prepared from biopsies from left colon (LC), right colon (RC), and terminal ileum (TI). T and B lymphocyte subsets, as well as EpCAM⁺ epithelial cells, were accurately enumerated by flow cytometry, using counting beads.

Results

No significant differences in the number of recovered epithelial cells were observed between the two subject groups. However, the median TI CD4⁺ T cell count/10⁶ epithelial cells was 2.4-fold lower in HIV⁺ subjects versus HNC (19,679 versus 47,504 cells; p = 0.02). Similarly, median LC CD4⁺ T cell counts were reduced in HIV⁺ subjects (8,358 versus 18,577; p = 0.03) but were not reduced in RC. Importantly, we found no significant differences in Tfh or IgA⁺ B cell counts at either site between HIV⁺ subjects and HNC. Further analysis showed no difference in CD4⁺, Tfh, or IgA⁺ B cell counts between subjects who commenced ART in primary compared to chronic HIV-1 infection. Despite the decrease in total CD4 T cells, we could not identify a selective decrease of other key subsets of CD4⁺ T cells, including CCR5⁺ cells, CD127⁺ long-term memory cells, CD103⁺ tissue-resident cells, or CD161⁺ cells (surrogate marker for Th17), but there was a slight increase in the proportion of T regulatory cells.

Conclusion

While there were lower absolute CD4⁺ counts in the TI and LC in HIV⁺ subjects on ART, they were not associated with significantly reduced Tfh cell counts or IgA⁺ B cells, suggesting that this important vanguard of adaptive immune defense against luminal microbial products is normalized following ART.

CD25+ FoxP3+ Memory CD4 T Cells Are Frequent Targets of HIV Infection In Vivo

Interleukin 2 (IL-2) signaling through the IL-2 receptor alpha chain (CD25) facilitates HIV replication in vitro and facilitates homeostatic proliferation of CD25(+) FoxP3(+) CD4(+) T cells. CD25(+) FoxP3(+) CD4(+) T cells may therefore constitute a suitable subset for HIV infection and plasma virion production. CD25(+) FoxP3(+) CD4(+) T cell frequencies, absolute numbers, and the expression of CCR5 and cell cycle marker Ki67 were studied in peripheral blood from HIV(+) and HIV(-) study volunteers. Different memory CD4(+) T cell subsets were then sorted for quantification of cell-associated HIV DNA and phylogenetic analyses of the highly variable EnvV1V3 region in comparison to plasma-derived virus sequences. In HIV(+) subjects, 51% (median) of CD25(+) FoxP3(+) CD4(+) T cells expressed the HIV coreceptor CCR5. Very high frequencies of Ki67(+) cells were detected in CD25(+) FoxP3(+) memory CD4(+) T cells (median, 27.6%) in comparison to CD25(-) FoxP3(-) memory CD4(+) T cells (median, 4.1%; P < 0.0001). HIV DNA content was 15-fold higher in CD25(+) FoxP3(+) memory CD4(+) T cells than in CD25(-) FoxP3(-) T cells (P = 0.003). EnvV1V3 sequences derived from CD25(+) FoxP3(+) memory CD4(+) T cells did not preferentially cluster with plasma-derived sequences. Quasi-identical cell-plasma sequence pairs were rare, and their proportion decreased with the estimated HIV infection duration. These data suggest that specific cellular characteristics of CD25(+) FoxP3(+) memory CD4(+) T cells might facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. The contribution of this cell population to plasma virion production remains unclear.

IMPORTANCE

Despite recent advances in the understanding of AIDS virus pathogenesis, which cell subsets support HIV infection and replication in vivo is incompletely understood. In vitro, the IL-2 signaling pathway and IL-2-dependent cell cycle induction are essential for HIV infection of stimulated T cells. CD25(+) FoxP3(+) memory CD4 T cells, often referred to as regulatory CD4 T cells, depend on IL-2 signaling for homeostatic proliferation in vivo Our results show that CD25(+) FoxP3(+) memory CD4(+) T cells often express the HIV coreceptor CCR5, are significantly more proliferative, and contain more HIV DNA than CD25(-) FoxP3(-) memory CD4 T cell subsets. The specific cellular characteristics of CD25(+) FoxP3(+) memory CD4(+) T cells probably facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. However, the contribution of this cell subset to plasma viremia remains unclear.

Decreased T Follicular Regulatory Cell/T Follicular Helper Cell (TFH) in Simian Immunodeficiency Virus-Infected Rhesus Macaques May Contribute to Accumulation of TFH in Chronic Infection

T follicular helper cells (TFH) are critical for the development and maintenance of germinal center (GC) and humoral immune responses. During chronic HIV/SIV infection, TFH accumulate, possibly as a result of Ag persistence. The HIV/SIV-associated TFH expansion may also reflect lack of regulation by suppressive follicular regulatory CD4(+) T cells (TFR). TFR are natural regulatory T cells (TREG) that migrate into the follicle and, similar to TFH, upregulate CXCR5, Bcl-6, and PD1. In this study, we identified TFR as CD4(+)CD25(+)FOXP3(+)CXCR5(+)PD1(hi)Bcl-6(+) within lymph nodes of rhesus macaques (RM) and confirmed their localization within the GC by immunohistochemistry. RNA sequencing showed that TFR exhibit a distinct transcriptional profile with shared features of both TFH and TREG, including intermediate expression of FOXP3, Bcl-6, PRDM1, IL-10, and IL-21. In healthy, SIV-uninfected RM, we observed a negative correlation between frequencies of TFR and both TFH and GC B cells, as well as levels of CD4(+) T cell proliferation. Post SIV infection, the TFR/TFH ratio was reduced with no change in the frequency of TREG or TFR within the total CD4(+) T cell pool. Finally, we examined whether higher levels of direct virus infection of TFR were responsible for their relative depletion post SIV infection. We found that TFH, TFR, and TREG sorted from SIV-infected RM harbor comparable levels of cell-associated viral DNA. Our data suggest that TFR may contribute to the regulation and proliferation of TFH and GC B cells in vivo and that a decreased TFR/TFH ratio in chronic SIV infection may lead to unchecked expansion of both TFH and GC B cells.

Differences in antigen-specific CD4+ responses to opportunistic infections in HIV infection

HIV-infected individuals with severe immunodeficiency are at risk of opportunistic infection (OI). Tuberculosis (TB) may occur without substantial immune suppression suggesting an early and sustained adverse impact of HIV on Mycobacterium tuberculosis (MTB)-specific cell mediated immunity (CMI). This prospective observational cohort study aimed to observe differences in OI-specific and MTB-specific CMI that might underlie this. Using polychromatic flow cytometry, we compared CD4+ responses to MTB, cytomegalovirus (CMV), Epstein-Barr virus (EBV) and Candida albicans in individuals with and without HIV infection. MTB-specific CD4+ T-cells were more polyfunctional than virus specific (CMV/EBV) CD4+ T-cells which predominantly secreted IFN-gamma (IFN-γ) only. There was a reduced frequency of IFN-γ and IL-2 (IL-2)-dual-MTB-specific cells in HIV-infected individuals, which was not apparent for the other pathogens. MTB-specific cells were less differentiated especially compared with CMV-specific cells. CD127 expression was relatively less frequent on MTB-specific cells in HIV co-infection. MTB-specific CD4+ T-cells PD-1 expression was infrequent in contrast to EBV-specific CD4+ T-cells. The variation in the inherent quality of these CD4+ T-cell responses and impact of HIV co-infection may contribute to the timing of co-infectious diseases in HIV infection.

CD4+CD25+CD127 regulatory cells play multiple roles in maintaining HIV-1 p24 production in patients on long-term treatment: HIV-1 p24-producing cells and suppression of anti-HIV immunity

BACKGROUND

A major question when attempting to eradicate and treat HIV-1 infection is how to reactivate latent proviruses. Stimulating HIV-1-specific cytolytic T lymphocytes (CTL) has been shown to facilitate the elimination of the latent viral reservoir after viral reactivation. Regulatory T (Treg) cells are known to be capable of lowering both HIV-specific immunoreactions and general immune activation during HIV-1 infection. It was hypothesized that the depletion of Treg cells could increase the HIV-1-specific cytolytic T lymphocyte response and reactivate HIV-1 p24 production.

METHODS

Treg cells were isolated by isolation kit according to the surface marker of Treg cells. Real-time PCR method was used to quantify HIV-1 DNA. P24 antigens in the cell culture supernatant was done by ELISA. Cells activation and HIV specific HIV-1 CD8+ T cells were analyses using a FACSCalibur flow cytometer and CELLQUEST software.

RESULTS

This study included both HIV-infected patients who were antiviral treatment-naïve and patients with sustained viral responses to antiretroviral therapy (ART) for 1 or 5 years. It was found that the HIV-DNA levels in Treg cells were approximately 10-fold higher than those in non-Treg CD4+ cells and that the depletion of Treg cells could enhance the frequency of HIV-1-specific CTL and immune activation after 5 years of effective ART.

CONCLUSIONS

CD4+CD25+CD127 regulatory cells play multiple roles in maintaining HIV-1 p24 production in long-term ART patients. Treg cells may be a target for eliminating the latent HIV reservoir after effective long-term ART.

Correlation of central memory CD4+ T-Cell decrease in the peripheral blood with disease progression in SIVmac251-infected Chinese rhesus macaques

BACKGROUND

Correlation of CD4(+) Tcm cells in the peripheral blood to disease progression in SIVmac251 infection was examined in Chinese rhesus macaques.

METHODS

Plasma viral RNA loads were measured by a quantitative real-time reverse transcription-PCR (qRT-PCR) assay for SIV gag. Disease progression was determined based on time of survival. Phenotyping of CD4(+) T-cell subsets in the peripheral blood was longitudinally performed by flow cytometry.

RESULTS

Although CD4(+) T-cell decrease and low CD4(+)/CD8(+) T-cell ratio in the peripheral blood after SIVmac251 infection did not correlate with disease progression, CD4(+) Tcm cell decrease was observed to be correlated to disease progression in the SIVmac251-infected Chinese rhesus macaques.

CONCLUSIONS

Our findings suggest that CD4(+) Tcm cell decrease could be used as a predictive marker for defining the pathogenesis of the SIV disease and consequently HIV/SIV vaccine efficacy in Chinese rhesus macaques.

Schistosome infection aggravates HCV-related liver disease and induces changes in the regulatory T-cell phenotype

Schistosome infections are renowned for their ability to induce regulatory networks such as regulatory T cells (Treg) that control immune responses against homologous and heterologous antigens such as allergies. However, in the case of co-infections with hepatitis C virus (HCV), schistosomes accentuate disease progression and we hypothesized that expanding schistosome-induced Treg populations change their phenotype and could thereby suppress beneficial anti-HCV responses. We therefore analysed effector T cells and n/iTreg subsets applying the markers Granzyme B (GrzB) and Helios in Egyptian cohorts of HCV mono-infected (HCV), schistosome-co-infected (Sm/HCV) and infection-free individuals. Interestingly, viral load and liver transaminases were significantly elevated in Sm/HCV individuals when compared to HCV patients. Moreover, overall Treg frequencies and Helios(pos) Treg were not elevated in Sm/HCV individuals, but frequencies of GrzB(+) Treg were significantly increased. Simultaneously, GrzB(+) CD8(+) T cells were not suppressed in co-infected individuals. This study demonstrates that in Sm/HCV co-infected cohorts, liver disease is aggravated with enhanced virus replication and Treg do not expand but rather change their phenotype with GrzB possibly being a more reliable marker than Helios for iTreg. Therefore, curing concurrent schistosome disease could be an important prerequisite for successful HCV treatment as co-infected individuals respond poorly to interferon therapy.

Expression of the IL-7 receptor alpha-chain is down regulated on the surface of CD4 T-cells by the HIV-1 Tat protein

HIV infection elicits defects in CD4 T-cell homeostasis in both a quantitative and qualitative manner. Interleukin-7 (IL-7) is essential to T-cell homeostasis and several groups have shown reduced levels of the IL-7 receptor alpha-chain (CD127) on both CD4 and CD8 T-cells in viremic HIV+ patients. We have shown previously that soluble HIV Tat protein specifically down regulates cell surface expression of CD127 on human CD8 T-cells in a paracrine fashion. The effects of Tat on CD127 expression in CD4 T-cells has yet to be described. To explore this effect, CD4 T-cells were isolated from healthy individuals and expression levels of CD127 were examined on cells incubated in media alone or treated with Tat protein. We show here that, similar to CD8 T-cells, the HIV-1 Tat protein specifically down regulates CD127 on primary human CD4 T-cells and directs the receptor to the proteasome for degradation. Down regulation of CD127 in response to Tat was seen on both memory and naive CD4 T-cell subsets and was blocked using either heparin or anti-Tat antibodies. Tat did not induce apoptosis in cultured primary CD4 T-cells over 72 hours as determined by Annexin V and PI staining. Pre-incubation of CD4 T-cells with HIV-1 Tat protein did however reduce the ability of IL-7 to up regulate Bcl-2 expression. Similar to exogenous Tat, endogenously expressed HIV Tat protein also suppressed CD127 expression on primary CD4 T-cells. In view of the important role IL-7 plays in lymphocyte proliferation, homeostasis and survival, down regulation of CD127 by Tat likely plays a central role in immune dysregulation and CD4 T-cell decline. Understanding this effect could lead to new approaches to mitigate the CD4 T-cell loss evident in HIV infection.

Lactose inhibits regulatory T-cell-mediated suppression of effector T-cell interferon-γ and IL-17 production

Our interest in lactose as an immunomodulatory molecule results from studies showing that lactose binds to galectin-9, which has been shown to have various regulatory functions in the immune system including regulation of T-cell responses. Impaired regulation of T helper (Th)1 and Th17 type immune responses and dysfunction of regulatory T cells (T_reg) have been implicated in many human immune-mediated diseases. In the present study, we investigated the effects of lactose on immune regulation using co-cultures of human peripheral blood mononuclear cell (PBMC)-derived T_reg and effector T cells (T_eff) obtained from twenty healthy adults. T_reg, i.e. CD4⁺CD25⁺CD127⁻, were isolated from PBMC by immunomagnetic separation. The fraction of CD4⁺CD127⁻ cells that was depleted of CD25⁺ cells was used as T_eff. T_reg and T_eff at a ratio 1:5 were activated and the effects of lactose on the secretion of interferon-γ (IFN-γ) and IL-17 were analysed using ELISA for protein and quantitative RT-PCR for mRNA. T_reg down-regulated the secretion of both IFN-γ (8·8–3·9 ng/ml, n 20, P= 0·003) and IL-17 (0·83–0·64 ng/ml, n 15, P= 0·04) in co-cultures, while in the presence of lactose the levels of secreted IFN-γ and IL-17 remained high and no down-regulation was observed (16·4 v. 3·99 ng/ml, n 20, P< 0·0001, and 0·74 v. 0·64 ng/ml, n 15, P= 0·005, respectively). We showed that lactose inhibits human T_reg-mediated suppression of Th1 and Th17 immune responses in vitro.

Exploiting differential expression of the IL-7 receptor on memory T cells to modulate immune responses

Interleukin-7 is a non-redundant growth, differentiation and survival factor for human T lymphocytes. Most circulating, mature T cells express the receptor for IL-7, but not all. Importantly, CD4 Tregs express greatly reduced levels of IL-7R compared to conventional CD4 T cells, presenting an opportunity to selectively target the latter cells with either more IL-7 to boost responses, or to block IL-7 signalling to limit responses. This article reviews what is known about regulation of IL-7R expression, and recent progress in therapeutic approaches related to IL-7 and its receptor.

Immunological function restoration with lopinavir/ritonavir versus efavirenz containing regimens in HIV-infected patients: a randomized clinical trial

CD4(+) count increase has been reported to be different with lopinavir/r (LPV/r) and efavirenz (EFV)-containing regimens. The different effect of these two regimens on other immune function parameters and the relationship with the gain of CD4(+) count have not been assessed in a randomized clinical trial. Fifty antiretroviral treatment (cART) naïve HIV-infected individuals were randomized to receive LPV/r or EFV both with tenofovir/emtricitabine for 48 weeks. A substudy of immunological function restoration was performed in 22 patients (LPV/r n=10 and EFV n=12). Activation, thymic function, apoptosis, senescence, exhaustion, Treg cells, interleukin (IL)-7-receptor/IL-7 system, thymic volume, and lymphoid tissue fibrosis were evaluated at baseline and at week 48. Both groups experienced a CD4(+) count increase that was higher in the EFV group (ΔCD4(+) 88 vs. 315 cells/μl LPV/r vs. EFV, respectively, p<0.001). Despite this difference in CD4(+) gain, the change in other immune function parameters was similar in both treatment groups. Most of parameters evaluated tended to normalize after 48 weeks of cART. A significant decrease in levels of activation, senescence, exhaustion, and apoptosis on CD4(+) and CD8(+) T cells (p<0.001 for all) and a significant increase in markers of thymic function, IL-7 receptor, and in the levels of central memory CD4(+) T cells and naive subsets of CD8(+) T cells (p<0.001 for all) with respect to baseline values were observed without any difference between groups. These data indicate that the differences in CD4(+) gain with different cART regimens are not immunologically meaningful and might explain the similar clinical efficacy of these regimens.

Interleukin-7 signalling defects in naive CD4+ T cells of HIV patients with CD4+ T-cell deficiency on antiretroviral therapy are associated with T-cell activation and senescence

OBJECTIVE

To examine the relationship of defects in interleukin (IL)-7-induced naive CD4 T-cell homeostasis with residual immune activation and CD4 T-cell senescence in HIV patients receiving antiretroviral therapy (ART) who exhibit persistent CD4 T-cell deficiency.

DESIGN

IL-7 induced proliferation of, and IL-7 receptor signalling in, total and naive CD4 T cells of HIV patients who had low (<350 cells/μl) or normal (>500 cells/μl) CD4 T-cell counts on ART was examined and related to markers of CD4 T-cell activation and senescence and innate immune activation.

METHODS

Total, naive (CD45RA CD27) and CD31 naive CD4 T cells from aviremic HIV patients (n=39) with nadir CD4 T-cell counts less than 100 cells/μl, who had received ART for a median time of 7 (range 1-11) years, were assessed for CD127 expression, proliferation (Ki67), signal transducer and activator of transcription 5 phosphorylation (pSTAT5) and CD127 modulation following IL-7 stimulation. Changes were related to proportions of CD4 T cells expressing HLA-DR or CD57 and plasma levels of sCD14, CXCL9 and CXCL10.

RESULTS

Patients with CD4 T-cell deficiency exhibited lower expression of CD127 on total, naive and CD31 naive CD4 T cells. Downregulation of CD127 after culture with IL-7 correlated inversely with CD4 T-cell counts and directly with Ki67 expression. Induction of pSTAT5 in CD4 T-cell subsets was greater in patients with normal CD4 T-cell counts. CD127 expression correlated inversely with proportions of CD4CD57 T cells, and pSTAT5 induction correlated inversely with CD4 T-cell expression of HLA-DR and CD57.

CONCLUSION

Defects of IL-7 signalling in HIV patients with persistent CD4 T-cell deficiency receiving ART are associated with CD4 T-cell activation and senescence.

High numbers of differentiated effector CD4 T cells are found in patients with cancer and correlate with clinical response after neoadjuvant therapy of breast cancer

CD4(+) T cells influence tumor immunity in complex ways that are not fully understood. In this study, we characterized a population of human differentiated effector CD4(+) T cells that is defined by low levels of the interleukin (IL)-2 and IL-7 receptors (CD25(-)CD127(-)). We found that this cell population expands in patients with various types of cancer, including breast cancer, to represent 2% to 20% of total CD4(+) blood T lymphocytes as compared with only 0.2% to 2% in healthy individuals. Notably, these CD25(-)CD127(-)CD4 T cells expressed effector markers such as CD244 and CD11b with low levels of CD27, contrasting with the memory phenotype dominating this population in healthy individuals. These cells did not cycle in patients, nor did they secrete IL-10 or IL-17, but instead displayed cytotoxic features. Moreover, they encompassed oligoclonal expansions paralleling an expansion of effector CD8(+) T cells that included tumor antigen-specific T cells. During neoadjuvant chemotherapy in patients with breast cancer, we found that the increase in CD25(-)CD127(-) CD4(+) T cells correlated with tumor regression. This observation suggested that CD4(+) T cells included tumor antigen-specific cells, which may be generated by or participate in tumor regressions during chemotherapy. In summary, our results lend support to the hypothesis that CD4(+) T cells are involved in human antitumor responses.

Early Decision: Effector and Effector Memory T Cell Differentiation in Chronic Infection

As effector memory T cells (Tem) are the predominant population elicited by chronic parasitic infections, increasing our knowledge of their function, survival and derivation, as phenotypically and functionally distinct from central memory and effector T cells will be critical to vaccine development for these diseases. In some infections, memory T cells maintain increased effector functions, however; this may require the presence of continued antigen, which can also lead to T cell exhaustion. Alternatively, in the absence of antigen, only the increase in the number of memory cells remains, without enhanced functionality as central memory. In order to understand the requirement for antigen and the potential for longevity or protection, the derivation of each type of memory must be understood. A thorough review of the data establishes the existence of both memory (Tmem) precursors and effector T cells (Teff) from the first hours of an immune response. This suggests a new paradigm of Tmem differentiation distinct from the proposition that Tmem only appear after the contraction of Teff. Several signals have been shown to be important in the generation of memory T cells, such as the integrated strength of “signals 1-3” of antigen presentation (antigen receptor, co-stimulation, cytokines) as perceived by each T cell clone. Given that these signals integrated at antigen presentation cells have been shown to determine the outcome of Teff and Tmem phenotypes and numbers, this decision must be made at a very early stage. It would appear that the overwhelming expansion of effector T cells and the inability to phenotypically distinguish memory T cells at early time points has masked this important decision point. This does not rule out an effect of repeated stimulation or chronic inflammatory milieu on populations generated in these early stages. Recent studies suggest that Tmem are derived from early Teff, and we suggest that this includes Tem as well as Tcm. Therefore, we propose a testable model for the pathway of differentiation from naïve to memory that suggests that Tem are not fully differentiated effector cells, but derived from central memory T cells as originally suggested by Sallusto et al. in 1999, but much debated since.

Immune activation and HIV persistence: implications for curative approaches to HIV infection

Despite complete or near-complete suppression of human immunodeficiency virus (HIV) replication with combination antiretroviral therapy, both HIV and chronic inflammation/immune dysfunction persist indefinitely. Untangling the association between the virus and the host immune environment during therapy might lead to novel interventions aimed at either curing the infection or preventing the development of inflammation-associated end-organ disease. Chronic inflammation and immune dysfunction might lead to HIV persistence by causing virus production, generating new target cells, enabling infecting of activated and resting target cells, altering the migration patterns of susceptible target cells, increasing the proliferation of infected cells, and preventing normal HIV-specific clearance mechanisms from function. Chronic HIV production or replication might contribute to persistent inflammation and immune dysfunction. The rapidly evolving data on these issues strongly suggest that a vicious cycle might exist in which HIV persistence causes inflammation that in turn contributes to HIV persistence.

T-cell immunophenotyping distinguishes active from latent tuberculosis

BACKGROUND

Changes in the phenotype and function of Mycobacterium tuberculosis (M. tuberculosis)-specific CD4+ and CD8+ T-cell subsets in response to stage of infection may allow discrimination between active tuberculosis and latent tuberculosis infection.

METHODS

A prospective comparison of M. tuberculosis-specific cellular immunity in subjects with active tuberculosis and latent tuberculosis infection, with and without human immunodeficiency virus (HIV) coinfection. Polychromatic flow cytometry was used to measure CD4+ and CD8+ T-cell subset phenotype and secretion of interferon γ (IFN-γ), interleukin 2 (IL-2), and tumor necrosis factor α (TNF-α).

RESULTS

Frequencies of CD4+ and CD8+ cells secreting IFN-γ-only, TNF-α-only and dual IFN-γ/TNF-α were greater in active tuberculosis vs latent tuberculosis infection. All M. tuberculosis-specific CD4+ subsets, with the exception of IL-2-only cells, switched from central to effector memory phenotype in active tuberculosis vs latent tuberculosis infection, accompanied by a reduction in IL-7 receptor α (CD127) expression. The frequency of PPDspecific CD4+ TNF-α-only-secreting T cells with an effector phenotype accurately distinguished active tuberculosis from latent tuberculosis infection with an area under the curve of 0.99, substantially more discriminatory than measurement of function alone.

CONCLUSIONS

Combined measurement of T-cell phenotype and function defines a highly discriminatory biomarker of tuberculosis disease activity. Unlocking the diagnostic and monitoring potential of this combined approach now requires validation in large-scale prospective studies.

CD4+ T effectors specific for the tumor antigen NY-ESO-1 are highly enriched at ovarian cancer sites and coexist with, but are distinct from, tumor-associated Treg

Whereas tumor infiltration by T effectors is generally associated with a more favorable prognosis, the accumulation of CD4(+) regulatory T cells (Treg) within tumors is instead often associated with poor disease outcome. Because approaches to improve antitumor immunity aim, on one hand, at expanding tumor antigen-specific T cells and, on the other, at eliminating or inactivating Treg, an outstanding question is whether, and to what extent, tumor antigen-specific CD4(+) T effectors present at tumor sites overlap with tumor-associated Treg. Here, we used MHC class II/peptide tetramers incorporating an immunodominant peptide from the human tumor-specific antigen NY-ESO-1 to assess antigen-specific CD4(+) T cells among conventional CD4(+) T effectors and Treg at sites of ovarian cancer. We found that, in patients who spontaneously respond to the antigen, the frequency of NY-ESO-1 tetramer(+) cells detected ex vivo was highly enriched in tumors as compared with the periphery. At tumor sites, NY-ESO-1 tetramer(+) cells were detected concomitantly with high proportions of Treg but were distinct from the latter and displayed characteristics of TH1 effectors. Thus, even in the presence of high proportions of Treg, tumor antigen-specific CD4(+) T cells can accumulate in ovarian tumors and maintain an effector phenotype.

Expression of IL-7 receptor in human peripheral regulatory T cells

INTRODUCTION

Regulatory T cells (Tregs, CD4 + CD25(high) Foxp3(+)) play a crucial role in allergy and other inflammatory diseases. However, the isolation of viable Tregs on the basis of intracellular expression of specific Forkhead Box Protein P3 (Foxp3) is difficult. In this study we checked if the expression of IL-7 receptor (CD127) on the Tregs could be a useful marker for isolation of viable Treg Foxp3(+) cells.

MATERIAL AND METHODS

Twenty-five patients sensitized to grass pollen with allergic rhinitis (AR) and ten healthy subjects were included. We compared Foxp3 expression in different CD4(+) T cell subsets by flow cytometry and we assessed the relationship between the expression of Foxp3 and CD127 within regulatory T cells.

RESULTS

Within the CD(4)+ lymphocytes 3.68 ±2.0% showed expression of Foxp3, 51.82 ±8.03% of CD4(+)CD25(high) were Foxp3 positive (Foxp3(+)), whereas 82.12 ±5.4% of CD4(+)CD25(high)CD127(low) were Foxp3(+). High intracellular expression of Foxp3 correlated with low superficial CD127 expression (r = 0.42, p = 0.017). There were no significant differences regarding the analysed markers between AR patients and healthy controls.

CONCLUSIONS

Regulatory T cells may be purified from the fresh peripheral blood as viable regulatory Foxp3 bright cells using CD4, high expression of CD25 and low expression of CD127 antigen.

Cytometry, immunology, and HIV infection: three decades of strong interactions

Flow cytometry (FCM) has been extensively used to investigate immunological changes that occur from infection with the human immunodeficiency virus (HIV). This review describes some of the most relevant cellular and molecular changes in the immune system that can be detected by FCM during HIV infection. Finally, it will be discussed how this technology has facilitated the understanding not only of the biology of the virus but also of the mechanisms that the immune system activates to fight HIV and is allowing to monitor the efficacy of antiretroviral therapy.

Excessive conversion and impaired thymic output contribute to disturbed regulatory T-cell homeostasis in AIDS patients with low CD4 cell counts

OBJECTIVE

T regulatory (Treg) cells are a heterogeneous population that consists of CD4(+)CD25(low)CD45RA(+) [naive Treg (nTreg) cells] and CD4(+)CD25(high)CD45RA(-) [activated Treg (aTreg) cells] subsets. We investigated the effects of HIV infection and HAART on distinct Treg subsets.

METHODS

HIV-infected adult patients naive to HAART (n=57), patients with acute HIV infection (n=13), and healthy controls (n=92) were recruited for a cross-sectional study. Patients receiving HAART were followed up in a longitudinal study.

RESULTS

Compared with healthy controls, we observed a reduced proportion of nTreg cells and an elevated frequency of aTreg cells in peripheral blood from HAART-naïve patients. Moreover, nTreg cells showed a decreased CD31(+) frequency, whereas aTreg cells showed an increased CD31(+) frequency, indicating impaired thymic output and excessive conversion from nTreg to aTreg cells. nTreg and aTreg cells both displayed higher levels of Ki67(+), reflecting hyperproliferation. The longitudinal study showed that HAART successfully recovered nTreg but not aTreg cell frequency. Higher baseline naïve CD4 T-cell percentages were associated with faster reconstitution of nTreg cell frequency as well as CD4(+) T-cell count.

CONCLUSION

Our data suggest that the disturbed homeostasis of Treg cells in HIV-infected patients is probably caused by excessive conversion from nTreg to aTreg cells, and impaired thymic output of nTreg cells. nTreg cells can be recovered by HAART, which was associated with baseline naive CD4(+) T-cell percentages, indicating that reconstitution of nTreg cells may benefit from earlier antiretroviral treatment.

Relationships between IL-17(+) subsets, Tregs and pDCs that distinguish among SIV infected elite controllers, low, medium and high viral load rhesus macaques

Comprehensive studies of the frequencies and absolute numbers of the various cell lineages that synthesize IL-17 in the blood and corresponding gastrointestinal (GI) tissues, their correlation with CD4(+) Tregs, CD8(+) Tregs, total and IFN-α synthesizing plasmacytoid dendritic cells (pDC) relative to plasma viral load in SIV infection has been lacking. The unique availability of SIV infected rhesus macaques (RM) classified as Elite Controllers (EC), and those with Low, Intermediate and High Viral Loads (HVL) provided a unique opportunity to address this issue. Results of these studies showed that EC demonstrated a remarkable ability to reverse changes that are induced acutely by SIV in the various cell lineages. Highlights of the differences between EC and HVL RM within Gastro-intestinal tissues (GIT) was the maintenance and/or increases in the levels of IL-17 synthesizing CD4, CD8, and NK cells and pDCs associated with slight decreases in the levels of CD4(+) Tregs and IFN-α synthesizing pDCs in EC as compared with decreases in the levels of IL-17 synthesizing CD4, CD8 and NK cells associated with increases in pDCs and IFN-α synthesizing pDCs in HVL monkeys. A previously underappreciated role for CD8(+) Tregs was also noted with a moderate increase in ECs but further increases of CD8(+) Tregs with increasing VL in viremic monkeys. Positive correlations between plasma VL and decreases in the levels of Th17, Tc17, NK-17, CD4(+) Tregs and increases in the levels of CD8(+) Tregs, total and IFN-α synthesizing pDCs were also noted. This study also identified 2 additional IL-17(+) subsets in GIT as CD3(-/)CD8(+)/NKG2a(-) and CD3(+)/CD8(+)/NKG2a(+) subsets. Studies also suggest a limited role for IFN-α synthesizing pDCs in chronic immune activation despite persistent up-regulation of ISGs. Finally, elevated persistent innate immune responses appear associated with poor prognosis. These findings provide an initial foundation for markers important to follow for vaccine design.