Memory CD8+ T cells vary in differentiation phenotype in different persistent virus infections

Clonal Deletion Prunes but Does Not Eliminate Self-Specific αβ CD8(+) T Lymphocytes

It has long been thought that clonal deletion efficiently removes almost all self-specific T cells from the peripheral repertoire. We found that self-peptide MHC-specific CD8(+) T cells in the blood of healthy humans were present in frequencies similar to those specific for non-self antigens. For the Y chromosome-encoded SMCY antigen, self-specific T cells exhibited only a 3-fold lower average frequency in males versus females and were anergic with respect to peptide activation, although this inhibition could be overcome by a stronger stimulus. We conclude that clonal deletion prunes but does not eliminate self-specific T cells and suggest that to do so would create holes in the repertoire that pathogens could readily exploit. In support of this hypothesis, we detected T cells specific for all 20 amino acid variants at the p5 position of a hepatitis C virus epitope in a random group of blood donors.

Large-Scale and Comprehensive Immune Profiling and Functional Analysis of Normal Human Aging

While many age-associated immune changes have been reported, a comprehensive set of metrics of immune aging is lacking. Here we report data from 243 healthy adults aged 40–97, for whom we measured clinical and functional parameters, serum cytokines, cytokines and gene expression in stimulated and unstimulated PBMC, PBMC phenotypes, and cytokine-stimulated pSTAT signaling in whole blood. Although highly heterogeneous across individuals, many of these assays revealed trends by age, sex, and CMV status, to greater or lesser degrees. Age, then sex and CMV status, showed the greatest impact on the immune system, as measured by the percentage of assay readouts with significant differences. An elastic net regression model could optimally predict age with 14 analytes from different assays. This reinforces the importance of multivariate analysis for defining a healthy immune system. These data provide a reference for others measuring immune parameters in older people.

T cell senescence and cardiovascular diseases

Age-related changes in the immune system, commonly termed "immunosenescence," contribute to deterioration of the immune response and fundamentally impact the health and survival of elderly individuals. Immunosenescence affects both the innate and adaptive immune systems; however, the most notable changes are in T cell immunity and include thymic involution, the collapse of T cell receptor (TCR) diversity, an imbalance in T cell populations, and the clonal expansion of senescent T cells. Senescent T cells have the ability to produce large quantities of proinflammatory cytokines and cytotoxic mediators; thus, they have been implicated in the pathogenesis of many chronic inflammatory diseases. Recently, an increasing body of evidence has suggested that senescent T cells also have pathogenic potential in cardiovascular diseases, such as hypertension, atherosclerosis, and myocardial infarction, underscoring the detrimental roles of these cells in various chronic inflammatory responses. Given that cardiovascular disease is the number one cause of death worldwide, there is great interest in understanding the contribution of age-related immunological changes to its pathogenesis. In this review, we discuss general features of age-related alterations in T cell immunity and the possible roles of senescent T cells in the pathogenesis of cardiovascular disease.

Age- and sex-related reference intervals of lymphocyte subsets in healthy ethnic Han Chinese children

Immunophenotyping of blood lymphocytes has become an important tool in the diagnosis of immunologic and hematologic disorders such as immunodeficiencies, lymphoproliferative and autoimmune diseases. Lymphocyte subsets include total T-cells (CD3(+)), TH (T helper, CD3(+) CD4(+)), TC (cytotoxic T cells, CD3(+) CD8(+)), B-cells (CD3(-) CD19(+)), and NK-cells (CD3(-) CD16(+) CD56(+)). Specific lymphocyte subset reference intervals should be locally established for meaningful comparison and to obtain an accurate interpretation of the results. Reference intervals of lymphocyte subsets for Chinese children are scarce. We performed dual-platform flow cytometry to determine the reference intervals of the percentages and absolute counts of lymphocyte subsets, including total T-cells, TH cells, TC cells, B-cells, and NK-cells in 1,027 ethnic Han children aged 4 months to 7 years in Henan, China. The children were divided into seven age groups. The percentages and absolute counts differed significantly with age, with the percentages of TH cells and B cells and the CD4/CD8 ratio peaking during the first year, while the percentages of total T cells, TC cells, and NK cells were obviously increased with age; girls showed a trend toward having a higher percentage of TH cells and a higher CD4/CD8 ratio than boys. The absolute counts of lymphocyte subsets peaked during first year and then decreased steadily with age. The reference intervals of lymphocyte subsets among children from China differed from the reported values in Hong Kong, the United States, Cameroon, and Italy. The differences observed could be due to genetic and environmental factors, coupled with the methodology used. The reference intervals of lymphocyte subsets could be used as initial national reference ranges in guidelines for children aged 4 months to 7 years.

Cytomegalovirus- and Epstein-Barr Virus-Induced T-Cell Expansions in Young Children Do Not Impair Naive T-cell Populations or Vaccination Responses: The Generation R Study

BACKGROUND

Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) induce effector memory T-cell expansions, which are variable and potentially depend on the age at primary exposure and coinfections. We evaluated the T-cell compartment and herpesvirus infections in 6-year-old children.

METHODS

T-cell subsets and immunoglobulin G seropositivity for CMV, EBV, herpes-simplex virus 1, and varicella-zoster virus were studied in 1079 6-year-old children. A random subgroup of 225 children was evaluated for CMV and EBV seropositivity before 2 years of age and for vaccination responses against measles and tetanus.

RESULTS

CMV and EBV infections were associated with significant expansions of CD27(-) and CD27(+) effector memory T cells, respectively. These expansions were enhanced in CMV-EBV-coinfected children and were independent of varicella-zoster virus or herpes-simplex virus 1 coinfection. Naive and central memory T-cell numbers were not affected, nor were anti-tetanus and anti-measles immunoglobulin G levels. Children infected before 2 years of age showed smaller effector memory T-cell expansions than those infected between 2 and 6 years of age.

CONCLUSIONS

CMV- and EBV-related T-cell expansions do not impair naive T-cell numbers or maintenance of protective responses against nonrelated pathogens. Duration of infection was not directly related to larger expansions of effector memory T cells in children, suggesting that other mechanisms affect these expansions at later age.

Immune aging, dysmetabolism, and inflammation in neurological diseases

As we age, the immune system undergoes a process of senescence accompanied by the increased production of proinflammatory cytokines, a chronic subclinical condition named as “inflammaging”. Emerging evidence from human and experimental models suggest that immune senescence also affects the central nervous system and promotes neuronal dysfunction, especially within susceptible neuronal populations. In this review we discuss the potential role of immune aging, inflammation and metabolic derangement in neurological diseases. The discovery of novel therapeutic strategies targeting age-linked inflammation may promote healthy brain aging and the treatment of neurodegenerative as well as neuropsychiatric disorders.

CD58/CD2 Is the Primary Costimulatory Pathway in Human CD28-CD8+ T Cells

A substantial proportion of CD8(+) T cells in adults lack the expression of the CD28 molecule, and the aging of the immune system is associated with a steady expansion of this T cell subset. CD28(-)CD8(+) T cells are characterized by potent effector functions but impaired responses to antigenic challenge. CD28 acts as the primary T cell costimulatory receptor, but there are numerous additional receptors that can costimulate the activation of T cells. In this study, we have examined such alternative costimulatory pathways regarding their functional role in CD28(-)CD8(+) T cells. Our study showed that most costimulatory molecules have a low capacity to activate CD28-deficient T cells, whereas the engagement of the CD2 molecule by its ligand CD58 clearly costimulated proliferation, cytokine production, and effector function in this T cell subset. CD58 is broadly expressed on APCs including dendritic cells. Blocking CD58 mAb greatly reduced the response of human CD28(-)CD8(+) T cells to allogeneic dendritic cells, as well as to viral Ags. Our results clearly identify the CD58/CD2 axis as the primary costimulatory pathway for CD8 T cells that lack CD28. Moreover, we show that engagement of CD2 amplifies TCR signals in CD28(-)CD8(+) T cells, demonstrating that the CD2-CD58 interaction has a genuine costimulatory effect on this T cell subset. CD2 signals might promote the control of viral infection by CD28(-)CD8(+) T cells, but they might also contribute to the continuous expansion of CD28(-)CD8(+) T cells during chronic stimulation by persistent Ag.

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.

Plasmacytoid dendritic cell and functional HIV Gag p55-specific T cells before treatment interruption can inform set-point plasma HIV viral load after treatment interruption in chronically suppressed HIV-1(+) patients

The identification of immune correlates of HIV control is important for the design of immunotherapies that could support cure or antiretroviral therapy (ART) intensification-related strategies. ART interruptions may facilitate this task through exposure of an ART partially reconstituted immune system to endogenous virus. We investigated the relationship between set-point plasma HIV viral load (VL) during an ART interruption and innate/adaptive parameters before or after interruption. Dendritic cell (DC), natural killer (NK) cell and HIV Gag p55-specific T-cell functional responses were measured in paired cryopreserved peripheral blood mononuclear cells obtained at the beginning (on ART) and at set-point of an open-ended interruption from 31 ART-suppressed chronically HIV-1(+) patients. Spearman correlation and linear regression modeling were used. Frequencies of plasmacytoid DC (pDC), and HIV Gag p55-specific CD3(+)  CD4(-)  perforin(+)  IFN-γ(+) cells at the beginning of interruption associated negatively with set-point plasma VL. Inclusion of both variables with interaction into a model resulted in the best fit (adjusted R(2)  = 0·6874). Frequencies of pDC or HIV Gag p55-specific CD3(+)  CD4(-)  CSFE(lo)  CD107a(+) cells at set-point associated negatively with set-point plasma VL. The dual contribution of pDC and anti-HIV T-cell responses to viral control, supported by our models, suggests that these variables may serve as immune correlates of viral control and could be integrated in cure or ART-intensification strategies.

Increased frequency of late-senescent T cells lacking CD127 in chronic hepatitis C disease

BACKGROUND

Hepatitis C virus (HCV) causes persistent disease in ~85% of infected individuals, where the viral replication appears to be tightly controlled by HCV-specific CD8+ T cells. Accumulation of senescent T cells during infection results in considerable loss of functional HCV-specific immune responses.

MATERIALS AND METHODS

We characterized the distinct T-cell phenotypes based on the expression of costimulatory molecules CD28 and CD27, senescence markers PD-1 and CD57, chronic immune activation markers CD38 and HLA-DR, and survival marker CD127 (IL-7R) by flow cytometry following activation of T cells using HCV peptides and phytohemagglutinin.

RESULTS

HCV-specific CD4+ and CD8+ T cells from chronic HCV (CHC) patients showed increased expression of PD-1. Furthermore, virus-specific CD4+ T cells of CHC-infected subjects displayed relatively increased expression of HLA-DR and CD38 relative to HCV-specific CD8+ T cells. The CD4+ and CD8+ T cells from HCV-infected individuals showed significant increase of late-differentiated T cells suggestive of immunosenescence. In addition, we found that the plasma viral loads positively correlated with the levels of CD57 and PD-1 expressed on T cells.

CONCLUSIONS

Chronic HCV infection results in increased turnover of late-senescent T cells that lack survival potentials, possibly contributing to viral persistence. Our findings challenge the prominence of senescent T-cell phenotypes in clinical hepatitis C infection.

Data analysis as a source of variability of the HLA-peptide multimer assay: from manual gating to automated recognition of cell clusters

Multiparameter flow cytometry is an indispensable method for assessing antigen-specific T cells in basic research and cancer immunotherapy. Proficiency panels have shown that cell sample processing, test protocols and data analysis may all contribute to the variability of the results obtained by laboratories performing ex vivo T cell immune monitoring. In particular, analysis currently relies on a manual, step-by-step strategy employing serial gating decisions based on visual inspection of one- or two-dimensional plots. It is therefore operator dependent and subjective. In the context of continuing efforts to support inter-laboratory T cell assay harmonization, the CIMT Immunoguiding Program organized its third proficiency panel dedicated to the detection of antigen-specific CD8(+) T cells by HLA-peptide multimer staining. We first assessed the contribution of manual data analysis to the variability of reported T cell frequencies within a group of laboratories staining and analyzing the same cell samples with their own reagents and protocols. The results show that data analysis is a source of variation in the multimer assay outcome. To evaluate whether an automated analysis approach can reduce variability of proficiency panel data, we used a hierarchical statistical mixture model to identify cell clusters. Challenges for automated analysis were the need to process non-standardized data sets from multiple centers, and the fact that the antigen-specific cell frequencies were very low in most samples. We show that this automated method can circumvent difficulties inherent to manual gating strategies and is broadly applicable for experiments performed with heterogeneous protocols and reagents.

Quantitative T cell subsets profile in peripheral blood from patients with idiopathic inflammatory myopathies: tilting the balance towards proinflammatory and pro-apoptotic subsets

The role of T cells in idiopathic inflammatory myopathies (IIM) is not yet clear. Some alterations in certain subsets have been reported in inflamed muscle cells. However, a broad quantitative assessment of peripheral T cell subsets has not been evaluated. The aim of this study was to address the quantitative profile of potential pathogenic T cell subsets, namely follicular helper T cells (Tfh), T helper type 17 (Th17), CD28(null) and regulatory T cells (Tregs ) in peripheral blood from IIM patients. Thirty IIM patients and 30 age- and gender-matched healthy donors were included. Peripheral blood mononuclear cells were isolated. T cell subsets were evaluated by flow cytometry, as follows: Tfh (CD4(+) CXCR5(+) ) and its subsets Tfh1 (CXCR3(+) CCR6(-) ), Tfh2 (CXCR3(-) CCR6(-) ), Tfh17 (CXCR3(-) CCR6(+) ), Th17 (CD4(+) IL17A(+) ), CD28(null) (CD4(+) CD28(-) CD244(+) ) and Tregs (CD4(+) CD25(high) forkhead box protein 3 (FoxP3(+) ); CD8(+) CD25(high) FoxP3(+) ). Percentage, absolute numbers and mean fluorescence intensity were analysed. We found increased numbers of total Tfh cells (28 ± 8.16 versus 6.64 ± 1.29, P=0.031) in IIM patients when compared to healthy controls. Moreover, this increment was dependent upon Tfh2 and Tfh17 (Tfh2:9.49 ± 2.19 versus 1.66 ± 0.46, P=0.005; Tfh17 9.48 ± 2.83 versus 1.18 ± 0.21, P=0.014). Also, IIM patients showed higher numbers of Th17 cells (30.25 ± 6.49 versus 13.46 ± 2.95, P=0.031) as well as decreased number of Tregs (5.98 ± 1.61 versus 30.82 ± 8.38, P=0.009). We also found an expansion of CD28(null) cells (162.88 ± 32.29 versus 64 ± 17.35, P=0.015). Our data suggest that IIM patients are characterized by an expansion of peripheral proinflammatory T cells, such as Tfh and Th17, as well as pro-apoptotic CD28 null cells and a deficiency of suppressor populations of Tregs (CD4(+) and CD8(+) ).

Single-Cell Characterization of in vitro Migration and Interaction Dynamics of T Cells Expanded with IL-2 and IL-7

T cells are pivotal in the immune defense against cancers and infectious agents. To mount an effector response against cancer cells, T cells need to migrate to the cancer-site, engage in contacts with cancer cells, and perform their effector functions. Adoptive T cell therapy is an effective strategy as treatment of complications such as relapse or opportunistic infections after hematopoietic stem cell transplantations. This requires a sufficient amount of cells that are able to expand and respond to tumor or viral antigens. The cytokines interleukin (IL)-2 and IL-7 drive T cell differentiation, proliferation, and survival and are commonly used to expand T cells ex vivo. Here, we have used microchip-based live-cell imaging to follow the migration of individual T cells, their interactions with allogeneic monocytes, cell division, and apoptosis for extended periods of time; something that cannot be achieved by commonly used methods. Our data indicate that cells grown in IL-7 + IL-2 had similar migration and contact dynamics as cells grown in IL-2 alone. However, the addition of IL-7 decreased cell death creating a more viable cell population, which should be beneficial when preparing cells for immunotherapy.

Coinhibitory receptors and CD8 T cell exhaustion in chronic infections

PURPOSE OF REVIEW

To describe the recent data on the role of coinhibitory receptors, such as PD-1, Tim-3, CD160, as mediators of the 'exhaustion' of virus-specific CD8 T cells in chronic infections and particularly in HIV.

RECENT FINDINGS

Exhaustion of chronic virus-specific CD8 T cells is a dynamic process characterized by altered differentiation, impaired function, and compromised proliferation/survival profile of these cells. This process is mediated by coinhibitory receptors expressed on the surface of virus-specific CD8 T cells and an orchestrated function of centrally connected pathways. Coexpression of several coinhibitory receptors characterizes severely exhausted virus-specific CD8 T cells. Several studies suggest a synergistic action, instead of a redundant role, of the different receptors. In-vivo manipulation of the coinhibitory network can rejuvenate exhausted virus-specific CD8 T cell responses and constrain replication of chronic viruses, including HIV.

SUMMARY

Revealing the molecular basis of virus-specific CD8 T cell exhaustion in chronic infections is critical for the understanding of the disease pathogenesis and the designing of novel vaccines aiming to enhance the cytolytic arm of the immune system. This is of particular interest for the development of immunotherapies in the context of a functional cure for HIV.

Effect of cytomegalovirus co-infection on normalization of selected T-cell subsets in children with perinatally acquired HIV infection treated with combination antiretroviral therapy

Background

We examined the effect of cytomegalovirus (CMV) co-infection and viremia on reconstitution of selected CD4+ and CD8+ T-cell subsets in perinatally HIV-infected (PHIV+) children ≥ 1-year old who participated in a partially randomized, open-label, 96-week combination antiretroviral therapy (cART)-algorithm study.

Methods

Participants were categorized as CMV-naïve, CMV-positive (CMV+) viremic, and CMV+ aviremic, based on blood, urine, or throat culture, CMV IgG and DNA polymerase chain reaction measured at baseline. At weeks 0, 12, 20 and 40, T-cell subsets including naïve (CD62L+CD45RA+; CD95-CD28+), activated (CD38+HLA-DR+) and terminally differentiated (CD62L-CD45RA+; CD95+CD28-) CD4+ and CD8+ T-cells were measured by flow cytometry.

Results

Of the 107 participants included in the analysis, 14% were CMV+ viremic; 49% CMV+ aviremic; 37% CMV-naïve. In longitudinal adjusted models, compared with CMV+ status, baseline CMV-naïve status was significantly associated with faster recovery of CD8+CD62L+CD45RA+% and CD8+CD95-CD28+% and faster decrease of CD8+CD95+CD28-%, independent of HIV VL response to treatment, cART regimen and baseline CD4%. Surprisingly, CMV status did not have a significant impact on longitudinal trends in CD8+CD38+HLA-DR+%. CMV status did not have a significant impact on any CD4+ T-cell subsets.

Conclusions

In this cohort of PHIV+ children, the normalization of naïve and terminally differentiated CD8+ T-cell subsets in response to cART was detrimentally affected by the presence of CMV co-infection. These findings may have implications for adjunctive treatment strategies targeting CMV co-infection in PHIV+ children, especially those that are now adults or reaching young adulthood and may have accelerated immunologic aging, increased opportunistic infections and aging diseases of the immune system.

Humoral responses to HIVconsv induced by heterologous vaccine modalities in rhesus macaques

Vaccines delivering T cell immunogen HIVconsv vectored by plasmid DNA, non-replicating simian adenovirus and non-replicating modified vaccinia virus Ankara (MVA) are under clinical evaluation in phase I/IIa trials in UK, Europe, and Africa. While these vaccines aim to induce effector T cell responses specific for HIV-1, we here characterized the humoral responses induced by HIVconsv administration to macaques using six different vaccine modalities: plasmid DNA, human adenovirus serotype 5, simian adenovirus serotype 63, MVA, Semliki Forest virus replicons, and adjuvanted overlapping synthetic long peptides (SLP). We found that only the SLP formulation, but none of the genetic vaccine platforms induced antibodies recognizing linear HIVconsv epitopes, median 32/46 SLP.HIVconsv peptides. These antibodies bound to 15-mer and SLP peptides, recombinant gp120 and trimeric gp140 of HIV-1 Bal, YU2, JRFL, and UG037, but failed to react with HIV-1 Bal and IIIB virions and HIV-1 Bal- and IIIB-infected human cells, and consequently failed to induce neutralizing antibodies. The HIVconsv immunogen contains conserved regions derived from Gag, Pol, Vif, and Env proteins of HIV-1, and antibodies induced by the SLP.HIVconsv vaccination resulted in positive signals in routine HIV-1 tests. Thus, only HIVconsv delivered by SLP resulted in seroconversion, an observation that provides important guidance for recruiting volunteers into future clinical trials. Furthermore, our data confirms that vaccine delivery by SLP induces humoral as well as cellular immune responses and could be considered for inclusion in future vaccine regimens where this is required.

Infection history determines the differentiation state of human CD8+ T cells

After the resolution of the acute phase of infection, otherwise quiescent antigen-experienced CD8(+) T cells confer rapid protection upon reinfection with viral pathogens or, in the case of persistent viruses, help to maintain control of the infection. Depending on the type of virus, antigen-specific CD8(+) T cells have distinct traits, ranging from typical memory cell properties in the case of rapidly cleared viruses to immediate effector functions for persistent viruses. We here show that both the differentiation stage, defined by the expression of cell surface markers, such as CD45RA, CCR7, CD28, and CD27, and distinct expression levels of T-bet and eomesodermin (Eomes) predict the functional profile of antigen-experienced CD8(+) T cells. Furthermore, virus-specific CD8(+) T cells targeting different respiratory syncytial virus-, influenza A virus-, Epstein-Barr virus (EBV)-, human cytomegalovirus (hCMV)-, and HIV-1-specific epitopes adopt distinct T-bet and Eomes expression patterns that appear to be installed early during the primary response. Importantly, the associations between surface phenotype, T-bet/Eomes expression levels, and the expression of markers that predict CD8(+) T-cell function change according to viral infection history, particularly against the background of HIV-1 and, to lesser extent, of human cytomegalovirus and/or Epstein-Barr virus infection. Thus, the functionality of human antigen-experienced CD8(+) T cells follows at least two dimensions, one outlined by the surface phenotype and another by the T-bet/Eomes expression levels, which are determined by previous or persistent viral challenges.

IMPORTANCE

Functional human CD8(+) T-cell subsets have been defined using surface markers like CD45RA, CCR7, CD28, and CD27. However, the induction of function-defining traits, like granzyme B expression, is controlled by transcription factors like T-bet and Eomes. Here, we describe how T-bet and Eomes levels distinctly relate to the expression of molecules predictive for CD8(+) T-cell function in a surface phenotype-independent manner. Importantly, we found that central memory and effector memory CD8(+) T-cell subsets differentially express T-bet, Eomes, and molecules predictive for function according to viral infection history, particularly so in the context of HIV-1 infection and, to lesser extent, of latent EBV- and/or hCMV-infected, otherwise healthy adults. Finally, we show that the distinct phenotypes and T-bet/Eomes levels of different virus-specific CD8(+) T-cell populations are imprinted early during the acute phase of primary infection in vivo. These findings broaden our understanding of CD8(+) T-cell differentiation.

IL-6 receptor α defines effector memory CD8+ T cells producing Th2 cytokines and expanding in asthma

RATIONALE

Cytokine receptors can be markers defining different T-cell subsets and considered as therapeutic targets. The association of IL-6 and IL-6 receptor α (IL-6Rα) with asthma was reported, suggesting their involvement in asthma.

OBJECTIVES

To determine whether and how IL-6Rα defines a distinct effector memory (EM) CD8+ T-cell population in health and disease.

METHODS

EM CD8+ T cells expressing IL-6Rα (IL-6Rα(high)) were identified in human peripheral blood and analyzed for function, gene, and transcription factor expression. The relationship of these cells with asthma was determined using blood and sputum.

MEASUREMENTS AND MAIN RESULTS

A unique population of IL-6Rα(high) EM CD8+ T cells was found in peripheral blood. These cells that potently proliferated, survived, and produced high levels of the Th2-type cytokines IL-5 and IL-13 had increased levels of GATA3 and decreased levels of T-bet and Blimp-1 in comparison with other EM CD8+ T cells. In fact, GATA3 was required for IL-6Rα expression. Patients with asthma had an increased frequency of IL-6Rα(high) EM CD8+ T cells in peripheral blood compared with healthy control subjects. Also, IL-6Rα(high) EM CD8+ T cells exclusively produced IL-5 and IL-13 in response to asthma-associated respiratory syncytial virus and bacterial superantigens.

CONCLUSIONS

Human IL-6Rα(high) EM CD8+ T cells is a unique cell subset that may serve as a reservoir for effector CD8+ T cells, particularly the ones producing Th2-type cytokines, and expand in asthma.

Mechanistic insights on immunosenescence and chronic immune activation in HIV-tuberculosis co-infection

Immunosenescence is marked by accelerated degradation of host immune responses leading to the onset of opportunistic infections, where senescent T cells show remarkably higher ontogenic defects as compared to healthy T cells. The mechanistic association between T-cell immunosenescence and human immunodeficiency virus (HIV) disease progression, and functional T-cell responses in HIV-tuberculosis (HIV-TB) co-infection remains to be elaborately discussed. Here, we discussed the association of immunosenescence and chronic immune activation in HIV-TB co-infection and reviewed the role played by mediators of immune deterioration in HIV-TB co-infection necessitating the importance of designing therapeutic strategies against HIV disease progression and pathogenesis.

Role of PD-1 co-inhibitory pathway in HIV infection and potential therapeutic options

Virus-specific CD8⁺ T cells play an important role in controlling viral infections including human immunodeficiency virus (HIV) infection. However, during chronic HIV infection, virus-specific CD8⁺ T cells undergo functional exhaustion, lose effector functions and fail to control viral infection. HIV-specific CD8 T cells expressing high levels of co-inhibitory molecule programmed death-1 (PD-1) during the chronic infection and are characterized by lower proliferation, cytokine production, and cytotoxic abilities. Although, antiretroviral therapy has resulted in dramatic decline in HIV replication, there is no effective treatment currently available to eradicate viral reservoirs or restore virus-specific T or B-cell functions that may complement ART in order to eliminate the virus. In recent years, studies in mice and non-human primate models of HIV infection demonstrated the functional exhaustion of virus-specific T and B cells could be reversed by blockade of interaction between PD-1 and its cognate ligands (PD-L1 and PD-L2). In this review, we discuss recent advances in our understanding of PD-1 pathway in HIV/SIV infection and discuss the beneficial effects of PD-1 blockade during chronic HIV/SIV infection and its potential role as immunotherapy for HIV/AIDS.

Lymphocytic choriomeningitis virus persistence promotes effector-like memory differentiation and enhances mucosal T cell distribution

Vaccines are desired that maintain abundant memory T cells at nonlymphoid sites of microbial exposure, where they may be anatomically positioned for immediate pathogen interception. Here, we test the impact of antigen persistence on mouse CD8 and CD4 T cell distribution and differentiation by comparing responses to infections with different strains of LCMV that cause either acute or chronic infections. We used in vivo labeling techniques that discriminate between T cells present within tissues and abundant populations that fail to be removed from vascular compartments, despite perfusion. LCMV persistence caused up to ∼30-fold more virus-specific CD8 T cells to distribute to the lung compared with acute infection. Persistent infection also maintained mucosal-homing α4β7 integrin expression, higher granzyme B expression, alterations in the expression of the TRM markers CD69 and CD103, and greater accumulation of virus-specific CD8 T cells in the large intestine, liver, kidney, and female reproductive tract. Persistent infection also increased LCMV-specific CD4 T cell quantity in mucosal tissues and induced maintenance of CXCR4, an HIV coreceptor. This study clarifies the relationship between viral persistence and CD4 and CD8 T cell distribution and mucosal phenotype, indicating that chronic LCMV infection magnifies T cell migration to nonlymphoid tissues.

Specificity and dynamics of effector and memory CD8 T cell responses in human tick-borne encephalitis virus infection

Tick-borne encephalitis virus (TBEV) is transferred to humans by ticks. The virus causes tick-borne encephalitis (TBE) with symptoms such as meningitis and meningoencephalitis. About one third of the patients suffer from long-lasting sequelae after clearance of the infection. Studies of the immune response during TBEV-infection are essential to the understanding of host responses to TBEV-infection and for the development of therapeutics. Here, we studied in detail the primary CD8 T cell response to TBEV in patients with acute TBE. Peripheral blood CD8 T cells mounted a considerable response to TBEV-infection as assessed by Ki67 and CD38 co-expression. These activated cells showed a CD45RA-CCR7-CD127- phenotype at day 7 after hospitalization, phenotypically defining them as effector cells. An immunodominant HLA-A2-restricted TBEV epitope was identified and utilized to study the characteristics and temporal dynamics of the antigen-specific response. The functional profile of TBEV-specific CD8 T cells was dominated by variants of mono-functional cells as the effector response matured. Antigen-specific CD8 T cells predominantly displayed a distinct Eomes+Ki67+T-bet+ effector phenotype at the peak of the response, which transitioned to an Eomes-Ki67-T-bet+ phenotype as the infection resolved and memory was established. These transcription factors thus characterize and discriminate stages of the antigen-specific T cell response during acute TBEV-infection. Altogether, CD8 T cells responded strongly to acute TBEV infection and passed through an effector phase, prior to gradual differentiation into memory cells with distinct transcription factor expression-patterns throughout the different phases.

Tick-borne encephalitis virus (TBEV) belongs to the flavivirus family and causes tick-borne encephalitis. This is a severe meningoencephalitic disease with no available treatment. Detailed studies of the immune response during human TBEV infection are essential to understand host responses to TBE and for the development of therapeutics. Herein, we studied the primary T cell-mediated immune response in patients diagnosed with TBEV infection. We show that CD8 T cells mount a vigorous TBEV-specific response within one week of hospitalization. Moreover, TBEV-specific CD8 T cells displayed a distinctive phenotypic and functional profile, paired with a distinct transcription factor expression-pattern during the peak of activation. In summary, this is the first comprehensive study of the CD8 T cell response during acute human TBEV infection, and provides a framework for understanding of CD8 T cell-mediated immunity in this emerging viral disease.

T cell exhaustion during persistent viral infections

Although robust and highly effective anti-viral T cells contribute to the clearance of many acute infections, viral persistence is associated with the development of functionally inferior, exhausted, T cell responses. Exhaustion develops in a step-wise and progressive manner, ranges in severity, and can culminate in the deletion of the anti-viral T cells. This disarming of the response is consequential as it compromises viral control and potentially serves to dampen immune-mediated damage. Exhausted T cells are unable to elaborate typical anti-viral effector functions. They are characterized by the sustained upregulation of inhibitory receptors and display a gene expression profile that distinguishes them from prototypic effector and memory T cell populations. In this review we discuss the properties of exhausted T cells; the virological and immunological conditions that favor their development; the cellular and molecular signals that sustain the exhausted state; and strategies for preventing and reversing exhaustion to favor viral control.

Direct and Indirect Effects of Cytomegalovirus-Induced γδ T Cells after Kidney Transplantation

Despite effective anti-viral therapies, cytomegalovirus (CMV) is still associated with direct (CMV disease) and indirect effects (rejection and poor graft survival) in kidney transplant recipients. Recently, an unconventional T cell population (collectively designated as Vδ2^neg γδ T cells) has been characterized during the anti-CMV immune response in all solid-organ and bone-marrow transplant recipients, neonates, and healthy people. These CMV-induced Vδ2^neg γδ T cells undergo a dramatic and stable expansion after CMV infection, in a conventional “adaptive” manner. Similarly, as CMV-specific CD8+ αβ T cells, they exhibit an effector/memory TEMRA phenotype and cytotoxic effector functions. Activation of Vδ2^neg γδ T cells by CMV-infected cells involves the γδ T cell receptor (TCR) and still ill-defined co-stimulatory molecules such as LFA-1. A multiple of Vδ2^neg γδ TCR ligands are apparently recognized on CMV-infected cells, the first one identified being the major histocompatibility complex-related molecule endothelial protein C receptor. A singularity of CMV-induced Vδ2^neg γδ T cells is to acquire CD16 expression and to exert an antibody-dependent cell-mediated inhibition on CMV replication, which is controlled by a specific cytokine microenvironment. Beyond the well-demonstrated direct anti-CMV effect of Vδ2^neg γδ T cells, unexpected indirect effects of these cells have been also observed in the context of kidney transplantation. CMV-induced Vδ2^neg γδ T cells have been involved in surveillance of malignancy subsequent to long-term immunosuppression. Moreover, CMV-induced CD16+ γδ T cells are cell effectors of antibody-mediated rejection of kidney transplants, and represent a new physiopathological contribution to the well-known association between CMV infection and poor graft survival. All these basic and clinical studies paved the road to the development of a future γδ T cell-based immunotherapy. In the meantime, γδ T cell monitoring should prove a valuable immunological biomarker in the management of CMV infection.

Memory T cells specific for murine cytomegalovirus re-emerge after multiple challenges and recapitulate immunity in various adoptive transfer scenarios

Reconstitution of CMV-specific immunity after transplant remains a primary clinical objective to prevent CMV disease, and adoptive immunotherapy of CMV-specific T cells can be an effective therapeutic approach. Because of viral persistence, most CMV-specific CD8(+) T cells become terminally differentiated effector phenotype CD8(+) T cells (TEFF). A minor subset retains a memory-like phenotype (memory phenotype CD8(+) T cells [TM]), but it is unknown whether these cells retain memory function or persist over time. Interestingly, recent studies suggest that CMV-specific CD8(+) T cells with different phenotypes have different abilities to reconstitute sustained immunity after transfer. The immunology of human CMV infections is reflected in the murine CMV (MCMV) model. We found that human CMV- and MCMV-specific T cells displayed shared genetic programs, validating the MCMV model for studies of CMV-specific T cells in vivo. The MCMV-specific TM population was stable over time and retained a proliferative capacity that was vastly superior to TEFF. Strikingly, after transfer, TM established sustained and diverse T cell populations even after multiple challenges. Although both TEFF and TM could protect Rag(-/-) mice, only TM persisted after transfer into immune replete, latently infected recipients and responded if recipient immunity was lost. Interestingly, transferred TM did not expand until recipient immunity was lost, supporting that competition limits the Ag stimulation of TM. Ultimately, these data show that CMV-specific TM retain memory function during MCMV infection and can re-establish CMV immunity when necessary. Thus, TM may be a critical component for consistent, long-term adoptive immunotherapy success.

Molecular mechanisms of CD8(+) T cell trafficking and localization

Cytotoxic CD8(+) T cells are potent mediators of host protection against disease due to their ability to directly kill cells infected with intracellular pathogens and produce inflammatory cytokines at the site of infection. To fully achieve this objective, naïve CD8(+) T cells must be able to survey the entire body for the presence of foreign or "non-self" antigen that is delivered to draining lymph nodes following infection or tissue injury. Once activated, CD8(+) T cells undergo many rounds of cell division, acquire effector functions, and are no longer restricted to the circulation and lymphoid compartments like their naïve counterparts, but rather are drawn to inflamed tissues to combat infection. As CD8(+) T cells transition from naïve to effector to memory populations, this is accompanied by dynamic changes in the expression of adhesion molecules and chemokine receptors that ultimately dictate their localization in vivo. Thus, an understanding of the molecular mechanisms regulating CD8(+) T cell trafficking and localization is critical for vaccine design, control of infectious diseases, treatment of autoimmune disorders, and cancer immunotherapy.

Cryopreservation of MHC multimers: Recommendations for quality assurance in detection of antigen specific T cells

Fluorescence-labeled peptide-MHC class I multimers serve as ideal tools for the detection of antigen-specific T cells by flow cytometry, enabling functional and phenotypical characterization of specific T cells at the single cell level. While this technique offers a number of unique advantages, MHC multimer reagents can be difficult to handle in terms of stability and quality assurance. The stability of a given fluorescence-labeled MHC multimer complex depends on both the stability of the peptide-MHC complex itself and the stability of the fluorochrome. Consequently, stability is difficult to predict and long-term storage is generally not recommended. We investigated here the possibility of cryopreserving MHC multimers, both in-house produced and commercially available, using a wide range of peptide-MHC class I multimers comprising virus and cancer-associated epitopes of different affinities presented by various HLA-class I molecules. Cryopreservation of MHC multimers was feasible for at least 6 months, when they were dissolved in buffer containing 5-16% glycerol (v/v) and 0.5% serum albumin (w/v). The addition of cryoprotectants was tolerated across three different T-cell staining protocols for all fluorescence labels tested (PE, APC, PE-Cy7 and Quantum dots). We propose cryopreservation as an easily implementable method for stable storage of MHC multimers and recommend the use of cryopreservation in long-term immunomonitoring projects, thereby eliminating the variability introduced by different batches and inconsistent stability.

Early-onset Evans syndrome, immunodeficiency, and premature immunosenescence associated with tripeptidyl-peptidase II deficiency

Autoimmune cytopenia is a frequent manifestation of primary immunodeficiencies. Two siblings presented with Evans syndrome, viral infections, and progressive leukopenia. DNA available from one patient showed a homozygous frameshift mutation in tripeptidyl peptidase II (TPP2) abolishing protein expression. TPP2 is a serine exopeptidase involved in extralysosomal peptide degradation. Its deficiency in mice activates cell death programs and premature senescence. Similar to cells from naïve, uninfected TPP2-deficient mice, patient cells showed increased major histocompatibility complex I expression and most CD8(+) T-cells had a senescent CCR7-CD127(-)CD28(-)CD57(+) phenotype with poor proliferative responses and enhanced staurosporine-induced apoptosis. T-cells showed increased expression of the effector molecules perforin and interferon-γ with high expression of the transcription factor T-bet. Age-associated B-cells with a CD21(-) CD11c(+) phenotype expressing T-bet were increased in humans and mice, combined with antinuclear antibodies. Moreover, markers of senescence were also present in human and murine TPP2-deficient fibroblasts. Telomere lengths were normal in patient fibroblasts and granulocytes, and low normal in lymphocytes, which were compatible with activation of stress-induced rather than replicative senescence programs. TPP2 deficiency is the first primary immunodeficiency linking premature immunosenescence to severe autoimmunity. Determination of senescent lymphocytes should be part of the diagnostic evaluation of children with refractory multilineage cytopenias.

Myocardial ischemia and reperfusion leads to transient CD8 immune deficiency and accelerated immunosenescence in CMV-seropositive patients

RATIONALE

There is mounting evidence of a higher incidence of coronary heart disease in cytomegalovirus-seropositive individuals.

OBJECTIVE

The aim of this study was to investigate whether acute myocardial infarction triggers an inflammatory T-cell response that might lead to accelerated immunosenescence in cytomegalovirus-seropositive patients.

METHODS AND RESULTS

Thirty-four patients with acute myocardial infarction undergoing primary percutaneous coronary intervention were longitudinally studied within 3 months after reperfusion (Cohort A). In addition, 54 patients with acute myocardial infarction and chronic myocardial infarction were analyzed in a cross-sectional study (Cohort B). Cytomegalovirus-seropositive patients demonstrated a greater fall in the concentration of terminally differentiated CD8 effector memory T cells (TEMRA) in peripheral blood during the first 30 minutes of reperfusion compared with cytomegalovirus-seronegative patients (-192 versus -63 cells/μL; P=0.008), correlating with the expression of programmed cell death-1 before primary percutaneous coronary intervention (r=0.8; P=0.0002). A significant proportion of TEMRA cells remained depleted for ≥3 months in cytomegalovirus-seropositive patients. Using high-throughput 13-parameter flow cytometry and human leukocyte antigen class I cytomegalovirus-specific dextramers, we confirmed an acute and persistent depletion of terminally differentiated TEMRA and cytomegalovirus-specific CD8(+) cells in cytomegalovirus-seropositive patients. Long-term reconstitution of the TEMRA pool in chronic cytomegalovirus-seropositive postmyocardial infarction patients was associated with signs of terminal differentiation including an increase in killer cell lectin-like receptor subfamily G member 1 and shorter telomere length in CD8(+) T cells (2225 versus 3397 bp; P<0.001).

CONCLUSIONS

Myocardial ischemia and reperfusion in cytomegalovirus-seropositive patients undergoing primary percutaneous coronary intervention leads to acute loss of antigen-specific, terminally differentiated CD8 T cells, possibly through programmed cell death-1-dependent programmed cell death. Our results suggest that acute myocardial infarction and reperfusion accelerate immunosenescence in cytomegalovirus-seropositive patients.

Short conserved sequences of HIV-1 are highly immunogenic and shift immunodominance

Cellular immunity is pivotal in HIV-1 pathogenesis but is hampered by viral sequence diversity. An approach to minimize this diversity is to focus immunity on conserved proteome sequences; therefore, we selected four relatively conserved regions (Gag amino acids 148 to 214 and 250 to 335, Env amino acids 521 to 606, and Nef amino acids 106 to 148), each created in three mosaics, to provide better coverage of M-group HIV-1 sequences. A conserved-region vaccine (CRV) delivering genes for these four regions as equal mixtures of three mosaics each (each region at a separate injection site) was compared to a whole-protein vaccine (WPV) delivering equimolar amounts of genes for whole Gag, Env, and Nef as clade B consensus sequences (separate injection sites). Three rhesus macaques were vaccinated via three DNA primes and a recombinant adenovirus type 5 boost (weeks 0, 4, 8, and 24, respectively). Although CRV inserts were about one-fifth that of WPV, the CRV generated comparable-magnitude blood CD4+ and CD8+ T lymphocyte responses against Gag, Env, and Nef. WPV responses preferentially targeted proteome areas outside the selected conserved regions in direct proportion to sequence lengths, indicating similar immunogenicities for the conserved regions and the outside regions. The CRV yielded a conserved-region targeting density that was approximately 5-fold higher than that of the WPV. A similar pattern was seen for bronchoalveolar lymphocytes, but with quadruple the magnitudes seen in blood. Overall, these findings demonstrate that the selected conserved regions are highly immunogenic and that anatomically isolated vaccinations with these regions focus immunodominance compared to the case for full-length protein vaccination.

IMPORTANCE

HIV-1 sequence diversity is a major barrier limiting the capability of cellular immunity to contain infection and the ability of vaccines to match circulating viral sequences. To date, vaccines tested in humans have delivered whole proteins or genes for whole proteins, and it is unclear whether including only conserved sequences would yield sufficient cellular immunogenicity. We tested a vaccine delivering genes for four small conserved HIV-1 regions compared to a control vaccine with genes for whole Gag, Env, and Nef. Although the conserved regions ranged from 43 to 86 amino acids and comprised less than one-fifth of the whole Gag/Env/Nef sequence, the vaccines elicited equivalent total magnitudes of both CD4+ and CD8+ T lymphocyte responses. These data demonstrate the immunogenicity of these small conserved regions and the potential for a vaccine to steer immunodominance toward conserved epitopes.

Immunity to cytomegalovirus in early life

Cytomegalovirus (CMV) is the most common congenital infection and is the leading non-genetic cause of neurological defects. CMV infection in early life is also associated with intense and prolonged viral excretion, indicating limited control of viral replication. This review summarizes our current understanding of the innate and adaptive immune responses to CMV infection during fetal life and infancy. It illustrates the fact that studies of congenital CMV infection have provided a proof of principle that the human fetus can develop anti-viral innate and adaptive immune responses, indicating that such responses should be inducible by vaccination in early life. The review also emphasizes the fact that our understanding of the mechanisms involved in symptomatic congenital CMV infection remains limited.

Manufacture of gene-modified human T-cells with a memory stem/central memory phenotype

Advances in genetic engineering have made it possible to generate human T-cell products that carry desired functionalities, such as the ability to recognize cancer cells. The currently used strategies for the generation of gene-modified T-cell products lead to highly differentiated cells within the infusion product, and on the basis of data obtained in preclinical models, this is likely to impact the efficacy of these products. We set out to develop a good manufacturing practice (GMP) protocol that yields T-cell receptor (TCR) gene-modified T-cells with more favorable properties for clinical application. Here, we show the robust clinical-scale production of human peripheral blood T-cells with an early memory phenotype that express a MART-1-specific TCR. By combining selection and stimulation using anti-CD3/CD28 beads for retroviral transduction, followed by expansion in the presence of IL-7 and IL-15, production of a well-defined clinical-scale TCR gene-modified T-cell product could be achieved. A major fraction of the T-cells generated in this fashion were shown to coexpress CD62L and CD45RA, and express CD27 and CD28, indicating a central memory or memory stemlike phenotype. Furthermore, these cells produced IFNγ, TNFα, and IL-2 and displayed cytolytic activity against target cells expressing the relevant antigen. The T-cell products manufactured by this robust and validated GMP production process are now undergoing testing in a phase I/IIa clinical trial in HLA-A*02:01 MART-1-positive advanced stage melanoma patients. To our knowledge, this is the first clinical trial protocol in which the combination of IL-7 and IL-15 has been applied for the generation of gene-modified T-cell products.

T cell differentiation in chronic infection and cancer: functional adaptation or exhaustion?

Chronic viral infections and malignant tumours induce T cells that have a reduced ability to secrete effector cytokines and have upregulated expression of the inhibitory receptor PD1 (programmed cell death protein 1). These features have so far been considered to mark terminally differentiated 'exhausted' T cells. However, several recent clinical and experimental observations indicate that phenotypically exhausted T cells can still mediate a crucial level of pathogen or tumour control. In this Opinion article, we propose that the exhausted phenotype results from a differentiation process in which T cells stably adjust their effector capacity to the needs of chronic infection. We argue that this phenotype is optimized to cause minimal tissue damage while still mediating a critical level of pathogen control. In contrast to the presently held view of functional exhaustion, this new concept better reflects the pathophysiology and clinical manifestations of persisting infections, and it provides a rationale for emerging therapies that enhance T cell activity in chronic infection and cancer by blocking inhibitory receptors.

IFNγ⁻TNFα⁻IL2⁻MIP1α⁻CD107a⁺PRF1⁺ CD8 pp65-Specific T-Cell Response Is Independently Associated With Time to Death in Elderly Humans

Persistent cytomegalovirus (CMV) infection has been suggested to be a major driving force in the immune deterioration and an underlying source of age-related diseases in the elderly. CMV antibody titers are associated with lower responses to vaccination, cardiovascular diseases, frailty, and mortality. CMV infection is also associated with shorter T-cell telomeres and replicative senescence. Although an age-related deregulation of CMV-specific T-cell responses could be an underlying cause of the relationship between CMV and immune defects, strong and polyfunctional responses are observed in elderly individuals, casting uncertainty on their direct role in age-related immune frailty. In this study, we longitudinally followed a cohort of healthy donors aged over 50 years, assessing their mortality rates and time to death during a 2-year period. Specific T-cell responses to the immunodominant antigen pp65 (IFNγ, TNFα, IL2, MIP1α, CD107a, and perforin production) were analyzed at the beginning of the 2-year observation period. A cytotoxic CD8 pp65-specific T-cell response, without cytokine or chemokine coexpression, was independently associated with all-cause mortality in these elderly individuals. This pp65-specific CD8 T-cell response could be a useful tool to identify individuals with depressed immune function and a higher risk of death.

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.

T-bet and Eomes are differentially linked to the exhausted phenotype of CD8+ T cells in HIV infection

CD8(+) T cell exhaustion represents a major hallmark of chronic HIV infection. Two key transcription factors governing CD8(+) T cell differentiation, T-bet and Eomesodermin (Eomes), have previously been shown in mice to differentially regulate T cell exhaustion in part through direct modulation of PD-1. Here, we examined the relationship between these transcription factors and the expression of several inhibitory receptors (PD-1, CD160, and 2B4), functional characteristics and memory differentiation of CD8(+) T cells in chronic and treated HIV infection. The expression of PD-1, CD160, and 2B4 on total CD8(+) T cells was elevated in chronically infected individuals and highly associated with a T-bet(dim)Eomes(hi) expressional profile. Interestingly, both resting and activated HIV-specific CD8(+) T cells in chronic infection were almost exclusively T-bet(dim)Eomes(hi) cells, while CMV-specific CD8(+) T cells displayed a balanced expression pattern of T-bet and Eomes. The T-bet(dim)Eomes(hi) virus-specific CD8(+) T cells did not show features of terminal differentiation, but rather a transitional memory phenotype with poor polyfunctional (effector) characteristics. The transitional and exhausted phenotype of HIV-specific CD8(+) T cells was longitudinally related to persistent Eomes expression after antiretroviral therapy (ART) initiation. Strikingly, these characteristics remained stable up to 10 years after ART initiation. This study supports the concept that poor human viral-specific CD8(+) T cell functionality is due to an inverse expression balance between T-bet and Eomes, which is not reversed despite long-term viral control through ART. These results aid to explain the inability of HIV-specific CD8(+) T cells to control the viral replication post-ART cessation.

Diverse specificities, phenotypes, and antiviral activities of cytomegalovirus-specific CD8+ T cells

CD8(+) T cells specific for pp65, IE1, and IE2 are present at high frequencies in human cytomegalovirus (HCMV)-seropositive individuals, and these have been shown to have phenotypes associated with terminal differentiation, as well as both cytokine and proliferative dysfunctions, especially in the elderly. However, more recently, T cell responses to many other HCMV proteins have been described, but little is known about their phenotypes and functions. Consequently, in this study, we chose to determine the diversity of HCMV-specific CD8(+) T cell responses to the products of 11 HCMV open reading frames (ORFs) in a cohort of donors aged 20 to 80 years old as well as the ability of the T cells to secrete gamma interferon (IFN-γ). Finally, we also tested their functional antiviral capacity using a novel viral dissemination assay. We identified substantial CD8(+) T cell responses by IFN-γ enzyme-linked immunospot (ELISPOT) assays to all 11 of these HCMV proteins, and across the cohort, individuals displayed a range of responses, from tightly focused to highly diverse, which were stable over time. CD8(+) T cell responses to the HCMV ORFs were highly differentiated and predominantly CD45RA(+), CD57(+), and CD28(-), across the cohort. These highly differentiated cells had the ability to inhibit viral spread even following direct ex vivo isolation. Taken together, our data argue that HCMV-specific CD8(+) T cells have effective antiviral activity irrespective of the viral protein recognized across the whole cohort and despite viral immune evasion.

IMPORTANCE

Human cytomegalovirus (HCMV) is normally carried without clinical symptoms and is widely prevalent in the population; however, it often causes severe clinical disease in individuals with compromised immune responses. HCMV is never cleared after primary infection but persists in the host for life. In HCMV carriers, the immune response to HCMV includes large numbers of virus-specific immune cells, and the virus has evolved many mechanisms to evade the immune response. While this immune response seems to protect healthy people from subsequent disease, the virus is never eliminated. It has been suggested that this continuous surveillance by the immune system may have deleterious effects in later life. The study presented in this paper examined immune responses from a cohort of donors and shows that these immune cells are effective at controlling the virus and can overcome the virus' lytic cycle immune evasion mechanisms.

Epigenetic repression of interleukin 2 expression in senescent CD4+ T cells during chronic HIV type 1 infection

The molecular mechanisms for IL2 gene-specific dysregulation during chronic human immunodeficiency virus type 1 (HIV-1) infection are unknown. Here, we investigated the role of DNA methylation in suppressing interleukin 2 (IL-2) expression in memory CD4(+) T cells during chronic HIV-1 infection. We observed that CpG sites in the IL2 promoter of CD4(+) T cells were fully methylated in naive CD4(+) T cells and significantly demethylated in the memory populations. Interestingly, we found that the memory cells that had a terminally differentiated phenotype and expressed CD57 had increased IL2 promoter methylation relative to less differentiated memory cells in healthy individuals. Importantly, early effector memory subsets from HIV-1-infected subjects expressed high levels of CD57 and were highly methylated at the IL2 locus. Furthermore, the increased CD57 expression on memory CD4(+) T cells was inversely correlated with IL-2 production. These data suggest that DNA methylation at the IL2 locus in CD4(+) T cells is coupled to immunosenescence and plays a critical role in the broad dysfunction that occurs in polyclonal T cells during HIV-1 infection.

Adaptive immunity to murine skin commensals

The adaptive immune system provides critical defense against pathogenic bacteria. Commensal bacteria have begun to receive much attention in recent years, especially in the gut where there is growing evidence of complex interactions with the adaptive immune system. In the present study, we observed that commensal skin bacteria are recognized by major populations of T cells in skin-draining lymph nodes of mice. Recombination activating gene 1 (Rag1)(-/-) mice, which lack adaptive immune cells, contained living skin-derived bacteria and bacterial sequences, especially mycobacteria, in their skin-draining lymph nodes. T cells from skin-draining lymph nodes of normal mice were shown, in vitro, to specifically recognize bacteria of several species that were grown from Rag1(-/-) lymph nodes. T cells from skin-draining lymph nodes, transferred into Rag1(-/-) mice proliferated in skin-draining lymph nodes, expressed a restricted T-cell receptor spectrotype and produced cytokines. Transfer of T cells into Rag1(-/-) mice had the effect of reducing bacterial sequences in skin-draining lymph nodes and in skin itself. Antibacterial effects of transferred T cells were dependent on IFNγ and IL-17A. These studies suggest a previously unrecognized role for T cells in controlling skin commensal bacteria and provide a mechanism to account for cutaneous infections and mycobacterial infections in T-cell-deficient patients.

Training status and sex influence on senescent T-lymphocyte redistribution in response to acute maximal exercise

PURPOSE

Investigate training status and sex effects on the redistribution of senescent and naïve T-lymphocytes following acute exercise.

METHODS

Sixteen (8 male, 8 female) trained (18.3±1.7yr) soccer players (Tr) and sixteen (8 male, 8 female) untrained (19.3±2.0yr) controls (UTr) performed a treadmill running test to volitional exhaustion. Blood lymphocytes were isolated before (Pre), immediately post, and 1-h post-exercise for assessment of cell surface expression of CD28 and CD57 on CD4(+) and CD8(+) T-lymphocyte subsets. Plasma was used to determine cytomegalovirus (CMV) serostatus.

RESULTS

Exercise elicited a redistribution of T-lymphocyte subsets. Senescent CD4(+) and CD8(+) T-lymphocytes increased by 42.4% and 45.9% respectively, while naïve CD4(+) and CD8(+) T-lymphocytes decreased by 8.7% and 22.5% respectively in response to exercise. A main effect (P<0.05) of training status was observed for senescent CD4(+), CD8(+) and naïve CD8(+) T-lymphocytes: UTr had a higher proportion of senescent and a lower proportion of naïve CD8(+) T-lymphocytes than Tr. A main effect (P<0.05) of sex was observed in senescent CD4(+), CD8(+) and naïve CD4(+), CD8(+) T-lymphocytes. Males had a higher proportion of senescent and lower proportion of naïve T-lymphocytes than females. A sex-by-training status interaction (P<0.05) was observed for the senescent and naïve CD4(+) T-lymphocytes (but not CD8(+)) with the highest percentage of senescent and lowest percentage of naïve T-lymphocytes observed in UTr males. CMV exerted a significant main covariate effect (P<0.05) in the senescent and naïve (P<0.05) CD8(+) T-lymphocytes but not in the senescent and naïve CD4(+) T-lymphocytes.

CONCLUSION

This study highlights important sex and training status differences in the senescent and naïve T-lymphocyte redistribution in response to exercise that warrants further investigation.

The effects of age and latent cytomegalovirus infection on the redeployment of CD8+ T cell subsets in response to acute exercise in humans

Dynamic exercise evokes a rapid redeployment of cytotoxic T cell subsets with high expression of β2 adrenergic receptors, presumably to enhance immunosurveillance during acute stress. As this response is affected by age and infection history, this study examined latent CMV infection as a potential confounder to age-related differences in blood CD8+ T-cell responses to exercise. Healthy young (n=16) and older (n=16) humans counterbalanced by CMV IgG serostatus (positive or negative) exercised for 30-min at ∼80% peak cycling power. Those with CMV redeployed ∼2-times more CD8+ T-cells and ∼6-times more KLRG1+/CD28- and CD45RA+/CCR7- CD8+ subsets than non-infected exercisers. Seronegative older exercisers had an impaired redeployment of total CD8+ T-cells, CD45RA+/CCR7+ and KLRG1-/CD28+ CD8+ subsets compared to young. Redeployed CD8+ T-cell numbers were similar between infected young and old. CMVpp65 specific CD8+ cells in HLA/A2(∗) subjects increased ∼2.7-fold after exercise, a response that was driven by the KLRG1+/CD28-/CD8+ subset. Stimulating PBMCs before and after exercise with CMVpp65 and CMV IE-1 antigens and overlapping peptide pools revealed a 2.1 and 4.4-fold increases in CMVpp65 and CMV IE-1 IFN-γ secreting cells respectively. The breadth of the T cell response was maintained after exercise with the magnitude of the response being amplified across the entire epitope repertoire. To conclude, latent CMV infection overrides age-related impairments in CD8+ T-cell redeployment with exercise. We also show for the first time that many T-cells redeployed with exercise are specific to CMVpp65 and CMV IE-1 antigens, have broad epitope specificity, and are mostly of a high-differentiated effector memory phenotype.

Age-associated Epstein-Barr virus-specific T cell responses in seropositive healthy adults

Epstein-Barr virus (EBV) is present in 95% of the world's adult population. The immune response participates in immune vigilance and persistent infection control, and this condition is maintained by both a good quality (functionality) and quantity of specific T cells throughout life. In the present study, we evaluated EBV-specific CD4(+) and CD8(+) T lymphocyte responses in seropositive healthy individuals younger and older than 50 years of age. The assessment comprised the frequency, phenotype, functionality and clonotypic distribution of T lymphocytes. We found that in both age groups a similar EBV-specific T cell response was found, with overlapping numbers of tumour necrosis factor (TNF)-α(+) T lymphocytes (CD4(+) and CD8(+)) within the memory and effector cell compartments, in addition to monofunctional and multi-functional T cells producing interleukin (IL)-2 and/or interferon (IFN)-γ. However, individuals aged more than 50 years showed significantly higher frequencies of IL-2-producing CD4(+) T lymphocytes in association with greater production of soluble IFN-γ, TNF-α and IL-6 than subjects younger than 50 years. A polyclonal T cell receptor (TCR)-variable beta region (Vβ) repertoire exists in both age groups under basal conditions and in response to EBV; the major TCR families found in TNF-α(+) /CD4(+) T lymphocytes were Vβ1, Vβ2, Vβ17 and Vβ22 in both age groups, and the major TCR family in TNF-α(+) /CD8(+) T cells was Vβ13·1 for individuals younger than 50 years and Vβ9 for individuals aged more than 50 years. Our findings suggest that the EBV-specific T cell response (using a polyclonal stimulation model) is distributed throughout several T cell differentiation compartments in an age-independent manner and includes both monofunctional and multi-functional T lymphocytes.

CD8+ T cell responses specific for hepatitis B virus core protein in patients with chronic hepatitis B virus infection

BACKGROUND

Chronic hepatitis B virus (HBV) infection includes a set of heterogeneous clinical patterns, and core-protein-specific T cell response is important for virus control and disease progression, yet is not well elucidated.

OBJECTIVES

To analyze the phenotypic and functional profiles of HBV-core-protein-specific CD8+ T cells in different clinical patterns of chronic HBV infection.

STUDY DESIGN

A total of 46 HBV patients were recruited and classified according to their clinical status. CD8+ T cell responses in different patterns of chronic HBV infections were tested with flow cytometry using overlapping 15-mer peptides covering HBV core protein. Meanwhile, the CCR7/CD27 phenotypes of these CD8+ T cells were also determined.

RESULTS

Frequencies of gamma interferon (IFN-γ) positive CD8+ T cells in inactive HBV surface antigen (HBsAg) carriers in response to the core protein peptide pools were generally stronger than those of chronic HBV carriers and resolved individuals, especially with regards to peptide pool C13-C24. Moreover, phenotypic studies further highlighted the group of CD8+ CCR7-CD27+ T memory cells, which showed significantly higher levels of IFN-γ secretion in inactive HBsAg carriers than those in chronic hepatitis B patients, chronic HBV carriers and resolved individuals.

CONCLUSIONS

Core-protein-specific T cell response plays an important role in chronic HBV infection. Inactive HBsAg carriers showed a much stronger core-protein-specific cytotoxic T cell response than other types of chronically infected patients. CD8+ CCR7-CD27+ T memory lymphocytes may be crucial in the immune pathogenesis of chronic HBV infection.

Excess body mass is associated with T cell differentiation indicative of immune ageing in children

Obesity has been associated with accelerated biological ageing and immunosenescence. As the prevalence of childhood obesity is increasing, we wanted to determine if associations between obesity and immunosenescence would manifest in children. We studied 123 Mexican American adolescents aged 10-14 (mean 12·3 ± 0·7) years, with body weights ranging from 30·1 to 115·2 kg (mean 52·5 ± 14·5 kg). Blood samples were obtained to determine proportions of naive, central memory (CM), effector memory (EM), senescent and early, intermediate and highly differentiated subsets of CD4(+) and CD8(+) T cells. Overweight and obese children had significantly lowered proportions of early CD8(+) T cells (B = -11·55 and -5·51%, respectively) compared to healthy weight. Overweight children also had more EM (B = +7·53%), late (B = +8·90%) and senescent (B = +4·86%) CD8(+) T cells than healthy weight children, while obese children had more intermediate CD8(+) (B = +4·59%), EM CD8(+) (B = +5·49%), late CD4(+) (B = +2·01%) and senescent CD4(+) (B = +0·98%) T cells compared to healthy weight children. These findings withstood adjustment for potentially confounding variables, including age, gender and latent cytomegalovirus and Epstein-Barr virus infections. We conclude that excess body mass, even in adolescence, may accelerate immunosenescence and predispose children to increased risks of incurring immune-related health problems in adulthood.

Protective immunity against hepatitis C: many shades of gray

The majority of individuals who become acutely infected with hepatitis C virus (HCV) develop chronic infection and suffer from progressive liver damage while approximately 25% are able to eliminate the virus spontaneously. Despite the recent introduction of new direct-acting antivirals, there is still no vaccine for HCV. As a result, new infections and reinfections will remain a problem in developing countries and among high risk populations like injection drug users who have limited access to treatment and who continue to be exposed to the virus. The outcome of acute HCV is determined by the interplay between the host genetics, the virus, and the virus-specific immune response. Studies in humans and chimpanzees have demonstrated the essential role of HCV-specific CD4 and CD8 T cell responses in protection against viral persistence. Recent data suggest that antibody responses play a more important role than what was previously thought. Individuals who spontaneously resolve acute HCV infection develop long-lived memory T cells and are less likely to become persistently infected upon reexposure. New studies examining high risk cohorts are identifying correlates of protection during real life exposures and reinfections. In this review, we discuss correlates of protective immunity during acute HCV and upon reexposure. We draw parallels between HCV and the current knowledge about protective memory in other models of chronic viral infections. Finally, we discuss some of the yet unresolved questions about key correlates of protection and their relevance for vaccine development against HCV.

Cytomegalovirus drives Vδ2neg γδ T cell inflation in many healthy virus carriers with increasing age

Cytomegalovirus (CMV) usually causes lifelong asymptomatic infection, but over time can distort immune profiles. Recent reports describe selective expansion of Vδ2^neg γδ T cells in healthy and immunocompromised CMV carriers. Having shown previously that virus-specific CD8⁺ and CD4⁺ T cell responses are increased significantly in elderly CMV carriers, probably driven by chronic stimulation, we hypothesized that Vδ2^neg γδ T cells may also be expanded with age. Our results show that Vδ2^neg γδ T cells are increased significantly in CMV-seropositive healthy individuals compared to CMV-seronegative controls in all age groups. The differences were most significant in older age groups (P < 0·0001). Furthermore, while Vδ2^neg γδ T- cells comprise both naive and memory cells in CMV-seronegative donors, highly differentiated effector memory cells are the dominant phenotype in CMV carriers, with naive cells reduced significantly in numbers in CMV-seropositive elderly. Although phenotypically resembling conventional CMV-specific T cells, Vδ2^neg γδ T cells do not correlate with changes in magnitude of CMV-specific CD4⁺ or CD8⁺ T cell frequencies within those individuals, and do not possess ex-vivo immediate effector function as shown by CMV-specific CD4⁺ and CD8⁺ T cells. However, after short-term culture, Vδ2^neg γδ T cells demonstrate effector T cell functions, suggesting additional requirements for activation. In summary, Vδ2^neg γδ T cells are expanded in many older CMV carriers, demonstrating a further level of lymphocyte subset skewing by CMV in healthy individuals. As others have reported shared reactivity of Vδ2^neg γδ T cells towards tumour cells, the composition of γδ T cell subsets may also have implications for risk of developing cancer in elderly people.