Accelerated T-Cell Immunosenescence in Cytomegalovirus-Seropositive Individuals After Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Cytomegalovirus (CMV) infection is a major driver of accelerated immunosenescence related to CD28null T cell expansion. CMV infection and these proatherogenic T cells have been independently associated with cardiovascular disease and coronavirus disease 2019 (COVID-19) severity. We investigated the potential contribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to immunosenescence and its relationship with CMV. Innate and adaptive immune subpopulations from individuals with mild or asymptomatic SARS-CoV-2 infection (mCOVID-19) and healthy donors were immunophenotyped. A significant increase in CD28nullCD57+CX3CR1+ T cell percentages (CD4+ [P ≤ .01], CD8+ [P ≤ .01], and TcRγδ (CD4-CD8-) [P ≤ .001]) was found in unnvaccinated CMV-seropositive mCOVID-19 individuals stable up to 12 months after infection. This expansion did not occur in CMV-seronegative mCOVID-19 individuals or in CMV-seropositive individuals infected after SARS-CoV-2 vaccination. There were no significant differences between mCOVID-19 and aortic stenosis groups. Thus, individuals coinfected with SARS-CoV-2 and CMV have accelerated T cell senescence, which might lead to an increased risk of cardiovascular disease.

A Straightforward Cytometry-Based Protocol for the Comprehensive Analysis of the Inflammatory Valve Infiltrate in Aortic Stenosis.

Aortic stenosis (AS) is a frequent cardiac disease in old individuals, characterized by valvular calcification, fibrosis, and inflammation. Recent studies suggest that AS is an active inflammatory atherosclerotic-like process. Particularly, it has been suggested that several immune cell types, present in the valve infiltrate, contribute to its degeneration and to the progression toward stenosis. Furthermore, the infiltrating T cell subpopulations mainly consist of oligoclonal expansions, probably specific for persistent antigens. Thus, the characterization of the cells implicated in the aortic valve calcification and the analysis of the antigens to which those cells respond to is of utmost importance to develop new therapies alternative to the replacement of the valve itself. However, calcified aortic valves have been only studied so far by histological and immunohistochemical methods, unable to render an in-depth phenotypical and functional cell profiling. Here we present, for the first time, a simple and efficient cytometry-based protocol that allows the identification and quantification of infiltrating inflammatory leukocytes in aortic valve explants. Our cytometry protocol saves time and facilitates the simultaneous analysis of numerous surface and intracellular cell markers and may well be also applied to the study of other cardiac diseases with an inflammatory component.

Functional Changes of T-Cell Subsets with Age and CMV Infection.

Cytomegalovirus (CMV) latent infection and aging contribute to alterations in the function and phenotype of the T-cell pool. We have demonstrated that CMV-seropositivity is associated with the expansion of polyfunctional CD57+ T-cells in young and middle-aged individuals in response to different stimuli. Here, we expand our results on the effects of age and CMV infection on T-cell functionality in a cohort of healthy middle-aged and older individuals stratified by CMV serostatus. Specifically, we studied the polyfunctional responses (degranulation, IFN-γ and TNF-α production) of CD4+, CD8+, CD8+CD56+ (NKT-like), and CD4-CD8- (DN) T-cells according to CD57 expression in response to Staphylococcal Enterotoxin B (SEB). Our results show that CD57 expression by T-cells is not only a hallmark of CMV infection in young individuals but also at older ages. CD57+ T-cells are more polyfunctional than CD57- T-cells regardless of age. CMV-seronegative individuals have no or a very low percentages of cytotoxic CD4+ T-cells (CD1017a+) and CD4+CD57+ T-cells, supporting the notion that the expansion of these T-cells only occurs in the context of CMV infection. There was a functional shift in T-cells associated with CMV seropositivity, except in the NKT-like subset. Here, we show that the effect of CMV infection and age differ among T-cell subsets and that CMV is the major driving force for the expansion of highly polyfunctional CD57+ T-cells, emphasizing the necessity of considering CMV serology in any study of immunosenescence.

Current progress in NK cell biology and NK cell-based cancer immunotherapy.

A better understanding of the complex interactions between the immune system and tumour cells from different origins has opened the possibility to design novel procedures of antitumoral immunotherapy. One of these novel approaches is based on the use of autologous or allogeneic natural killer (NK) cells to treat cancer. In the last decade, different strategies to activate NK cells and their use in adoptive NK cell-based therapy have been established. Although NK cells are often considered as a uniform cell population, several phenotypic and functionally distinct NK cells subsets exist in healthy individuals, that are differentially affected by ageing or by apparently innocuous viruses such as cytomegalovirus (CMV). In addition, further alterations in the expression of activating and inhibitory receptors are found in NK cells from cancer patients, likely because of their interaction with tumour cells. Thus, NK cells represent a promising strategy for adoptive immunotherapy of cancer already tested in phase 1/2 clinical trials. However, the existence of NK cell subpopulations expressing different patterns of activating and inhibitory receptors and different functional capacities, that can be found to be altered not only in cancer patients but also in healthy individuals stratified by age or CMV infection, makes necessary a personalized definition of the procedures used in the selection, expansion, and activation of the relevant NK cell subsets to be successfully used in NK cell-based immunotherapy.

Immunosenescence: limitations of natural killer cell-based cancer immunotherapy.

Cancer is primarily considered a disease of old age. Immunosenescence refers to the age-associated changes in the immune system, and its contribution to the increased risk of cancer in old individuals has been discussed for many years. Natural killer (NK) cells are cytotoxic innate immune cells specialized in defence against tumour and virus-infected cells. NK cell cytotoxicity is the result of a fine balance between activating and inhibitory receptors. Several activating receptors have been identified that recognize different ligands frequently found over-expressed on tumour cells or virus-infected cells. The most important NK cell inhibitory receptors interact with major histocompatibility complex class I molecules expressed on almost all nucleated cells preventing NK cell-mediated lysis of healthy cells. NK cell immunosenescence is characterized by a redistribution of NK cell subsets, a diminished expression of several activating receptors and lower per-cell cytotoxicity. Altered expression of activating receptors has also been described in young and elderly cancer patients probably due to chronic exposure to ligands on tumour cells. Thus, the effect of both age and cancer may act synergistically to diminish NK cell-mediated tumour immunosurveillance. Different strategies harnessing the power of NK cells to target tumour cells have been designed including adoptive therapy with autologous or allogeneic expanded NK cells. In addition, checkpoint blockade of inhibitory receptors and the use of agonist antibodies to stimulate activating receptors are emerging areas of research. In this context, the effect of immunosenescence should be considered to improve the efficiency of cancer immunotherapy.

Effect of Cytomegalovirus (CMV) and Ageing on T-Bet and Eomes Expression on T-Cell Subsets.

The differential impact of ageing and cytomegalovirus (CMV) latent infection on human T-cell subsets remains to some extent controversial. The purpose of this study was to analyse the expression of the transcription factors T-bet and Eomes and CD57 on CD4+, CD4hiCD8lo and CD8+ T-cell subsets in healthy individuals, stratified by age and CMV serostatus. The percentage of CD4+ T-cells expressing T-bet or Eomes was very low, in particular in CD4+ T-cells from young CMV-seronegative individuals, and were higher in CMV-seropositive older individuals, in both CD57- and CD57+ CD4+ T-cells. The study of the minor peripheral blood double-positive CD4hiCD8lo T-cells showed that the percentage of these T-cells expressing both Eomes and T-bet was higher compared to CD4+ T-cells. The percentage of CD4hiCD8lo T-cells expressing T-bet was also associated with CMV seropositivity and the coexpression of Eomes, T-bet and CD57 on CD4hiCD8lo T-cells was only observed in CMV-seropositive donors, supporting the hypothesis that these cells are mature effector memory cells. The percentage of T-cells expressing Eomes and T-bet was higher in CD8+ T-cells than in CD4+ T-cells. The percentages of CD8+ T-cells expressing Eomes and T-bet increased with age in CMV-seronegative and -seropositive individuals and the percentages of CD57- CD8+ and CD57+ CD8+ T-cells coexpressing both transcription factors were similar in the different groups studied. These results support that CMV chronic infection and/or ageing are associated to the expansion of highly differentiated CD4+, CD4hiCD8lo and CD8+ T-cells that differentially express T-bet and Eomes suggesting that the expression of these transcription factors is essential for the generation and development of an effector-memory and effector T lymphocytes involved in conferring protection against chronic CMV infection.

Natural killer cell immunosenescence in acute myeloid leukaemia patients: new targets for immunotherapeutic strategies?

Several age-associated changes in natural killer (NK) cell phenotype have been reported that contribute to the defective NK cell response observed in elderly patients. A remodelling of the NK cell compartment occurs in the elderly with a reduction in the output of immature CD56(bright) cells and an accumulation of highly differentiated CD56(dim) NK cells. Acute myeloid leukaemia (AML) is generally a disease of older adults. NK cells in AML patients show diminished expression of several activating receptors that contribute to impaired NK cell function and, in consequence, to AML blast escape from NK cell immunosurveillance. In AML patients, phenotypic changes in NK cells have been correlated with disease progression and survival. NK cell-based immunotherapy has emerged as a possibility for the treatment of AML patients. The understanding of age-associated alterations in NK cells is therefore necessary to define adequate therapeutic strategies in older AML patients.

Expression of NKp30, NKp46 and DNAM-1 activating receptors on resting and IL-2 activated NK cells from healthy donors according to CMV-serostatus and age.

Human natural killer (NK) cells are innate lymphoid cells with capacity to kill tumor cells and virus-infected cells. According to the expression of CD56 and CD16 several NK cell subsets have been identified, a major CD56dimCD16+ subpopulation characterized by higher cytotoxic capacity, two CD56bright subsets (CD16-and CD16+) that represent different maturation stages and the fourth CD56-CD16+ subset that correspond to activated dysfunctional NK cells. Previous studies have shown quantitative changes in the frequency, phenotype and distribution of NK cell subsets depending on CMV-serostatus and age. We have analyzed the expression of NKp30, NKp46 and DNAM-1 NK activating receptors on resting and IL-2 activated NK cells from CMV-seronegative and seropositive healthy young donors and from CMV-seropositive elderly individuals. Our results showed that CMV-serostatus of healthy young donors is associated with phenotypic differences on both CD56bright and CD56dim NK cells with an increase of NKp46 and a decrease of NKp30 expression respectively. A reduced expression of DNAM-1 related to ageing and a lower NKp30 expression associated with CMV-seropositivity were observed. The expression of NKp46 and NKp30 was lower in CD57+ NK cells while the expression of DNAM-1 was increased. In vitro NK cell activation by IL-2 increased the expression of NKp46 and NKp30. In summary, both age and CMV-serostatus influence the expression of these cytotoxicity activating receptors that will have functional consequences. In elderly donors is difficult to isolate age from the effect of chronic CMV infection since in our study all elderly donors were CMV-seropositive. The possibility of modulating the expression of these activating receptors by cytokines such as IL-2 may open new opportunities for improving age-associated deterioration of NK cell function.

Marked skewing of entire T-cell memory compartment occurs only in a minority of CMV-infected individuals and is unrelated to the degree of memory subset skewing among CMV-specific T-cells.

Background: Chronic CMV infection drives the clonal expansion and accumulation of terminally differentiated, dysfunctional CMV-specific T-cells. CMV infection also appears to accelerate the differentiation of non-CMV-specific T-cells; however, the extent of this phenomenon is unclear. Methods: The distribution of CD4 and CD8 T-cells into four memory subsets determined by CD45RA and CCR7 expression was analyzed in 96 CMV-infected (CMV+) and 81 CMV-uninfected (CMV-) older individuals. In CMV+ individuals, the distribution of IFN-γ producing CMV-specific T-cells into the same subsets was analyzed following stimulation with 16 different CMV antigens using flowcytometry (intracellular cytokine staining). We used previously published results to extrapolate the relative size of the entire CMV-specific CD4 and CD8 T-cell response from the summated response to selected antigens. The T-cell memory subset distribution across all CMV antigen-induced responses (weighted mean) was then used to calculate memory subset proportions (in % of CD4 or CD8 T-cells) of CMV-specific and non-CMV-specific T-cells. These were compared to the corresponding proportions in CMV- individuals. Results: Only a minority (20%-30%) of CMV+ individuals displayed overall proportions of terminally differentiated T-cell memory subsets above an upper outlier boundary defined in CMV- individuals. The calculated proportions of these subsets among non-CMV-specific T-cells in CMV+ individuals also exceeded the corresponding proportions in CMV- people, suggesting that their differentiation could be CMV-driven. In CMV+ people showing overall subset distributions within the outlier limits, the memory subset distributions of non-CMV-specific T-cells were more like those in CMV- people. Logistic regression revealed that CMV infection, age, and sex all had significant effects on one or more of the non-CMV-specific CD4 or CD8 T-cell memory subsets in CMV+ individuals, with CMV infection showing the strongest effect overall. Surprisingly, except for the CD45RA-/CCR7- CD4 T-cell subset, we only found weak correlations between corresponding memory subset proportions among all T-cells and CMV-specific T-cells. Conclusion: Our analysis supports an effect of CMV infection on non-CMV-specific T-cells; however, it is limited to a minority of individuals and not closely related to the degree of memory subset differentiation of CMV-specific T-cells. We propose that unknown predisposing factors might determine to what extent CMV infection affects non-CMV-specific T-cell differentiation.

Enhanced expression of natural cytotoxicity receptors on cytokine-induced memory-like natural killer cells correlates with effector function.

Introduction: Natural killer (NK) cells are a key component of the innate immune system, involved in defending the host against virus-infected cells and tumor immunosurveillance. Under in vitro culture conditions, IL-12/15/18 can induce a memory-like phenotype in NK cells. These cytokine-induced memory-like (CIML) NK cells possess desirable characteristics for immunotherapies, including a longer lifespan and increased cytotoxicity. Methods: In this study, NK cells were isolated from peripheral blood of healthy donors and stimulated with IL-12/15/18 to induce a memory-like phenotype or with IL-15 alone as a control. After seven days of culture, multiparametric flow cytometry analysis was performed to evaluate the phenotypic and functional profiles of CIML and control NK cells. Results: Our results showed a significantly higher expression of CD25, CD69, NKG2D, NKp30, NKp44, NKp46, TACTILE, and Granzyme B in CIML NK cells compared to control NK cells. In contrast, KIR2D expression was significantly lower in CIML NK cells than in control NK cells. Moreover, functional experiments demonstrated that CIML NK cells displayed enhanced degranulation capacity and increased intracellular IFN-γ production against the target cell line K562. Interestingly, the degranulation capacity of CIML NK cells was positively correlated with the expression of the activating receptors NKp46 and NKp30, as well as with the inhibitory receptor TACTILE. Discussion: In conclusion, this study provides a deep phenotypic characterization of in vitro-expanded CIML NK cells. Moreover, the correlations found between NK cell receptors and degranulation capacity of CIML NK cells allowed the identification of several biomarkers that could be useful in clinical settings.

Spanish HCMV Seroprevalence in the 21st Century.

Human cytomegalovirus (HCMV) is linked to age-related diseases like cardiovascular disease, neurodegenerative conditions, and cancer. It can also cause congenital defects and severe illness in immunocompromised individuals. Accurate HCMV seroprevalence assessment is essential for public health planning and identifying at-risk individuals. This is the first HCMV seroprevalence study conducted in the general Spanish adult population in 30 years. We studied HCMV seroprevalence and HCMV IgG antibody titres in healthy adult donors (HDs) and HCMV-related disease patients from 2010 to 2013 and 2020 to 2023, categorized by sex and age. We compared our data with 1993 and 1999 studies in Spain. The current HCMV seroprevalence among HDs in Spain is 73.48%. In women of childbearing age, HCMV seroprevalence has increased 1.4-fold in the last decade. HCMV-seropositive individuals comprise 89.83% of CVD patients, 69% of SMI patients, and 70.37% of COVID-19 patients. No differences in HCMV seroprevalence or HCMV IgG antibody titres were observed between patients and HDs. A significant reduction in Spanish HCMV seroprevalence among HDs was observed in 1993. However, women of childbearing age have shown an upturn in the last decade that may denote a health risk in newborns and a change in HCMV seroprevalence trends.

Clinical significance of glycogen synthase kinase 3 (GSK-3) expression and tumor budding grade in colorectal cancer: Implications for targeted therapy.

INTRODUCTION: Glycogen synthase kinase 3 (GSK-3) has been proposed as a novel cancer target due to its regulating role in both tumor and immune cells. However, the connection between GSK-3 and immunoevasive contexture, including tumor budding (TB) has not been previously examined. METHODS: we investigated the expression levels of total GSK-3 as well as its isoforms (GSK-3ß and GSK-3α) and examined their potential correlation with TB grade and the programmed cell death-ligand 1 (PD-L1) in colorectal cancer (CRC) tumor samples. Additionally, we compared the efficacy of GSK-3-inhibition with PD-1/PD-L1 blockade in humanized patient-derived (PDXs) xenografts models of high-grade TB CRC. RESULTS: we show that high-grade (BD3) TB CRC is associated with elevated expression levels of total GSK-3, specifically the GSK-3ß isoform, along with increased expression of PD-L1 in tumor cells. Moreover, we define an improved risk stratification of CRC patients based on the presence of GSK-3+/PD-L1+/BD3 tumors, which are associated with a worse prognosis. Significantly, in contrast to the PD-L1/PD-1 blockade approach, the inhibition GSK-3 demonstrated a remarkable enhancement in the antitumor response. This was achieved through the reduction of tumor buds via necrosis and apoptosis pathways, along with a notable increase of activated tumor-infiltrating CD8+ T cells, NK cells, and CD4- CD8- T cells. CONCLUSIONS: our study provides compelling evidence for the clinical significance of GSK-3 expression and TB grade in risk stratification of CRC patients. Moreover, our findings strongly support GSK-3 inhibition as an effective therapy specifically targeting high-grade TB in CRC.

NK cells in healthy aging and age-associated diseases.

NK cells exhibit the highest cytotoxic capacity within the immune system. Alteration of their number or functionality may have a deep impact on overall immunity. This is of particular relevance in aging where the elderly population becomes more susceptible to infection, cancer, autoimmune diseases, and neurodegenerative diseases amongst others. As the fraction of elderly increases worldwide, it becomes urgent to better understand the aging of the immune system to prevent and cure the elderly population. For this, a better understanding of the function and phenotype of the different immune cells and their subsets is necessary. We review here NK cell functions and phenotype in healthy aging as well as in various age-associated diseases.

CMV and Immunosenescence: from basics to clinics.

Alone among herpesviruses, persistent Cytomegalovirus (CMV) markedly alters the numbers and proportions of peripheral immune cells in infected-vs-uninfected people. Because the rate of CMV infection increases with age in most countries, it has been suggested that it drives or at least exacerbates "immunosenescence". This contention remains controversial and was the primary subject of the Third International Workshop on CMV & Immunosenescence which was held in Cordoba, Spain, 15-16th March, 2012. Discussions focused on several main themes including the effects of CMV on adaptive immunity and immunosenescence, characterization of CMV-specific T cells, impact of CMV infection and ageing on innate immunity, and finally, most important, the clinical implications of immunosenescence and CMV infection. Here we summarize the major findings of this workshop.

Immune Checkpoint Inhibitors for Vaccine Improvements: Current Status and New Approaches.

In recent years, the use of immune checkpoint inhibitors (ICIs) in combination with approved or experimental vaccines has proven to be a promising approach to improve vaccine immunogenicity and efficacy. This strategy seeks to overcome the immunosuppressive mechanisms associated with the vaccine response, thereby achieving increased immunogenicity and efficacy. Most of the information on the use of ICIs combined with vaccines derives from studies on certain anti-tumor vaccines combined with monoclonal antibodies (mAbs) against either cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), or programmed death-ligand 1 (PD-L1). However, over the past few years, emerging strategies to use new-generation ICIs as molecular adjuvants are paving the way for future advances in vaccine research. Here, we review the current state and future directions of the use of ICIs in experimental and clinical settings, including mAbs and alternative new approaches using antisense oligonucleotides (ASOs), small non-coding RNAs, aptamers, peptides, and other small molecules for improving vaccine efficacy. The scope of this review mainly includes the use of ICIs in therapeutic antitumor vaccines, although recent research on anti-infective vaccines will also be addressed.

Functional assessment of allelic variants in the SLC26A4 gene involved in Pendred syndrome and nonsyndromic EVA.

Pendred syndrome is an autosomal recessive disorder characterized by sensorineural hearing loss, with malformations of the inner ear, ranging from enlarged vestibular aqueduct (EVA) to Mondini malformation, and deficient iodide organification in the thyroid gland. Nonsyndromic EVA (ns-EVA) is a separate type of sensorineural hearing loss showing normal thyroid function. Both Pendred syndrome and ns-EVA seem to be linked to the malfunction of pendrin (SLC26A4), a membrane transporter able to exchange anions between the cytosol and extracellular fluid. In the past, the pathogenicity of SLC26A4 missense mutations were assumed if the mutations fulfilled two criteria: low incidence of the mutation in the control population and substitution of evolutionary conserved amino acids. Here we show that these criteria are insufficient to make meaningful predictions about the effect of these SLC26A4 variants on the pendrin-induced ion transport. Furthermore, we functionally characterized 10 missense mutations within the SLC26A4 ORF, and consistently found that on the protein level, an addition or omission of a proline or a charged amino acid in the SLC26A4 sequence is detrimental to its function. These types of changes may be adequate for predicting SLC26A4 functionality in the absence of direct functional tests.

Regulatory T cells and vaccine effectiveness in older adults. Challenges and prospects.

Since the discovery of lymphocytes with immunosuppressive activity, increasing interest has arisen in their possible influence on the immune response induced by vaccines. Regulatory T cells (Tregs) are essential for maintaining peripheral tolerance, preventing autoimmune diseases, and limiting chronic inflammatory diseases. However, they also limit beneficial immune responses by suppressing anti-infectious and anti-tumor immunity. Mounting evidence suggests that Tregs are involved, at least in part, in the low effectiveness of immunization against various diseases where it has been difficult to obtain protective vaccines. Interestingly, increased activity of Tregs is associated with aging, suggesting a key role for these cells in the lower vaccine effectiveness observed in older people. In this review, we analyze the impact of Tregs on vaccination, with a focus on older adults. Finally, we address an overview of current strategies for Tregs modulation with potential application to improve the effectiveness of future vaccines targeting older populations.

In-Depth Profiling of T-Cell Responsiveness to Commonly Recognized CMV Antigens in Older People Reveals Important Sex Differences.

The impact of biological sex on T-cell immunity to Cytomegalovirus (CMV) has not been investigated in detail with only one published study comparing CMV-specific T-cell responses in men and women. Many studies, however, have shown an association between CMV infection and immunosenescence, with broad effects on peripheral blood lymphocyte subsets as well as the T and B-cell repertoires. Here, we provide a detailed analysis of CMV-specific T-cell responses in (n=94) CMV+ older people, including 47 women and 47 men aged between 60 and 93 years. We explore sex differences with respect to 16 different CMV proteins arranged in 14 peptide pools (overlapping peptides). Following ex vivo stimulation, CD4 and CD8 T-cells producing IFN-γ, TNF, and IL-2 were enumerated by flow-cytometry (intracellular cytokine staining). T-cell responses were evaluated in terms of each cytokine separately or in terms of cytokines produced simultaneously (polyfunctionality). Surface memory phenotype and CD3 downmodulation were assessed in parallel. The polyfunctionality index and a memory subset differentiation score were used to identify associations between response size, cytokine production, polyfunctionality, and memory subset distribution. While no significant sex differences were found with respect to overall CMV target protein selection, the T-cell response in men appeared more focused and accompanied by a more prominent accumulation of CMV-specific memory CD4 and CD8 T-cells. T-cell polyfunctionality and differentiation were similar in the sexes, however, CMV-specific T-cells in men produced more pro-inflammatory cytokines. Particularly, TNF production by CD4 T-cells was stronger in men than in women. Also, compared with women, men had larger responses to CMV proteins with immediate-early/early kinetics than women, which might have been driven by CMV reactivation. In conclusion, the CMV-specific T-cell response in men was larger and more pro-inflammatory than in women. Our findings may help explain sex differences in CMV-associated pathologies.

Impact of Cytomegalovirus and Age on T-Cell Subsets Defined by CD161, CD300a, and/or CD57 Expression in Healthy Andalusians.

Immunosenescence affects innate and adaptive immunity impairing the response to pathogens and vaccines. Chronic infection with cytomegalovirus (CMV) has been shown to drive "early immunosenescence" and can considerably affect both the function and phenotype of immune cells, especially T cells. We have previously shown that the expression of CD57, CD300a, and CD161 was differentially affected by age and chronic CMV infection, indicating that these markers are a hallmark of CMV infection and T-cell aging. The aim of this present study was to clarify whether these 3 markers define distinct T-cell subpopulations with a specific functional and molecular signature. Specifically, we analyzed the effect of age and chronic CMV infection on the functionality of T cells according to CD161, CD300a, and CD57 expression. We found that these markers defined different T-cell subsets, both at the phenotypic and functional levels. CD57 was the best biomarker for CD4+ T-cell cytotoxicity and was a hallmark of CMV infection. CD300a+ T cells were heterogeneous and included different cell subsets. The population of CD161+ T cells dramatically decreased with age, independently of CMV infection, and represented a sign of age-associated immune system alterations. The latter could contribute to an increased risk of autoimmune disease and infection in older adults. Our results underline the importance of better understanding the factors involved in the immunosenescence process to be able to uncover new biomarkers and open new avenues for the investigation and development of novel age-related disease therapies.