DNA Methylation Regulates the Differential Expression of CX3CR1 on Human IL-7Rαlow and IL-7Rαhigh Effector Memory CD8+ T Cells with Distinct Migratory Capacities to the Fractalkine

SATB1, senescence and senescence-related diseases

Aging leads to an accumulation of cellular mutations and damage, increasing the risk of senescence, apoptosis, and malignant transformation. Cellular senescence, which is pivotal in aging, acts as both a guard against cellular transformation and as a check against cancer progression. It is marked by stable cell cycle arrest, widespread macromolecular changes, a pro-inflammatory profile, and altered gene expression. However, it remains to be determined whether these differing subsets of senescent cells result from unique intrinsic programs or are influenced by their environmental contexts. Multiple transcription regulators and chromatin modifiers contribute to these alterations. Special AT-rich sequence-binding protein 1 (SATB1) stands out as a crucial regulator in this process, orchestrating gene expression by structuring chromatin into loop domains and anchoring DNA elements. This review provides an overview of cellular senescence and delves into the role of SATB1 in senescence-related diseases. It highlights SATB1's potential in developing antiaging and anticancer strategies, potentially contributing to improved quality of life and addressing aging-related diseases.

Mucosal Immunity Related to CD8+ T Lymphocytes in Children with Helicobacter pylori Gastritis

Purpose

We investigated the role of CD8+T cells as host immune factors in pediatric patients with Helicobacter pylori gastritis.

Methods

Gastric mucosal tissue and blood samples were collected from 39 children, including 11 children with H. pylori infection and 28 children as controls. Anti-CD8 and anti-T-bet antibodies were used for immunohistochemistry of the gastric mucosa. For the cell surface and intracellular staining, peripheral blood mononuclear cells were stained with anti-IL7Rα, anti-CX3CR1, anti-CD8, anti-T-bet, and anti-IFN-γ antibodies. Cytokines of sera such as tumor necrosis factor alpha (TNF-α) and CX3CL1 were analyzed using enzyme- linked immunosorbent assay (ELISA).

Results

In the immunohistochemistry of gastric mucosa, the frequency of CD8+ and T-bet+ T cells cells was higher in the H. pylori-positive group than in the control group (26.9± 7.8% vs. 16.9±3.3%, p<0.001; 5.0±2.5% vs. 2.2±0.7%, p=0.001). Between the control and H. pylori-positive groups, the frequency of IL-7RαlowCX3CR1+ CD8+ and T-bet+ INF-γ+ CD8+ T cells were not significantly different between surface and intracellular staining, respectively (40.4±24.0% vs. 38.2±17.8%, p=0.914; 40.4±24.0% vs. 38.2±17.8%, p=0.914). In the ELISA, no significant differences in TNF-α and CX3CL1 concentrations were observed between the control and H. pylori-positive groups (34.3±12.1 pg/mL vs. 47.0±22.6 pg/mL, p=0.114/0.5± 0.1 pg/mL vs. 0.5±0.1 pg/mL, p=0.188).

Conclusion

CD8+ T and Th1 cells, which secrete IFN-γ, might play important roles in the mucosal immunity of the stomach in children with H. pylori infection.

Aging gene signature of memory CD8+ T cells is associated with neurocognitive functioning in Alzheimer's disease

BACKGROUND

Memory CD8+ T cells expand with age. We previously demonstrated an age-associated expansion of effector memory (EM) CD8+ T cells expressing low levels of IL-7 receptor alpha (IL-7Rαlow) and the presence of its gene signature (i.e., IL-7Rαlow aging genes) in peripheral blood of older adults without Alzheimer's disease (AD). Considering age as the strongest risk factor for AD and the recent finding of EM CD8+ T cell expansion, mostly IL-7Rαlow cells, in AD, we investigated whether subjects with AD have alterations in IL-7Rαlow aging gene signature, especially in relation to genes possibly associated with AD and disease severity.

RESULTS

We identified a set of 29 candidate genes (i.e., putative AD genes) which could be differentially expressed in peripheral blood of patients with AD through the systematic search of publicly available datasets. Of the 29 putative AD genes, 9 genes (31%) were IL-7Rαlow aging genes (P < 0.001), suggesting the possible implication of IL-7Rαlow aging genes in AD. These findings were validated by RT-qPCR analysis of 40 genes, including 29 putative AD genes, additional 9 top IL-7R⍺low aging but not the putative AD genes, and 2 inflammatory control genes in peripheral blood of cognitively normal persons (CN, 38 subjects) and patients with AD (40 mild cognitive impairment and 43 dementia subjects). The RT-qPCR results showed 8 differentially expressed genes between AD and CN groups; five (62.5%) of which were top IL-7Rαlow aging genes (FGFBP2, GZMH, NUAK1, PRSS23, TGFBR3) not previously reported to be altered in AD. Unbiased clustering analysis revealed 3 clusters of dementia patients with distinct expression levels of the 40 analyzed genes, including IL-7Rαlow aging genes, which were associated with neurocognitive function as determined by MoCA, CDRsob and neuropsychological testing.

CONCLUSIONS

We report differential expression of "normal" aging genes associated with IL-7Rαlow EM CD8+ T cells in peripheral blood of patients with AD, and the significance of such gene expression in clustering subjects with dementia due to AD into groups with different levels of cognitive functioning. These results provide a platform for studies investigating the possible implications of age-related immune changes, including those associated with CD8+ T cells, in AD.

Type-2 CD8+ T-cell formation relies on interleukin-33 and is linked to asthma exacerbations

CD4+ T helper 2 (Th2) cells and group 2 innate lymphoid cells are considered the main producers of type-2 cytokines that fuel chronic airway inflammation in allergic asthma. However, CD8+ cytotoxic T (Tc) cells - critical for anti-viral defense - can also produce type-2 cytokines (referred to as 'Tc2' cells). The role of Tc cells in asthma and virus-induced disease exacerbations remains poorly understood, including which micro-environmental signals and cell types promote Tc2 cell formation. Here we show increased circulating Tc2 cell abundance in severe asthma patients, reaching peak levels during exacerbations and likely emerging from canonical IFNγ+ Tc cells through plasticity. Tc2 cell abundance is associated with increased disease burden, higher exacerbations rates and steroid insensitivity. Mouse models of asthma recapitulate the human disease by showing extensive type-2 skewing of lung Tc cells, which is controlled by conventional type-1 dendritic cells and IFNγ. Importantly, we demonstrate that the alarmin interleukin-33 (IL-33) critically promotes type-2 cytokine production by lung Tc cells in experimental allergic airway inflammation. Our data identify Tc cells as major producers of type-2 cytokines in severe asthma and during exacerbations that are remarkably sensitive to alterations in their inflammatory tissue micro-environment, with IL-33 emerging as an important regulator of Tc2 formation.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4+ and CD8+ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4+ helper and CD8+ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4+ and CD8+ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4+ and CD8+ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8+ T cell differentiation trajectory, CD4+ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Aging gene signature of IL-7 receptor alpha low effector memory CD8+ T cells is associated with neurocognitive functioning in Alzheimer's disease

CD45RA+ effector memory (EM) CD8+ T cell expansion was reported in Alzheimer's disease (AD). Such cells are IL-7 receptor alpha (IL-7Rα)low EM CD8+ T cells, which expand with age and have a unique aging gene signature (i.e., IL-7Rαlow aging genes). Here we investigated whether IL-7Rαlow aging genes and previously reported AD and memory (ADM) genes overlapped with clinical significance in AD patients. RT-qPCR analysis of 40 genes, including 29 ADM, 9 top IL-7Ralow aging and 2 control genes, showed 8 differentially expressed genes between AD and cognitively normal groups; five (62.5%) of which were top IL-7Rαlow aging genes. Over-representation analysis revealed that these genes were highly present in molecular and biological pathways associated with AD. Distinct expression levels of these genes were associated with neuropsychological testing performance in 3 subgroups of dementia participants. Our findings support the possible implication of the IL-7Rαlow aging gene signature with AD.

The Crossroads of Cancer Epigenetics and Immune Checkpoint Therapy

Immune checkpoint inhibitors (ICI) have significantly improved treatment outcomes for several types of cancer over the past decade, but significant challenges that limit wider effectiveness of current immunotherapies remain to be addressed. Certain "cold" tumor types, such as pancreatic cancer, exhibit very low response rates to ICI due to intrinsically low immunogenicity. In addition, many patients who initially respond to ICI lack a sustained response due to T-cell exhaustion. Several recent studies show that epigenetic modifiers, such as SETDB1 and LSD1, can play critical roles in regulating both tumor cell-intrinsic immunity and T-cell exhaustion. Here, we review the evidence showing that multiple epigenetic regulators silence the expression of endogenous antigens, and their loss induces viral mimicry responses bolstering the response of "cold" tumors to ICI in preclinical models. Similarly, a previously unappreciated role for epigenetic enzymes is emerging in the establishment and maintenance of stem-like T-cell populations that are critical mediators of response to ICI. Targeting the crossroads of epigenetics and immune checkpoint therapy has tremendous potential to improve antitumor immune responses and herald the next generation of sustained responses in immuno-oncology.

Implication of IL-7 receptor alpha chain expression by CD8+ T cells and its signature in defining biomarkers in aging

CD8+ T cells play an important role in host defense against infections and malignancies as well as contribute to the development of inflammatory disorders. Alterations in the frequency of naïve and memory CD8+ T cells are one of the most significant changes in the immune system with age. As the world population rapidly ages, a better understanding of aging immune function or immunosenescence could become a basis for discovering treatments of illnesses that commonly occur in older adults. In particular, biomarkers for immune aging could be utilized to identify individuals at high risk of developing age-associated conditions and help monitor the efficacy of therapeutic interventions targeting such conditions. This review details the possible role of CD8+ T cell subsets expressing different levels of the cytokine receptor IL-7 receptor alpha chain (IL-7Rα) and the gene signature associated with IL-7Rα as potential biomarkers for immune aging given the association of CD8+ T cells in host defense, inflammation, and immunosenescence.

Alterations in high-dimensional T-cell profile and gene signature of immune aging in HIV-infected older adults without viremia

Alterations in the components of the immune system occur with aging. The introduction of combination antiretroviral therapy (ART) has dramatically improved life expectancy in human immunodeficiency virus (HIV) infected individuals by suppressing viral replication and increasing CD4+ T-cell counts. Immunosenescence-like changes, including the expansion of memory CD8+ T cells with senescent features, are reported in young HIV-infected individuals who do not have clinically detectable viremia on ART. However, it is less known whether HIV infection affects the immunosenescent status in older HIV-infected individuals. Here, we addressed this question in older HIV-infected, HIV-uninfected, and frail individuals (all groups age ≥65 years) by examining a set of aging-associated genes in peripheral blood mononuclear cells (PBMCs) as well as by analyzing subsets of CD4+ and CD8+ T cells in depth using high-dimensional CyTOF analysis. Older HIV-infected individuals had increased expression of aging-associated genes such as CX3CR1 in PBMCs which are related to IL-7 receptor low effector memory (IL-7Rαlow EM) CD8+ T cells, a cell population known to expand with age. The subsets of IL-7Rαlow EM CD8+ T cells expressing senescent, cytotoxic, and inflammatory molecules, including CD57, perforin, and CX3CR1, as well as memory CD4+ T cells expressing CD161 and CXCR3, molecules associated with replication-competent HIV-1 harboring cells, were increased in older HIV-infected individuals. Overall, older HIV-infected individuals without detectable viremia on ART had augmented levels of age-associated immune alterations in PBMCs, suggesting that HIV infection has a persistent impact on senescence in older HIV-infected individuals despite the clinically controlled viremia.

Evaluation of CX3CR1 gene DNA methylation in developmental dysplasia of the hip (DDH)

INTRODUCTION AND OBJECTIVE

Developmental dysplasia of the hip (DDH) is a musculoskeletal disorder. Genetic and epigenetic changes in C-X3-C motif chemokine receptor 1 (CX3CR1) may lead to disturbance in chondrocyte development and change the labrum dimensions, which indirectly result in hip joint instability. Considering the important role of this gene in cell migration, cell adhesion and bone and cartilage development, we aimed to evaluate the CX3CR1 gene methylation in DDH pathogenesis.

METHODS

Our study comprised of forty-five DDH patients and forty-five healthy control subjects with healthy femoral neck cartilage. The healthy controls had total or hemiarthroplasty for the femoral neck fracture. Samples were collected from the femoral head (cartilage) of DDH patients and healthy controls. Genomic DNA was obtained from the samples, and DNA methylation of CX3CR1 gene was analyzed via metabisulfite method.

RESULTS

Methylation analysis reveals no significant differences in promoter of CX3CR1 gene in cartilage samples from DDH patients and healthy control subjects (P = 0.33).

CONCLUSION

Methylation status of CX3CR1 gene showed no significant difference between the patient and control groups. Our results indicate that DNA methylation may not modulate this gene in this disease and other epigenetic mechanisms such as non-coding RNAs and histone modifications could be implicated.

Enhancing anti-tumor efficacy and immune memory by combining 3p-GPC-3 siRNA treatment with PD-1 blockade in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is associated with a high mortality rate and presents a major challenge for human health. Activation of multiple oncogenes has been reported to be strongly associated with the progression of HCC. Moreover, the immunosuppressive tumor microenvironment (TME) and the host immune system are also implicated in the development of malignant HCC tumors. Glypican-3 (GPC-3), a proteoglycan involved in the regulation of cell proliferation and apoptosis, is aberrantly expressed in HCC. We synthesized a short 5'-triphosphate (3p) RNA targeting GPC-3, 3p-GPC-3 siRNA, and found that it effectively inhibited subcutaneous HCC growth by raising type I IFN levels in tumor cells and serum and promoting tumor cell apoptosis. Moreover, 3p-GPC-3 siRNA was able to enhance the activation of CD4⁺ T cells, CD8⁺ T cells, and natural killer (NK) cells while reducing the proportion of regulatory T cells (Tregs) in the TME. Most intriguingly, a blocking anti-PD-1 antibody improved the anti-tumor effect of 3p-GPC-3 siRNA, predominantly by activating the immune response, reversing immune exhaustion, and improving immune memory. Our study suggests that the combination of 3p-GPC-3 siRNA administration and PD-1 blockade may represent a promising therapeutic strategy for HCC.

DNA Methylation and Immune Memory Response

The generation of memory is a cardinal feature of the adaptive immune response, involving different factors in a complex process of cellular differentiation. This process is essential for protecting the second encounter with pathogens and is the mechanism by which vaccines work. Epigenetic changes play important roles in the regulation of cell differentiation events. There are three types of epigenetic regulation: DNA methylation, histone modification, and microRNA expression. One of these epigenetic changes, DNA methylation, occurs in cytosine residues, mainly in CpG dinucleotides. This brief review aimed to analyse the literature to verify the involvement of DNA methylation during memory T and B cell development. Several studies have highlighted the importance of the DNA methyltransferases, enzymes that catalyse the methylation of DNA, during memory differentiation, maintenance, and function. The methylation profile within different subsets of naïve activated and memory cells could be an interesting tool to help monitor immune memory response.

Epigenetic strategies to boost CAR T cell therapy

Chimeric antigen receptor (CAR) T cell therapy has led to a paradigm shift in cancer immunotherapy, but still several obstacles limit CAR T cell efficacy in cancers. Advances in high-throughput technologies revealed new insights into the role that epigenetic reprogramming plays in T cells. Mechanistic studies as well as comprehensive epigenome maps revealed an important role for epigenetic remodeling in T cell differentiation. These modifications shape the overall immune response through alterations in T cell phenotype and function. Here, we outline how epigenetic modifications in CAR T cells can overcome barriers limiting CAR T cell effectiveness, particularly in immunosuppressive tumor microenvironments. We also offer our perspective on how selected epigenetic modifications can boost CAR T cells to ultimately improve the efficacy of CAR T cell therapy.

Effector Memory CD8+ and CD4+ T Cell Immunity Associated with Metabolic Syndrome in Obese Children

PURPOSE

We investigated the association of effector memory (EM) CD8⁺ T cell and CD4⁺ T cell immunity with metabolic syndrome (MS).

METHODS

Surface and intracellular staining of peripheral blood mononuclear cells was performed. Anti-interleukin-7 receptor-alpha (IL-7Rα) and CX3CR1 antibodies were used to stain the subsets of EM CD8⁺ T cells, while anti-interferon-gamma (IFN-γ), interleukin-17 (IL-17), and forkhead box P3 (FOXP3) antibodies were used for CD4⁺ T cell subsets.

RESULTS

Of the 47 obese children, 11 were female. Children with MS had significantly higher levels of serum insulin (34.8±13.8 vs. 16.4±6.3 μU/mL, p<0.001) and homeostasis model assessment of insulin resistance (8.9±4.1 vs. 3.9±1.5, p<0.001) than children without MS. Children with MS revealed significantly higher frequencies of IL-7Rα^low CD8⁺ T cells (60.1 ±19.1% vs. 48.4±11.5%, p=0.047) and IL-7Rα^lowCX3CR1⁺ CD8⁺ T cells (53.8±20.1% vs. 41.5 ±11.9%, p=0.036) than children without MS. As the serum triglyceride levels increased, the frequency of IL-7Rα^lowCX3CR1⁺ and IL-7Rα^highCX3CR1^- CD8⁺ T cells increased and decreased, respectively (r=0.335, p=0.014 and r=-0.350, p=0.010, respectively), in 47 children. However, no CD4⁺ T cell subset parameters were significantly different between children with and without MS.

CONCLUSION

In obese children with MS, the changes in immunity due to changes in EM CD8⁺ T cells might be related to the morbidity of obesity.

Yin and yang of immunological memory in controlling infections: Overriding self defence mechanisms

Immunological memory is critical for host immunity and decisive for individual to respond exponentially to previously encountered infection. Both T and B cell memory are known to orchestrate immunological memory with their central and effector memory arms contributing in prolonged immunity/defence mechanisms of host. While central memory helps in maintaining prolonged immunity for a particular infection, effector memory helps in keeping local/seasonal infection in control. In addition to this, generation of long-lived plasma cells is pivotal for generating neutralizing antibodies which can enhance recall and B cell memory to control re-infection. In view of this, scaling up memory response is one of the major objectives for the expected outcome of vaccination. In this line, this review deals with the significance of memory cells, molecular pathways of their development, maintenance, epigenetic regulation and negative regulation in various infections. We have also highlighted the significance of both T and B cell memory responses in the vaccination approaches against range of infections which is not fully explored so far.[Box: see text].

PDTC ameliorates neuropathic pain by inhibiting microglial activation <em>via</em> blockage of the TNFα-CX3CR1 pathway

Previous studies have suggested that pyrrolidine dithiocarbamate (PDTC), a nuclear factor κB (NF-κB) inhibitor, play a role in deterring nerve injury-induced neuropathic pain (NP) The activation of NF-κB pathway may contribute to spinal microglial activation, CX3CR1 and tumor necrosis factor-alpha (TNF-a) up-regulation. The aim of this study was to clarify whether PDTC could inhibit the development of neuropathic pain via decreasing TNF-a-induced CX3CR1 up-regulation. Sprague-Dawley rats were randomly divided into sham group and NP group. Rats in each group were treated with intrathecal infusion of PDTC (100 or 1000 pmol/d) or saline. The sciatic nerve chronic constriction injury (CCI) model was used to induce NP in rats. Mechanical stimuli and radiant heat were used to evaluate mechanical allodynia and thermal hyperalgesia. Spinal microglial marker OX42 and TNF-a were detected by immunohistochemistry. In vitro BV-2 microglia activation was induced by TNF-a incubation, and the levels of CX3CR1 were assessed by Western blot and reverse transcription-polymerase chain reaction. Pain behavior and immunohistochemistry results showed that intrathecal infusion of PDTC at 100 or 1000 pmol/d prevented the development of mechanical and thermal hyperalgesia, spinal microglial activation and TNF-a expression induced by sciatic nerve CCI in rats. In vitro experiment results showed that PDTC inhibited the TNF-a-induced CX3CR1 up-regulation in BV-2 microglial cells. In conclusion, intrathecal infusion of PDTC could attenuate the pain-related behaviors induced by sciatic nerve CCI through suppressing the spinal microglia activation and TNF-a up-regulation in rats. The NF-κB activation might be responsible for TNF-a-induced CX3CR1 up-regulation in microglia.

Deep immune profiling of MIS-C demonstrates marked but transient immune activation compared to adult and pediatric COVID-19

Pediatric COVID-19 following SARS-CoV-2 infection is associated with fewer hospitalizations and often milder disease than in adults. A subset of children, however, present with Multisystem Inflammatory Syndrome in Children (MIS-C) that can lead to vascular complications and shock, but rarely death. The immune features of MIS-C compared to pediatric COVID-19 or adult disease remain poorly understood. We analyzed peripheral blood immune responses in hospitalized SARS-CoV-2 infected pediatric patients (pediatric COVID-19) and patients with MIS-C. MIS-C patients had patterns of T cell-biased lymphopenia and T cell activation similar to severely ill adults, and all patients with MIS-C had SARS-CoV-2 spike-specific antibodies at admission. A distinct feature of MIS-C patients was robust activation of vascular patrolling CX3CR1+ CD8+ T cells that correlated with the use of vasoactive medication. Finally, whereas pediatric COVID-19 patients with acute respiratory distress syndrome (ARDS) had sustained immune activation, MIS-C patients displayed clinical improvement over time, concomitant with decreasing immune activation. Thus, non-MIS-C versus MIS-C SARS-CoV-2 associated illnesses are characterized by divergent immune signatures that are temporally distinct from one another and implicate CD8+ T cells in the clinical presentation and trajectory of MIS-C.

Deep Immune Profiling of MIS-C demonstrates marked but transient immune activation compared to adult and pediatric COVID-19

Pediatric COVID-19 following SARS-CoV-2 infection is associated with fewer hospitalizations and often milder disease than in adults. A subset of children, however, present with Multisystem Inflammatory Syndrome in Children (MIS-C) that can lead to vascular complications and shock, but rarely death. The immune features of MIS-C compared to pediatric COVID-19 or adult disease remain poorly understood. We analyzed peripheral blood immune responses in hospitalized SARS-CoV-2 infected pediatric patients (pediatric COVID-19) and patients with MIS-C. MIS-C patients had patterns of T cell-biased lymphopenia and T cell activation similar to severely ill adults, and all patients with MIS-C had SARS-CoV-2 spike-specific antibodies at admission. A distinct feature of MIS-C patients was robust activation of vascular patrolling CX3CR1+ CD8 T cells that correlated with use of vasoactive medication. Finally, whereas pediatric COVID-19 patients with acute respiratory distress syndrome (ARDS) had sustained immune activation, MIS-C patients displayed clinical improvement over time, concomitant with decreasing immune activation. Thus, non-MIS-C versus MIS-C SARS-CoV-2 associated illnesses are characterized by divergent immune signatures that are temporally distinct and implicate CD8 T cells in clinical presentation and trajectory of MIS-C.

Novel Strategies to Combat CMV-Related Cardiovascular Disease

Cytomegalovirus (CMV), a ubiquitous human pathogen that is never cleared from the host, has long been thought to be relatively innocuous in immunocompetent adults, but causes severe complications including blindness, end-organ disease, and death in newborns and in immuno-compromised individuals, such as organ transplant recipients and those suffering from AIDS. Yet even in persons with intact immunity, CMV infection is associated with profound stimulation of immune and inflammatory pathways. Carriers of CMV infection also have an elevated risk of developing cardiovascular complications. In this review, we define the proposed mechanisms of how CMV contributes to cardiovascular disease (CVD), describe current approaches to target CMV, and discuss how these strategies may or may not alleviate cardiovascular complications in those with CMV infection. In addition, we discuss the special situation of CMV coinfection in people with HIV infection receiving antiretroviral therapy, and describe how these 2 viral infections may interact to potentiate CVD in this especially vulnerable population.

IL-7 receptor alpha defines heterogeneity and signature of human effector memory CD8+ T cells in high dimensional analysis

The IL-7 receptor alpha chain (IL-7Rα or CD127) can be differentially expressed in memory CD8+ T cells. Here we investigated whether IL-7Rα could serve as a key molecule in defining a comprehensive landscape of heterogeneity in human effector memory (EM) CD8+ T cells using high-dimensional Cytometry by Time-Of-Flight (CyTOF) and single-cell RNA-seq (scRNA-seq). IL-7Rα had diverse, but organized, expressional relationship in EM CD8+ T cells with molecules related to cell function and gene regulation, which rendered an immune landscape defining heterogeneous cell subsets. The differential expression of these molecules likely has biological implications as we found in vivo signatures of transcription factors and homeostasis cytokine receptors, including T-bet and IL-7Rα. Our findings indicate the existence of heterogeneity in human EM CD8+ T cells as defined by distinct but organized expression patterns of multiple molecules in relationship to IL-7Rα and its possible biological significance in modulating downstream events.

CX3CL1 and IL-15 Promote CD8 T cell chemoattraction in HIV and in atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) remains an important cause of morbidity in the general population and risk for ASCVD is increased approximately 2-fold in persons living with HIV infection (PLWH). This risk is linked to elevated CD8 T cell counts that are abundant in atherosclerotic plaques and have been implicated in disease pathogenesis yet the mechanisms driving T cell recruitment to and activation within plaques are poorly defined. Here we investigated the role of CD8 T cells in atherosclerosis in a non-human primate model of HIV infection and in the HIV-uninfected elderly; we sought to identify factors that promote the activation, function, and recruitment to endothelium of CX3CR1+ CD8 T cells. We measured elevated expression of CX3CL1 and IL-15, and increased CD8 T cell numbers in the aortas of rhesus macaques infected with SIV or SHIV, and demonstrated similar findings in atherosclerotic vessels of HIV-uninfected humans. We found that recombinant TNF enhanced the production and release of CX3CL1 and bioactive IL-15 from aortic endothelial cells, but not from aortic smooth muscle cells. IL-15 in turn promoted CX3CR1 surface expression on and TNF synthesis by CD8 T cells, and IL-15-treated CD8 T cells exhibited enhanced CX3CL1-dependent chemoattraction toward endothelial cells in vitro. Finally, we show that CD8 T cells in human atherosclerotic plaques have an activated, resident phenotype consistent with in vivo IL-15 and CX3CL1 exposure. In this report, we define a novel model of CD8 T cell involvement in atherosclerosis whereby CX3CL1 and IL-15 operate in tandem within the vascular endothelium to promote infiltration by activated CX3CR1+ memory CD8 T cells that drive further endothelial activation via TNF. We propose that these interactions are prevalent in aging and in PLWH, populations where circulating activated CX3CR1+ CD8 T cell numbers are often expanded.

Inflammescent CX3CR1+CD57+CD8+ T cells are generated and expanded by IL-15

HIV infection is associated with an increase in the proportion of activated CD8+ memory T cells (Tmem) that express CX3CR1, but how these cells are generated and maintained in vivo is unclear. We demonstrate that increased CX3CR1 expression on CD8+ Tmem in people living with HIV (PLWH) is dependent on coinfection with human CMV, and CX3CR1+CD8+ Tmem are enriched for a putatively immunosenescent CD57+CD28- phenotype. The cytokine IL-15 promotes the phenotype, survival, and proliferation of CX3CR1+CD57+CD8+ Tmem in vitro, whereas T cell receptor stimulation leads to their death. IL-15-driven survival is dependent on STAT5 and Bcl-2 activity, and IL-15-induced proliferation requires STAT5 and mTORC1. Thus, we identify mechanistic pathways that could explain how "inflammescent" CX3CR1+CD57+ CD8+ Tmem dominate the overall memory T cell pool in CMV-seropositive PLWH and that support reevaluation of immune senescence as a nonproliferative dead end.

Inflammescent CX3CR1+CD57+CD8+ T cells are generated and expanded by IL-15

HIV infection is associated with an increase in the proportion of activated CD8+ memory T cells (Tmem) that express CX3CR1, but how these cells are generated and maintained in vivo is unclear. We demonstrate that increased CX3CR1 expression on CD8+ Tmem in people living with HIV (PLWH) is dependent on coinfection with human CMV, and CX3CR1+CD8+ Tmem are enriched for a putatively immunosenescent CD57+CD28- phenotype. The cytokine IL-15 promotes the phenotype, survival, and proliferation of CX3CR1+CD57+CD8+ Tmem in vitro, whereas T cell receptor stimulation leads to their death. IL-15-driven survival is dependent on STAT5 and Bcl-2 activity, and IL-15-induced proliferation requires STAT5 and mTORC1. Thus, we identify mechanistic pathways that could explain how "inflammescent" CX3CR1+CD57+ CD8+ Tmem dominate the overall memory T cell pool in CMV-seropositive PLWH and that support reevaluation of immune senescence as a nonproliferative dead end.

Anti-Pituitary and Anti-Hypothalamus Autoantibody Associations with Inflammation and Persistent Hypogonadotropic Hypogonadism in Men with Traumatic Brain Injury

Traumatic brain injury (TBI) and can lead to persistent hypogonadotropic hypogonadism (PHH) and poor outcomes. We hypothesized that autoimmune and inflammatory mechanisms contribute to PHH pathogenesis. Men with moderate-to-severe TBI (n = 143) were compared with healthy men (n = 39). The TBI group provided blood samples 1-12 months post-injury (n = 1225). TBI and healthy control (n = 39) samples were assayed for testosterone (T) and luteinizing hormone (LH) to adjudicate PHH status. TBI samples 1-6 months post-injury and control samples were assayed for immunoglobulin M (IgM)/immunoglobulin G (IgG) anti-pituitary autoantibodies (APA) and anti-hypothalamus autoantibodies (AHA). Tissue antigen specificity for APA and AHA was confirmed via immunohistochemistry (IHC). IgM and IgG autoantibodies for glial fibrillary acid protein (GFAP) (AGA) were evaluated to gauge APA and AHA production as a generalized autoimmune response to TBI and to evaluate the specificity of APA and AHA to PHH status. An inflammatory marker panel was used to assess relationships to autoantibody profiles and PHH status. Fifty-one men with TBI (36%) had PHH. An age-related decline in T levels by both TBI and PHH status were observed. Injured men had higher APA IgM, APA IgG, AHA IgM, AHA IgG, AGA IgM, and AGA IgG than controls (p < 0.0001 all comparisons). However, only APA IgM (p = 0.03) and AHA IgM (p = 0.03) levels were lower in the PHH than in the non-PHH group in multivariate analysis. There were no differences in IgG levels by PHH status. Multiple inflammatory markers were positively correlated with IgM autoantibody production. PHH was associated with higher soluble tumor-necrosis-factor receptors I/II, (sTNFRI, sTNFRII), regulated on activation, normal T-cell expressed and secreted (RANTES) and soluble interleukin-2-receptor-alpha (sIL-2Rα) levels. Higher IgM APA, and AHA, but not AGA, in the absence of PHH may suggest a beneficial or reparative role for neuroendocrine tissue-specific IgM autoantibody production against PHH development post-TBI.

CX3CL1 Signaling in the Tumor Microenvironment

CX3CL1 (Fractalkine) is a multifunctional inflammatory chemokine with a single receptor CX3CR1. The biological effects elicited by CX3CL1 on surrounding cells vary depending on a number of factors including its structure, the expression pattern of CX3CR1, and the cell type. For instance, the transmembrane form of CX3CL1 primarily serves as an adhesion molecule, but when cleaved to a soluble form, CX3CL1 predominantly functions as a chemotactic cytokine (Fig. 1.1). However, the biological functions of CX3CL1 also extend to immune cell survival and retention. The pro-inflammatory nature of CX3CR1-expressing immune cells place the CX3CL1:CX3CR1 axis as a central player in multiple inflammatory disorders and position this chemokine pathway as a potential therapeutic target. However, the emerging role of this chemokine pathway in the maintenance of effector memory cytotoxic T cell populations implicates it as a key chemokine in anti-viral and anti-tumor immunity, and therefore an unsuitable therapeutic target in inflammation. The reported role of CX3CL1 as a key regulator of cytotoxic T cell-mediated immunity is supported by several studies that demonstrate CX3CL1 as an important TIL-recruiting chemokine and a positive prognostic factor in colorectal, breast, and lung cancer. Such reports are conflicting with an overwhelming number of studies demonstrating a pro-tumorigenic and pro-metastatic role of CX3CL1 across multiple blood and solid malignancies.This chapter will review the unique structure, function, and biology of CX3CL1 and address the diversity of its biological effects in the immune system and the tumor microenvironment. Overall, this chapter highlights how we have just scratched the surface of CX3CL1's capabilities and suggests that further in-depth and mechanistic studies incorporating all CX3CL1 interactions must be performed to fully appreciate its role in cancer and its potential as a therapeutic target.

Epigenetic Regulation of T Cell Memory: Recalling Therapeutic Implications

Memory T cells possess functional differences from naïve T cells that powerfully contribute to the efficiency of secondary immune responses. These abilities are imprinted during the primary response, linked to the acquisition of novel patterns of gene expression. Underlying this are alterations at the chromatin level (epigenetic modifications) that regulate constitutive and inducible gene transcription. T cell epigenetic memory can persist long-term, contributing to long-lasting immunity after infection or vaccination. However, acquired epigenetic states can also hinder effective tumor immunity or contribute to autoimmunity. The growing understanding of epigenetic gene regulation as it relates to both the stability and malleability of T cell memory may offer the potential to selectively modify T cell memory in disease by targeting epigenetic mechanisms.

Transcriptomic analysis of human IL-7 receptor alpha low and high effector memory CD8+ T cells reveals an age-associated signature linked to influenza vaccine response in older adults

Here, we investigated the relationship of the age‐associated expansion of IL‐7 receptor alpha low (IL‐7Rα^low) effector memory (EM) CD8⁺ T cells with the global transcriptomic profile of peripheral blood cells in humans. We found 231 aging signature genes of IL‐7Rα^low EM CD8⁺ T cells that corresponded to 15% of the age‐associated genes (231/1,497) reported by a meta‐analysis study on human peripheral whole blood from approximately 15,000 individuals, having high correlation with chronological age. These aging signature genes were the target genes of several transcription factors including MYC, SATB1, and BATF, which also belonged to the 231 genes, supporting the upstream regulatory role of these transcription factors in altering the gene expression profile of peripheral blood cells with aging. We validated the differential expression of these transcription factors between IL‐7Rα^low and ^high EM CD8⁺ T cells as well as in peripheral blood mononuclear cells (PBMCs) of young and older adults. Finally, we found a significant association with influenza vaccine responses in older adults, suggesting the possible biological significance of the aging signature genes of IL‐7Rα^low EM CD8⁺ T cells. The results of our study support the relationship of the expansion of IL‐7Rα^low EM CD8⁺ T cells with the age‐associated changes in the gene expression profile of peripheral blood cells and its possible biological implications.

Therapeutic Cancer Vaccines-T Cell Responses and Epigenetic Modulation

There is great interest in developing efficient therapeutic cancer vaccines, as this type of therapy allows targeted killing of tumor cells as well as long-lasting immune protection. High levels of tumor-infiltrating CD8⁺ T cells are associated with better prognosis in many cancers, and it is expected that new generation vaccines will induce effective production of these cells. Epigenetic mechanisms can promote changes in host immune responses, as well as mediate immune evasion by cancer cells. Here, we focus on epigenetic modifications involved in both vaccine-adjuvant-generated T cell immunity and cancer immune escape mechanisms. We propose that vaccine-adjuvant systems may be utilized to induce beneficial epigenetic modifications and discuss how epigenetic interventions could improve vaccine-based therapies. Additionally, we speculate on how, given the unique nature of individual epigenetic landscapes, epigenetic mapping of cancer progression and specific subsequent immune responses, could be harnessed to tailor therapeutic vaccines to each patient.

Epigenetic control of CD8+ T cell differentiation

Upon stimulation, small numbers of naive CD8+ T cells proliferate and differentiate into a variety of memory and effector cell types. CD8+ T cells can persist for years and kill tumour cells and virally infected cells. The functional and phenotypic changes that occur during CD8+ T cell differentiation are well characterized, but the epigenetic states that underlie these changes are incompletely understood. Here, we review the epigenetic processes that direct CD8+ T cell differentiation and function. We focus on epigenetic modification of DNA and associated histones at genes and their regulatory elements. We also describe structural changes in chromatin organization that affect gene expression. Finally, we examine the translational potential of epigenetic interventions to improve CD8+ T cell function in individuals with chronic infections and cancer.

Differentially Expressed Potassium Channels Are Associated with Function of Human Effector Memory CD8+ T Cells

The voltage-gated potassium channel, Kv1.3, and the Ca²⁺-activated potassium channel, KCa3.1, regulate membrane potentials in T cells, thereby controlling T cell activation and cytokine production. However, little is known about the expression and function of potassium channels in human effector memory (EM) CD8⁺ T cells that can be further divided into functionally distinct subsets based on the expression of the interleukin (IL)-7 receptor alpha (IL-7Rα) chain. Herein, we investigated the functional expression and roles of Kv1.3 and KCa3.1 in EM CD8⁺ T cells that express high or low levels of the IL-7 receptor alpha chain (IL-7Rα^high and IL-7Rα^low, respectively). In contrast to the significant activity of Kv1.3 and KCa3.1 in IL-7Rα^high EM CD8⁺ T cells, IL-7Rα^low EM CD8⁺ T cells showed lower expression of Kv1.3 and insignificant expression of KCa3.1. Kv1.3 was involved in the modulation of cell proliferation and IL-2 production, whereas KCa3.1 affected the motility of EM CD8⁺ T cells. The lower motility of IL-7Rα^low EM CD8⁺ T cells was demonstrated using transendothelial migration and motility assays with intercellular adhesion molecule 1- and/or chemokine stromal cell-derived factor-1α-coated surfaces. Consistent with the lower migration property, IL-7Rα^low EM CD8⁺ T cells were found less frequently in human skin. Stimulating IL-7Rα^low EM CD8⁺ T cells with IL-2 or IL-15 increased their motility and recovery of KCa3.1 activity. Our findings demonstrate that Kv1.3 and KCa3.1 are differentially involved in the functions of EM CD8⁺ T cells. The weak expression of potassium channels in IL-7Rα^low EM CD8⁺ T cells can be revived by stimulation with IL-2 or IL-15, which restores the associated functions. This study suggests that IL-7Rα^high EM CD8⁺ T cells with functional potassium channels may serve as a reservoir for effector CD8⁺ T cells during peripheral inflammation.

Phenotypic characteristics of aged CD4+ CD28null T lymphocytes are determined by changes in the whole-genome DNA methylation pattern

Aging is associated with a progressive loss of the CD28 costimulatory molecule in CD4⁺ lymphocytes (CD28^null T cells), which is accompanied by the acquisition of new biological and functional properties that give rise to an impaired immune response. The regulatory mechanisms that govern the appearance and function of this cell subset during aging and in several associated inflammatory disorders remain controversial. Here, we present the whole‐genome DNA methylation and gene expression profiles of CD28^null T cells and its CD28⁺ counterpart. A comparative analysis revealed that 296 genes are differentially methylated between the two cell subsets. A total of 160 genes associated with cytotoxicity (e.g. GRZB,TYROBP, and RUNX3) and cytokine/chemokine signaling (e.g. CX3CR1,CD27, and IL‐1R) are demethylated in CD28^null T cells, while 136 de novo‐methylated genes matched defects in the TCR signaling pathway (e.g. ITK,TXK,CD3G, and LCK). TCR‐landscape analysis confirmed that CD28^null T cells have an oligo/monoclonal expansion over the polyclonal background of CD28⁺ T cells, but feature a Vβ family repertoire specific to each individual. We reported that CD28^null T cells show a preactivation state characterized by a higher level of expression of inflammasome‐related genes that leads to the release of IL‐1β when activated. Overall, our results demonstrate that CD28^null T cells have a unique DNA methylation landscape, which is associated with differences in gene expression, contributing to the functionality of these cells. Understanding these epigenetic regulatory mechanisms could suggest novel therapeutic strategies to prevent the accumulation and activation of these cells during aging.

Inflammatory Function of CX3CR1+ CD8+ T Cells in Treated HIV Infection Is Modulated by Platelet Interactions

Increases in inflammation, coagulation, and CD8⁺ T-cell numbers are associated with an elevated cardiovascular disease (CVD) risk in human immunodeficiency virus (HIV)-infected antiretroviral therapy (ART) recipients. Circulating memory CD8⁺ T cells that express the vascular endothelium-homing receptor CX3CR1 (fractalkine receptor) are enriched in HIV-infected ART recipients. Thrombin-activated receptor (PAR-1) expression is increased in HIV-infected ART recipients and is particularly elevated on CX3CR1⁺ CD8⁺ T cells, suggesting that these cells could interact with coagulation elements. Indeed, thrombin directly enhanced T-cell receptor-mediated interferon γ production by purified CD8⁺ T cells but was attenuated by thrombin-induced release of transforming growth factor β by platelets. We have therefore identified a population of circulating memory CD8⁺ T cells in HIV infection that may home to endothelium, can be activated by clot-forming elements, and are susceptible to platelet-mediated regulation. Complex interactions between inflammatory elements and coagulation at endothelial surfaces may play an important role in CVD risk in HIV-infected ART recipients.