Benefit delayed immunosenescence by regulating CD4+T cells: A promising therapeutic target for aging-related diseases.

CD4+T cells play a notable role in immune protection at different stages of life. During aging, the interaction between the body's internal and external environment and CD4+T cells results in a series of changes in the CD4+T cells pool making it involved in immunosenescence. Many studies have extensively examined the subsets and functionality of CD4+T cells within the immune system, highlighted their pivotal role in disease pathogenesis, progression, and therapeutic interventions. However, the underlying mechanism of CD4+T cells senescence and its intricate association with diseases remains to be elucidated and comprehensively understood. By summarizing the immunosenescent progress and network of CD4+T cell subsets, we reveal the crucial role of CD4+T cells in the occurrence and development of age-related diseases. Furthermore, we provide new insights and theoretical foundations for diseases targeting CD4+T cell subsets aging as a treatment focus, offering novel approaches for therapy, especially in infections, cancers, autoimmune diseases, and other diseases in the elderly.

Alloreactive memory CD4 T cells promote transplant rejection by engaging DCs to induce innate inflammation and CD8 T cell priming.

Alloreactive memory T cells have been implicated as central drivers of transplant rejection. Perplexingly, innate cytokines, such as IL-6, IL-1ß, and IL-12, are also associated with rejection of organ transplants. However, the pathways of innate immune activation in allogeneic transplantation are unclear. While the role of microbial and cell death products has been previously described, we identified alloreactive memory CD4 T cells as the primary triggers of innate inflammation. Memory CD4 T cells engaged MHC II-mismatched dendritic cells (DCs), leading to the production of innate inflammatory cytokines. This innate inflammation was independent of several pattern recognition receptors and was primarily driven by TNF superfamily ligands expressed by alloreactive memory CD4 T cells. Blocking of CD40L and TNFα resulted in dampened inflammation, and mice genetically deficient in these molecules exhibited prolonged survival of cardiac allografts. Furthermore, myeloid cell and CD8 T cell infiltration into cardiac transplants was compromised in both CD40L- and TNFα-deficient recipients. Strikingly, we found that priming of naive alloreactive CD8 T cells was dependent on licensing of DCs by memory CD4 T cells. This study unravels the key mechanisms by which alloreactive memory CD4 T cells contribute to destructive pathology and transplant rejection.

Identification of the differentially expressed activated memory CD4+ T-cells-related genes and ceRNAs in oral lichen planus.

Background: Oral lichen planus (OLP) is a common chronic oral mucosal disease with 1.4 % malignant transformation rate, and its etiology especially immune pathogenesis remains unclear. This study was aimed at investigating the immune cells related molecular underlying the pathophysiology of OLP through bioinformatics analysis. Methods: The dataset GSE52130 obtained from the Gene Expression Omnibus (GEO) database was conducted a comprehensive analysis in this study. The CIBERSORTx was used for investigating immune cells infiltration. The gene set enrichment analysis (GSEA) and gene ontology (GO) enrichment were performed for exploring the biological functions and gene annotation. The protein-protein interactions (PPI) were constructed by STRING database and visualized by Cytoscape software. The cytohubba plugin was utilized for screening hub genes. The receiver operating characteristic (ROC) was performed for evaluating diagnostic value of hub genes. The miRNAs, lncRNAs and drugs were respectively predicted by NetworkAnalyst, miRTarbase, ENCORI, and DGIdb database. Results: This study identified 595 differentially expressed genes (DEGs). The GSEA indicated keratinization, innate immune system and biological oxidation were involved in OLP. GO analysis showed extracellular matrix and keratinocyte were mainly enriched. And we found the activated memory CD4+ T cells were lowly infiltrated in OLP. We identified 101 activated memory CD4+ T-cells-related DEGs. Three hub genes (APP, IL1B, TF) were selected. APP and IL1B were significantly up-regulated, whereas TF was down-regulated in OLP. The three hub genes show high diagnostic value in OLP. Additionally, they were involved in MAPK signal, NF-kappaB signal and iron metabolism in OLP. What's more, NEAT1/XIST - miR - 15a - 5p/miR - 155-5p - APP/IL1B signal axis was focused in competing endogenous RNA (ceRNA) network. In addition, 35 drugs were predicted for OLP. Conclusion: Three activated memory CD4+ T-cells-related DEGs were identified by integrative analysis. It may provide novel insight into the pathogenesis of OLP and suggest potential therapeutic targets for OLP.

Analysis of T cell repertoires of CD45RO CD4 T cells in cohorts of patients with bullous pemphigoid: A pilot study.

Autoimmune diseases develop over years - starting from a subclinical phenotype to clinically manifest autoimmune disease. The factors that drive this transition are ill-defined. To predict the turning point towards clinical disease and to intervene in the progress of autoimmune-mediated dysfunction, the establishment of new biomarkers is needed. Especially CD4 T cells are crucially involved in autoimmunity: first, during the initiation phase, because they lose their tolerance towards self-peptides, and second, by the subsequent ongoing presentation of self-peptides during the active autoimmune disease. Accordingly, changes in the degree of diversity of T cell receptor (TCR) repertoires in autoimmunity have been reported. These findings led to the hypothesis that transition from pre-disease to autoimmune disease is associated with an increase of abnormally expanded T cell clones that occupy large portions of the TCR repertoire. In this pilot study, we asked whether the ratio and the diversity of the TCR repertoires of circulating memory (CD45RO) and naïve (CD45RA) CD4 T cells could serve as a predictive factor for the development of autoimmunity. To find out, we analyzed the TCRß repertoires of memory and naïve CD4 T cells in a small cohort of four gender- and age-matched elderly patients having the autoimmune blistering disease bullous pemphigoid or non-melanoma skin cancers. We found that the extent of clonal expansions in the TCRß repertoires from the circulating memory and naïve CD4 populations did not differ between the patient groups. This result shows that the diversity of TCR repertoires from peripheral CD4 T cells does not reflect the manifestation of the skin-associated autoimmune disease BP and does not qualify as a prognostic factor. We propose that longitudinal TCR repertoire analysis of younger patients might be more informative.

Identification of two potential immune-related biomarkers of Graves' disease based on integrated bioinformatics analyses.

BACKGROUND: Graves' disease (GD) is an autoimmune disease, the incidence of which is increasing yearly. GD requires long-life therapy. Therefore, the potential immune-related biomarkers of GD need to be studied. METHOD: In our study, differentially expressed genes (DEGs) were derived from the online Gene Expression Omnibus (GEO) microarray expression dataset GSE71956. Protein‒protein interaction (PPI) network analyses were used to identify hub genes, which were validated by qPCR. GSEA was used to screen potential pathways and related immune cells. Next, CIBERSORT analysis was used to further explore the immune subtype distribution pattern among hub genes. ROC curves were used to analyze the specificity and sensitivity of hub genes. RESULT: 44 DEGs were screened from the GEO dataset. Two hub genes, EEF1A1 and EIF4B, were obtained from the PPI network and validated by qPCR (p < 0.05). GSEA was conducted to identify potential pathways and immune cells related to these the two hub genes. Immune cell subtype analysis revealed that hub genes had extensive associations with many different types of immune cells, particularly resting memory CD4+ T cells. AUCs of ROC analysis were 0.687 and 0.733 for EEF1A1 and EIF4B, respectively. CONCLUSION: Our study revealed two hub genes, EEF1A1 and EIF4B, that are associated with resting memory CD4+ T cells and potential immune-related molecular biomarkers and therapeutic targets of GD.

Crohn's Disease Patients Uniquely Contain Inflammatory Responses to Flagellin in a CD4 Effector Memory Subset.

BACKGROUND: Specific microbial antigens stimulate production of antibodies indicative of the aberrant immune response in Crohn's disease (CD). We tested for T cell reactivity linkage to B cell responses and now report on the prevalence, functionality, and phenotypic differences of flagellin-specific T cells among CD patients, ulcerative colitis (UC) patients, and control subjects and association with clinical features and flagellin seropositivity within CD patients. METHODS: Sera from non-inflammatory bowel disease control subjects, CD patients, and UC patients were probed for antibody reactivity to gut bacterial recombinant flagellin antigens. Peripheral blood mononuclear cells were measured for flagellin antigen (CBir1, A4 Fla2, FlaX) or control (Candida albicans, and CytoStim) reactivity analyzed by flow cytometry for CD154 and cytokine expression on CD4+ T cells. Supernatants from post-flagellin-stimulated and unstimulated cells were used to measure effects on epithelial barrier function. RESULTS: CD patients had a significantly higher percentage of flagellin-specific CD154+ CD4+ cells that have an effector memory T helper 1 and T helper 17 phenotype compared with UC patients and healthy control subjects. There was a positive correlation between the frequency of flagellin-specific CD154+ CD4+ effector memory T cells and serum levels of anti-flagellin immunoglobulin G in the CD patients. In addition, A4 Fla2-reactive T cells from active CD patients produced cytokines that can decrease barrier function in a gut epithelium. CONCLUSIONS: These findings demonstrate a Crohn's-associated flagellin-reactive CD4 cell subset distinct from UC patients and control subjects. There is a link between these cells and flagellin seropositivity. This CD4 cell subset could reflect a particular endophenotype of CD, leading to novel insight into its pathology and treatment.

Crohn's disease patients display inflammatory cytokine responses to flagellin antigens in an expanded effector memory CD4 subset that is not seen in ulcerative colitis or non­inflammatory bowel disease control subjects. These cells correlate with levels of the specific cognate anti-flagellin antibodies.

LFA1 and ICAM1 are critical for fusion and spread of murine leukemia virus in vivo.

Murine leukemia virus (MLV)-presenting cells form stable intercellular contacts with target cells during infection of lymphoid tissue, indicating a role of cell-cell contacts in retrovirus dissemination. Whether host cell adhesion proteins are required for retrovirus spread in vivo remains unknown. Here, we demonstrate that the lymphocyte-function-associated-antigen-1 (LFA1) and its ligand intercellular-adhesion-molecule-1 (ICAM1) are important for cell-contact-dependent transmission of MLV between leukocytes. Infection experiments in LFA1- and ICAM1-deficient mice demonstrate a defect in MLV spread within lymph nodes. Co-culture of primary leukocytes reveals a specific requirement for ICAM1 on donor cells and LFA1 on target cells for cell-contact-dependent spread through trans- and cis-infection. Importantly, adoptive transfer experiments combined with a newly established MLV-fusion assay confirm that the directed LFA1-ICAM1 interaction is important for retrovirus fusion and transmission in vivo. Taken together, our data provide insights on how retroviruses exploit host proteins and the biology of cell-cell interactions for dissemination.

The Chemokine Receptor CCR5 Links Memory CD4+ T Cell Metabolism to T Cell Antigen Receptor Nanoclustering.

The inhibition of anabolic pathways, such as aerobic glycolysis, is a metabolic cornerstone of memory T cell differentiation and function. However, the signals that hamper these anabolic pathways are not completely known. Recent evidence pinpoints the chemokine receptor CCR5 as an important player in CD4+ T cell memory responses by regulating T cell antigen receptor (TCR) nanoclustering in an antigen-independent manner. This paper reports that CCR5 specifically restrains aerobic glycolysis in memory-like CD4+ T cells, but not in effector CD4+ T cells. CCR5-deficient memory CD4+ T cells thus show an abnormally high glycolytic/oxidative metabolism ratio. No CCR5-dependent change in glucose uptake nor in the expression of the main glucose transporters was detected in any of the examined cell types, although CCR5-deficient memory cells did show increased expression of the hexokinase 2 and pyruvate kinase M2 isoforms, plus the concomitant downregulation of Bcl-6, a transcriptional repressor of these key glycolytic enzymes. Further, the TCR nanoclustering defects observed in CCR5-deficient antigen-experienced CD4+ T cells were partially reversed by incubation with 2-deoxyglucose (2-DG), suggesting a link between inhibition of the glycolytic pathway and TCR nanoscopic organization. Indeed, the treatment of CCR5-deficient lymphoblasts with 2-DG enhanced IL-2 production after antigen re-stimulation. These results identify CCR5 as an important regulator of the metabolic fitness of memory CD4+ T cells, and reveal an unexpected link between T cell metabolism and TCR organization with potential influence on the response of memory T cells upon antigen re-encounter.

Age-Related Dynamics of Circulating Innate Lymphoid Cells in an African Population.

Innate lymphoid cell (ILC) lineages mirror those of CD4+ T helper cell subsets, producing type 1, 2 and 3 cytokines respectively. Studies in adult human populations have shown contributions of non-cytotoxic ILC to immune regulation or pathogenesis in a wide range of diseases and have prompted investigations of potential functional redundancy between ILC and T helper cell compartments in neonates and children. To investigate the potential for ILC to contribute to immune responses across the human lifespan, we examined the numbers and frequencies of peripheral blood ILC subsets in a cohort of Gambians aged between 5 and 73 years of age. ILC2 were the most abundant peripheral blood ILC subset in this Gambian cohort, while ILC1 were the rarest at all ages. Moreover, the frequency of ILC1s (as a proportion of all lymphocytes) was remarkably stable over the life course whereas ILC3 cell frequencies and absolute numbers declined steadily across the life course and ILC2 frequencies and absolute numbers declined from childhood until the age of approx. 30 years of age. Age-related reductions in ILC2 cell numbers appeared to be partially offset by increasing numbers of total and GATA3+ central memory (CD45RA-CCR7+) CD4+ T cells, although there was also a gradual decline in numbers of total and GATA3+ effector memory (CD45RA-CCR7-) CD4+ T cells. Despite reduced overall abundance of ILC2 cells, we observed a coincident increase in the proportion of CD117+ ILC2, indicating potential for age-related adaptation of these cells in childhood and early adulthood. While both CD117+ and CD117- ILC2 cells produced IL-13, these responses occurred predominantly within CD117- cells. Furthermore, comparison of ILC frequencies between aged-matched Gambian and UK young adults (25-29 years) revealed an overall higher proportion of ILC1 and ILC2, but not ILC3 in Gambians. Thus, these data indicate ongoing age-related changes in ILC2 cells throughout life, which retain the capacity to differentiate into potent type 2 cytokine producing cells, consistent with an ongoing role in immune modulation.

IRF1 association with tumor immune microenvironment and use as a diagnostic biomarker for colorectal cancer recurrence.

Colorectal cancer (CRC) is considered to be one of the most lethal cancer types globally, and its recurrence is a major treatment challenge. Identifying the factors involved when determining the risk of CRC recurrence is required to improve personalized therapy for patients with CRC. Based on the GSE39582 dataset, the present study demonstrated that a higher ratio of M1 macrophages and activated memory CD4+ T cells indicated a better recurrence-free survival (RFS) time for CRC, using CIBERSORT and Pearson's correlation analysis. Through weighted correlation network analysis (WGCNA), an immune-associated module was identified that was significantly positively correlated with the ratio of M1 macrophages and activated memory CD4+ T cells. In this module, using WGCNA and a protein-protein interaction network, interferon regulatory factor 1 (IRF1), chemokine ligand 5, ubiquitin/ISG15-conjugating enzyme E2 L6, guanylate binding protein 1 and interleukin 2 receptor subunit beta were identified as hub genes. Among these genes, univariate Cox and multivariate Cox analysis revealed that IRF1 may be a potential diagnostic biomarker for RFS in patients with CRC. This was further validated using The Cancer Genome Atlas data. Gene set enrichment analysis demonstrated that IRF1 influenced the genes and pathways that are associated with immune cell recruitment and activation. Additionally, the DNA methylation of cg27587780 and cg15375424 CpG sites in the IRF1 gene region was indicated to be negatively correlated with IRF1 mRNA expression and positively correlated with the recurrence of CRC. Collectively, the results of the present study demonstrated that IRF1 may be a potential diagnostic biomarker for RFS in patients with CRC.

MHC class II tetramer analyses in AE37-vaccinated prostate cancer patients reveal vaccine-specific polyfunctional and long-lasting CD4(+) T-cells.

Realizing the basis for generating long-lasting clinical responses in cancer patients after therapeutic vaccinations provides the means to further ameliorate clinical efficacy. Peptide cancer vaccines stimulating CD4(+) T helper cells are often promising for inducing immunological memory and persistent CD8(+) cytotoxic T cell responses. Recent reports from our clinical trial with the AE37 vaccine, which is a HER2 hybrid polypeptide, documented its efficacy to induce CD4(+) T cell immunity, which was associated with clinical improvements preferentially among HLA-DRB1*11(+) prostate cancer patients. Here, we performed in-depth investigation of the CD4(+) T cell response against the AE37 vaccine. We used the DR11/AE37 tetramer in combination with multicolor flow cytometry to identify and characterize AE37-specific CD4(+) T cells regarding memory and Tregs phenotype in HLA-DRB1*11(+) vaccinated patients. To verify vaccine-specific immunological memory in vivo, we also assessed AE37-specific CD4(+) T cells in defined CD4(+) memory subsets by cell sorting. Finally, vaccine-induced AE37-specific CD4(+) T cells were assessed regarding their functional profile. AE37-specific memory CD4(+) T cells could be detected in peptide-stimulated cultures from prostate cancer patients following vaccination even 4 y post-vaccination. The vast majority of vaccine-induced AE37-specific CD4(+) T cells exhibited a multifunctional, mostly Th1 cytokine signature, with the potential of granzyme B production. In contrast, we found relatively low frequencies of Tregs among AE37-specific CD4(+) T cells. This is the first report on the identification of vaccine-induced HER2-specific multifunctional long-lasting CD4(+) T cells in vaccinated prostate cancer patients.

BCG vaccination-induced long-lasting control of Mycobacterium tuberculosis correlates with the accumulation of a novel population of CD4⁺IL-17⁺TNF⁺IL-2⁺ T cells.

Mycobacterium bovis Bacille Calmette-Guerin (BCG) is the only vaccine in use to prevent Mycobacterium tuberculosis (Mtb) infection. Here we analyzed the protective efficacy of BCG against Mtb challenges 21 or 120 days after vaccination. Only after 120 days post-vaccination were mice able to efficiently induce early Mtb growth arrest and maintain long-lasting control of Mtb. This protection correlated with the accumulation of CD4(+) T cells expressing IL-17(+)TNF(+)IL-2(+). In contrast, mice challenged with Mtb 21 days after BCG vaccination exhibited only a mild and transient protection, associated with the accumulation of CD4(+) T cells that were mostly IFN-γ(+)TNF(+) and to a lesser extent IFN-γ(+)TNF(+)IL-2(+). These data suggest that the memory response generated by BCG vaccination is functionally distinct depending upon the temporal proximity to BCG vaccination. Understanding how these responses are generated and maintained is critical for the development of novel vaccination strategies against tuberculosis.

Targeting HIV latency: resting memory T cells, hematopoietic progenitor cells and future directions.

Current therapy for HIV effectively suppresses viral replication and prolongs life, but the infection persists due, at least in part, to latent infection of long-lived cells. One favored strategy toward a cure targets latent virus in resting memory CD4(+) T cells by stimulating viral production. However, the existence of an additional reservoir in bone marrow hematopoietic progenitor cells has been detected in some treated HIV-infected people. This review describes approaches investigators have used to reactivate latent proviral genomes in resting CD4(+) T cells and hematopoietic progenitor cells. In addition, the authors review approaches for clearance of these reservoirs along with other important topics related to HIV eradication.

OX40 and IL-7 play synergistic roles in the homeostatic proliferation of effector memory CD4⁺ T cells.

T-cell homeostasis preserves the numbers, the diversity and functional competence of different T-cell subsets that are required for adaptive immunity. Naïve CD4(+) T (TN ) cells are maintained in the periphery via the common γ-chain family cytokine IL-7 and weak antigenic signals. However, it is not clear how memory CD4(+) T-cell subsets are maintained in the periphery and which factors are responsible for the maintenance. To examine the homeostatic mechanisms, CFSE-labeled CD4(+) CD44(high) CD62L(low) effector memory T (TEM ) cells were transferred into sublethally-irradiated syngeneic C57BL/6 mice, and the systemic cell proliferative responses, which can be divided distinctively into fast and slow proliferations, were assessed by CFSE dye dilution. We found that the fast homeostatic proliferation of TEM cells was strictly regulated by both antigen and OX40 costimulatory signals and that the slow proliferation was dependent on IL-7. The simultaneous blockade of both OX40 and IL-7 signaling completely inhibited the both fast and slow proliferation. The antigen- and OX40-dependent fast proliferation preferentially expanded IL-17-producing helper T cells (Th17 cells). Thus, OX40 and IL-7 play synergistic, but distinct roles in the homeostatic proliferation of CD4(+) TEM cells.

HIV replication in conjunction with granzyme B production by CCR5+ memory CD4 T cells: Implications for bystander cell and tissue pathologies.

Granzyme B (GrzB) is expressed by activated T cells and mediates cellular apoptosis. GrzB also acts as an extracellular protease involved in tissue degradation. We hypothesized that GrzB production from activated memory CD4 T cells may be associated with HIV pathogenesis. We found that stimulated memory CD4 T cells (via costimulation, cytokines, and TLR ligands) concomitantly produced GrzB and HIV. Both GrzB and HIV expression were mainly restricted to CCR5-expressing memory CD4+CD45RO+ T cells, including Th1 and Th17 subsets. Activated memory CD4 T cells also mediated tissue damage, such as disruption of intestinal epithelial monolayers. In non-human primates, CD4 T cells of rhesus macaques (pathogenic SIV hosts) expressed higher GrzB compared to African green monkeys (non-pathogenic SIV hosts). These results suggest that GrzB from CCR5+ memory CD4 T cells may have a role in cellular and tissue pathologies during HIV infection.

Decreased memory T-cell response and function in human immunodeficiency virus-infected patients with tegumentary leishmaniasis

The effects of human immunodeficiency virus (HIV) on the immune response in patients with cutaneous leishmaniasis have not yet been fully delineated. This study quantified and evaluated the function of memory T-cell subsets in response to soluble Leishmania antigens (SLA) from patients coinfected with HIV and Leishmania with tegumentary leishmaniasis (TL). Eight TL/HIV coinfected subjects and 10 HIV seronegative subjects with TL were evaluated. The proliferative response of CD4+and CD8+T-cells and naïve, central memory (CM) and effector memory (EM) CD4+T-cells in response to SLA were quantified using flow cytometry. The median cell division indices for CD4+and CD8+T-cells of coinfected patients in response to SLA were significantly lower than those in patients with Leishmania monoinfection (p < 0.05). The proportions of CM and EM CD4+T-cells in response to SLA were similar between the coinfected patients and patients with Leishmania monoinfection. However, the median CM and EM CD4+T-cell counts from coinfected patients were significantly lower (p < 0.05). The reduction in the lymphoproliferative response to Leishmania antigens coincides with the decrease in the absolute numbers of both EM and CM CD4+T-cells in response to Leishmania antigens in patients coinfected with HIV/Leishmania.

Eradication of HIV and Cure of AIDS, Now and How?

Recent studies have highlighted the importance of eradication of human immunodeficiency virus (HIV) and cure of acquired immunodeficiency syndrome (AIDS). However, a pivotal point that the patient immunity controls HIV reactivation after highly active anti-retroviral therapy [HAART or combination anti-retroviral therapy (cART)] remains less well addressed. In spite of the fact that both innate and adaptive immunities are indispensable and numerous cells participate in the anti-HIV immunity, memory CD4 T-cells are indisputably the key cells organizing all immune actions against HIV while being the targets of HIV. Here we present a view and multidisciplinary approaches to HIV/AIDS eradication and cure. We aim at memory CD4 T-cells, utilizing the stem cell properties of these cells to reprogram an anti-HIV memory repertoire to eliminate the viral reservoir, toward achieving an AIDS-free world.