Loss of CD127 Expression Defines an Expansion of Effector CD8+T Cells in HIV-Infected Individuals

OMIP-109: 45-color full spectrum flow cytometry panel for deep immunophenotyping of the major lineages present in human peripheral blood mononuclear cells with emphasis on the T cell memory compartment

The need for more in-depth exploration of the human immune system has moved the flow cytometry field forward with advances in instrumentation, reagent development and availability, and user-friendly implementation of data analysis methods. We developed a high-quality human 45-color panel, for comprehensive characterization of major cell lineages present in circulation including T cells, γδ T cells, NKT-like cells, B cells, NK cells, monocytes, basophils, dendritic cells, and ILCs. Assay optimization steps are described in detail to ensure that each marker in the panel was optimally resolved. In addition, we highlight the outstanding discernment of cell activation, exhaustion, memory, and differentiation states of CD4+ and CD8+ T cells using this 45-color panel. The panel enabled an in-depth description of very distinct phenotypes associated with the complexity of the T cell memory response. Furthermore, we present how this panel can be effectively used for cell sorting on instruments with a similar optical layout to achieve the same level of resolution. Functional evaluation of sorted specific rare cell subsets demonstrated significantly different patterns of immunological responses to stimulation, supporting functional and phenotypic differences within the T cell memory subsets. In summary, the combination of full spectrum profiling technology and careful assay design and optimization results in a high resolution multiparametric 45-color assay. This panel offers the opportunity to fully characterize immunological profiles present in peripheral blood in the context of infectious diseases, autoimmunity, neurodegeneration, immunotherapy, and biomarker discovery.

ApoE ε4-dependent alteration of CXCR3 + CD127 + CD4 + T cells is associated with elevated plasma neurofilament light chain in Alzheimer's disease

Recent findings indicate a correlation between the peripheral adaptive immune system and neuroinflammation in Alzheimer's disease (AD). To characterize the composition of adaptive immune cells in the peripheral blood of AD patients, we utilized single-cell mass cytometry (CyTOF) to profile peripheral blood mononuclear cells (PBMCs). Concurrently, we assessed the concentration of proteins associated with AD and neuroinflammation in the plasma of the same subjects. We found that the abundance of proinflammatory CXCR3 + CD127 + Type 1 T helper (Th1) cells in AD patients was negatively correlated with the abundance of neurofilament light chain (NfL) protein. This correlation is apolipoprotein E (ApoE) ε4-dependent. Analyzing public single-cell RNA-sequencing (scRNA-seq) data, we found that, contrary to the scenario in the peripheral blood, the cell frequency of CXCR3 + CD127 + Th1 cells in the cerebrospinal fluid (CSF) of AD patients was increased compared to healthy controls (HCs). Moreover, the proinflammatory capacity of CXCR3 + CD127 + Th1 cells in the CSF of AD patients was further increased compared to HCs. These results reveal an association of a peripheral T-cell change with neuroinflammation in AD and suggest that dysregulation of peripheral adaptive immune responses, particularly involving CXCR3 + CD127 + Th1 cells, may potentially be mediated by factors such as ApoE ε4 genotype.

One sentence summary

An apolipoprotein E (ApoE) ε4-dependent alteration of CD4 T cell subpopulation in peripheral blood is associated with neuroinflammation in patients with Alzheimer's disease.

Innate phase production of IFN-γ by memory and effector T cells expressing early activation marker CD69 during infection with Cryptococcus deneoformans in the lungs

Cryptococcus deneoformans is a yeast-type fungus that causes fatal meningoencephalitis in immunocompromised patients and evades phagocytic cell elimination through an escape mechanism. Memory T (Tm) cells play a central role in preventing the reactivation of this fungal pathogen. Among these cells, tissue-resident memory T (TRM) cells quickly respond to locally invaded pathogens. This study analyzes the kinetics of effector T (Teff) cells and Tm cells in the lungs after cryptococcal infection. Emphasis is placed on the kinetics and cytokine expression of TRM cells in the early phase of infection. CD4+ Tm cells exhibited a rapid increase by day 3, peaked at day 7, and then either maintained their levels or exhibited a slight decrease until day 56. In contrast, CD8+ Tm cells reached their peak on day 3 and thereafter decreased up to day 56 post-infection. These Tm cells were predominantly composed of CD69+ TRM cells and CD69+ CD103+ TRM cells. Disruption of the CARD9 gene resulted in reduced accumulation of these TRM cells and diminished interferon (IFN) -γ expression in TRM cells. TRM cells were derived from T cells with T cell receptors non-specific to ovalbumin in OT-II mice during cryptococcal infection. In addition, TRM cells exhibited varied behavior in different tissues. These results underscore the importance of T cells, which produce IFN-γ in the lungs during the early stage of infection, in providing early protection against cryptococcal infection through CARD9 signaling.

Compound heterozygous mutations in the kinase domain of IKKα lead to immunodeficiency and immune dysregulation

IKKα, encoded by CHUK , is crucial in the non-canonical NF-κB pathway and part of the IKK complex activating the canonical pathway alongside IKKβ. Absence of IKKα cause fetal encasement syndrome in human, fatal in utero, while an impaired IKKα-NIK interaction was reported in a single patient and cause combined immunodeficiency. Here, we describe compound heterozygous variants in the kinase domain of IKKα in a female patient with hypogammaglobulinemia, recurrent lung infections, and Hay-Wells syndrome-like features. We showed that both variants were loss-of-function. Non-canonical NF-κB activation was profoundly diminished in stromal and immune cells while the canonical pathway was partially impaired. Reintroducing wild-type CHUK restored non-canonical NF-κB activation. The patient had neutralizing autoantibodies against type I IFN, akin to non-canonical NF-κB pathway deficiencies. Thus, this is the first case of bi-allelic CHUK mutations disrupting IKKα kinase function, broadening non-canonical NF-κB defect understanding and suggesting IKKα's role in canonical NF-κB target gene expression in human.

Multiparameter Flow Cytometry Monitoring of T Cell Responses

Multiparameter flow cytometry is a common tool for assessing responses of T, B, and other cells to pathogens or vaccines. Such responses are likely to be important for predicting the efficacy of an HIV vaccine, despite the elusive findings in HIV vaccine trials to date. Fortunately, flow cytometry has evolved to be capable of readily measuring 30-40 parameters, providing the ability to dissect detailed phenotypes and functions that may be correlated with disease protection. Nevertheless, technical hurdles remain, and standardization of assays is still largely lacking. Here an optimized protocol for antigen-specific T cell monitoring is presented, with specific variations for particular markers. It covers the analysis of multiple cytokines, cell surface proteins, and other functional markers such as CD107, CD154, CD137, etc. References are given to published panels of 8-28 colors.

Immune reconstitution following alemtuzumab therapy is characterized by exhausted T cells, increased regulatory control of proinflammatory T cells and reduced B cell control

Alemtuzumab is a monoclonal antibody targeting CD52 on the surface of immune cells, approved for the treatment of active relapsing-remitting multiple sclerosis (RRMS). The purpose of this study was to analyze the repopulation of peripheral lymphocytes following alemtuzumab-induced lymphocyte depletion and investigate associations with disease activity and development of secondary autoimmunity. For this, blood samples were collected two years after initiation of alemtuzumab treatment and lymphocytes were subjected to a comprehensive flow cytometry analysis. Included in the study were 40 patients treated with alemtuzumab and 40 treatment-naïve patients with RRMS. Disease activity and development of secondary autoimmune disease was evaluated after three years of treatment. Our study confirms that alemtuzumab treatment profoundly alters the circulating lymphocyte phenotype and describes a reconstituted immune system characterized by T cell activation/exhaustion, an increased regulatory control of IL-17 producing effector T cells and CD20+ T cells, and a reduced control of B cells. There were no obvious associations between immune cell subsets and disease activity or development of secondary autoimmune disease during treatment with alemtuzumab. Our results indicate that the reconstituted immune response is skewed towards a more effective regulatory control of MS-associated proinflammatory T cell responses. Also, the enlarged pool of naïve B cells together with the apparent decrease in control of B cell activity may explain why alemtuzumab-treated patients retain the ability to mount a humoral immune response towards new antigens.

The role of immune activation and antigen persistence in acute and long COVID

In late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggered the global coronavirus disease 2019 (COVID-19) pandemic. Although most infections cause a self-limited syndrome comparable to other upper respiratory viral pathogens, a portion of individuals develop severe illness leading to substantial morbidity and mortality. Furthermore, an estimated 10%-20% of SARS-CoV-2 infections are followed by post-acute sequelae of COVID-19 (PASC), or long COVID. Long COVID is associated with a wide variety of clinical manifestations including cardiopulmonary complications, persistent fatigue, and neurocognitive dysfunction. Severe acute COVID-19 is associated with hyperactivation and increased inflammation, which may be an underlying cause of long COVID in a subset of individuals. However, the immunologic mechanisms driving long COVID development are still under investigation. Early in the pandemic, our group and others observed immune dysregulation persisted into convalescence after acute COVID-19. We subsequently observed persistent immune dysregulation in a cohort of individuals experiencing long COVID. We demonstrated increased SARS-CoV-2-specific CD4+ and CD8+ T-cell responses and antibody affinity in patients experiencing long COVID symptoms. These data suggest a portion of long COVID symptoms may be due to chronic immune activation and the presence of persistent SARS-CoV-2 antigen. This review summarizes the COVID-19 literature to date detailing acute COVID-19 and convalescence and how these observations relate to the development of long COVID. In addition, we discuss recent findings in support of persistent antigen and the evidence that this phenomenon contributes to local and systemic inflammation and the heterogeneous nature of clinical manifestations seen in long COVID.

Impact of SIV infection on mycobacterial lipid-reactive T cell responses in Bacillus Calmette-Guérin (BCG) inoculated macaques

Background

Although BCG vaccine protects infants from tuberculosis (TB), it has limited efficacy in adults against pulmonary TB. Further, HIV coinfection significantly increases the risk of developing active TB. In the lack of defined correlates of protection in TB disease, it is essential to explore immune responses beyond conventional CD4 T cells to gain a better understanding of the mechanisms of TB immunity.

Methods

Here, we evaluated unconventional lipid-reactive T cell responses in cynomolgus macaques following aerosol BCG inoculation and examined the impact of subsequent SIV infection on these responses. Immune responses to cellular lipids of M. bovis and M. tuberculosis were examined ex vivo in peripheral blood and bronchioalveolar lavage (BAL).

Results

Prior to BCG inoculation, innate-like IFN-γ responses to mycobacterial lipids were observed in T cells. Aerosol BCG exposure induced an early increase in frequencies of BAL γδT cells, a dominant subset of lipid-reactive T cells, along with enhanced IL-7R and CXCR3 expression. Further, BCG exposure stimulated greater IFN-γ responses to mycobacterial lipids in peripheral blood and BAL, suggesting the induction of systemic and local Th1-type response in lipid-reactive T cells. Subsequent SIV infection resulted in a significant loss of IL-7R expression on blood and BAL γδT cells. Additionally, IFN-γ responses of mycobacterial lipid-reactive T cells in BAL fluid were significantly lower in SIV-infected macaques, while perforin production was maintained through chronic SIV infection.

Conclusions

Overall, these data suggest that despite SIV-induced decline in IL-7R expression and IFN-γ production by mycobacterial lipid-reactive T cells, their cytolytic potential is maintained. A deeper understanding of anti-mycobacterial lipid-reactive T cell functions may inform novel approaches to enhance TB control in individuals with or without HIV infection.

Control of Simian Immunodeficiency Virus Infection in Prophylactically Vaccinated, Antiretroviral Treatment-Naive Macaques Is Required for the Most Efficacious CD8 T Cell Response during Treatment with the Interleukin-15 Superagonist N-803

The IL-15 superagonist N-803 has been shown to enhance the function of CD8 T cells and NK cells. We previously found that in a subset of vaccinated, ART-naive, SIV⁺ rhesus macaques, N-803 treatment led to a rapid but transient decline in plasma viremia that positively correlated with an increase in the frequency of CD8 T cells. Here, we tested the hypothesis that prophylactic vaccination was required for the N-803 mediated suppression of SIV plasma viremia. We either vaccinated rhesus macaques with a DNA prime/Ad5 boost regimen using vectors expressing SIVmac239 gag with or without a plasmid expressing IL-12 or left them unvaccinated. The animals were then intravenously infected with SIVmac239M. 6 months after infection, the animals were treated with N-803. We found no differences in the control of plasma viremia during N-803 treatment between vaccinated and unvaccinated macaques. Interestingly, when we divided the SIV⁺ animals based on their plasma viral load set-points prior to the N-803 treatment, N-803 increased the frequency of SIV-specific T cells expressing ki-67⁺ and granzyme B⁺ in animals with low plasma viremia (<10⁴ copies/mL; SIV controllers) compared to animals with high plasma viremia (>10⁴ copies/mL; SIV noncontrollers). In addition, Gag-specific CD8 T cells from the SIV⁺ controllers had a greater increase in CD8⁺CD107a⁺ T cells in ex vivo functional assays than did the SIV⁺ noncontrollers. Overall, our results indicate that N-803 is most effective in SIV⁺ animals with a preexisting immunological ability to control SIV replication. IMPORTANCE N-803 is a drug that boosts the immune cells involved in combating HIV/SIV infection. Here, we found that in SIV⁺ rhesus macaques that were not on antiretroviral therapy, N-803 increased the proliferation and potential capacity for killing of the SIV-specific immune cells to a greater degree in animals that spontaneously controlled SIV than in animals that did not control SIV. Understanding the mechanism of how N-803 might function differently in individuals that control HIV/SIV (for example, individuals on antiretroviral therapy or spontaneous controllers) compared to settings where HIV/SIV are not controlled, could impact the efficacy of N-803 utilization in the field of HIV cure.

Single-cell analysis of immune cell transcriptome during HIV-1 infection and therapy

BACKGROUND

Cellular immune responses are phenotypically and functionally perturbed during HIV-1 infection, with the majority of function restored upon antiretroviral therapy (ART). Despite ART, residual inflammation remains that can lead to HIV-related co-morbidities and mortality, indicating that ART does not fully restore normal immune cell function. Thus, understanding the dynamics of the immune cell landscape during HIV-1 infection and ART is critical to defining cellular dysfunction that occurs during HIV-1 infection and imprints during therapy.

RESULTS

Here, we have applied single-cell transcriptome sequencing of peripheral blood immune cells from chronic untreated HIV-1 individuals, HIV-1-infected individuals receiving ART and HIV-1 negative individuals. We also applied single-cell transcriptome sequencing to a primary cell model of early HIV-1 infection using CD4+ T cells from healthy donors. We described changes in the transcriptome at high resolution that occurred during HIV-1 infection, and perturbations that remained during ART. We also determined transcriptional differences among T cells expressing HIV-1 transcripts that identified key regulators of HIV-1 infection that may serve as targets for future therapies to block HIV-1 infection.

CONCLUSIONS

This work identified key molecular pathways that are altered in immune cells during chronic HIV-1 infection that could remain despite therapy. We also identified key genes that are upregulated during early HIV-1 infection that provide insights on the mechanism of HIV-1 infection and could be targets for future therapy.

Diffuse large B-cell lymphoma (DLBCL) is infiltrated with activated CD8+ T-cells despite immune checkpoint signaling

Background

B-cell non-Hodgkin lymphomas (NHL) are hematologic malignancies that arise in the lymph node. Despite this, the malignant cells are not cleared by the immune cells present. The failure of anti-tumor immunity may be due to immune checkpoints such as the PD-1/PDL-1 axis, which can cause T-cell exhaustion. Unfortunately, unlike Hodgkin lymphoma, checkpoint blockade in NHL has shown limited efficacy.

Methods

We performed an extensive functional analysis of malignant and non-malignant lymph nodes using high dimensional flow cytometry. We compared follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), and lymph nodes harboring reactive hyperplasia (RH).

Results

We identified an expansion of CD8⁺PD1⁺ T-cells in the lymphomas relative to RH. Moreover, we demonstrate that these cells represent a mixture of activated and exhausted T-cells in FL. In contrast, these cells are nearly universally activated and functional in DLBCL. This is despite expression of counter-regulatory molecules such as PD-1, TIM-3, and CTLA-4, and the presence of regulatory T-cells.

Conclusion

These data may explain the failure of single-agent immune checkpoint inhibitors in the treatment of DLBCL. Accordingly, functional differences of CD8⁺ T-cells between FL and DLBCL may inform future therapeutic targeting strategies.

IL-7 in SARS-CoV-2 Infection and as a Potential Vaccine Adjuvant

IL-7/IL-7R signaling is critical for development, maturation, maintenance and survival of many lymphocytes in the thymus and periphery. IL-7 has been used as immunotherapy in pre-clinical and clinical studies to treat cancer, HIV infection and sepsis. Here, we discuss the critical function of IL-7 in diagnosis, prognosis and treatment of COVID-19 patients. We also summarize a promising role of IL-7 as a vaccine adjuvant. It could potentially enhance the immune responses to vaccines especially against SARS-CoV-2 or other new vaccines.

Locoregional infusion of HER2-specific CAR T cells in children and young adults with recurrent or refractory CNS tumors: an interim analysis

Locoregional delivery of chimeric antigen receptor (CAR) T cells has resulted in objective responses in adults with glioblastoma, but the feasibility and tolerability of this approach is yet to be evaluated for pediatric central nervous system (CNS) tumors. Here we show that engineering of a medium-length CAR spacer enhances the therapeutic efficacy of human erb-b2 receptor tyrosine kinase 2 (HER2)-specific CAR T cells in an orthotopic xenograft medulloblastoma model. We translated these findings into BrainChild-01 ( NCT03500991 ), an ongoing phase 1 clinical trial at Seattle Children's evaluating repetitive locoregional dosing of these HER2-specific CAR T cells to children and young adults with recurrent/refractory CNS tumors, including diffuse midline glioma. Primary objectives are assessing feasibility, safety and tolerability; secondary objectives include assessing CAR T cell distribution and disease response. In the outpatient setting, patients receive infusions via CNS catheter into either the tumor cavity or the ventricular system. The initial three patients experienced no dose-limiting toxicity and exhibited clinical, as well as correlative laboratory, evidence of local CNS immune activation, including high concentrations of CXCL10 and CCL2 in the cerebrospinal fluid. This interim report supports the feasibility of generating HER2-specific CAR T cells for repeated dosing regimens and suggests that their repeated intra-CNS delivery might be well tolerated and activate a localized immune response in pediatric and young adult patients.

HIV-1 infection and the lack of viral control are associated with greater expression of interleukin-21 receptor on CD8+ T cells

OBJECTIVES

Interleukin-21 (IL-21) has been linked with the generation of virus-specific memory CD8+ T cells following acute infection with HIV-1 and reduced exhaustion of CD8+ T cells. IL-21 has also been implicated in the promotion of CD8+ T-cell effector functions during viral infection. Little is known about the expression of interleukin-21 receptor (IL-21R) during HIV-1 infection or its role in HIV-1-specific CD8+ T-cell maintenance and subsequent viral control.

METHODS

We compared levels of IL-21R expression on total and memory subsets of CD8+ T cells from HIV-1-negative and HIV-1-positive donors. We also measured IL-21R on antigen-specific CD8+ T cells in volunteers who were positive for HIV-1 and had cytomegalovirus-responding T cells. Finally, we quantified plasma IL-21 in treatment-naive HIV-1-positive individuals and compared this with IL-21R expression.

RESULTS

IL-21R expression was significantly higher on CD8+ T cells (P = 0.0256), and on central memory (P = 0.0055) and effector memory (P = 0.0487) CD8+ T-cell subsets from HIV-1-positive individuals relative to HIV-1-negative individuals. For those infected with HIV-1, the levels of IL-21R expression on HIV-1-specific CD8+ T cells correlated significantly with visit viral load (r = 0.6667, P = 0.0152, n = 13) and inversely correlated with plasma IL-21 (r = -0.6273, P = 0.0440, n = 11). Lastly, CD8+ T cells from individuals with lower set point viral load who demonstrated better viral control had the lowest levels of IL-21R expression and highest levels of plasma IL-21.

CONCLUSION

Our data demonstrates significant associations between IL-21R expression on peripheral CD8+ T cells and viral load, as well as disease trajectory. This suggests that the IL-21 receptor could be a novel marker of CD8+ T-cell dysfunction during HIV-1 infection.

Lentiviral vector induces high-quality memory T cells via dendritic cells transduction

We report a lentiviral vector harboring the human β2-microglobulin promoter, with predominant expression in immune cells and minimal proximal enhancers to improve vector safety. This lentiviral vector efficiently transduces major dendritic cell subsets in vivo. With a mycobacterial immunogen, we observed distinct functional signatures and memory phenotype in lentiviral vector- or Adenovirus type 5 (Ad5)-immunized mice, despite comparable antigen-specific CD8⁺ T cell magnitudes. Compared to Ad5, lentiviral vector immunization resulted in higher multifunctional and IL-2-producing CD8⁺ T cells. Furthermore, lentiviral vector immunization primed CD8⁺ T cells towards central memory phenotype, while Ad5 immunization favored effector memory phenotype. Studies using HIV antigens in outbred rats demonstrated additional clear-cut evidence for an immunogenic advantage of lentiviral vector over Ad5. Additionally, lentiviral vector provided enhance therapeutic anti-tumor protection than Ad5. In conclusion, coupling lentiviral vector with β2-microglobulin promoter represents a promising approach to produce long-lasting, high-quality cellular immunity for vaccinal purposes.

Soluble IL-7Rα/sCD127 in Health, Disease, and Its Potential Role as a Therapeutic Agent

Soluble cytokine receptors can influence immune responses by modulating the biological functions of their respective ligands. These effects can be either agonistic or antagonistic and a number of soluble cytokine receptors have been shown to play critical roles in both maintenance of health and disease pathogenesis. Soluble IL-7Ra (sCD127) is one such example. With its impact on the IL-7/CD127 pathway, which is fundamental for the development and homeostasis of T cells, the role of sCD127 in health and disease has been extensively studied in recent years. Within this review, the role of sCD127 in maintaining host immune function is presented. Next, by addressing genetic factors affecting sCD127 expression and the associated levels of sCD127 production, the roles of sCD127 in autoimmune disease, infections and cancer are described. Finally, advances in the field of soluble cytokine therapy and the potential for sCD127 as a biomarker and therapeutic agent are discussed.

Cancer immunotherapy: Re-programming cells of the innate and adaptive immune systems

Cancers utilize multiple mechanisms to overcome immune responses. Emerging evidence suggest that immunotherapy of cancer should focus on inducing and re-programming cells of the innate and adaptive immune systems rather than focusing solely on T cells. Recently, we have shown that such a multifaceted approach can improve immunotherapy of breast cancer.

IL-7Rαlow CD8+ T Cells from Healthy Individuals Are Anergic with Defective Glycolysis

Effector memory (EM) CD8⁺ T cells expressing lower levels of IL-7R α (IL-7Rα^low) from healthy individuals are partly compromised in vitro, but the identity of these cells has remained unclear. In this study, we demonstrate that human IL-7Rα^low EM CD8⁺ T cells are naturally occurring anergic cells in vivo and impaired in proliferation and IL-2 production but competent in IFN-γ and TNF-α production, a state that can be restored by IL-2 stimulation. IL-7Rα^low EM CD8⁺ T cells show decreased expression of GATA3 and c-MYC and are defective in metabolic reprogramming toward glycolysis, a process required for the proliferation of T cells. However, IL-7Rα^low EM CD8⁺ T cells can proliferate with TCR stimulation in the presence of IL-2 and IL-15, suggesting that these cells can be restored to normality or increased activity by inflammatory conditions and may serve as a reservoir for functional immunity.

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.

Immunometabolism and HIV-1 pathogenesis: food for thought

Antiretroviral therapies efficiently block HIV-1 replication but need to be maintained for life. Moreover, chronic inflammation is a hallmark of HIV-1 infection that persists despite treatment. There is, therefore, an urgent need to better understand the mechanisms driving HIV-1 pathogenesis and to identify new targets for therapeutic intervention. In the past few years, the decisive role of cellular metabolism in the fate and activity of immune cells has been uncovered, as well as its impact on the outcome of infectious diseases. Emerging evidence suggests that immunometabolism has a key role in HIV-1 pathogenesis. The metabolic pathways of CD4⁺ T cells and macrophages determine their susceptibility to infection, the persistence of infected cells and the establishment of latency. Immunometabolism also shapes immune responses against HIV-1, and cell metabolic products are key drivers of inflammation during infection. In this Review, we summarize current knowledge of the links between HIV-1 infection and immunometabolism, and we discuss the potential opportunities and challenges for therapeutic interventions.

Delineation of Homeostatic Immune Signatures Defining Viremic Non-progression in HIV-1 Infection

Viremic non-progressors (VNPs), a distinct group of HIV-1-infected individuals, exhibit no signs of disease progression and maintain persistently elevated CD4+ T cell counts for several years despite high viral replication. Comprehensive characterization of homeostatic cellular immune signatures in VNPs can provide unique insights into mechanisms responsible for coping with viral pathogenesis as well as identifying strategies for immune restoration under clinically relevant settings such as antiretroviral therapy (ART) failure. We report a novel homeostatic signature in VNPs, the preservation of the central memory CD4+ T cell (CD4+ T_CM) compartment. In addition, CD4+ T_CM preservation was supported by ongoing interleukin-7 (IL-7)-mediated thymic repopulation of naive CD4+ T cells leading to intact CD4+ T cell homeostasis in VNPs. Regulatory T cell (Treg) expansion was found to be a function of preserved CD4+ T cell count and CD4+ T cell activation independent of disease status. However, in light of continual depletion of CD4+ T cell count in progressors but not in VNPs, Tregs appear to be involved in lack of disease progression despite high viremia. In addition to these homeostatic mechanisms resisting CD4+ T cell depletion in VNPs, a relative diminution of terminally differentiated effector subset was observed exclusively in these individuals that might ameliorate consequences of high viral replication. VNPs also shared signatures of impaired CD8+ T cell cytotoxic function with progressors evidenced by increased exhaustion (PD-1 upregulation) and CD127 (IL-7Rα) downregulation contributing to persistent viremia. Thus, the homeostatic immune signatures reported in our study suggest a complex multifactorial mechanism accounting for non-progression in VNPs.

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.

TCR activation mimics CD127lowPD-1high phenotype and functional alterations of T lymphocytes from septic shock patients

Background

Sepsis is the leading cause of mortality for critically ill patients worldwide. Patients develop T lymphocyte dysfunctions leading to T-cell exhaustion associated with increased risk of death. As interleukin-7 (IL-7) is currently tested in clinical trials to reverse these dysfunctions, it is important to evaluate the expression of its specific CD127 receptor on the T-cell surface of patients with septic shock. Moreover, the CD127^lowPD-1^high phenotype has been proposed as a T-cell exhaustion marker in chronic viral infections but has never been evaluated in sepsis. The objective of this study was first to evaluate CD127 and CD127^lowPD-1^high phenotype in septic shock in parallel with functional T-cell alterations. Second, we aimed to reproduce septic shock–induced T-cell alterations in an ex vivo model.

Methods

CD127 expression was followed at the protein and mRNA levels in patients with septic shock and healthy volunteers. CD127^lowPD-1^high phenotype was also evaluated in parallel with T-cell functional alterations after ex vivo activation. To reproduce T-cell alterations observed in patients, purified T cells from healthy volunteers were activated ex vivo and their phenotype and function were evaluated.

Results

In patients, neither CD127 expression nor its corresponding mRNA transcript level was modified compared with normal values. However, the percentage of CD127^lowPD-1^high T cells was increased while T cells also presented functional alterations. CD127^lowPD-1^high T cells co-expressed HLA-DR, an activation marker, suggesting a role for T-cell activation in the development of this phenotype. Indeed, T-cell receptor (TCR) activation of normal T lymphocytes ex vivo reproduced the increase of CD127^lowPD-1^high T cells and functional alterations following a second stimulation, as observed in patients. Finally, in this model, as observed in patients, IL-7 could improve T-cell proliferation.

Conclusions

The proportion of CD127^lowPD-1^high T cells in patients was increased compared with healthy volunteers, although no global CD127 regulation was observed. Our results suggest that TCR activation participates in the occurrence of this T-cell population and in the development of T-cell alterations in septic shock. Furthermore, we provide an ex vivo model for the investigation of the pathophysiology of sepsis-induced T-cell immunosuppression and the testing of innovative immunostimulant treatments.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2305-5) contains supplementary material, which is available to authorized users.

Abnormal T Cell Frequencies, Including Cytomegalovirus-Associated Expansions, Distinguish Seroconverted Subjects at Risk for Type 1 Diabetes

We analyzed T cell subsets from cryopreserved PBMC obtained from the TrialNet Pathway to Prevention archives. We compared subjects who had previously seroconverted for one or more autoantibodies with non-seroconverted, autoantibody negative individuals. We observed a reduced frequency of MAIT cells among seroconverted subjects. Seroconverted subjects also possessed decreased frequencies of CCR4-expressing CD4 T cells, including a regulatory-like subset. Interestingly, we found an elevation of CD57+, CD28–, CD127–, CD27– CD8 T cells (SLEC) among seroconverted subjects that was most pronounced among those that progressed to disease. The frequency of these SLEC was strongly correlated with CMV IgG abundance among seroconverted subjects, associated with IA-2 levels, and most elevated among CMV+ seroconverted subjects who progressed to disease. Combined, our data indicate discrete, yet profound T cell alterations are associated with islet autoimmunity among at-risk subjects.

HIV and Age Do Not Synergistically Affect Age-Related T-Cell Markers

INTRODUCTION

Despite major progress in controlling HIV disease through antiretroviral therapy, changes in immune phenotype and function persist in individuals with chronic HIV, raising questions about accelerated aging of the immune system.

METHODS

We conducted a cross-sectional study (2005-2007) of HIV-infected (n = 111) and uninfected (n = 114) men from the Veterans Aging Cohort Study. All HIV-infected subjects were on antiretroviral therapy with VL <400 copies/mL for at least 3 years. T-cell markers were examined using flow cytometry. We evaluated the impact of HIV serostatus and age on T-cell phenotypes (expressed as percentages of the total CD4 and CD8 T-cell population) using multivariate linear regression, adjusted for smoking, alcohol, and race/ethnicity. We tested for interactions between HIV and age by including interaction terms.

RESULTS

Among both HIV-infected and uninfected subjects, increasing age was associated with a decreased proportion of naive CD4 T cells (P = 0.014) and CD8 T cells (P < 0.0001). Both HIV infection and increasing age were associated with higher proportions of effector memory CD4 T cells (P < 0.0001 for HIV; P = 0.04 for age) and CD8 T cells (P = 0.0001 for HIV; P = 0.0004 for age). HIV infection, but not age, was associated with a higher proportion of activated CD8 T cells (P < 0.0001). For all T-cell subsets tested, there were no significant interactions between HIV infection and age.

CONCLUSIONS

Age and HIV status independently altered the immune system, but we found no conclusive evidence that HIV infection and advancing age synergistically result in accelerated changes in age-associated T-cell markers among virally suppressed individuals.

Immune Responses to Retroviruses

Retroviruses are genome invaders that have shared a long history of coevolution with vertebrates and their immune system. Found endogenously in genomes as traces of past invasions, retroviruses are also considerable threats to human health when they exist as exogenous viruses such as HIV. The immune response to retroviruses is engaged by germline-encoded sensors of innate immunity that recognize viral components and damage induced by the infection. This response develops with the induction of antiviral effectors and launching of the clonal adaptive immune response, which can contribute to protective immunity. However, retroviruses efficiently evade the immune response, owing to their rapid evolution. The failure of specialized immune cells to respond, a form of neglect, may also contribute to inadequate antiretroviral immune responses. Here, we discuss the mechanisms by which immune responses to retroviruses are mounted at the molecular, cellular, and organismal levels. We also discuss how intrinsic, innate, and adaptive immunity may cooperate or conflict during the generation of immune responses.

Aberrant plasma IL-7 and soluble IL-7 receptor levels indicate impaired T-cell response to IL-7 in human tuberculosis

T-cell proliferation and generation of protective memory during chronic infections depend on Interleukin-7 (IL-7) availability and receptivity. Regulation of IL-7 receptor (IL-7R) expression and signalling are key for IL-7-modulated T-cell functions. Aberrant expression of soluble (s) and membrane-associated (m) IL-7R molecules is associated with development of autoimmunity and immune failure in acquired immune deficiency syndrome (AIDS) patients. Here we investigated the role of IL-7/IL-7R on T-cell immunity in human tuberculosis. We performed two independent case-control studies comparing tuberculosis patients and healthy contacts. This was combined with follow-up examinations for a subgroup of tuberculosis patients under therapy and recovery. Blood plasma and T cells were characterised for IL-7/sIL-7R and mIL-7R expression, respectively. IL-7-dependent T-cell functions were determined by analysing STAT5 phosphorylation, antigen-specific cytokine release and by analysing markers of T-cell exhaustion and inflammation. Tuberculosis patients had lower soluble IL-7R (p < 0.001) and higher IL-7 (p < 0.001) plasma concentrations as compared to healthy contacts. Both markers were largely independent and aberrant expression normalised during therapy and recovery. Furthermore, tuberculosis patients had lower levels of mIL-7R in T cells caused by post-transcriptional mechanisms. Functional in vitro tests indicated diminished IL-7-induced STAT5 phosphorylation and impaired IL-7-promoted cytokine release of Mycobacterium tuberculosis-specific CD4⁺ T cells from tuberculosis patients. Finally, we determined T-cell exhaustion markers PD-1 and SOCS3 and detected increased SOCS3 expression during therapy. Only moderate correlation of PD-1 and SOCS3 with IL-7 expression was observed. We conclude that diminished soluble IL-7R and increased IL-7 plasma concentrations, as well as decreased membrane-associated IL-7R expression in T cells, reflect impaired T-cell sensitivity to IL-7 in tuberculosis patients. These findings show similarities to pathognomonic features of impaired T-cell functions and immune failure described in AIDS patients.

IL-7 is important for the development and homeostasis of T cells and promotes antigen-specific T-cell responses. Aberrant expression of plasma IL-7 and soluble IL-7R are found in autoimmune diseases and chronic viral infections. In AIDS patients—especially those who fail to reconstitute T-cell numbers during therapy—impaired IL-7-promoted T-cell functions indicated T-cell exhaustion/senescence. In order to evaluate the potential impact of IL-7 on tuberculosis, we characterised various parameters involved in the IL-7-response of tuberculosis patients and healthy contacts. Despite IL-7 being available at higher plasma levels among tuberculosis patients, the T-cell response to IL-7 was impaired when compared to healthy contacts. Soluble IL-7R levels were aberrantly low in plasma during acute tuberculosis but did not account for impaired IL-7 usage. Chronic inflammation in tuberculosis patients—reflected by increased IL-6 plasma levels—did not account for dysfunctional T-cell responses and analysed T-cell exhaustion markers were only moderately correlated. Our findings demonstrate that availability of IL-7 alone is not sufficient to promote protective T-cell immunity against tuberculosis. We describe aberrant IL-7/soluble IL-7R expression and impaired IL-7-mediated T-cell functions in tuberculosis patients with similarities and differences to described IL-7 dysregulation seen in patients with AIDS.

IL-7 and CD4 T Follicular Helper Cells in HIV-1 Infection

IL-7 was previously shown to upregulate the expression of molecules important for interaction of CD4+ T cells with B cells. It is poorly studied whether IL-7 has a role in the biology of T follicular helper (Tfh) cells and whether IL-7 dysregulates the expression of B-cell costimulatory molecules on Tfh cells. We review the literature and provide arguments in favor of IL-7 being involved in the biology of human Tfh cells. The CD127 IL-7 receptor is expressed on circulating Tfh and non-Tfh cells, and we show that IL-7, but not IL-6 or IL-21, upregulates the expression of CD70 and PD-1 on these cells. We conclude that IL-7, a cytokine whose level is elevated during HIV-1 infection, may have a role in increased expression of B cell costimulatory molecules on Tfh cells and lead to abnormal B cell differentiation.

The PD-1: PD-L1 pathway promotes development of brain-resident memory T cells following acute viral encephalitis

Background

Previous work from our laboratory has demonstrated that during acute viral brain infection, glial cells modulate antiviral T cell effector responses through the PD-1: PD-L1 pathway, thereby limiting the deleterious consequences of unrestrained neuroinflammation. Here, we evaluated the PD-1: PD-L1 pathway in development of brain-resident memory T cells (bT_RM) following murine cytomegalovirus (MCMV) infection.

Methods

Flow cytometric analysis of immune cells was performed at 7, 14, and 30 days post-infection (dpi) to assess the shift of brain-infiltrating CD8⁺ T cell populations from short-lived effector cells (SLEC) to memory precursor effector cells (MPEC), as well as generation of bT_RMs.

Results

In wild-type (WT) animals, we observed a switch in the phenotype of brain-infiltrating CD8⁺ T cell populations from KLRG1⁺ CD127⁻ (SLEC) to KLRG1⁻ CD127⁺ (MPEC) during transition from acute through chronic phases of infection. At 14 and 30 dpi, the majority of CD8⁺ T cells expressed CD127, a marker of memory cells. In contrast, fewer CD8⁺ T cells expressed CD127 within brains of infected, PD-L1 knockout (KO) animals. Notably, in WT mice, a large population of CD8⁺ T cells was phenotyped as CD103⁺ CD69⁺, markers of bT_RM, and differences were observed in the numbers of these cells when compared to PD-L1 KOs. Immunohistochemical studies revealed that brain-resident CD103⁺ bT_RM cells were localized to the parenchyma. Higher frequencies of CXCR3 were also observed among WT animals in contrast to PD-L1 KOs.

Conclusions

Taken together, our results indicate that bT_RMs are present within the CNS following viral infection and the PD-1: PD-L1 pathway plays a role in the generation of this brain-resident population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0860-3) contains supplementary material, which is available to authorized users.

Immunosenescence and hurdles in the clinical management of older HIV-patients

People living with HIV (PLWH) who are treated with effective highly active antiretroviral therapy (HAART) have a similar life expectancy to the general population. Moreover, an increasing proportion of new HIV diagnoses are made in people older than 50 y. The number of older HIV-infected patients is thus constantly growing and it is expected that by 2030 around 70% of PLWH will be more than 50 y old. On the other hand, HIV infection itself is responsible for accelerated immunosenescence, a progressive decline of immune system function in both the adaptive and the innate arm, which impairs the ability of an individual to respond to infections and to give rise to long-term immunity; furthermore, older patients tend to have a worse immunological response to HAART. In this review we focus on the pathogenesis of HIV-induced immunosenescence and on the clinical management of older HIV-infected patients.

Silymarin suppresses basal and stimulus-induced activation, exhaustion, differentiation, and inflammatory markers in primary human immune cells

Silymarin (SM), and its flavonolignan components, alter cellular metabolism and inhibit inflammatory status in human liver and T cell lines. In this study, we hypothesized that SM suppresses both acute and chronic immune activation (CIA), including in the context of HIV infection. SM treatment suppressed the expression of T cell activation and exhaustion markers on CD4+ and CD8+ T cells from chronically-infected, HIV-positive subjects. SM also showed a trend towards modifying CD4+ T cell memory subsets from HIV+ subjects. In the HIV-negative setting, SM treatment showed trends towards suppressing pro-inflammatory cytokines from non-activated and pathogen-associated molecular pattern (PAMP)-activated primary human monocytes, and non-activated and cytokine- and T cell receptor (TCR)-activated mucosal-associated invariant T (MAIT) cells. The data suggest that SM elicits broad anti-inflammatory and immunoregulatory activity in primary human immune cells. By using novel compounds to alter cellular inflammatory status, it may be possible to regulate inflammation in both non-disease and disease states.

Partial recovery of senescence and differentiation disturbances in CD8+ T cell effector-memory cells in HIV-1 infection after initiation of anti-retroviral treatment

Immune senescence as well as disturbed CD8⁺ T cell differentiation are a hallmark of chronic HIV infection. Here, we investigated to what extent immune senescence is reversible after initiation of anti-retroviral treatment (ART). Peripheral blood mononuclear cells (PBMCs) from a cohort of HIV patients with different disease courses, including untreated viral controllers (n = 10), viral non-controllers (n = 16) and patients on ART (n = 20), were analysed and compared to uninfected controls (n = 25) by flow cytometry on bulk and HIV-specific major histocompatibility complex (MHC) class I tetramer⁺ CD8⁺ T cells for expression of the memory markers CCR7 and CD45RO, as well as the senescence marker CD57 and the differentiation and survival marker CD127. Furthermore, a subset of patients was analysed longitudinally before and after initiation of ART. Frequencies of CD57⁺ CD8⁺ T cells decreased after initiation of ART in central memory (Tcm) but not in effector memory T cell populations (TemRO and TemRA). The frequency of CD127⁺ CD8⁺ cells increased in Tcm and TemRO. We observed a reduction of CD127^- T cells in Tcm, TemRO and partially in TemRA subsets after initiation of ART. Importantly, HIV-specific CD8⁺ TemRO cells predominantly displayed a CD127^- CD57⁺ phenotype in untreated HIV-patients, whereas the CD127⁺ CD57^- phenotype was under-represented in these patients. The frequency of the CD127⁺ CD57^- CD8⁺ T cell subpopulation correlated strongly with absolute CD4⁺ counts in HIV-infected patients before and after initiation of ART. These findings can be interpreted as a phenotypical correlate of CD8⁺ memory T cell differentiation and the premature 'ageing' of the immune system, which was even observed in successfully virally suppressed HIV patients.

Transcriptional regulation of the IL-7Rα gene by dexamethasone and IL-7 in primary human CD8 T cells

Interleukin-7 is essential for the development and maintenance of T cells, and the expression of the IL-7 receptor is tightly regulated at every stage of the T cell's lifespan. In mature CD8 T cells, IL-7 plays important roles in cell survival, peripheral homeostasis, and cytolytic function. The IL-7 receptor alpha-chain (CD127) is expressed at high levels on naïve and memory cells, but it is rapidly downregulated upon IL-7 stimulation. In this study, we illustrate the dynamicity of the CD127 promoter and show that it possesses positive as well as negative regulatory sites involved in upregulating and downregulating CD127 expression, respectively. We cloned the CD127 gene promoter and identified key cis-regulatory elements required for CD127 expression in mature resting primary CD8 T cells. The core promoter necessary for efficient basal transcription is contained within the first 262 bp upstream of the TATA box. Additional positive regulatory elements are located between -1200 and -2406 bp, conferring a further 2- to 4-fold enhancement in gene expression. While transcription of the CD127 gene is increased directly through a glucocorticoid response element located between -2255 and -2269 bp upstream of the TATA box, we identified a suppressive region that lies upstream of 1760 bp from the TATA box, which is likely involved in the IL-7-mediated suppression of CD127 transcription. Finally, we illustrated IL-7 does not bias alternative splicing of CD127 transcripts in primary human CD8 T cells.

Suppressor of cytokine signaling (SOCS) proteins are induced by IL-7 and target surface CD127 protein for degradation in human CD8 T cells

Given the essential role interleukin (IL)-7 plays in T-cell survival, homeostasis and function, it is no surprise expression of the IL-7 receptor alpha-chain (CD127) is tightly regulated. We have previously shown IL-7 binding to its receptor on the surface of CD8 T cells leads to both suppression of CD127 gene transcription and loss of existing CD127 protein from the cell membrane. Indeed upon binding IL-7, CD127 is rapidly internalized into early endosomes where phosphorylation by JAK targets the receptor for degradation. We now show that IL-7 induces the expression of suppressor of cytokine signaling (SOCS) proteins CIS, SOCS1 and SOCS2 through the JAK/STAT-5 pathway and that CIS and SOCS2 specifically interact with CD127 in early endosomes and direct the receptor complex to the proteasome for degradation. These results illustrate how expression of the IL-7 receptor and thus IL-7 signaling is modulated in human CD8 T cells by a negative feedback mechanism dependent on members of the SOCS family of proteins.

Generalized Liver- and Blood-Derived CD8+ T-Cell Impairment in Response to Cytokines in Chronic Hepatitis C Virus Infection

Generalized CD8⁺ T-cell impairment in chronic hepatitis C virus (HCV) infection and the contribution of liver-infiltrating CD8⁺ T-cells to the immunopathogenesis of this infection remain poorly understood. It is hypothesized that this impairment is partially due to reduced CD8⁺ T-cell activity in response to cytokines such as IL-7, particularly within the liver. To investigate this, the phenotype and cytokine responsiveness of blood- and liver-derived CD8⁺ T-cells from healthy controls and individuals with HCV infection were compared. In blood, IL-7 receptor α (CD127) expression on bulk CD8⁺ T-cells in HCV infection was no different than controls yet was lower on central memory T-cells, and there were fewer naïve cells. IL-7-induced signalling through phosphorylated STAT5 was lower in HCV infection than in controls, and differed between CD8⁺ T-cell subsets. Production of Bcl-2 following IL-7 stimulation was also lower in HCV infection and inversely related to the degree of liver fibrosis. In liver-derived CD8⁺ T-cells, STAT5 activation could not be increased with cytokine stimulation and basal Bcl-2 levels of liver-derived CD8⁺ T-cells were lower than blood-derived counterparts in HCV infection. Therefore, generalized CD8⁺ T-cell impairment in HCV infection is characterized, in part, by impaired IL-7-mediated signalling and survival, independent of CD127 expression. This impairment is more pronounced in the liver and may be associated with an increased potential for apoptosis. This generalized CD8⁺ T-cell impairment represents an important immune dysfunction in chronic HCV infection that may alter patient health.

Dysfunctional phenotypes of CD4+ and CD8+ T cells are comparable in patients initiating ART during early or chronic HIV-1 infection

Early initiation of antiretroviral therapy (ART) is becoming a common clinical practice according to current guidelines recommending treatment to all HIV-1-infected patients. However, it is not known whether ART initiated during the early phase of infection prevents the establishment of abnormal phenotypic features previously reported in CD4+ and CD8+T cells during chronic HIV-1 infection. In this cross-sectional study, blood specimens were obtained from 17 HIV-1-infected patients who began ART treatment shortly after infection (early ART [EA]), 17 age-matched HIV-1-infected patients who started ART during chronic phase of infection (late ART [LA]), and 25 age-matched non-HIV-1-infected controls. At collection of specimens, patients in EA and LA groups had received ART for comparable periods of time. Total HIV-1 DNA was measured in white blood cells by quantitative PCR. The concentration of 9 inflammatory parameters and 1 marker of fibrosis, including sCD14 and β-2 microglobulin, was measured in plasma. Furthermore, expression of markers of abnormal immune activation (human leukocyte antigen - antigen D related [HLA-DR] and CD38), exhaustion (programmed death 1, CD28, CD57) and terminal differentiation (CD127) was measured on CD4+ and CD8+T cells. T-cell proliferation was measured through Ki67 expression. The copies of total HIV-1 DNA in blood were significantly lower (P = 0.009) in EA compared with that in LA group. Only the expression of HLA-DR on naïve CD4+ T cells distinguished EA from LA, whereas expression of 3 surface markers distinguished T-cell populations of HIV-1-infected patients from controls. These included HLA-DR distinguishing CD4+ T cells from EA compared with controls, and also CD38 and CD127 on CD4+ and CD8+ T cells, respectively, distinguishing both groups of patients from controls. The sCD14 levels were significantly higher in EA patients, and β-2 microglobulin levels were higher in LA group compared with that in controls. Our results demonstrate an equivalent abnormal expression of activation (HLA-DR and CD38 on CD4+ T cells) and terminal differentiation (CD127 on CD8+ T cells) markers in T cells from both EA and LA patients. The size of total HIV-1 DNA copies in blood of EA was lower compared with LA patients. These findings suggest that some abnormalities taking place in the T-cell compartment during primary HIV-1 infection may not be corrected by early ART.

Efforts of the human immune system to maintain the peripheral CD8+ T cell compartment after childhood thymectomy

Background

Homeostatic mechanisms to maintain the T cell compartment diversity indicate an ongoing process of thymic activity and peripheral T cell renewal during human life. These processes are expected to be accelerated after childhood thymectomy and by the influence of cytomegalovirus (CMV) inducing a prematurely aged immune system.

The study aimed to investigate proportional changes and replicative history of CD8+ T cells, of recent thymic emigrants (RTEs) and CD103+ T cells (mostly gut-experienced) and the role of Interleukin-(IL)-7 and IL-7 receptor (CD127)-expressing T cells in thymectomized patients compared to young and old healthy controls.

Results

Decreased proportions of naive and CD31 + CD8+ T cells were demonstrated after thymectomy, with higher proliferative activity of CD127-expressing T cells and significantly shorter relative telomere lengths (RTLs) and lower T cell receptor excision circles (TRECs). Increased circulating CD103+ T cells and a skewed T cell receptor (TCR) repertoire were found after thymectomy similar to elderly persons. Naive T cells were influenced by age at thymectomy and further decreased by CMV.

Conclusions

After childhood thymectomy, the immune system demonstrated constant efforts of the peripheral CD8+ T cell compartment to maintain homeostasis. Supposedly it tries to fill the void of RTEs by peripheral T cell proliferation, by at least partly IL-7-mediated mechanisms and by proportional increase of circulating CD103+ T cells, reminiscent of immune aging in elderly. Although other findings were less significant compared to healthy elderly, early thymectomy demonstrated immunological alterations of CD8+ T cells which mimic features of premature immunosenescence in humans.

A Preliminary Comparative Assessment of the Role of CD8+ T Cells in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis and Multiple Sclerosis

Background. CD8+ T cells have putative roles in the regulation of adaptive immune responses during infection. The purpose of this paper is to compare the status of CD8+ T cells in Multiple Sclerosis (MS) and Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME). Methods. This preliminary investigation comprised 23 CFS/ME patients, 11 untreated MS patients, and 30 nonfatigued controls. Whole blood samples were collected from participants, stained with monoclonal antibodies, and analysed on the flow cytometer. Using the following CD markers, CD27 and CD45RA (CD45 exon isoform 4), CD8+ T cells were divided into naïve, central memory (CM), effector memory CD45RA− (EM), and effector memory CD45RA+ (EMRA) cells. Results. Surface expressions of BTLA, CD127, and CD49/CD29 were increased on subsets of CD8+ T cells from MS patients. In the CFS/ME patients CD127 was significantly decreased on all subsets of CD8+ T cells in comparison to the nonfatigued controls. PSGL-1 was significantly reduced in the CFS/ME patients in comparison to the nonfatigued controls. Conclusions. The results suggest significant deficits in the expression of receptors and adhesion molecules on subsets of CD8+ T cells in both MS and CFS/ME patients. These deficits reported may contribute to the pathogenesis of these diseases. However, larger sample size is warranted to confirm and support these encouraging preliminary findings.

T cells Exhibit Reduced Signal Transducer and Activator of Transcription 5 Phosphorylation and Upregulated Coinhibitory Molecule Expression After Kidney Transplantation

BACKGROUND

T-cell depletion therapy is associated with diminished interleukin (IL)-7/IL-15-dependent homeostatic proliferation resulting in incomplete T-cell repopulation. Furthermore, it is associated with impaired T-cell functions. We hypothesized that this is the result of impaired cytokine responsiveness of T cells, through affected signal transducer and activator of transcription (STAT)5 phosphorylation and upregulation of coinhibitory molecules.

MATERIALS AND METHODS

Patients were treated with T cell-depleting rabbit antithymocyte globulin (rATG) (6 mg/kg, n = 17) or nondepleting, anti-CD25 antibody (basiliximab, 2 × 40 mg, n = 25) induction therapy, in combination with tacrolimus, mycophenolate mofetil, and steroids. Before and the first year after transplantation, IL-7 and IL-2 induced STAT5 phosphorylation, and the expression of the coinhibitory molecules programmed cell death protein 1 (PD-1), T cell immunoglobulin mucin-3 (TIM-3), lymphocyte activation gene-3 (LAG-3), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), cluster of differentiation (CD) 160, and CD244 was measured by flow cytometry.

RESULTS

The first year after rATG, CD4+, and CD8+ T cells were affected in their IL-7-dependent phosphorylation of STAT5 (pSTAT5) which was most outspoken in the CD8+ memory population. The capacity of CD4+ and CD8+ T cells to pSTAT5 in response to IL-2 decreased after both rATG and basiliximab therapy. After kidney transplantation, the percentage of TIM-3+, PD-1+, and CD160+CD4+ T cells and the percentage of CD160+ and CD244+CD8+ T cells increased, with no differences in expression between rATG- and basiliximab-treated patients. The decrease in pSTAT5 capacity CD8+ T cells and the increase in coinhibitory molecules were correlated.

CONCLUSIONS

We show that memory T cells in kidney transplant patients, in particular after rATG treatment, have decreased cytokine responsiveness by impaired phosphorylation of STAT5 and have increased expression of coinhibitory molecules, processes which were correlated in CD8+ T cells.

IL7R gene expression network associates with human healthy ageing

Background

The level of expression of the interleukin 7 receptor (IL7R) gene in blood has recently been found to be associated with familial longevity and healthy ageing. IL7R is crucial for T cell development and important for immune competence. To further investigate the IL7R pathway in ageing, we identified the closest interacting genes to construct an IL7R gene network that consisted of IL7R and six interacting genes: IL2RG, IL7, TSLP, CRLF2, JAK1 and JAK3. This network was explored for association with chronological age, familial longevity and immune-related diseases (type 2 diabetes, chronic obstructive pulmonary disease and rheumatoid arthritis) in 87 nonagenarians, 337 of their middle-aged offspring and 321 middle-aged controls from the Leiden Longevity Study (LLS).

Results

We observed that expression levels within the IL7R gene network were significantly different between the nonagenarians and middle-aged controls (P = 4.6 × 10⁻⁴), being driven by significantly lower levels of expression in the elderly of IL7, IL2RG and IL7R. After adjustment for multiple testing and white blood cell composition and in comparison with similarly aged controls, middle-aged offspring of nonagenarian siblings exhibit a lower expression level of IL7R only (P = 0.006). Higher IL7R gene expression in the combined group of middle-aged offspring and controls is associated with a higher prevalence of immune-related disease (P = 0.001). On the one hand, our results indicate that lower IL7R expression levels, as exhibited by the members of long-lived families that can be considered as ‘healthy agers’, are beneficial in middle age. This is augmented by the observation that higher IL7R gene expression associates with immune-related disease. On the other hand, IL7R gene expression in blood is lower in older individuals, indicating that low IL7R gene expression might associate with reduced health. Interestingly, this contradictory result is supported by the observation that a higher IL7R gene expression level is associated with better prospective survival, both in the nonagenarians (Hazard ratio (HR) = 0.63, P = 0.037) and the middle-aged individuals (HR = 0.33, P = 1.9 × 10^–4).

Conclusions

Overall, we conclude that the IL7R network reflected by gene expression levels in blood may be involved in the rate of ageing and health status of elderly individuals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-015-0048-6) contains supplementary material, which is available to authorized users.

Impact of Donation Mode on the Proportion and Function of T Lymphocytes in the Liver

BACKGROUND

Liver T-cells respond to the inflammatory insult generated during organ procurement and contribute to the injury following reperfusion. The mode of liver donation alters various metabolic and inflammatory pathways but the way it affects intrahepatic T-cells is still unclear.

METHODS

We investigated the modifications occurring in the proportion and function of T-cells during liver procurement for transplantation. We isolated hepatic mononuclear cells (HMC) from liver perfusate of living donors (LD) and donors after brain death (DBD) or cardiac death (DCD) and assessed the frequency of T-cell subsets, their cytokine secretion profile and CD8 T-cell cytotoxicity function, responsiveness to a danger associated molecular pattern (High Mobility Group Box1, HMGB1) and association with donor and recipient clinical parameters and immediate graft outcome.

RESULTS

We found that T-cells in healthy human livers were enriched in memory CD8 T-cells exhibiting a phenotype of non-circulating tissue-associated lymphocytes, functionally dominated by more cytotoxicity and IFN-γ-production in DBD donors, including upon activation by HMGB1 and correlating with peak of post-transplant AST. This liver-specific pattern of CD8 T-cell was prominent in DBD livers compared to DCD and LD livers suggesting that it was influenced by events surrounding brain death, prior to retrieval.

CONCLUSION

Mode of liver donation can affect liver T-cells with increased liver damage in DBD donors. These findings may be relevant in designing therapeutic strategies aimed at organ optimization prior to transplantation.

Regulation of CD8+ T-cell cytotoxicity in HIV-1 infection

Understanding the mechanisms involved in cellular immune responses against control of human immunodeficiency virus (HIV) infection is key to development of effective immunotherapeutic strategies against viral proliferation. Clear insights into the regulation of cytotoxic CD8+ T cells is crucial to development of effective immunotherapeutic strategies due to their unique ability to eliminate virus-infected cells during the course of infection. Here, we reviewed the roles of transcription factors, co-inhibitory molecules and regulatory cytokines following HIV infection and their potential significance in regulating the cytotoxic potentials of CD8+ T cells.

Success and failure of the cellular immune response against HIV-1

The cellular immune response to HIV-1 has now been studied in extraordinary detail. A very large body of data provides the most likely reasons that the HIV-specific cellular immune response succeeds in a small number of people but fails in most. Understanding the success and failure of the HIV-specific cellular immune response has implications that extend not only to immunotherapies and vaccines for HIV-1 but also to the cellular immune response in other disease states. This Review focuses on the mechanisms that are most likely responsible for durable and potent immunologic control of HIV-1. Although we now have a detailed picture of the cellular immune responses to HIV-1, important questions remain regarding the nature of these responses and how they arise.

Concurrent loss of co-stimulatory molecules and functional cytokine secretion attributes leads to proliferative senescence of CD8(+) T cells in HIV/TB co-infection

The role of T-cell immunosenescence and functional CD8(+) T-cell responses in HIV/TB co-infection is unclear. We examined and correlated surrogate markers of HIV disease progression with immune activation, immunosenescence and differentiation using T-cell pools of HIV/TB co-infected, HIV-infected and healthy controls. Our investigations showed increased plasma viremia and reduced CD4/CD8 T-cell ratio in HIV/TB co-infected subjects relative to HIV-infected, and also a closer association with changes in the expression of CD38, a cyclic ADP ribose hydrolase and CD57, which were consistently expressed on late-senescent CD8(+) T cells. Up-regulation of CD57 and CD38 were directly proportional to lack of co-stimulatory markers on CD8(+) T cells, besides diminished expression of CD127 (IL-7Rα) on CD57(+)CD4(+) T cells. Notably, intracellular IFN-γ, perforin and granzyme B levels in HIV-specific CD8(+) T cells of HIV/TB co-infected subjects were diminished. Intracellular CD57 levels in HIV gag p24-specific CD8(+) T cells were significantly increased in HIV/TB co-infection. We suggest that HIV-TB co-infection contributes to senescence associated with chronic immune activation, which could be due to functional insufficiency of CD8(+) T cells.

Hantaan virus infection induces both Th1 and ThGranzyme B+ cell immune responses that associated with viral control and clinical outcome in humans

Hantaviruses infection causing severe emerging diseases with high mortality rates in humans has become public health concern globally. The potential roles of CD4(+)T cells in viral control have been extensively studied. However, the contribution of CD4(+)T cells to the host response against Hantaan virus (HTNV) infection remains unclear. Here, based on the T-cell epitopes mapped on HTNV glycoprotein, we studied the effects and characteristics of CD4(+)T-cell responses in determining the outcome of hemorrhagic fever with renal syndrome. A total of 79 novel 15-mer T-cell epitopes on the HTNV glycoprotein were identified, among which 20 peptides were dominant target epitopes. Importantly, we showed the presence of both effective Th1 responses with polyfunctional cytokine secretion and ThGranzyme B(+) cell responses with cytotoxic mediators production against HTNV infection. The HTNV glycoprotein-specific CD4(+)T-cell responses inversely correlated with the plasma HTNV RNA load in patients. Individuals with milder disease outcomes showed broader epitopes targeted and stronger CD4(+)T-cell responses against HTNV glycoproteins compared with more severe patients. The CD4(+)T cells characterized by broader antigenic repertoire, stronger polyfunctional responses, better expansion capacity and highly differentiated effector memory phenotype(CD27-CD28-CCR7-CD45RA-CD127(hi)) would elicit greater defense against HTNV infection and lead to much milder outcome of the disease. The host defense mediated by CD4(+)T cells may through the inducing antiviral condition of the host cells and cytotoxic effect of ThGranzyme B+ cells. Thus, these findings highlight the efforts of CD4(+)T-cell immunity to HTNV control and provide crucial information to better understand the immune defense against HTNV infection.

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.

Marked anti-tumor effects of CD8(+)CD62L(+) T cells from melanoma-bearing mice

CD8(+)CD62L(+) T cells have been shown to play pivotal roles in anti-viral immunity, chronic myeloid leukemia and renal cell carcinoma. Recently, CD8(+)CD62L(+) T cells from naïve mice (nCD8(+)CD62L(+) T cells) have shown superior anti-tumor properties in melanoma-bearing mice. Considering that antigen-specific memory T cells have shown to possess more potent immunity than non-specific memory T cells, we hypothesized that CD8(+)CD62L(+) T cells from tumor-bearing individuals (mCD8(+)CD62L(+) T cells) might have superior anti-tumor effect than nCD8(+)CD62L(+) T cells. Therefore, we investigated phenotypes, functions and the in vivo distribution of mCD8(+)CD62L(+) T cells in tumor-bearing mice. We found that, while keeping the features of central memory T cells, the frequency of mCD8(+)CD62L(+) T cell in the spleen of tumor-bearing mice was significantly higher than that the one of nCD8(+)CD62L(+) T cell in naive mice. Moreover, we demonstrated that mCD8(+)CD62L(+) T cells had higher proliferation rate and IFN-γ production than nCD8(+)CD62L(+) T cells, in vitro. We performed adoptive transfer of mCD8(+)CD62L(+) T cells into melanoma-bearing mice and tracked them in spleen, lymph nodes and in melanoma tissues. Our results show that mCD8(+)CD62L(+) T cells had stronger in vivo anti-tumoral activity than nCD8(+)CD62L(+) T cells. This study highlights the therapeutic potential of mCD8(+)CD62L(+) T cells in the immunotherapy of melanoma and possibly other tumors.

HIV-1 Tat affects the programming and functionality of human CD8⁺ T cells by modulating the expression of T-box transcription factors

OBJECTIVE

HIV infection is characterized by several immune dysfunctions of both CD8⁺ and CD4⁺ T cells as hyperactivation, impairment of functionality and expansion of memory T cells. CD8⁺ T-cell dysfunctions have been associated with increased expression of T-bet, Eomesdermin and pro-inflammatory cytokines, and with down-regulation of CD127. The HIV-1 trans-activator of transcription (Tat) protein, which is released by infected cells and detected in tissues of HIV-positive individuals, is known to contribute to the dysregulation of CD4⁺ T cells; however, its effects on CD8⁺ T cells have not been investigated. Thus, in this study, we sought to address whether Tat may affect CD8⁺ T-cell functionality and programming.

METHODS

CD8⁺ T cells were activated by T-cell receptor engagement in the presence or absence of Tat. Cytokine production, killing capacity, surface phenotype and expression of transcription factors important for T-cell programming were evaluated.

RESULTS

Tat favors the secretion of interleukin-2, interferon-γ and granzyme B in CD8⁺ T cells. Behind this functional modulation we observed that Tat increases the expression of T-bet, Eomesdermin, Blimp-1, Bcl-6 and Bcl-2 in activated but not in unstimulated CD8⁺ T lymphocytes. This effect is associated with the down-regulation of CD127 and the up-regulation of CD27.

CONCLUSION

Tat deeply alters the programming and functionality of CD8⁺ T lymphocytes.