CD27 and CD57 expression reveals atypical differentiation of human immunodeficiency virus type 1-specific memory CD8+ T cells

Inflammation and cytomegalovirus viremia during pregnancy drive sex-differentiated differences in mortality and immune development in HIV-exposed infants

Children who are HIV-exposed but uninfected have increased infectious mortality compared to HIV-unexposed children, raising the possibility of immune abnormalities following exposure to maternal viraemia, immune dysfunction, and co-infections during pregnancy. In a secondary analysis of the SHINE trial in rural Zimbabwe we explored biological pathways underlying infant mortality, and maternal factors shaping immune development in HIV-exposed uninfected infants. Maternal inflammation and cytomegalovirus viraemia were independently associated with infant deaths: mortality doubled for each log10 rise in maternal C-reactive protein (adjusted hazard ratio (aHR) 2.09; 95% CI 1.33-3.27), and increased 1.6-fold for each log10 rise in maternal cytomegalovirus viral load (aHR 1.62; 95% CI 1.11-2.36). In girls, mortality was more strongly associated with maternal C-reactive protein than cytomegalovirus; in boys, mortality was more strongly associated with cytomegalovirus than C-reactive protein. At age one month, HIV-exposed uninfected infants had a distinct immune milieu, characterised by raised soluble CD14 and an altered CD8 + T-cell compartment. Alterations in immunophenotype and systemic inflammation were generally greater in boys than girls. Collectively, these findings show how the pregnancy immune environment in women with HIV underlies mortality and immune development in their offspring in a sex-differentiated manner, and highlights potential new intervention strategies to transform outcomes of HIV-exposed children. ClinicalTrials.gov/NCT01824940.

A Key Role of CD8+ T Cells in Controlling of Tuberculosis Infection

The main role in the control of tuberculosis infection is played by macrophages and Th1 and CD8+ T cells. The study aimed to identify the most diagnostically significant CD8+ T cell subsets in tuberculosis patients.

METHODS

Peripheral blood samples from patients with clinical, radiological, and bacteriologically confirmed pulmonary tuberculosis (TB, n = 32) and healthy subjects (HC, n = 31) were collected and analyzed using 10-color flow cytometry.

RESULTS

The frequency of the EM4 CD3+CD8+ cells was reduced in the peripheral blood of patients with pulmonary tuberculosis, while the relative and absolute number of EM1 CD3+CD8+ cells increased compared to the control group. CD57 expression was reduced in patients with pulmonary tuberculosis on EM1, EM2, and pE1 CD3+CD8+ cells, whereas the EM3 cells had a high level of CD57 expression. The relative and absolute number of Tc2 (CCR6-CXCR3-) cells in peripheral blood in patients with pulmonary tuberculosis was increased, while the frequency of Tc1 (CCR6-CXCR3+) was decreased, compared to healthy donors.

CONCLUSIONS

Patients with pulmonary tuberculosis have an abnormal CD3+CD8+ cell profile and demonstrate their impaired maturation and functional activity.

Single-Cell Immune Mapping of Melanoma Sentinel Lymph Nodes Reveals an Actionable Immunotolerant Microenvironment

PURPOSE

Improving our understanding of the immunologic response to cancer cells within the sentinel lymph nodes (SLN) of primary tumors is expected to identify new approaches to stimulate clinically meaningful cancer immunity.

EXPERIMENTAL DESIGN

We used mass cytometry by time-of-flight (CyTOF), flow cytometry, and T-cell receptor immunosequencing to conduct simultaneous single-cell analyses of immune cells in the SLNs of patients with melanoma.

RESULTS

We found increased effector-memory αβ T cells, TCR clonality, and γδ T cells selectively in the melanoma-bearing SLNs relative to non-melanoma-bearing SLNs, consistent with possible activation of an antitumor immune response. However, we also observed a markedly immunotolerant environment in the melanoma-bearing SLNs indicated by reduced and impaired NK cells and increased levels of CD8+CD57+PD-1+ cells, which are known to display low melanoma killing capabilities. Other changes observed in melanoma-bearing SLNs when compared with non-melanoma-bearing SLNs include (i) reduced CD8+CD69+ T cell/T regulatory cell ratio, (ii) high PD-1 expression on CD4+ and CD8+ T cells, and (iii) high CTLA-4 expression on γδ T cells.

CONCLUSIONS

Our data suggest that these immunologic changes compromise antimelanoma immunity and contribute to a high relapse rate. We propose the development of clinical trials to test the neo-adjuvant administration of anti-PD-1 antibodies prior to SLN resection in patients with stage III melanoma. See related commentary by Lund, p. 1996.

PD-L1+CD8+ T cells enrichment in lung cancer exerted regulatory function and tumor-promoting tolerance

Immunotherapy targeting checkpoint blockade to rescue T cells from exhaustion has become an essential therapeutic strategy in treating cancers. Till now, little is known about the PD-L1 graphic pattern and characteristics in CD8⁺ T cells. We combined cytometry by time-of-flight (CyTOF) and imaging mass cytometry (IMC) approaches to analyze CD8⁺ T cells from primary lung cancers and discovered that PD-L1⁺CD8⁺ T cells were enriched in tumor lesions, spatially localized with PD-1⁺CD8⁺ T cells. Furthermore, PD-L1⁺CD8⁺ T cells exerted regulatory functions that inhibited CD8⁺ T cells proliferation and cytotoxic abilities through the PD-L1/PD-1 axis. Moreover, tumor-derived IL-27 promotes PD-L1⁺CD8⁺ T cells development through STAT1/STAT3 signaling. Single-cell RNA sequencing data analysis further clarified PD-L1⁺CD8⁺ T cells elevated in the components related to downregulation of adaptive immune response. Collectively, our data demonstrated that PD-L1⁺CD8⁺ T cells enriched in lung cancer engaged in tolerogenic effects and may become a therapeutic target in lung cancer.

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CyTOF and IMC revealed PD-L1⁺CD8⁺ T cells were enriched in human lung cancer

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PD-L1⁺CD8⁺ T cells inhibited CD8⁺ T cells function through PD-1/PD-L1 axis

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IL27 promoted PD-L1⁺CD8 T cells development through STAT1/STAT3 signaling

Age and CMV-Infection Jointly Affect the EBV-Specific CD8+ T-Cell Repertoire

CD8⁺ T cells play an important role in protection against viral infections. With age, changes in the T-cell pool occur, leading to diminished responses against both new and recurring infections in older adults. This is thought to be due to a decrease in both T-cell numbers and T-cell receptor (TCR) diversity. Latent infection with cytomegalovirus (CMV) is assumed to contribute to this age-associated decline of the immune system. The observation that the level of TCR diversity in the total memory T-cell pool stays relatively stable during aging is remarkable in light of the constant input of new antigen-specific memory T cells. What happens with the diversity of the individual antigen-specific T-cell repertoires in the memory pool remains largely unknown. Here we studied the effect of aging on the phenotype and repertoire diversity of CMV-specific and Epstein-Barr virus (EBV)-specific CD8⁺ T cells, as well as the separate effects of aging and CMV-infection on the EBV-specific T-cell repertoire. Antigen-specific T cells against both persistent viruses showed an age-related increase in the expression of markers associated with a more differentiated phenotype, including KLRG-1, an increase in the fraction of terminally differentiated T cells, and a decrease in the diversity of the T-cell repertoire. Not only age, but also CMV infection was associated with a decreased diversity of the EBV-specific T-cell repertoire. This suggests that both CMV infection and age can impact the T-cell repertoire against other antigens.

Exhaustion and senescence of CD4 and CD8 T cells that express co-stimulatory molecules CD27 and CD28 in subjects that acquired HIV by drug use or by sexual route

Introduction

The human immunodeficiency virus (HIV) infection leads to immune activation, senescence and exhaustion of T cells. Co-stimulatory molecules play important roles in controlling these processes. The CD28 signaling triggers efficient T cell activation, while CD27 provides survival signals to CD28- T cells. Loss of these molecules was associated with senescent phenotype and resistance to checkpoint inhibitors.Romania has faced an HIV outbreak among people who inject drugs (PWID), most of them chronically infected with hepatitis C virus (HCV). HIV/HCV co-infection was associated with increased immune activation and rapid disease progression.

Methods

We evaluated by flow cytometry the expression of CD27, CD28, CD38, HLA-DR, CD57 and PD-1 on CD4 and CD8 T cells from 34 subjected infected with HIV (22 PWID and 12 people who acquired HIV by sexual route - PWHS) and 18 HIV-negative individuals (controls).

Results

We found that as compared to controls, HIV patients, regardless of infection route, have high percentages of intermediately differentiated (CD27+CD28-) and low percentages of less differentiated (CD27+CD28+) CD8 T cells. Significantly higher levels of CD8+CD27+CD28- T cells were found in PWHS than in PWID. A lower percentage of intermediately and highly differentiated (CD27-CD28-) CD8 T cells express CD57 in people living with HIV (PLWH) than in controls. Increased levels of less and intermediately differentiated CD4 and CD8 T cells expressing PD-1 were identified in PLWH, especially in PWID; these directly correlated with HIV viral load and T cell activation and negatively correlated with CD4 counts.

Conclusions

Our data show that induction of PD-1 on T cells expressing co-stimulatory molecules CD27 and/or CD28 might contribute to poor control of HIV infection and to immune activation.

Grant M. The Immune Response Against Human Cytomegalovirus Links Cellular to Systemic Senescence

Aging reflects long-term decline in physiological function and integrity. Changes arise at a variable pace governed by time-dependent and -independent mechanisms that are themselves complex, interdependent and variable. Molecular decay produces inferior cells that eventually dominate over healthy counterparts in tissues they comprise. In a form of biological entropy, progression from molecular through cellular to tissue level degeneration culminates in organ disease or dysfunction, affecting systemic health. To better understand time-independent contributors and their potential modulation, common biophysical bases for key molecular and cellular changes underlying age-related physiological deterioration must be delineated. This review addresses the potential contribution of cytomegalovirus (CMV)-driven T cell proliferation to cellular senescence and immunosenescence. We first describe molecular processes imposing cell cycle arrest, the foundation of cellular senescence, then focus on the unique distribution, phenotype and function of CMV-specific CD8⁺ T cells in the context of cellular senescence and "inflammaging". Their features position CMV infection as a pathogenic accelerant of immune cell proliferation underlying immune senescence. In human immunodeficiency virus (HIV) infection, where increased inflammation and exaggerated anti-CMV immune responses accelerate immune senescence, CMV infection has emerged as a major factor in unhealthy aging. Thus, we speculate on mechanistic links between CMV-specific CD8⁺ T-cell expansion, immune senescence and prevalence of age-related disorders in HIV infection.

Early KLRG1+ but Not CD57+CD8+ T Cells in Primary Cytomegalovirus Infection Predict Effector Function and Viral Control

CMV remains an important opportunistic pathogen in high-risk lung transplant recipients. We characterized the phenotype and function of CD8⁺ T cells from acute/primary into chronic CMV infection in 23 (donor+/recipient-; D+R-) lung transplant recipients and found rapid induction of both KLRG1⁺ and/or CD57⁺ CMV-specific CD8⁺ T cells with unexpected coexpression of CD27. These cells demonstrated maturation from an acute effector T cell (T_AEFF) to an effector memory T cell (T_EM) phenotype with progressive enrichment of KLRG1⁺CD57⁺CD27^- cells into memory. CMV-specific KLRG1⁺ T_AEFF were capable of in vitro proliferation that diminished upon acquisition of CD57, whereas only KLRG1⁺ expression correlated with T-bet expression and effector function. In contrast to blood T_AEFF, lung mucosal T_AEFF demonstrated reduced KLRG1/T-bet expression but similar CD57 levels. Additionally, increased KLRG1⁺T_AEFF were associated with early immune viral control following primary infection. To our knowledge, our findings provide new insights into the roles of KLRG1 and CD57 expression in human T cells, forming the basis for a refined model of CD8⁺ T cell differentiation during CMV infection.

The hallmarks of CMV-specific CD8 T-cell differentiation

Upon cytomegalovirus (CMV) infection, large T-cell responses are elicited that remain high or even increase over time, a phenomenon named memory T-cell inflation. Besides, the maintained robust T-cell response, CMV-specific T cells seem to have a distinctive phenotype, characterized by an advanced differentiation state. Here, we will review this "special" differentiation status by discussing the cellular phenotype based on the expression of CD45 isoforms, costimulatory, inhibitory and natural killer receptors, adhesion and lymphocyte homing molecules, transcription factors, cytokines and cytotoxic molecules. In addition, we focus on whether the differentiation state of CMV-specific CD8 T cells is unique in comparison with other chronic viruses and we will discuss the possible impact of factors such as antigen exposure and aging on the advanced differentiation status of CMV-specific CD8 T cells.

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.

A Unique T-Cell Receptor Amino Acid Sequence Selected by Human T-Cell Lymphotropic Virus Type 1 Tax301-309-Specific Cytotoxic T Cells in HLA-A24:02-Positive Asymptomatic Carriers and Adult T-Cell Leukemia/Lymphoma Patients

We previously reported that the T-cell receptor (TCR) repertoire of human T-cell lymphotropic virus type 1 (HTLV-1) Tax_301-309-specific CD8⁺ cytotoxic T cells (Tax_301-309-CTLs) was highly restricted and a particular amino acid sequence motif, the PDR motif, was conserved among HLA-A*24:02-positive (HLA-A*24:02⁺) adult T-cell leukemia/lymphoma (ATL) patients who had undergone allogeneic hematopoietic cell transplantation (allo-HSCT). Furthermore, we found that donor-derived PDR⁺ CTLs selectively expanded in ATL long-term HSCT survivors with strong CTL activity against HTLV-1. On the other hand, the TCR repertoires in Tax_301-309-CTLs of asymptomatic HTLV-1 carriers (ACs) remain unclear. In this study, we directly identified the DNA sequence of complementarity-determining region 3 (CDR3) of the TCR-β chain of Tax_301-309-CTLs at the single-cell level and compared not only the TCR repertoires but also the frequencies and phenotypes of Tax_301-309-CTLs between ACs and ATL patients. We did not observe any essential difference in the frequencies of Tax_301-309-CTLs between ACs and ATL patients. In the single-cell TCR repertoire analysis of Tax_301-309-CTLs, 1,458 Tax_301-309-CTLs and 140 clones were identified in this cohort. Tax_301-309-CTLs showed highly restricted TCR repertoires with a strongly biased usage of BV7, and PDR, the unique motif in TCR-β CDR3, was exclusively observed in all ACs and ATL patients. However, there was no correlation between PDR⁺ CTL frequencies and HTLV-1 proviral load (PVL). In conclusion, we have identified, for the first time, a unique amino acid sequence, PDR, as a public TCR-CDR3 motif against Tax in HLA-A*24:02⁺ HTLV-1-infected individuals. Further investigations are warranted to elucidate the role of the PDR⁺ CTL response in the progression from carrier state to ATL.IMPORTANCE ATL is an aggressive T-cell malignancy caused by HTLV-1 infection. The HTLV-1 regulatory protein Tax aggressively promotes the proliferation of HTLV-1-infected lymphocytes and is also a major target antigen for CD8⁺ CTLs. In our previous evaluation of Tax_301-309-CTLs, we found that a unique amino acid sequence motif, PDR, in CDR3 of the TCR-β chain of Tax_301-309-CTLs was conserved among ATL patients after allo-HSCT. Furthermore, the PDR⁺ Tax_301-309-CTL clones selectively expanded and showed strong cytotoxic activities against HTLV-1. On the other hand, it remains unclear how Tax_301-309-CTL repertoire exists in ACs. In this study, we comprehensively compared Tax-specific TCR repertoires at the single-cell level between ACs and ATL patients. Tax_301-309-CTLs showed highly restricted TCR repertoires with a strongly biased usage of BV7, and PDR, the unique motif in TCR-β CDR3, was conserved in all ACs and ATL patients, regardless of clinical subtype in HTLV-1 infection.

Are cytotoxic effector cells changes in peripheral blood of patients with Sjögren's syndrome related to persistent virus infection: Suggestions and conundrums

Etiology of Sjögren's syndrome (SS) is still unknown, but there is strong evidence that certain pathogens of bacterial or viral origin can incite autoimmune response. The aim of this study was to quantitatively evaluate changes of the main cell populations (dendritic cells, natural killer, natural killer T and cytotoxic T lymphocytes) presumably participating in virus clearance in peripheral blood of patients with primary SS (pSS). In analyzing cytotoxic T lymphocytes (CTL) populations we observed alterations in the frequency of highly cytotoxic effector CD8^high/57⁺/27^-/45RA⁺, less cytotoxic CD8^high/57^-/27^-/45RA⁺ effector cells and cytotoxic memory CD8^high/57⁺/27⁺/45RA^- effector cells. We found a decrease of conventional dendritic cells (cDC) population in peripheral blood of pSS patients. It is possible that, a decrease of effector CTL and cDC, accompanied by increase of transitory phenotype memory CTL in peripheral blood of pSS patients may be associated with viral etiopathogenesis of Sjögren's syndrome.

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.

Distribution of Peripheral Lymphocyte Populations in Primary Sjögren's Syndrome Patients

Purpose of this study was to evaluate the lymphocyte populations' distribution changes in peripheral blood of patients with primary Sjögren's syndrome (pSS). Lymphocyte populations' distribution changes in peripheral blood of pSS patients were investigated in 52 patients with pSS and in 28 healthy controls by flow cytometry. We found decreased absolute count of CD3⁺ T cell population in pSS patients. Analysis of CD4⁺ T cell population showed significant proportion and absolute count differences in pSS patient's blood with SSA/SSB antibodies (Abs) in comparison to controls. No significant differences were observed analyzing CD4⁺ and CD8⁺ Treg subpopulation. Proportion and absolute counts of Th17 cells were significantly lower in pSS patient's blood. Absolute counts of CD8⁺ T cells were significantly lower in pSS patients in comparison to controls and also impaired proportion and absolute counts of CD8⁺ subpopulations according to CD27⁺ and CD57⁺ were observed. Absolute counts of NKT and NK cells were decreased in pSS with Abs. B cells proportion was increased only in blood of pSS with Abs. Lymphocyte distribution impairment can be due to genetically determined lymphopenia or lymphocyte migration from periphery to inflammatory sites or/and increased susceptibility to apoptosis.

New insights on the role of CD8(+)CD57(+) T-cells in cancer

Incomplete differentiation of CD8+ cytotoxic T-lymphocytes (CTLs) in the tumor microenvironment is associated with cancer progression. We describe a new type of tumor-infiltrating CD8+CD57+ T cell in cancer with hybrid phenotypic and functional properties of both an early effector-memory cell and a terminally-differentiated effector cell. These cells behave as incompletely-differentiated CTLs.

Increased T-bet is associated with senescence of influenza virus-specific CD8 T cells in aged humans

Aged individuals have increased morbidity and mortality following influenza and other viral infections, despite previous exposure or vaccination. Mouse and human studies suggest increased senescence and/or exhaustion of influenza virus-specific CD8 T cells with advanced age. However, neither the relationship between senescence and exhaustion nor the underlying transcriptional pathways leading to decreased function of influenza virus-specific cellular immunity in elderly humans are well-defined. Here, we demonstrate that increased percentages of CD8 T cells from aged individuals express CD57 and KLRG1, along with PD-1 and other inhibitory receptors, markers of senescence, or exhaustion, respectively. Expression of T-box transcription factors, T-bet and Eomes, were also increased in CD8 T cells from aged subjects and correlated closely with expression of CD57 and KLRG1. Influenza virus-specific CD8 T cells from aged individuals exhibited decreased functionality with corresponding increases in CD57, KLRG1, and T-bet, a molecular regulator of terminal differentiation. However, in contrast to total CD8 T cells, influenza virus-specific CD8 T cells had altered expression of inhibitory receptors, including lower PD-1, in aged compared with young subjects. Thus, our data suggest a prominent role for senescence and/or terminal differentiation for influenza virus-specific CD8 T cells in elderly subjects.

Long-term persistence of limited HTLV-I Tax-specific cytotoxic T cell clones in a patient with adult T cell leukemia/lymphoma after allogeneic stem cell transplantation

PURPOSE

Adult T cell leukemia/lymphoma (ATL) is a highly aggressive malignancy of T cells caused by human T cell lymphotropic virus type 1 (HTLV-1). Recent clinical studies have suggested that allogeneic stem cell transplantation (HSCT) improves the clinical course of ATL by harnessing a graft-versus-ATL effect, and that donor-derived HTLV-1 Tax-specific CD8(+) cytotoxic T cells (CTLs) contribute to the graft-versus-ATL effect after HSCT. However, little is known about the immunological characteristics of Tax-specific CTLs in ATL patients who underwent HSCT.

METHODS

We serially analyzed frequencies, differentiation, functions and clonal dynamics of Tax-specific CTLs in paired samples of peripheral blood (PB) and bone marrow (BM) from an ATL patient after HSCT at the single-cell level. We used flowcytometric and single-cell T cell receptor (TCR) repertoire analysis methods without culture steps.

RESULTS

Donor-derived Tax-specific CTLs effectively suppressed HTLV-1 replication in both PB and BM at least during chronic graft-versus-host disease after HSCT. Furthermore, Tax-specific CTLs had comparable properties between BM and PB, except for preferential accumulation in BM rather than PB. Tax-specific CTLs persistently existed as less-differentiated CD45RA(-)CCR7(-) effector memory CTLs based on predominant phenotypes of CD27(+), CD28(+/-) and CD57(+/-). Our approach using single-cell TCR repertoire analysis method showed highly restricted oligoclonal responses of Tax-specific CTLs, and TCR BV7- or BV30- expressing two predominant CTL clones persistently existed and maintained strong cytotoxic activities against HTLV-1 in both PB and BM over three years after HSCT.

CONCLUSIONS

These findings about Tax-specific CTLs provide insights into future directions for studies on immunotherapy against ATL.

Detection and characterization of a novel subset of CD8⁺CD57⁺ T cells in metastatic melanoma with an incompletely differentiated phenotype

PURPOSE

Tumor-specific T cells are frequently induced naturally in melanoma patients and infiltrate tumors. It is enigmatic why these patients fail to experience tumor regression. Given that CD8(+) T cells mediate antigen-specific killing of tumor cells, the focus of this study was to identify alterations in the differentiation of CD8(+) residing at the tumor site, with emphasis on a population expressing CD57, a marker for terminal differentiation.

EXPERIMENTAL DESIGN

We conducted flow cytometric analysis of CD8(+) tumor-infiltrating lymphocytes (TIL) isolated from 44 resected melanoma metastases with known T-cell differentiation markers. For comparison, peripheral blood mononuclear cells were isolated from matched melanoma patients. We sorted different CD8(+) subsets found in TIL and determined their effector functions. In addition, we carried out Vβ clonotype expression analysis of T-cell receptors to determine lineage relationship between the CD8(+) TIL subsets.

RESULTS

The majority of CD8(+) TIL was in the early-effector memory stage of differentiation. A significant population consisted of an oligoclonal subset of cells coexpressing CD27, CD28, CD57, and Granzyme B, with little or no perforin. These cells could be induced to proliferate, produce a high level of IFN-γ, and differentiate into CD27(-)CD57(+), perforin(high) mature CTL in vitro. Addition of TGF-β1 prevented further differentiation.

CONCLUSIONS

Our studies identified a novel subset of incompletely differentiated CD8(+) CTL coexpressing early effector memory and late CTL markers. This population resembles that found in patients with uncontrolled chronic viral infections. TGF-β1, frequently produced by melanoma tumors, may be a key cytokine inhibiting further maturation of this subset.

Expansion of a CD8(+)PD-1(+) replicative senescence phenotype in early stage CLL patients is associated with inverted CD4:CD8 ratios and disease progression

PURPOSE

Patients with chronic lymphocytic leukemia (CLL) display immune deficiency that is most obvious in advanced stage disease. Here we investigated whether this immune dysfunction plays a pathologic role in the progression of early stage disease patients.

EXPERIMENTAL DESIGN

We carried out eight-color immunophenotyping analysis in a cohort of 110 untreated early stage CLL patients and 22 age-matched healthy donors and correlated our findings with clinical outcome data.

RESULTS

We found a significant reduction in naive CD4(+) and CD8(+) T cells in CLL patients. Only the CD4(+) subset showed significantly increased effector memory cells (T(EM) and T(EMRA)) in the whole cohort (P = 0.004 and P = 0.04, respectively). However, patients with inverted CD4:CD8 ratios (52 of 110) showed preferential expansion of the CD8 compartment, with a skewing of CD8(+) T(EMRA) (P = 0.03) coupled with increased percentage of CD57(+)CD28(-)CD27(-) T cells (P = 0.008) and PD-1 positivity (P = 0.027), consistent with a replicative senescence phenotype. Furthermore, inverted CD4:CD8 ratios were associated with shorter lymphocyte doubling time (P = 0.03), shorter time to first treatment (P = 0.03), and reduced progression-free survival (P = 0.005).

CONCLUSIONS

Our data show that the emergence of CD8(+)PD-1(+) replicative senescence phenotype in early stage CLL patients is associated with more aggressive clinical disease. Importantly, these findings were independent of tumor cell prognostic markers and could not be accounted for by patient age, changes in regulatory T-cell frequency, or cytomegalovirus serostatus (n = 217).

Astrocyte and macrophage regulation of YKL-40 expression and cellular response in neuroinflammation

Numerous inflammatory conditions are associated with elevated YKL-40 expression by infiltrating macrophages. Thus, we were surprised to observe minimal macrophage and abundant astrocyte expression of YKL-40 in neuroinflammatory conditions. The aims of the current study were to better delineate this discrepancy, characterize the factors that regulate YKL-40 expression in macrophages and astrocytes and study whether YKL-40 expression correlates with cell morphology and/or activation state. In vitro, macrophages expressed high levels of YKL-40 that was induced by classical activation and inhibited by alternative activation. Cytokines released from macrophages induced YKL-40 transcription in astrocytes that was accompanied by morphological changes and altered astrocytic motility. Because coculturing of astrocytes and macrophages did not reverse this in vitro expression pattern, additional components of the in vivo central nervous system (CNS) milieu must be required to suppress macrophage and induce astrocyte expression of YKL-40.

Altered T cell differentiation associated with loss of CD27 and CD28 in HIV infected Indian individuals

BACKGROUND

HIV-1 infection is associated with depletion of naïve T cell subsets and skewed T cell differentiation and maturation, leading to accumulation of T cells at intermediate and end stages of differentiation. CD27 and CD28 expression have been utilized in assessing these population subsets.

METHODS

We characterized T cell subsets based on expression of CD45RA, CCR7, CD27, and CD28 and compared these subsets in HIV-1 infected Indian subjects and uninfected controls.

RESULTS

HIV-1 infection was associated with an increase in effector and memory T cell subsets and a concomitant decrease in naïve T cells. HIV-1 infected subjects showed accumulation of intermediate CD8 T cell (CD27+CD28-) differentiation subsets, whereas CD4 T cells progressed to late stage differentiation (CD27-CD28-). These subsets were negatively associated with CD4 T cell counts and positively associated with plasma viremia. CD57, an immunosenescence marker, was also increased on T cell subsets from HIV-1 infected individuals. Antiretroviral therapy resulted in partial restoration of differentiation status.

CONCLUSION

Persistent HIV-1 replication and chronic immune activation, along with altered cytokine secretion profile, lead to impaired T cell differentiation and maturation. Detailed understanding of factors associated with differentiation defects in HIV-1 infected Indian individuals will strongly assist in Indian HIV-1 vaccine efforts and add to our knowledge of HIV-1 subtype C pathogenesis.

Opposing effects of CD70 costimulation during acute and chronic lymphocytic choriomeningitis virus infection of mice

T cell costimulation is important for T cell activation. The CD27/CD70 pathway contributes to effector and memory T cell development and is involved in T cell and B cell activation. CD27/CD70 is known for having opposing roles during different models of antigenic challenges. During primary T cell responses to influenza virus infection or during tumor challenges, CD27/CD70 costimulation has a positive role on T cell responses. However, during some chronic infections, constitutive triggering of this signaling pathway has a negative role on T cell responses. It is currently unclear what specific characteristic of an antigen determines the outcome of CD27/CD70 costimulation. We investigated the effect of a transient CD70 blockade during an acute or a chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. Blockade of this pathway during acute LCMV infection (Armstrong strain) resulted in delayed T cell responses and decreased CD127 (interleukin-7 receptor α [IL-7Rα] chain) conversion. Upregulation of CD127 is an important event in T cell differentiation that heralds the passage of an effector T cell to a long-lived memory T cell. In contrast to the reduced CD8 T cell responses after CD70 blockade during acute infection, CD70 blockade during chronic LCMV infection resulted in increased CD8 T cell responses. Our data show the dual roles of this costimulatory pathway in acute versus persistent antigen challenge. Our findings suggest that antigen persistence may determine the effect of CD27/CD70 signaling on CD8 T cell responses. Tailored triggering or blockade of this costimulatory pathway may be important in vaccination regimens against acute or chronic pathogens.

Phenotypically and functionally distinct subsets contribute to the expansion of CD56-/CD16+ natural killer cells in HIV infection

OBJECTIVE

Chronic HIV infection has been associated with activation and increased turnover of natural killer (NK) cells as well as with disturbed homeostasis of the NK cell compartment, including loss of CD56(+) NK cells and accumulation of dysfunctional CD56(-)/CD16(+) NK cells. We performed a comprehensive phenotypical and functional characterization of this population.

DESIGN

A cross-sectional study was performed to analyze CD56(-)/CD16(+) NK cells from 34 untreated HIV-infected and 15 seronegative individuals.

METHODS

NK cells were analyzed by flow cytometry. Degranulation was assessed by measuring their expression of CD107a after stimulation with K562 cells, interleukin-12 and interleukin-15.

RESULTS

CD56(-)/CD16(+) NK cells are heterogeneous and composed of two populations, namely CD122(-)/CCR7(+) cells and CD122(-)/CCR7(+) cells. We show that expanded CD122(+) but not CCR7(+) cells in HIV-seropositive individuals are characterized by expression of senescence marker CD57 similarly to CD56(dim)/CD16(+) NK cells along with expression of KIRs, CD8, perforin and granzyme B. Despite expression of perforin and granzyme B, CD57 expressing cells exhibited less numbers of degranulating cells as measured by CD107a, indicating their functional impairment. However, there was no correlation between expansion of total CD56(-)/CD16(+) NK cells or the distinct subpopulations and viral load or CD4 cell count.

CONCLUSION

These data indicate that expansion of CD56(-)/CD16(+) cells in HIV infection is driven by a distinct subset within this population with high expression of terminal differentiation marker with a phenotype resembling CD56(-)/CD16(+) NK cells.

Novel soluble HLA-A2/MELAN-A complexes selectively stain a differentiation defective subpopulation of CD8+ T cells in patients with melanoma

Multimeric MHC I-peptide complexes containing phycoerythrin-streptavidin are widely used to detect and investigate antigen-specific CD8+ (and CD4+) T cells. Because such reagents are heterogeneous, we compared their binding characteristics with those of monodisperse dimeric, tetrameric and octameric complexes containing linkers of variable length and flexibility on Melan-A-specific CD8+ T cell clones and peripheral blood mononuclear cells (PBMC) from HLA-A*0201(+) melanoma patients. Striking binding differences were observed for different defined A2/Melan-A(26-35) complexes on T cells depending on their differentiation stage. In particular, short dimeric but not octameric A2/Melan-A(26-35) complexes selectively and avidly stained incompletely differentiated effector-memory T cells clones and populations expressing CD27 and CD28 and low levels of cytolytic mediators (granzymes and perforin). This subpopulation was found in PBMC from all six melanoma patients analyzed and proliferated on peptide stimulation with only modest phenotypic changes. By contrast influenza matrix(58-66) -specific CD8+ PBMC from nine HLA-A*0201(+) healthy donors were efficiently stained by A2/Flu matrix(58-61) multimers, but not dimer and upon peptide stimulation proliferated and differentiated from memory into effector T cells. Thus PBMC from melanoma patients contain a differentiation defective sub-population of Melan-A-specific CD8+ T cells that can be selectively and efficiently stained by short dimeric A2/Melan- A(26-35) complexes, which makes them directly accessible for longitudinal monitoring and further investigation.

Phenotype and function of protective T cell immune responses in HIV

PURPOSE OF REVIEW

Definition of T cell immune correlates in HIV infection remains a lofty goal towards our understanding of the HIV-specific immune response. This review will focus upon recent developments and controversies in our understanding of protective T cell responses against HIV.

RECENT FINDINGS

It has become clear that multiple functions and phenotypic markers of T cells must be assessed to accurately characterize the complexity of CD4 and CD8 T cell responses. While evidence indicates that a hallmark of protective immune responses in HIV infection is the presence of 'polyfunctional' T cell responses, a disconnect remains between the function and phenotype of effective HIV-specific T cells. Moreover, there may be inherent differences in the ability of specific human leukocyte antigen class I families to promote CD8 T cell effector versus polyfunctional responses. It remains to be determined how polyfunctional responses arise in HIV infection, which functions are important for control, and whether surface phenotype markers provide an indication of protective capacity.

SUMMARY

Polyfunctional and phenotypic assessment of T cell responses have clearly advanced our understanding of HIV specific immune responses. Critical questions remain, however, especially whether polyfunctional T cell responses control, or are controlled by, HIV replication.

CD57+ T lymphocytes and functional immune deficiency

CD57(+) expression in T lymphocytes has been recognized for decades as a marker of in vitro replicative senescence. In recent years, accumulating evidences have pointed on the utility of this marker to measure functional immune deficiency in patients with autoimmune disease, infectious diseases, and cancers. We review here the relevant literature and implications in clinical settings.

Primary human immunodeficiency virus type 1-specific CD8+ T-cell responses induced by myeloid dendritic cells

Induction of an antigenically broad and vigorous primary T-cell immune response by myeloid dendritic cells (DC) in blood and tissues could be important for an effective prophylactic or therapeutic vaccine to human immunodeficiency virus type 1 (HIV-1). Here we show that a primary CD8(+) T-cell response can be induced by HIV-1 peptide-loaded DC derived from blood monocytes of HIV-1-negative adults and neonates (moDC) and by Langerhans cells (LC) and interstitial, dermal-intestinal DC (idDC) derived from CD34(+) stem cells of neonatal cord blood. Optimal priming of single-cell gamma interferon (IFN-gamma) production by CD8(+) T cells required CD4(+) T cells and was broadly directed to multiple regions of Gag, Env, and Nef that corresponded to known and predicted major histocompatibility complex class I epitopes. Polyfunctional CD8(+) T-cell responses, defined as single-cell production of more than one cytokine (IFN-gamma, interleukin 2, or tumor necrosis factor alpha), chemokine (macrophage inhibitory factor 1beta), or cytotoxic degranulation marker CD107a, were primed by moDC, LC, and idDC to HIV-1 Gag and reverse transcriptase epitopes, as well as to Epstein-Barr virus and influenza A virus epitopes. Thus, three major types of blood and tissue myeloid DC targeted by HIV-1, i.e., moDC, LC, and idDC, can prime multispecific, polyfunctional CD8(+) T-cell responses to HIV-1 and other viral antigens.

Proliferation and foxp3 expression in virus-specific memory CD8+ T lymphocytes

Foxp3 plays a critical role in development of CD4+ regulatory T lymphocytes (Tregs). It was originally proposed as a specific marker for Tregs, but recent studies have shown that Foxp3 can be expressed in proliferating CD8+ and CD4+ T lymphocytes. We further investigated the association between Foxp3 expression and proliferation of peripheral blood CD4+ and CD8+ T lymphocytes and focused on virus-specific memory CD8+ T lymphocytes. We found that resting peripheral blood bulk and cytomegalovirus- or HIV-1-specific CD8+ T lymphocytes do not normally express Foxp3. However, stimulation in vitro triggered these cells to express Foxp3 as well as CD25, and the addition of interleukin-2 possibly enhanced the expression of Foxp3. These data demonstrate that proliferation itself is sufficient to induce the Treg-like phenotype. Given that others have demonstrated Treg functional activity in such "induced Tregs," these results suggest that virus-specific CD8+ T lymphocytes have the capacity to acquire regulatory functions. Although the implications of Foxp3 expression in virus-specific CD8+ T lymphocytes in the immunologic control of persistent HIV-1 viremia remain to be determined, our results are consistent with Foxp3 expression playing an essential role in regulation of cell proliferation and functional outcomes for HIV-1-specific CD8+ T lymphocytes.

Detailed analysis of Epstein-Barr virus-specific CD4+ and CD8+ T cell responses during infectious mononucleosis

We studied simultaneously Epstein-Barr virus (EBV)-specific CD4(+) and CD8(+) T cell responses during and after infectious mononucleosis (IM), using a previously described 12-day stimulation protocol with EBNA1 or BZLF1 peptide pools. Effector function of EBV-specific T cells was determined after restimulation by measuring intracellular interferon-gamma production. During IM, BZLF1-specifc CD4(+) T cell responses were dominant compared with CD8(+) T cell responses. EBNA1-specific CD4(+) and CD8(+) T cell responses were low and remained similar for 6 months. However, 6 months after IM, BZLF1-specific CD4(+) T cell responses had declined, but CD8(+) T cell responses had increased. At diagnosis, EBV-specific CD8(+) T cells as studied by human leucocyte antigen class I tetramer staining comprised a tetramer(bright)CD8(bright) population consisting mainly of CD27(+) memory T cells and a tetramer(dim)CD8(dim) population consisting primarily of CD27(-) effector T cells. The remaining EBV-specific CD8(+) T cell population 6 months after the diagnosis of IM consisted mainly of tetramer(bright)CD8(bright) CD27(+) T cells, suggesting preferential preservation of memory T cells after contraction of the EBV-specific T cell pool.

Antiviral NK cell responses in HIV infection: II. viral strategies for evasion and lessons for immunotherapy and vaccination

As is the case in other viral infections, humans respond to HIV infection by activating their NK cells. However, the virus uses several strategies to neutralize and evade the host's NK cell responses. Consequently, it is not surprising that NK cell functions become compromised in HIV-infected individuals in early stages of the infection. The compromised NK cell functions also adversely affect several aspects of the host's antiviral adaptive immune responses. Researchers have made significant progress in understanding how HIV counters NK cell responses of the host. This knowledge has opened new avenues for immunotherapy and vaccination against this infection. In the first part of this review article, we gave an overview of our current knowledge of NK cell biology and discussed how the genes encoding NK cell receptors and their ligands determine innate genetic resistance/susceptibilty of humans against HIV infections and AIDS. In this second part, we discuss NK cell responses, viral strategies to counter these responses, and finally, their implications for anti-HIV immunotherapy and vaccination.