Distribution of human CMV-specific memory T cells among the CD8pos. subsets defined by CD57, CD27, and CD45 isoforms

Programming cytomegalovirus as an HIV vaccine

The initial development of cytomegalovirus (CMV) as a vaccine vector for HIV/simian immunodeficiency virus (SIV) was predicated on its potential to pre-position high-frequency, effector-differentiated, CD8+ T cells in tissues for immediate immune interception of nascent primary infection. This goal was achieved and also led to the unexpected discoveries that non-human primate (NHP) CMVs can be programmed to differentially elicit CD8+ T cell responses that recognize viral peptides via classical MHC-Ia, and/or MHC-II, and/or MHC-E, and that MHC-E-restricted CD8+ T cell responses can uniquely mediate stringent arrest and subsequent clearance of highly pathogenic SIV, an unprecedented type of vaccine-mediated protection. These discoveries delineate CMV vector-elicited MHC-E-restricted CD8+ T cells as a functionally distinct T cell response with the potential for superior efficacy against HIV-1, and possibly other infectious agents or cancers.

Late gene expression-deficient cytomegalovirus vectors elicit conventional T cells that do not protect against SIV

Rhesus cytomegalovirus-based (RhCMV-based) vaccine vectors induce immune responses that protect ~60% of rhesus macaques (RMs) from SIVmac239 challenge. This efficacy depends on induction of effector memory-based (EM-biased) CD8+ T cells recognizing SIV peptides presented by major histocompatibility complex-E (MHC-E) instead of MHC-Ia. The phenotype, durability, and efficacy of RhCMV/SIV-elicited cellular immune responses were maintained when vector spread was severely reduced by deleting the antihost intrinsic immunity factor phosphoprotein 71 (pp71). Here, we examined the impact of an even more stringent attenuation strategy on vector-induced immune protection against SIV. Fusion of the FK506-binding protein (FKBP) degradation domain to Rh108, the orthologue of the essential human CMV (HCMV) late gene transcription factor UL79, generated RhCMV/SIV vectors that conditionally replicate only when the FK506 analog Shield-1 is present. Despite lacking in vivo dissemination and reduced innate and B cell responses to vaccination, Rh108-deficient 68-1 RhCMV/SIV vectors elicited high-frequency, durable, EM-biased, SIV-specific T cell responses in RhCMV-seropositive RMs at doses of ≥ 1 × 106 PFU. Strikingly, elicited CD8+ T cells exclusively targeted MHC-Ia-restricted epitopes and failed to protect against SIVmac239 challenge. Thus, Rh108-dependent late gene expression is required for both induction of MHC-E-restricted T cells and protection against SIV.

Post-infusion CAR TReg cells identify patients resistant to CD19-CAR therapy

Approximately 60% of patients with large B cell lymphoma treated with chimeric antigen receptor (CAR) T cell therapies targeting CD19 experience disease progression, and neurotoxicity remains a challenge. Biomarkers associated with resistance and toxicity are limited. In this study, single-cell proteomic profiling of circulating CAR T cells in 32 patients treated with CD19-CAR identified that CD4+Helios+ CAR T cells on day 7 after infusion are associated with progressive disease and less severe neurotoxicity. Deep profiling demonstrated that this population is non-clonal and manifests hallmark features of T regulatory (TReg) cells. Validation cohort analysis upheld the link between higher CAR TReg cells with clinical progression and less severe neurotoxicity. A model combining expansion of this subset with lactate dehydrogenase levels, as a surrogate for tumor burden, was superior for predicting durable clinical response compared to models relying on each feature alone. These data credential CAR TReg cell expansion as a novel biomarker of response and toxicity after CAR T cell therapy and raise the prospect that this subset may regulate CAR T cell responses in humans.

Aberrant newborn T cell and microbiota developmental trajectories predict respiratory compromise during infancy

Neonatal immune-microbiota co-development is poorly understood, yet age-appropriate recognition of - and response to - pathogens and commensal microbiota is critical to health. In this longitudinal study of 148 preterm and 119 full-term infants from birth through one year of age, we found that postmenstrual age or weeks from conception is a central factor influencing T cell and mucosal microbiota development. Numerous features of the T cell and microbiota functional development remain unexplained; however, by either age metric and are instead shaped by discrete perinatal and postnatal events. Most strikingly, we establish that prenatal antibiotics or infection disrupt the normal T cell population developmental trajectory, influencing subsequent respiratory microbial colonization and predicting respiratory morbidity. In this way, early exposures predict the postnatal immune-microbiota axis trajectory, placing infants at later risk for respiratory morbidity in early childhood.

CCR5+ T-Cells Homed to the Liver Exhibit Inflammatory and Profibrogenic Signatures in Chronic HIV/HCV-Coinfected Patients

Liver fibrosis is accelerated in patients coinfected with hepatitis C virus and human immunodeficiency virus (HIV), compared with HCV monoinfected patients, although the underlying mechanisms are unknown. We hypothesize that T cells expressing the HIV co-receptor, chemokine receptor 5 (CCR5), preferentially migrate to the inflamed liver and contribute to enhanced fibrogenesis. We compared the peripheral and intrahepatic CCR5 expression on CD4+ and CD8+ T cells in 21 HIV/HCV-coinfected patients with 14 chronic HCV monoinfected patients. Using 12-color flow cytometry, phenotypic and functional characterization of CCR5+ and negative cells pre- and post-stimulation with HCV genotype specific overlapping pooled peptides was conducted. Patients with HIV/HCV coinfection had significantly more CD4+CCR5+ and CD8+CCR5+ T cells in the liver as compared with peripheral blood (p = 0.0001 for both). Compared with patients with HCV monoinfection, patients with HIV/HCV coinfection also had fewer peripheral CD4+CCR5+ and CD8+CCR5+ T cells (p = 0.02, p = 0.001 respectively), but more intrahepatic CD4+CCR5+ and CD8+CCR5+ cells (p = 0.0001 for both). Phenotypic analysis of CCR5+ sorted cells demonstrated an increased expression of markers of exhaustion, senescence, immune activation and liver homing (PD1, CD57, CD38, HLADR, and CXCR3). Post-stimulation with HCV peptides, CCR5+ T cells secreted more proinflammatory and profibrogenic cytokines and chemokines rather than antiviral cytokines. Phenotypic and functional analyses of CCR5+ T cells in HIV/HCV-coinfected patients revealed a pathogenic role for CCR5+ T cells in hepatic fibrogenesis. These cells are functionally proinflammatory, pro-fibrogenic and preferentially accumulate in liver, accelerating fibrosis. These findings suggest that targeting CCR5 may be a therapeutic strategy for be ameliorating liver fibrosis.

FOXO1 constrains activation and regulates senescence in CD8 T cells

Naive and memory T cells are maintained in a quiescent state, yet capable of rapid response and differentiation to antigen challenge via molecular mechanisms that are not fully understood. In naive cells, the deletion of Foxo1 following thymic development results in the increased expression of multiple AP-1 family members, rendering T cells less able to respond to antigenic challenge. Similarly, in the absence of FOXO1, post-infection memory T cells exhibit the characteristics of extended activation and senescence. Age-based analysis of human peripheral T cells reveals that levels of FOXO1 and its downstream target, TCF7, are inversely related to host age, whereas the opposite is found for AP-1 factors. These characteristics of aging also correlate with the formation of T cells manifesting features of cellular senescence. Our work illustrates a role for FOXO1 in the active maintenance of stem-like properties in T cells at the timescales of acute infection and organismal life span.

CD57+ Memory T Cells Proliferate In Vivo

A central paradigm in the field of lymphocyte biology asserts that replicatively senescent memory T cells express the carbohydrate epitope CD57. These cells nonetheless accumulate with age and expand numerically in response to persistent antigenic stimulation. Here, we use in vivo deuterium labeling and ex vivo analyses of telomere length, telomerase activity, and intracellular expression of the cell-cycle marker Ki67 to distinguish between two non-exclusive scenarios: (1) CD57+ memory T cells do not proliferate and instead arise via phenotypic transition from the CD57- memory T cell pool; and/or (2) CD57+ memory T cells self-renew via intracompartmental proliferation. Our results provide compelling evidence in favor of the latter scenario and further suggest in conjunction with mathematical modeling that self-renewal is by far the most abundant source of newly generated CD57+ memory T cells. Immunological memory therefore appears to be intrinsically sustainable among highly differentiated subsets of T cells that express CD57.

Enhancing safety of cytomegalovirus-based vaccine vectors by engaging host intrinsic immunity

Rhesus cytomegalovirus (RhCMV)-based vaccines maintain effector memory T cell responses (T_EM) that protect ~50% of rhesus monkeys (RMs) challenged with simian immunodeficiency virus (SIV). Because human CMV (HCMV) causes disease in immunodeficient subjects, clinical translation will depend upon attenuation strategies that reduce pathogenic potential without sacrificing CMV's unique immunological properties. We demonstrate that "intrinsic" immunity can be used to attenuate strain 68-1 RhCMV vectors without impairment of immunogenicity. The tegument proteins pp71 and UL35 encoded by UL82 and UL35 of HCMV counteract cell-intrinsic restriction via degradation of host transcriptional repressors. When the corresponding RhCMV genes, Rh110 and Rh59, were deleted from 68-1 RhCMV (ΔRh110 and ΔRh59), we observed only a modest growth defect in vitro, but in vivo, these modified vectors manifested little to no amplification at the injection site and dissemination to distant sites, in contrast to parental 68-1 RhCMV. ΔRh110 was not shed at any time after infection and was not transmitted to naïve hosts either by close contact (mother to infant) or by leukocyte transfusion. In contrast, ΔRh59 was both shed and transmitted by leukocyte transfusion, indicating less effective attenuation than pp71 deletion. The T cell immunogenicity of ΔRh110 was essentially identical to 68-1 RhCMV with respect to magnitude, T_EM phenotype, epitope targeting, and durability. Thus, pp71 deletion preserves CMV vector immunogenicity while stringently limiting vector spread, making pp71 deletion an attractive attenuation strategy for HCMV vectors.

TIGIT Expression Is Associated with T-cell Suppression and Exhaustion and Predicts Clinical Outcome and Anti-PD-1 Response in Follicular Lymphoma

PURPOSE

T-cell immunoglobulin and ITIM domain (TIGIT), a member of the immune checkpoint family, is important in normal T-cell biology. However, the phenotypical profile and clinical relevance of TIGIT in follicular lymphoma is largely unknown.

EXPERIMENTAL DESIGN

Biopsy specimens from a cohort of 82 patients with follicular lymphoma were analyzed using mass cytometry to explore the phenotype and biological and clinical significance of TIGIT⁺ T cells.

RESULTS

TIGIT is highly expressed on intratumoral T cells and its expression alters T-cell phenotype in follicular lymphoma. TIGIT is abundantly expressed on T_reg cells, resulting in an enhanced suppressive property. TIGIT expression on non-T_reg/T_FH T cells defines a population that exhibits an exhausted phenotype. Clinically, increased numbers of TIGIT⁺ T cells are associated with inferior patient outcomes and poor survival. We observe that anti-PD-1 therapy with pembrolizumab alters the phenotype of TIGIT⁺ T subsets and identifies a role for CD28 expression on TIGIT⁺ T cells in treatment response.

CONCLUSIONS

The current study provides a comprehensive analysis of the phenotypic profile of intratumoral TIGIT⁺ T subsets and their prognostic relevance in follicular lymphoma. Inhibition of TIGIT signaling may be an additional mechanism to prevent T-cell suppression and exhaustion in B-cell lymphoma.

Low IL-2 Expressing T Cells in Thalassemia Major Patients: Is It Immune Aging

Several studies have demonstrated T cell alteration and some features of immunosenescence in thalassemia major. Repeated alloimmunization converts naïve T-cells to memory cells and iron overload causes oxidative stress accelerating immune aging. To determine whether the alteration of T-cell cytokine is matched with early immune aging, the quantity of cytokine expressing T cells and their correlation to some immune aging markers were investigated. The proportion of IL2- and IFNγ expressing CD4+ and CD8+ T-cells was measured in 27 hepatitis B, C and HIV negative B-thalassemia patients and a control group aged 10-30 years, following stimulation for 6 h with streptococcus enterotoxin B and intracellular cytokine staining. This proportion then were analyzed versus the percentage of the T-cells expressing each phenotyping marker, CD27, CD28, CD57 and CCR7. CD4+ and CD8+ positive T cells expressing IL-2 were significantly lower in β-thalassemia major compared to matched controls, but not T cells expressing IFNγ. No significant difference was observed between splenectomized and non-splenectomized patients in cytokine expressing T cells. A negative correlation was noted between the percentage of T cells expressing IFNγ and T-cells expressing CD-27, but not other markers. Lower T cells expressing IL-2 may reveal the decline of naïve and central memory T cells and is likely to be a feature of early immune aging. Decreased antigenic stimulation and iron overload may help to prevent this phenomenon.

Arterial Stiffness Is Associated With Cytomegalovirus-Specific Senescent CD8+ T Cells

Background

Arterial stiffness is a well‐known predictor of future cardiovascular events. Search for the underlying mechanism of arterial stiffening is still under way. We investigated the relationship between arterial stiffness and cytomegalovirus infection in terms of T‐cell senescence.

Methods and Results

Arterial stiffness was evaluated using pulse wave velocity measurements in 415 Koreans (age 59±12 years). We also investigated the frequency of CD57⁺ or CD28^null senescent T cells in peripheral blood lymphocytes and analyzed which immune parameters were correlated with pulse wave velocity. Furthermore, cytomegalovirus‐specific T cells were stimulated with overlapping peptides covering pp65 protein, and T‐cell function was evaluated by intracellular cytokine staining of interferon‐γ, tumor necrosis factor‐α, and CD107a. In a multivariate analysis, it was found that the frequency of CD57⁺ cells in the CD8⁺ T‐cell subset was independently correlated with pulse wave velocity after adjusting for traditional cardiovascular risk factors such as age, sex, diabetes mellitus history, smoking history, body mass index, blood pressure, serum creatinine, high‐density lipoprotein cholesterol, and high‐sensitivity C‐reactive protein. Cytomegalovirus pp65‐specific T cells were more frequently observed in the CD8⁺CD57⁺ population than in the CD8⁺CD57⁻ population, and multivariate analysis revealed that the frequency of cytomegalovirus pp65‐specific interferon‐γ⁺, tumor necrosis factor‐α⁺, or CD107a⁺ cells in the CD8⁺ T‐cell subset was independently correlated with pulse wave velocity as well.

Conclusions

We demonstrate that arterial stiffness is associated with senescent CD57⁺ T cells and CMV pp65‐specific T cells in the CD8⁺ T‐cell subset. The precise role of cytomegalovirus‐specific, senescent T cells in vascular aging needs to be further investigated.

T Cell Subpopulations in Healthy Elderly and Lung Cancer Patients: Insights from Cuban Studies

The senescence of the immune system and the risk of cancer increase with aging. Age itself entails changes in the immune system, which are related to a decrease in thymic output of naïve lymphocytes, an accumulation of chronic antigenic load, notably chronic viral infections such as cytomegalovirus (CMV), and replicative senescence of lymphocytes. These changes could eventually contribute to cancer risk and affect the response to cancer treatment. However, several confounding factors make it difficult to draw a picture of causal relationships. Studies in diverse human populations could contribute to clarify these complex relationships. Here, we summarize the current knowledge about the senescence of the T cells, the relationship with CMV infection, cancer, and cancer treatment. We also review the results of a series of studies performed in Cuba whose population is characterized by the unusual combination of long life expectancy and high antigenic load, including high seroprevalence of CMV, typical of tropical countries. Although immunosenescence affects almost all components and functions of the immune response, its most salient feature is a decrease in numbers and proportions of naïve CD8⁺ T lymphocytes and an accretion of terminally differentiated CD8⁺ T lymphocytes. These features were confirmed by the Cuban studies, but interestingly a clear gender effect also appeared. Moreover, as aging is a global phenomenon, a fast increase in elderly with malignancies is expected; therefore, the evaluation of patient’s immune status would support the decision of treating them with immunotherapy and predict the efficacy of such treatments, thereby improving benefits for the patients.

Polyfunctional T-Cell Signatures to Predict Protection from Cytomegalovirus after Lung Transplantation

RATIONALE

Cytomegalovirus (CMV), which is one of the most common infections after lung transplantation, is associated with chronic lung allograft dysfunction and worse post-transplantation survival. Current approaches for at-risk patients include a fixed duration of antiviral prophylaxis despite the associated cost and side effects.

OBJECTIVES

We sought to identify a specific immunologic signature that predicted protection from subsequent CMV.

METHODS

CMV-seropositive lung transplantation recipients were included in the discovery (n = 43) and validation (n = 28) cohorts. Polyfunctional CMV-specific immunity was assessed by stimulating peripheral blood mononuclear cells with CMV pp65 or IE-1 peptide pools and then by measuring T-cell expression of CD107a, IFN-γ, tumor necrosis factor-α (TNF-α), and IL-2. Recipients were prospectively monitored for subsequent viremia. A Cox proportional hazards regression model that considered cytokine responses individually and in combination was used to create a predictive model for protection from CMV reactivation. This model was then applied to the validation cohort.

MEASUREMENTS AND MAIN RESULTS

Using the discovery cohort, we identified a specific combination of polyfunctional T-cell subsets to pp65 that predicted protection from subsequent CMV viremia (concordance index 0.88 [SE, 0.087]). The model included both protective (CD107a(-)/IFN-γ(+)/IL-2(+)/TNF-α(+) CD4(+) T cells, CD107a(-)/IFN-γ(+)/IL-2(+)/TNF-α(+) CD8(+) T cells) and detrimental (CD107a(+)/IFN-γ(+)/IL-2(-)/TNF-α(-) CD8(+) T cells) subsets. The model was robust in the validation cohort (concordance index 0.81 [SE, 0.103]).

CONCLUSIONS

We identified and validated a specific T-cell polyfunctional response to CMV antigen stimulation that provides a clinically useful prediction of subsequent cytomegalovirus risk. This novel diagnostic approach could inform the optimal duration of individual prophylaxis.

Alteration of T Cell Subtypes in Beta-Thalassaemia Major: Impact of Ferritin Level

INTRODUCTION

Oxidative damage and regular antigenic stimulation are main factors in accelerating immunosenescence. The present study was conducted to investigate new concepts of early immunosenescence in thalassaemia patients.

MATERIALS AND METHODS

Twenty seven beta-thalassaemia major patients and a group of matched healthy volunteers aged 10-30 years in Shahrekord, Iran were recruited into the study. Ferritin level was determined and CD4 or CD8 T cells were analysed versus phenotyping markers, CD27, CD28, CD57 and CCR7, by flowcytometry. Data were analysed by Mann-Whitney and Spearman's correlation coefficient test in SPSS 11.5.

RESULTS

Absolute lymphocytosis and partial decrease in T cells were observed in the patients. CD4+CD57+ and CD4+CCR7- T cells were significantly higher, whereas CD8+CD27+ and CD8+CCR7+ T cells were partially higher in patients. A negative correlation was observed between ferritin level and number of CD8+CD27+ and CD8+CCR7+ T cells, whereas the correlation was positive between ferritin level and number of CD57+ T cells.

CONCLUSION

Moderate alteration of T cell repertoire and increase in CCR27-, CCR7-, and CD57+ T cells could reflect antigenic stimulation, decline in naïve T cells, and being closer to terminally differentiated cells. Effect of iron overload is potentially explained by positive correlation of blood transfusion and ferritin level with frequency of CD3+CD27- and that of ferritin with frequency of CD57+ T cells.

Regulation of Adaptive NK Cells and CD8 T Cells by HLA-C Correlates with Allogeneic Hematopoietic Cell Transplantation and with Cytomegalovirus Reactivation

Mass cytometry was used to investigate the effect of CMV reactivation on lymphocyte reconstitution in hematopoietic cell transplant patients. For eight transplant recipients (four CMV negative and four CMV positive), we studied PBMCs obtained 6 mo after unrelated donor hematopoietic cell transplantation (HCT). Forty cell-surface markers, distinguishing all major leukocyte populations in PBMC, were analyzed with mass cytometry. This group included 34 NK cell markers. Compared with healthy controls, transplant recipients had higher HLA-C expression on CD56(-)CD16(+) NK cells, B cells, CD33(bright) myeloid cells, and CD4CD8 T cells. The increase in HLA-C expression was greater for CMV-positive HCT recipients than for CMV negative recipients. Present in CMV-positive HCT recipients, but not in CMV-negative HCT recipients or controls, is a population of killer cell Ig-like receptor (KIR)-expressing CD8 T cells not previously described. These CD8 T cells coexpress CD56, CD57, and NKG2C. The HCT recipients also have a population of CD57(+)NKG2A(+) NK cells that preferentially express KIR2DL1. An inverse correlation was observed between the frequencies of CD57(+)NKG2C(+) NK cells and CD57(+)NKG2A(+) NK cells. Although CD57(+)NKG2A(+) NK cells are less abundant in CMV-positive recipients, their phenotype is of a more activated cell than the CD57(+)NKG2A(+) NK cells of controls and CMV-negative HCT recipients. These data demonstrate that HCT and CMV reactivation are associated with an increased expression of HLA-C. This could influence NK cell education during lymphocyte reconstitution. The increased inhibitory KIR expression by proliferating CMV-specific CD8 T cells suggests regulatory interactions between HLA-C and KIR might promote Graft-versus-Leukemia effects following transplantation.

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.

Novel vaccine vectors for HIV-1

The ultimate solution to the global HIV-1 epidemic will probably require the development of a safe and effective vaccine. Multiple vaccine platforms have been evaluated in preclinical and clinical trials, but given the disappointing results of clinical efficacy studies so far, novel vaccine approaches are needed. In this Opinion article, we discuss the scientific basis and clinical potential of novel adenovirus and cytomegalovirus vaccine vectors for HIV-1 as two contrasting but potentially complementary vector approaches. Both of these vector platforms have demonstrated partial protection against stringent simian immunodeficiency virus challenges in rhesus monkeys using different immunological mechanisms.

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.

Independent skewing of the T cell and NK cell compartments associated with cytomegalovirus infection suggests division of labor between innate and adaptive immunity

Cytomegalovirus (CMV) infection induces profound changes in different subsets of the cellular immune system. We have previously identified an immune risk profile (IRP) where CMV-associated changes in the T cell compartment, defined as a CD4/CD8 ratio < 1, are associated with increased mortality in elderly people. Since natural killer (NK) cells have an important role in the defense against viral infections, we examined whether the expansion of CD8 + T cells seen in individuals with CD4/CD8 ratio < 1 is coupled to a parallel skewing of the NK cell compartment. A number of 151 subjects were examined with CMV serology and a flow cytometry panel for assessment of T cell and NK cell subsets. CMV-seropositive individuals had higher frequencies of CD57 + and NKG2C + NK cells and lower frequencies of NKG2A + NK cells, in line with a more differentiated NK cell compartment. Intriguingly, however, there was no correlation between CD4/CD8 ratio and NK cell repertoires among CMV-seropositive donors, despite the profound skewing of the T cell compartment in the group with CD4/CD8 ratio < 1. Conversely, donors with profound expansion of NK cells, defined as NKG2C + NK cells with high expression of CD57 and ILT-2, did not display more common changes in their T cell repertoire, suggesting that NK cell expansion is independent of the T cell-defined IRP. Altogether, these results indicate that the effect of CMV on CD8 T cells and NK cells is largely nonoverlapping and independent.

Aging and cytomegalovirus infection differentially and jointly affect distinct circulating T cell subsets in humans

The impact of intrinsic aging upon human peripheral blood T cell subsets remains incompletely quantified and understood. This impact must be distinguished from the influence of latent persistent microorganisms, particularly CMV, which has been associated with age-related changes in the T cell pool. In a cross-sectional cohort of 152 CMV-negative individuals, aged 21-101 y, we found that aging correlated strictly to an absolute loss of naive CD8, but not CD4, T cells but, contrary to many reports, did not lead to an increase in memory T cell numbers. The loss of naive CD8 T cells was not altered by CMV in 239 subjects (range 21-96 y), but the decline in CD4(+) naive cells showed significance in CMV(+) individuals. These individuals also exhibited an absolute increase in the effector/effector memory CD4(+) and CD8(+) cells with age. That increase was seen mainly, if not exclusively, in older subjects with elevated anti-CMV Ab titers, suggesting that efficacy of viral control over time may determine the magnitude of CMV impact upon T cell memory, and perhaps upon immune defense. These findings provide important new insights into the age-related changes in the peripheral blood pool of older adults, demonstrating that aging and CMV exert both distinct and joint influence upon blood T cell homeostasis in humans.

Cytomegalovirus-seropositive children show inhibition of in vitro EBV infection that is associated with CD8+CD57+ T cell enrichment and IFN-γ

EBV, a human herpesvirus, is commonly acquired during childhood and persists latently in B cells. EBV seropositivity has been connected to immunomodulatory effects such as altered T and NK cell functional responses as well as protection against early IgE sensitization; however, owing to the asymptomatic presentation during childhood little is known regarding the infection process in children of different ages. In this study, we used mononuclear cells from cord blood and from 2- and 5-y-old EBV-naive children for in vitro EBV infection. We show that the degree of EBV-induced B cell activation and expansion differs between age groups and in particular in relationship to IFN-γ production capacity. EBV infection induced redistribution between B cell subsets with enrichment of IgD(+)CD27(+) cells (commonly referred to as non-switched memory) in infected cord blood cell cultures, and of IgD(-)CD27(+) cells (switched memory) in cell cultures from older children. We also related results to serostatus to CMV, a persistent herpesvirus that can affect differentiation status of T and NK cells. As compared with CMV(-) children, the EBV-induced enrichment of IgD(-)CD27(+) B cells was significantly reduced in infected cell cultures from CMV(+) children. This effect was associated with high levels of IFN-γ and frequencies of highly mature CD8(+)CD57(+) T cells in CMV(+) children. Our results demonstrate that both a child's age and serostatus to CMV will have an impact on EBV-induced B cell activation and expansion, and they point to the ability of viruses with immunomodulatory functions, such as CMV, to affect immune responses within the host system.

A cytomegalovirus-based vaccine expressing a single tumor-specific CD8+ T-cell epitope delays tumor growth in a murine model of prostate cancer

Cytomegalovirus (CMV) is a highly immunogenic virus that results in a persistent, life-long infection in the host typically with no ill effects. Certain unique features of CMV, including its capacity to actively replicate in the presence of strong host CMV-specific immunity, may give CMV an advantage compared with other virus-based vaccine delivery platforms. In the present study, we tested the utility of mouse CMV (mCMV)-based vaccines expressing human prostate-specific antigen (PSA) for prostate cancer immunotherapy in double-transgenic mice expressing PSA and HLA-DRB1*1501 (DR2bxPSA F1 mice). We assessed the capacity of 2 mCMV-based vectors to induce PSA-specific CD8 T-cell responses and affect the growth of PSA-expressing Transgenic Adenocarcinoma of the Mouse Prostate tumors (TRAMP-PSA). In the absence of tumor challenge, immunization with mCMV vectors expressing either a H2-D(b)-restricted epitope PSA(65-73) (mCMV/PSA(65-73)) or the full-length gene for PSA (mCMV/PSA(FL)) induced comparable levels of CD8 T-cell responses that increased (inflated) with time. Upon challenge with TRAMP-PSA tumor cells, animals immunized with mCMV/PSA(65-73) had delay of tumor growth and increased PSA-specific CD8 T-cell responses, whereas animals immunized with mCMV/PSA(FL) showed progressive tumor growth and no increase in number of splenic PSA(65-73)-specific T cells. The data show that a prototype CMV-based prostate cancer vaccine can induce an effective antitumor immune response in a "humanized" double-transgenic mouse model. The observation that mCMV/PSA(FL) is not effective against TRAMP-PSA is consistent with our previous findings that HLA-DRB1*1501-restricted immune responses to PSA are associated with suppression of effective CD8 T-cell responses to TRAMP-PSA tumors.

Immunosenescence and gender: a study in healthy Cubans

Background

The progressive decline in the immune function during ageing is termed immunosenescence. Previous studies have reported differences between males and females in the distribution and cell responses of lymphocyte subsets. Most studies of immunosenescence have been done in populations of industrialized countries living in a rather cold environment, and facing lower antigenic challenges such as Cytomegalovirus (CMV). The aim of this study was to determine the effect of ageing on lymphocytes in a population with a high prevalence of CMV infection in all ages, and to compare gender differences related to the immunosenescence markers.

Results

Different populations of peripheral blood leukocytes from healthy young and old IgG-CMV seropositive individuals were examined using flow cytometry. With age, the number and frequency of B cells and T cells significantly decreased, while highly differentiated T cells increased. Such changes were different in males and females. The age-associated decline of less differentiated lymphocyte subsets (CD19, CD4 and CD8 cells) and the increase of highly differentiated T cells were more prominent in females. In males, there were no significant changes in CD19, CD4 and CD8 subsets but there was a significant increase in the proportion of highly differentiated T cells.

Conclusion

Shifts in lymphocyte subsets distribution were influenced by age and gender in an IgG-CMV seropositive population. These results suggest different patterns of immunosenescence in respect to gender differences. These patterns could have implications in the design of immunotherapy in the elderly.

Immune regulation of human herpesviruses and its implications for human transplantation

Human herpesviruses including cytomegalovirus, Epstein-Barr virus, HHV6, HHV7, HHV8, Herpes simplex virus (HSV)-1 and HSV-2 and varicella zoster virus (VZV) have developed an intricate relationship with the human immune system. This is characterized by the interplay between viral immune evasion mechanisms that promote the establishment of a lifelong persistent infection and the induction of a broad humoral and cellular immune response, which prevents the establishment of viral disease. Understanding the immune parameters that control herpesvirus infection, and the strategies the viruses use to evade immune recognition, has been critical in understanding why immunological dysfunction in transplant patients can lead to disease, and in the development of immunological strategies to prevent and control herpesvirus associated diseases.

Reconstitution of protective immune responses against cytomegalovirus and varicella zoster virus does not require disease development in pediatric recipients of umbilical cord blood transplantation

CMV and varicella zoster virus (VZV) are significant causes of morbidity and mortality following umbilical cord blood transplantation (UCBT). However, the kinetics of reconstitution and protective potential of antiviral cell-mediated immune responses following UCBT remain poorly characterized. In this study, the reconstitution of CMV- and VZV-specific T cell responses was assessed using IFN-γ ELISPOT in 28 children who underwent UCBT to treat hematological or inherited disorders. Barely detectable in the first 3 mo posttransplantation, CMV- and VZV-specific T cell responses were observed in 30.4% and 40.3% of study subjects after 36 mo of follow-up. Four of five CMV-seropositive subjects developed detectable levels of circulating CMV DNA (DNAemia), and 5 of 17 VZV-seropositive patients experienced herpes zoster during the posttransplant period. Four CMV-seronegative subjects developed IFN-γ responses against CMV, and four subjects developed a VZV-specific IFN-γ response without clinical signs of infection. No CMV- or VZV-related events were observed in study subjects following the development of CMV- or VZV-specific responses > 150 spot-forming units/10(6) PBMCs, consistent with T cell-mediated protection. Finally, famciclovir prophylaxis did not strictly prevent the reconstitution of the VZV-specific T cell repertoire, because the frequency of T cells producing IFN-γ in response to VZV Ags reached levels consistent with protection in two nonzoster subjects. Monitoring of CMV- and VZV-specific cell-mediated immunity could inform immunocompetence and guide the initiation and cessation of antiherpetic prophylaxis in UCBT recipients.

Effector memory and central memory NY-ESO-1-specific re-directed T cells for treatment of multiple myeloma

The cancer-testis antigen NY-ESO-1 is a potential target antigen for immune therapy expressed in a subset of patients with multiple myeloma. We generated chimeric antigen receptors (CARs) recognizing the immunodominant NY-ESO-1 peptide 157-165 in the context of HLA-A*02:01 to re-direct autologous CD8(+) T cells towards NY-ESO-1(+) myeloma cells. These re-directed T cells specifically lysed NY-ESO-1(157-165)/HLA-A*02:01-positive cells and secreted IFNγ. A total of 40% of CCR7(-) re-directed T cells had an effector memory phenotype and 5% a central memory phenotype. Based on CCR7 cell sorting, effector and memory CAR-positive T cells were separated and CCR7(+) memory cells demonstrated after antigen-specific re-stimulation downregulation of CCR7 as sign of differentiation towards effector cells accompanied by an increased secretion of memory signature cytokines such as IL-2. To evaluate NY-ESO-1 as potential target antigen, we screened 78 bone marrow biopsies of multiple myeloma patients where NY-ESO-1 protein was found to be expressed by immunohistochemistry in 9.7% of samples. Adoptively transferred NY-ESO-1-specific re-directed T cells protected mice against challenge with endogenously NY-ESO-1-positive myeloma cells in a xenograft model. In conclusion, re-directed effector- and central memory T cells specifically recognized NY-ESO-1(157-165)/ HLA-A*02:01-positive cells resulting in antigen-specific functionality in vitro and in vivo.

Amyloid-specific T-cells differentiate Alzheimer's disease from Lewy body dementia

Alzheimer's disease and dementia with Lewy bodies are the most common neurodegenerative dementias in old age. Accurate diagnosis of these conditions has important clinical implications because they tend to be confounded. In the brain of Alzheimer's disease patients amyloid-beta is produced in excess and deposited as plaques, forming the hallmark of this condition. Lymphocytes have been implicated in the process of amyloid-beta removal and inflammation occurrence. Here we investigated peripheral amyloid-beta1-42-specific T-cells by multicolor flow cytometry to simultaneously detect and characterize activation markers and cell signaling proteins (phospho-protein kinase C) in patients with Alzheimer's disease or Lewy body dementia and in healthy controls. Results indicate that only Alzheimer's disease patients display small subsets of peripheral amyloid-beta1-42-specific T-cells, characterized by bright expression of phosphorylated-protein kinase C-delta or -zeta whose significance although discussed, is far from being understood. The identification of such subsets, anyhow, may strongly contribute to distinguish Alzheimer's disease from dementia with Lewy bodies, opening possible new routes to early therapeutic strategies.

The impact of aging on memory T cell phenotype and function in the human bone marrow

Recently, the BM has been shown to play a key role in regulating the survival and function of memory T cells. However, the impact of aging on these processes has not yet been studied. We demonstrate that the number of CD4⁺ and CD8⁺ T cells in the BM is maintained during aging. However, the composition of the T cell pool in the aged BM is altered with a decline of naïve and an increase in T(EM) cells. In contrast to the PB, a highly activated CD8⁺CD28⁻ T cell population, which lacks the late differentiation marker CD57, accumulates in the BM of elderly persons. IL-6 and IL-15, which are both increased in the aged BM, efficiently induce the activation, proliferation, and differentiation of CD8⁺ T cells in vitro, highlighting a role of these cytokines in the age-dependent accumulation of highly activated CD8⁺CD28⁻ T cells in the BM. Yet, these age-related changes do not impair the maintenance of a high number of polyfunctional memory CD4⁺ and CD8⁺ T cells in the BM of elderly persons. In summary, aging leads to the accumulation of a highly activated CD8⁺CD28⁻ T cell population in the BM, which is driven by the age-related increase of IL-6 and IL-15. Despite these changes, the aged BM is a rich source of polyfunctional memory T cells and may thus represent an important line of defense to fight recurrent infections in old age.

Cytomegalovirus-specific T cell immunity is maintained in immunosenescent rhesus macaques

Although CMV infection is largely benign in immunocompetent people, the specific T cell responses associated with control of this persistent virus are enormous and must be maintained for life. These responses may increase with advanced age and have been linked to an "immune risk profile" that is associated with poor immune responsiveness and increased mortality in aged individuals. Based on this association, it has been suggested that CMV-specific T cell responses might become dysfunctional with age and thereby contribute to the development of immune senescence by homeostatic disruption of other T cell populations, diminished control of CMV replication, and/or excess chronic inflammation. In this study, we use the rhesus macaque (RM) model of aging to ask whether the quantity and quality of CMV-specific T cell responses differ between healthy adult RMs and elderly RMs that manifest hallmarks of immune aging. We demonstrate that the size of the CD4(+) and CD8(+) CMV-specific T cell pools are similar in adult versus old RMs and show essentially identical phenotypic and functional characteristics, including a dominant effector memory phenotype, identical patterns of IFN-γ, TNF-α, and IL-2 production and cytotoxic degranulation, and comparable functional avidities of optimal epitope-specific CD8(+) T cells. Most importantly, the response to and protection against an in vivo CMV challenge were identical in adult and aged RMs. These data indicate that CMV-specific T cell immunity is well maintained in old RMs and argue against a primary role for progressive dysfunction of these responses in the development of immune senescence.

PD-1 expression on peripheral CD8+ TEM/TEMRA subsets closely correlated with HCV viral load in chronic hepatitis C patients

BACKGROUND

Tight correlation between host circulating CD8+ T cell-mediated immune response and control of viral replication is classical characteristic of long-term HCV infection. CD8+ T cell maturation/activation markers are expected to be associated with viral replication and disease progression in chronic HCV infection. The aim of the present study was to explore novel markers on CD8+ T cells with ability to evaluate HCV viral replication and disease progression.

METHODS

PBMCs were isolated from 37 chronic HCV-infected patients and 17 healthy controls. Distributed pattern of CD8+ T cells subsets and expression of PD-1, CD38, HLA-DR and CD127 were analyzed by flow cytometry. The correlation between expression of surface markers and HCV viral load or ALT was studied.

RESULTS

Declined naïve and increased TEMRA CD8+ T subsets were found in HCV-infected individuals compared with healthy controls. Percentage and MFI of PD-1, CD38 and HLA-DR on all CD8+ T cell subsets were higher in HCV-infected patients than healthy controls. In contrast, CD127 expression on CD8+ TCM showed an opposite trend as PD-1, CD38 and HLA-DR did. In chronic HCV infection, MFI of PD-1 on CD8+ TEM (p < 0.0001) and TEMRA (p = 0.0015) was positively correlated with HCV viral load while HLA-DR expression on non-naive CD8+ T cell subsets (p < 0.05) was negatively correlated with HCV viral load.

CONCLUSION

PD-1 level on peripheral CD8+ TEM/TEMRA was highly correlated with HCV viral load in chronic HCV-infected patients, which made PD-1 a novel indicator to evaluate HCV replication and disease progression in chronic hepatitis C patients.

Human cytomegalovirus immunity and immune evasion

Human cytomegalovirus (HCMV) infection induces both innate immune responses including Natural Killer cells as well as adaptive humoral and cell mediated (CD4+ helper, CD8+ cytotoxic and γδ T cell) responses which lead to the resolution of acute primary infection. Despite such a robust primary immune response, HCMV is still able to establish latency. Long term memory T cell responses are maintained at high frequency and are thought to prevent clinical disease following periodic reactivation of the virus. As such, a balance is established between the immune response and viral reactivation. Loss of this balance in the immunocompromised host can lead to unchecked viral replication following reactivation of latent virus, with consequent disease and mortality. HCMV encodes multiple immune evasion mechanisms that target both the innate and acquired immune system. This article describes the current understanding of Natural killer cell, antibody and T cell mediated immune responses and the mechanisms that the virus utilizes to subvert these responses.

Human late memory CD8+ T cells have a distinct cytokine signature characterized by CC chemokine production without IL-2 production

Late memory T cell skewing is observed in the setting of immune recovery after cord blood transplantation, and may be associated with inferior control of viral reactivation and cancers. Therefore, we sought to understand how late memory cells differ functionally from earlier stage memory T cells, and whether surface phenotypes associated with differentiation stages were predictably associated with functional signatures. Higher order cytokine flow cytometry allows characterization of human T cells based on complex phenotypic markers and their differential capacity to simultaneously secrete effector proteins, including cytokines and chemokines. We used 8-color, 10-parameter cytokine flow cytometry to characterize the functional activation of human late memory CD8(+) T cells defined by CD45RA and CD27 expression (CD27(-)CD45RA(+)). We assessed the 15 possible functional signatures of cells defined by production of IL-2, IFN-gamma, TNF-alpha, and MIP-1beta alone or in combination, following activation with Ags stimulating bypassing surface proteins (PMA:ionomycin) or through the TCR (e.g., viral Ags). Late memory CD8(+) T cells produced abundant amounts of CC chemokines (MIP-1beta, MIP-1alpha, and RANTES) but not IL-2. IL-2/IFN-gamma coproduction, characteristic of protective immune responses to viral infections, was absent in late memory CD8(+) T cells. These data demonstrate that functional cytokine signatures are predictably associated with CD8(+) maturation stages, and that the polarization of late memory CD8(+) T cells toward CC chemokine production and away from IL-2 production suggests a unique functional role for this subset.

Effector memory T cell responses are associated with protection of rhesus monkeys from mucosal simian immunodeficiency virus challenge

The rapid onset of massive, systemic viral replication during primary HIV or simian immunodeficiency virus (SIV) infection and the immune evasion capabilities of these viruses pose fundamental problems for vaccines that depend upon initial viral replication to stimulate effector T cell expansion and differentiation. We hypothesized that vaccines designed to maintain differentiated effector memory T cell (TEM cell) responses at viral entry sites might improve efficacy by impairing viral replication at its earliest stage, and we have therefore developed SIV protein-encoding vectors based on rhesus cytomegalovirus (RhCMV), the prototypical inducer of life-long TEM cell responses. RhCMV vectors expressing SIV Gag, Rev-Tat-Nef and Env persistently infected rhesus macaques, regardless of preexisting RhCMV immunity, and primed and maintained robust, SIV-specific CD4+ and CD8+ TEM cell responses (characterized by coordinate tumor necrosis factor, interferon-gamma and macrophage inflammatory protein-1beta expression, cytotoxic degranulation and accumulation at extralymphoid sites) in the absence of neutralizing antibodies. Compared to control rhesus macaques, these vaccinated rhesus macaques showed increased resistance to acquisition of progressive SIVmac239 infection upon repeated limiting-dose intrarectal challenge, including four macaques who controlled rectal mucosal infection without progressive systemic dissemination. These data suggest a new paradigm for AIDS vaccine development--vaccines capable of generating and maintaining HIV-specific TEM cells might decrease the incidence of HIV acquisition after sexual exposure.

Impact of cytomegalovirus and grafts versus host disease on the dynamics of CD57+CD28-CD8+ T cells after bone marrow transplant

OBJECTIVES

The present study aimed to evaluate the dynamics of CD28 and CD57 expression in CD8+ T lymphocytes during cytomegalovirus viremia in bone marrow transplant recipients.

METHODS

In a prospective study, blood samples were obtained once weekly once from 33 healthy volunteers and weekly from 33 patients. To evaluate the expression of CD57 and CD28 on CD8+ T lymphocytes, flow cytometry analysis was performed on blood samples for four months after bone marrow transplant, together with cytomegalovirus antigenemia assays.

RESULTS

Compared to cytomegalovirus-seronegative healthy subjects, seropositive healthy subjects demonstrated a higher percentage of CD57+ and a lower percentage of CD28+ cells (p<0.05). A linear regression model demonstrated a continuous decrease in CD28+ expression and a continuous increase in CD57+ expression after bone marrow transplant. The occurrence of cytomegalovirus antigenemia was associated with a steep drop in the percentage of CD28+ cells (5.94%, p<0.01) and an increase in CD57+ lymphocytes (5.60%, p<0.01). This cytomegalovirus-dependent effect was for the most part concentrated in the allogeneic bone marrow transplant patients. The development of acute graft versus host disease, which occurred at an earlier time than antigenemia (day 26 vs. day 56 post- bone marrow transplant), also had an impact on the CD57+ subset, triggering an increase of 4.9% in CD57+ lymphocytes (p<0.05).

CONCLUSION

We found continuous relative changes in the CD28+ and CD57+ subsets during the first 120 days post- bone marrow transplant, as part of immune system reconstitution and maturation. A clear correlation was observed between the expansion of the CD57+CD28-CD8+ T lymphocyte subpopulation and the occurrence of graft versus host disease and cytomegalovirus viremia.

Phenotype and functional characterization of long-term gp100-specific memory CD8+ T cells in disease-free melanoma patients before and after boosting immunization

PURPOSE

Effective cancer vaccines must both drive a strong CTL response and sustain long-term memory T cells capable of rapid recall responses to tumor antigens. We sought to characterize the phenotype and function of gp100 peptide-specific memory CD8+ T cells in melanoma patients after primary gp100(209-2M) immunization and assess the anamnestic response to boosting immunization.

EXPERIMENTAL DESIGN

Eight-color flow cytometry analysis of gp100-specific CD8+ T cells was done on peripheral blood mononuclear cells collected shortly after the primary vaccine regimen, 12 to 24 months after primary vaccination, and after boosting immunization. The anamnestic response was assessed by comparing the frequency of circulating gp100-specific T cells before and after boosting. Gp100 peptide-induced in vitro functional avidity and proliferation responses and melanoma-stimulated T-cell CD107 mobilization were compared for cells from all three time points for multiple patients.

RESULTS

The frequency of circulating gp100-specific memory CD8+ T cells was comparable with cytomegalovirus-specific and FLU-specific T cells in the same patients, and the cells exhibited anamnestic proliferation after boosting. Their phenotypes were not unique, and individual patients exhibited one of two distinct phenotype signatures that were homologous to either cytomegalovirus-specific or FLU-specific memory T cells. Gp100-specific memory T cells showed some properties of competent memory T cells, such as heightened in vitro peptide-stimulated proliferation and increase in central memory (TCM) differentiation when compared with T-cell responses measured after the primary vaccine regimen. However, they did not acquire enhanced functional avidity usually associated with competent memory T-cell maturation.

CONCLUSIONS

Although vaccination with class I-restricted melanoma peptides alone can break tolerance to self-tumor antigens, it did not induce fully competent memory CD8+ T cells--even in disease-free patients. Data presented suggest other vaccine strategies will be required to induce functionally robust long-term memory T cells.

Hepatitis C virus-specific T-cell gamma interferon and proliferative responses are more common in perihepatic lymph nodes than in peripheral blood or liver

The activation state, differentiation state, and functions of liver lymphocytes and perihepatic lymph nodes during chronic hepatitis C virus (HCV) infection are not well understood. Here, we performed phenotypic and functional analyses of freshly prepared lymphocytes isolated from the livers, perihepatic lymph nodes, and peripheral blood compartments of chronic HCV-infected and disease control subjects with end-stage liver disease undergoing liver transplantation. We measured lymphocyte subset frequency and memory T-cell gamma interferon (IFN-gamma) and proliferative responses to HCV peptide and control viral antigens in direct ex vivo assays. We found higher frequencies of CD4 cells in the lymph node compartment than in the other compartments for both HCV-infected and disease control subjects. Lymph node CD4 and CD8 cells less commonly expressed the terminal differentiation marker CD57, a finding consistent with an earlier differentiation state. In HCV-infected subjects, HCV-specific IFN-gamma-producing and proliferative responses were commonly observed in the lymph node fraction, while they were uncommonly observed in the peripheral blood or liver fractions. In contrast, control viral CD4 protein antigen and CD8 peptide antigen-specific IFN-gamma responses were commonly observed in the periphery and uncommonly observed in the lymph nodes of these same subjects. These findings are consistent with a selective defect in HCV-specific T-cell effector function or distribution in patients with advanced chronic HCV infection. The high frequency of HCV-reactive T cells in perihepatic lymph nodes indicates that a failure to generate or sustain T-lymphocyte HCV reactivity is not responsible for the paucity of functional cells even in end-stage liver disease.

Proliferation and interleukin 5 production by CD8hi CD57+ T cells

CD8hi CD57+ T cells have previously been described as effector memory T cells with minimal expansion capacity and high susceptibility to activation-induced cell death. In contrast, we demonstrate here that CD8hi CD57+ T cells are capable of rapid expansion using multiple techniques including [(3)H]thymidine uptake, flow cytometric bead-based enumeration and standard haemocytometer counting. Previous reports can be explained by marked inhibition of activation-induced expansion and increased 7-amino-actinomycin D uptake by CD8hi CD57+ T cells following treatment with CFSE, a dye previously used to measure their proliferation, combined with specific media requirements for the growth of this cell subset. The ability of CD8hi CD57+ T cells to further differentiate is highlighted by a distinct cytokine profile late after activation that includes the unexpected release of high levels of interleukin 5. These data indicate that CD8hi CD57+ T cells should not be considered as "end-stage" effector T cells incapable of proliferation, but represent a highly differentiated subset capable of rapid division and exhibiting novel functions separate from their previously described cytotoxic and IFN-gamma responses.

Dynamics of T cell memory in human cytomegalovirus infection

Primary human cytomegalovirus (HCMV) infection of an immunocompetent individual leads to the generation of a robust CD4+ and CD8+ T cell response which subsequently controls viral replication. HCMV is never cleared from the host and enters into latency with periodic reactivation and viral replication, which is controlled by reactivation of the memory T cells. In this article, we discuss the magnitude, phenotype and clonality of the T cell response following primary HCMV infection, the selection of responding T cells into the long-term memory pool and maintenance of this memory T cell population in the face of a latent/persistent infection. The article also considers the effect that this long-term surveillance of HCMV has on the T cell memory phenotype, their differentiation, function and the associated concepts of T cell memory inflation and immunosenescence.

Expansion of human cytomegalovirus-specific T lymphocytes from unfractionated peripheral blood mononuclear cells with artificial antigen-presenting cells

BACKGROUND

The aim of this study was to find a simple and feasible method for ex vivo expansion of human cytomegalovirus (CMV)-specific cytotoxic T cells from unfractionated peripheral blood mononuclear cells (PBMNCs).

STUDY DESIGN AND METHODS

Unfractionated PBMNCs from three HLA-A*0201-CMV-seropositive donors were stimulated with CMVpp65(495-503) peptide-loaded HLA-A*0201-immunoglobulin fusion protein (HLA-A2-Ig) based artificial antigen-presenting cells (aAPCs) on Day 1. Once a week the CMV-specific T cells were harvested and restimulated with fresh aAPCs. T-cell cultures were maintained for 28 days and then analyzed.

RESULTS

With aAPCs and starting with 1x10(7) freshly isolated PBMNCs that were less than 0.1 percent CMV-specific, more than 1x10(7) T cells with a CMV-specific frequency greater than 93 percent in all donors tested were generated. Expanded CD8+ cytotoxic T lymphocytes were functionally active and showed antigen-specific secretion of interferon-gamma and cytotoxic activity. No alloreactivity against unpulsed HLA-A*0201-positive cells was detected.

CONCLUSION

Herein is reported the successful in vitro expansion of CMV-specific cytotoxic CD8+ T cells from unfractionated PBMNCs of healthy CMV-seropositive blood donors by the use of HLA-A2-Ig-based aAPCs. This study demonstrates that more than 1x10(7) CMV-specific T cells can be generated from approximately 1x10(7) unfractionated PBMNCs within 1 month under highly reproducible conditions.

Differential costimulation through CD137 (4-1BB) restores proliferation of human virus-specific "effector memory" (CD28(-) CD45RA(HI)) CD8(+) T cells

In healthy carriers of human cytomegalovirus (HCMV), the virus-specific memory CD8(+) T-cell population is often dominated by CD28(-) CD45RA(hi) cells that exhibit direct ex vivo cytotoxicity but whose capacity for proliferation and generation of further memory cells has been questioned. We show that when highly purified CD28(-) CD45RA(hi) CD8(+) T cells are stimulated with viral peptide presented by autologous monocytes, the virus-specific T cells show early up-regulation of CD137 (4-1BB) and CD278 (ICOS), re-express CD28, and proliferate with similarly high cloning efficiency in limiting dilution analysis as CD28(+) CD45RO(hi) cells or CD28(-) CD45RO(hi) cells. Using peptide-pulsed autologous fibroblasts transfected with individual costimulatory ligands as antigen presenting cells, we showed CD137L to be a key costimulatory ligand for proliferation of CD28(-) CD45RA(hi) CD8(+) T cells and not CD80, CD86, or CD275 (ICOSL). Therefore, CD28(-) CD45RA(hi) CD8(+) T cells were not terminally differentiated but required a specific costimulatory signal for proliferation.

CD57 expression correlates with alveolitis severity in subjects with beryllium-induced disease

BACKGROUND

Despite numerous studies in human beings linking surface phenotype of blood T cells with their functional characteristics, little is known about this relationship on antigen-specific CD4(+) T cells residing in a target organ.

OBJECTIVE

The aims of this study were to determine the relationship between CD57 expression, a marker of T-cell senescence, and severity of chronic beryllium disease (CBD) and to determine the phenotypic and functional characteristics that differentiate beryllium-specific CD4(+) T cells in lung and blood.

METHODS

CD57 expression on beryllium-responsive IFN-gamma-expressing and IL-2-expressing CD4(+) T cells in blood and lung of 17 beryllium-sensitized and 20 CBD subjects was determined.

RESULTS

CD57 expression was significantly higher on bronchoalveolar lavage (BAL) than blood CD4(+) T cells in both beryllium-sensitized and CBD subjects. Expression of CD57 on BAL CD4(+) T cells was directly correlated with the lymphocytic alveolitis. In blood and BAL, higher CD57 expression was seen on more differentiated CD4(+) memory T-cell subsets. Although CD57 expression on blood and BAL cells was associated with a reduced proliferative potential, examination of beryllium-specific CD4(+) T cells in blood and lung revealed no difference in CD57 expression on cells that produced IFN-gamma only versus IFN-gamma and IL-2.

CONCLUSION

These data suggest that CD57 expression on CD4(+) T cells is an important phenotypic marker to assess lung inflammation and the functional competence of the CD4(+) T-cell compartment in CBD.

CLINICAL IMPLICATIONS

These findings suggest that CD57 is a marker of lung inflammation and potentially, disease severity.