RESUMO
The intestinal microbiota plays a crucial role in influencing the development of host immunity, and in turn the immune system also acts to regulate the microbiota through intestinal barrier maintenance and immune exclusion. Normally, these interactions are homeostatic, tightly controlled, and organized by both innate and adaptive immune responses. However, a combination of environmental exposures and genetic defects can result in a break in tolerance and intestinal homeostasis. The outcomes of these interactions at the mucosal interface have broad, systemic effects on host immunity and the development of chronic inflammatory or autoimmune disease. The underlying mechanisms and pathways the microbiota can utilize to regulate these diseases are just starting to emerge. Here, we discuss the recent evidence in this area describing the impact of microbiota-immune interactions during inflammation and autoimmunity, with a focus on barrier function and CD4+ T cell regulation.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Diabetes Mellitus Tipo 1/microbiologia , Microbioma Gastrointestinal/imunologia , Inflamação/microbiologia , Doenças Inflamatórias Intestinais/microbiologia , Mucosa Intestinal/microbiologia , Animais , Autoimunidade , Diabetes Mellitus Tipo 1/imunologia , Homeostase , Humanos , Tolerância Imunológica , Imunomodulação , Inflamação/imunologia , Doenças Inflamatórias Intestinais/imunologia , Mucosa Intestinal/imunologiaRESUMO
While CD4+ T cell depletion is key to disease progression in people living with HIV and SIV-infected macaques, the mechanisms underlying this depletion remain incompletely understood, with most cell death involving uninfected cells. In contrast, SIV infection of "natural" hosts such as sooty mangabeys does not cause CD4+ depletion and AIDS despite high-level viremia. Here, we report that the CARD8 inflammasome is activated immediately after HIV entry by the viral protease encapsulated in incoming virions. Sensing of HIV protease activity by CARD8 leads to rapid pyroptosis of quiescent cells without productive infection, while T cell activation abolishes CARD8 function and increases permissiveness to infection. In humanized mice reconstituted with CARD8-deficient cells, CD4+ depletion is delayed despite high viremia. Finally, we discovered loss-of-function mutations in CARD8 from "natural hosts," which may explain the peculiarly non-pathogenic nature of these infections. Our study suggests that CARD8 drives CD4+ T cell depletion during pathogenic HIV/SIV infections.
Assuntos
Infecções por HIV , Inflamassomos , Síndrome de Imunodeficiência Adquirida dos Símios , Animais , Humanos , Camundongos , Proteínas Adaptadoras de Sinalização CARD/genética , Proteínas Adaptadoras de Sinalização CARD/metabolismo , Linfócitos T CD4-Positivos/metabolismo , Progressão da Doença , Infecções por HIV/patologia , Inflamassomos/metabolismo , Proteínas de Neoplasias/metabolismo , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Vírus da Imunodeficiência Símia/fisiologia , Viremia , HIV/fisiologiaRESUMO
The brain is a site of relative immune privilege. Although CD4 T cells have been reported in the central nervous system, their presence in the healthy brain remains controversial, and their function remains largely unknown. We used a combination of imaging, single cell, and surgical approaches to identify a CD69+ CD4 T cell population in both the mouse and human brain, distinct from circulating CD4 T cells. The brain-resident population was derived through in situ differentiation from activated circulatory cells and was shaped by self-antigen and the peripheral microbiome. Single-cell sequencing revealed that in the absence of murine CD4 T cells, resident microglia remained suspended between the fetal and adult states. This maturation defect resulted in excess immature neuronal synapses and behavioral abnormalities. These results illuminate a role for CD4 T cells in brain development and a potential interconnected dynamic between the evolution of the immunological and neurological systems. VIDEO ABSTRACT.
Assuntos
Encéfalo/citologia , Linfócitos T CD4-Positivos/metabolismo , Feto/citologia , Microglia/citologia , Microglia/metabolismo , Sinapses/metabolismo , Adulto , Animais , Antígenos CD/metabolismo , Antígenos de Diferenciação de Linfócitos T/metabolismo , Escala de Avaliação Comportamental , Células Sanguíneas/citologia , Células Sanguíneas/metabolismo , Encéfalo/embriologia , Encéfalo/metabolismo , Criança , Feminino , Feto/embriologia , Humanos , Lectinas Tipo C/metabolismo , Pulmão/citologia , Pulmão/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pessoa de Meia-Idade , Neurogênese/genética , Parabiose , Células Piramidais/metabolismo , Células Piramidais/fisiologia , Análise de Célula Única , Baço/citologia , Baço/metabolismo , Sinapses/imunologia , TranscriptomaRESUMO
Responses to anti-PD-1 immunotherapy occur but are infrequent in bladder cancer. The specific T cells that mediate tumor rejection are unknown. T cells from human bladder tumors and non-malignant tissue were assessed with single-cell RNA and paired T cell receptor (TCR) sequencing of 30,604 T cells from 7 patients. We find that the states and repertoires of CD8+ T cells are not distinct in tumors compared with non-malignant tissues. In contrast, single-cell analysis of CD4+ T cells demonstrates several tumor-specific states, including multiple distinct states of regulatory T cells. Surprisingly, we also find multiple cytotoxic CD4+ T cell states that are clonally expanded. These CD4+ T cells can kill autologous tumors in an MHC class II-dependent fashion and are suppressed by regulatory T cells. Further, a gene signature of cytotoxic CD4+ T cells in tumors predicts a clinical response in 244 metastatic bladder cancer patients treated with anti-PD-L1.
Assuntos
Linfócitos T CD4-Positivos/metabolismo , Neoplasias da Bexiga Urinária/genética , Neoplasias da Bexiga Urinária/metabolismo , Antígeno B7-H1/genética , Antígeno B7-H1/imunologia , Biomarcadores Farmacológicos/análise , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Regulação Neoplásica da Expressão Gênica/genética , Genes MHC da Classe II , Humanos , Inibidores de Checkpoint Imunológico/farmacologia , Imunoterapia , Linfócitos do Interstício Tumoral , Receptor de Morte Celular Programada 1/genética , Receptores de Antígenos de Linfócitos T/genética , Análise de Célula Única/métodos , Linfócitos T Reguladores , Neoplasias da Bexiga Urinária/imunologiaRESUMO
The contribution of CD4+ T cells to protective or pathogenic immune responses to SARS-CoV-2 infection remains unknown. Here, we present single-cell transcriptomic analysis of >100,000 viral antigen-reactive CD4+ T cells from 40 COVID-19 patients. In hospitalized patients compared to non-hospitalized patients, we found increased proportions of cytotoxic follicular helper cells and cytotoxic T helper (TH) cells (CD4-CTLs) responding to SARS-CoV-2 and reduced proportion of SARS-CoV-2-reactive regulatory T cells (TREG). Importantly, in hospitalized COVID-19 patients, a strong cytotoxic TFH response was observed early in the illness, which correlated negatively with antibody levels to SARS-CoV-2 spike protein. Polyfunctional TH1 and TH17 cell subsets were underrepresented in the repertoire of SARS-CoV-2-reactive CD4+ T cells compared to influenza-reactive CD4+ T cells. Together, our analyses provide insights into the gene expression patterns of SARS-CoV-2-reactive CD4+ T cells in distinct disease severities.
Assuntos
COVID-19/imunologia , SARS-CoV-2/genética , Células T Auxiliares Foliculares/imunologia , Linfócitos T Citotóxicos/imunologia , Linfócitos T Reguladores/imunologia , Transcriptoma , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Antivirais/sangue , Anticorpos Antivirais/imunologia , Contagem de Linfócito CD4 , COVID-19/epidemiologia , COVID-19/virologia , Estudos de Coortes , Inglaterra/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Índice de Gravidade de Doença , Análise de Célula Única/métodos , Glicoproteína da Espícula de Coronavírus/imunologiaRESUMO
Adaptive immunity provides life-long protection by generating central and effector memory T cells and the most recently described tissue resident memory T (TRM) cells. However, the cellular origin of CD4 TRM cells and their contribution to host defense remain elusive. Using IL-17A tracking-fate mouse models, we found that a significant fraction of lung CD4 TRM cells derive from IL-17A-producing effector (TH17) cells following immunization with heat-killed Klebsiella pneumonia (Kp). These exTH17 TRM cells are maintained in the lung by IL-7, produced by lymphatic endothelial cells. During a memory response, neither antibodies, γδ T cells, nor circulatory T cells are sufficient for the rapid host defense required to eliminate Kp. Conversely, using parabiosis and depletion studies, we demonstrated that exTH17 TRM cells play an important role in bacterial clearance. Thus, we delineate the origin and function of airway CD4 TRM cells during bacterial infection, offering novel strategies for targeted vaccine design.
Assuntos
Infecções por Klebsiella/imunologia , Células Th17/imunologia , Animais , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Toxina Diftérica/farmacologia , Modelos Animais de Doenças , Feminino , Memória Imunológica , Interleucina-17/genética , Interleucina-17/metabolismo , Infecções por Klebsiella/patologia , Klebsiella pneumoniae/imunologia , Klebsiella pneumoniae/patogenicidade , Pulmão/efeitos dos fármacos , Pulmão/metabolismo , Pulmão/microbiologia , Camundongos , Camundongos Endogâmicos C57BL , Células Th17/citologia , Células Th17/metabolismoRESUMO
Differentiation of proinflammatory CD4+ conventional T cells (Tconv) is critical for productive antitumor responses yet their elicitation remains poorly understood. We comprehensively characterized myeloid cells in tumor draining lymph nodes (tdLN) of mice and identified two subsets of conventional type-2 dendritic cells (cDC2) that traffic from tumor to tdLN and present tumor-derived antigens to CD4+ Tconv, but then fail to support antitumor CD4+ Tconv differentiation. Regulatory T cell (Treg) depletion enhanced their capacity to elicit strong CD4+ Tconv responses and ensuing antitumor protection. Analogous cDC2 populations were identified in patients, and as in mice, their abundance relative to Treg predicts protective ICOS+ PD-1lo CD4+ Tconv phenotypes and survival. Further, in melanoma patients with low Treg abundance, intratumoral cDC2 density alone correlates with abundant CD4+ Tconv and with responsiveness to anti-PD-1 therapy. Together, this highlights a pathway that restrains cDC2 and whose reversal enhances CD4+ Tconv abundance and controls tumor growth.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Células Dendríticas/imunologia , Animais , Antígenos de Neoplasias/imunologia , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/metabolismo , Diferenciação Celular , Linhagem Celular Tumoral , Citocinas/metabolismo , Células Dendríticas/citologia , Células Dendríticas/metabolismo , Toxina Diftérica/imunologia , Fatores de Transcrição Forkhead/metabolismo , Humanos , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Linfonodos/imunologia , Linfonodos/metabolismo , Ativação Linfocitária , Melanoma Experimental/imunologia , Melanoma Experimental/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Quimiocinas/metabolismo , Linfócitos T Reguladores/imunologia , Microambiente TumoralRESUMO
Tissue health is dictated by the capacity to respond to perturbations and then return to homeostasis. Mechanisms that initiate, maintain, and regulate immune responses in tissues are therefore essential. Adaptive immunity plays a key role in these responses, with memory and tissue residency being cardinal features. A corresponding role for innate cells is unknown. Here, we have identified a population of innate lymphocytes that we term tissue-resident memory-like natural killer (NKRM) cells. In response to murine cytomegalovirus infection, we show that circulating NK cells were recruited in a CX3CR1-dependent manner to the salivary glands where they formed NKRM cells, a long-lived, tissue-resident population that prevented autoimmunity via TRAIL-dependent elimination of CD4+ T cells. Thus, NK cells develop adaptive-like features, including long-term residency in non-lymphoid tissues, to modulate inflammation, restore immune equilibrium, and preserve tissue health. Modulating the functions of NKRM cells may provide additional strategies to treat inflammatory and autoimmune diseases.
Assuntos
Infecções por Citomegalovirus , Muromegalovirus , Humanos , Animais , Camundongos , Células Matadoras Naturais , Imunidade Adaptativa , Linfócitos T , Imunidade InataRESUMO
Commensal microbes induce cytokine-producing effector tissue-resident CD4+ T cells, but the function of these T cells in mucosal homeostasis is not well understood. Here, we report that commensal-specific intestinal Th17 cells possess an anti-inflammatory phenotype marked by expression of interleukin (IL)-10 and co-inhibitory receptors. The anti-inflammatory phenotype of gut-resident commensal-specific Th17 cells was driven by the transcription factor c-MAF. IL-10-producing commensal-specific Th17 cells were heterogeneous and derived from a TCF1+ gut-resident progenitor Th17 cell population. Th17 cells acquired IL-10 expression and anti-inflammatory phenotype in the small-intestinal lamina propria. IL-10 production by CD4+ T cells and IL-10 signaling in intestinal macrophages drove IL-10 expression by commensal-specific Th17 cells. Intestinal commensal-specific Th17 cells possessed immunoregulatory functions and curbed effector T cell activity in vitro and in vivo in an IL-10-dependent and c-MAF-dependent manner. Our results suggest that tissue-resident commensal-specific Th17 cells perform regulatory functions in mucosal homeostasis.
Assuntos
Microbioma Gastrointestinal , Células Th17 , Interleucina-10/metabolismo , Mucosa Intestinal/metabolismo , Anti-InflamatóriosRESUMO
Upon infection, HIV disseminates throughout the human body within 1-2 weeks. However, its early cellular targets remain poorly characterized. We used a single-cell approach to retrieve the phenotype and TCR sequence of infected cells in blood and lymphoid tissue from individuals at the earliest stages of HIV infection. HIV initially targeted a few proliferating memory CD4+ T cells displaying high surface expression of CCR5. The phenotype of productively infected cells differed by Fiebig stage and between blood and lymph nodes. The TCR repertoire of productively infected cells was heavily biased, with preferential infection of previously expanded and disseminated clones, but composed almost exclusively of unique clonotypes, indicating that they were the product of independent infection events. Latent genetically intact proviruses were already archived early in infection. Hence, productive infection is initially established in a pool of phenotypically and clonotypically distinct T cells, and latently infected cells are generated simultaneously.
Assuntos
Infecções por HIV , HIV-1 , Infecção Latente , Humanos , Linfócitos T CD4-Positivos/metabolismo , HIV-1/genética , Infecção Latente/metabolismo , Infecção Latente/patologia , Receptores de Antígenos de Linfócitos T/metabolismo , Latência ViralRESUMO
CD4+ T cell responses are exquisitely antigen specific and directed toward peptide epitopes displayed by human leukocyte antigen class II (HLA-II) on antigen-presenting cells. Underrepresentation of diverse alleles in ligand databases and an incomplete understanding of factors affecting antigen presentation in vivo have limited progress in defining principles of peptide immunogenicity. Here, we employed monoallelic immunopeptidomics to identify 358,024 HLA-II binders, with a particular focus on HLA-DQ and HLA-DP. We uncovered peptide-binding patterns across a spectrum of binding affinities and enrichment of structural antigen features. These aspects underpinned the development of context-aware predictor of T cell antigens (CAPTAn), a deep learning model that predicts peptide antigens based on their affinity to HLA-II and full sequence of their source proteins. CAPTAn was instrumental in discovering prevalent T cell epitopes from bacteria in the human microbiome and a pan-variant epitope from SARS-CoV-2. Together CAPTAn and associated datasets present a resource for antigen discovery and the unraveling genetic associations of HLA alleles with immunopathologies.
Assuntos
COVID-19 , Aprendizado Profundo , Humanos , Captana , SARS-CoV-2 , Antígenos HLA , Epitopos de Linfócito T , PeptídeosRESUMO
CD4+ T cell-mediated immunity against Streptococcus pneumoniae (pneumococcus) can protect against recurrent bacterial colonization and invasive pneumococcal diseases (IPDs). Although such immune responses are common, the pertinent antigens have remained elusive. We identified an immunodominant CD4+ T cell epitope derived from pneumolysin (Ply), a member of the bacterial cholesterol-dependent cytolysins (CDCs). This epitope was broadly immunogenic as a consequence of presentation by the pervasive human leukocyte antigen (HLA) allotypes DPB1∗02 and DPB1∗04 and recognition via architecturally diverse T cell receptors (TCRs). Moreover, the immunogenicity of Ply427-444 was underpinned by core residues in the conserved undecapeptide region (ECTGLAWEWWR), enabling cross-recognition of heterologous bacterial pathogens expressing CDCs. Molecular studies further showed that HLA-DP4-Ply427-441 was engaged similarly by private and public TCRs. Collectively, these findings reveal the mechanistic determinants of near-global immune focusing on a trans-phyla bacterial epitope, which could inform ancillary strategies to combat various life-threatening infectious diseases, including IPDs.
Assuntos
Linfócitos T CD4-Positivos , Citotoxinas , Humanos , Bactérias , Epitopos de Linfócito T , ColesterolRESUMO
Understanding how HIV-1-infected cells proliferate and persist is key to HIV-1 eradication, but the heterogeneity and rarity of HIV-1-infected cells hamper mechanistic interrogations. Here, we used single-cell DOGMA-seq to simultaneously capture transcription factor accessibility, transcriptome, surface proteins, HIV-1 DNA, and HIV-1 RNA in memory CD4+ T cells from six people living with HIV-1 during viremia and after suppressive antiretroviral therapy. We identified increased transcription factor accessibility in latent HIV-1-infected cells (RORC) and transcriptionally active HIV-1-infected cells (interferon regulatory transcription factor [IRF] and activator protein 1 [AP-1]). A proliferation program (IKZF3, IL21, BIRC5, and MKI67 co-expression) promoted the survival of transcriptionally active HIV-1-infected cells. Both latent and transcriptionally active HIV-1-infected cells had increased IKZF3 (Aiolos) expression. Distinct epigenetic programs drove the heterogeneous cellular states of HIV-1-infected cells: IRF:activation, Eomes:cytotoxic effector differentiation, AP-1:migration, and cell death. Our study revealed the single-cell epigenetic, transcriptional, and protein states of latent and transcriptionally active HIV-1-infected cells and cellular programs promoting HIV-1 persistence.
Assuntos
Infecções por HIV , HIV-1 , Humanos , Infecções por HIV/genética , HIV-1/fisiologia , Latência Viral/genética , Linfócitos T CD4-Positivos , Fator de Transcrição AP-1 , Epigênese Genética , Fator de Transcrição Ikaros/genéticaRESUMO
CD4+ T cell-derived interleukin 21 (IL-21) sustains CD8+ T cell responses during chronic viral infection, but the helper subset that confers this protection remains unclear. Here, we applied scRNA and ATAC-seq approaches to determine the heterogeneity of IL-21+CD4+ T cells during LCMV clone 13 infection. CD4+ T cells were comprised of three transcriptionally and epigenetically distinct populations: Cxcr6+ Th1 cells, Cxcr5+ Tfh cells, and a previously unrecognized Slamf6+ memory-like (Tml) subset. T cell differentiation was specifically redirected toward the Tml subset during chronic, but not acute, LCMV infection. Although this subset displayed an enhanced capacity to accumulate and some developmental plasticity, it remained largely quiescent, which may hinder its helper potential. Conversely, mixed bone marrow chimera experiments revealed that Tfh cell-derived IL-21 was critical to sustain CD8+ T cell responses and viral control. Thus, strategies that bolster IL-21+Tfh cell responses may prove effective in enhancing CD8+ T cell-mediated immunity.
Assuntos
Células T Auxiliares Foliculares , Viroses , Linfócitos T CD8-Positivos , Humanos , InterleucinasRESUMO
Interleukin (IL)-22 is central to immune defense at barrier sites. We examined the contributions of innate lymphoid cell (ILC) and T cell-derived IL-22 during Citrobacter rodentium (C.r) infection using mice that both report Il22 expression and allow lineage-specific deletion. ILC-derived IL-22 activated STAT3 in C.r-colonized surface intestinal epithelial cells (IECs) but only temporally restrained bacterial growth. T cell-derived IL-22 induced a more robust and extensive activation of STAT3 in IECs, including IECs lining colonic crypts, and T cell-specific deficiency of IL-22 led to pathogen invasion of the crypts and increased mortality. This reflected a requirement for T cell-derived IL-22 for the expression of a host-protective transcriptomic program that included AMPs, neutrophil-recruiting chemokines, and mucin-related molecules, and it restricted IFNγ-induced proinflammatory genes. Our findings demonstrate spatiotemporal differences in the production and action of IL-22 by ILCs and T cells during infection and reveal an indispensable role for IL-22-producing T cells in the protection of the intestinal crypts.
Assuntos
Citrobacter rodentium , Infecções por Enterobacteriaceae , Animais , Antibacterianos , Imunidade Inata , Interleucinas/metabolismo , Mucosa Intestinal , Linfócitos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Linfócitos T/metabolismo , Interleucina 22RESUMO
Antigenic stimulation promotes T cell metabolic reprogramming to meet increased biosynthetic, bioenergetic, and signaling demands. We show that the one-carbon (1C) metabolism enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) regulates de novo purine synthesis and signaling in activated T cells to promote proliferation and inflammatory cytokine production. In pathogenic T helper-17 (Th17) cells, MTHFD2 prevented aberrant upregulation of the transcription factor FoxP3 along with inappropriate gain of suppressive capacity. MTHFD2 deficiency also promoted regulatory T (Treg) cell differentiation. Mechanistically, MTHFD2 inhibition led to depletion of purine pools, accumulation of purine biosynthetic intermediates, and decreased nutrient sensor mTORC1 signaling. MTHFD2 was also critical to regulate DNA and histone methylation in Th17 cells. Importantly, MTHFD2 deficiency reduced disease severity in multiple in vivo inflammatory disease models. MTHFD2 is thus a metabolic checkpoint to integrate purine metabolism with pathogenic effector cell signaling and is a potential therapeutic target within 1C metabolism pathways.
Assuntos
Inflamação/imunologia , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Metilenotetra-Hidrofolato Desidrogenase (NADP)/metabolismo , Purinas/biossíntese , Linfócitos T Reguladores/imunologia , Células Th17/imunologia , Animais , Diferenciação Celular , Citocinas/metabolismo , Metilação de DNA , Modelos Animais de Doenças , Humanos , Mediadores da Inflamação/metabolismo , Ativação Linfocitária , Metilenotetra-Hidrofolato Desidrogenase (NADP)/genética , Camundongos , Camundongos Transgênicos , Mutação/genética , Transdução de SinaisRESUMO
Soon after activation, CD4+ T cells are segregated into BCL6+ follicular helper (Tfh) and BCL6- effector (Teff) T cells. Here, we explored how these subsets are maintained during chronic antigen stimulation using the mouse chronic LCMV infection model. Using single cell-transcriptomic and epigenomic analyses, we identified a population of PD-1+ TCF-1+ CD4+ T cells with memory-like features. TCR clonal tracing and adoptive transfer experiments demonstrated that these cells have self-renewal capacity and continue to give rise to both Teff and Tfh cells, thus functioning as progenitor cells. Conditional deletion experiments showed Bcl6-dependent development of these progenitors, which were essential for sustaining antigen-specific CD4+ T cell responses to chronic infection. An analogous CD4+ T cell population developed in draining lymph nodes in response to tumors. Our study reveals the heterogeneity and plasticity of CD4+ T cells during persistent antigen exposure and highlights their population dynamics through a stable, bipotent intermediate state.
Assuntos
Antígenos , Linfócitos T Auxiliares-Indutores , Transferência Adotiva , Animais , Diferenciação Celular , Camundongos , Proteínas Proto-Oncogênicas c-bcl-6/genética , Células-TroncoRESUMO
As the establishment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell memory in children remains largely unexplored, we recruited convalescent COVID-19 children and adults to define their circulating memory SARS-CoV-2-specific CD4+ and CD8+ T cells prior to vaccination. We analyzed epitope-specific T cells directly ex vivo using seven HLA class I and class II tetramers presenting SARS-CoV-2 epitopes, together with Spike-specific B cells. Unvaccinated children who seroconverted had comparable Spike-specific but lower ORF1a- and N-specific memory T cell responses compared with adults. This agreed with our TCR sequencing data showing reduced clonal expansion in children. A strong stem cell memory phenotype and common T cell receptor motifs were detected within tetramer-specific T cells in seroconverted children. Conversely, children who did not seroconvert had tetramer-specific T cells of predominantly naive phenotypes and diverse TCRαß repertoires. Our study demonstrates the generation of SARS-CoV-2-specific T cell memory with common TCRαß motifs in unvaccinated seroconverted children after their first virus encounter.
Assuntos
COVID-19 , SARS-CoV-2 , Linfócitos T CD4-Positivos , Linfócitos T CD8-Positivos , Epitopos de Linfócito T , Humanos , Memória Imunológica , Receptores de Antígenos de Linfócitos T , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Glicoproteína da Espícula de CoronavírusRESUMO
SARS-CoV-2 infection and vaccination generates enormous host-response heterogeneity and an age-dependent loss of immune-response quality. How the pre-exposure T cell repertoire contributes to this heterogeneity is poorly understood. We combined analysis of SARS-CoV-2-specific CD4+ T cells pre- and post-vaccination with longitudinal T cell receptor tracking. We identified strong pre-exposure T cell variability that correlated with subsequent immune-response quality and age. High-quality responses, defined by strong expansion of high-avidity spike-specific T cells, high interleukin-21 production, and specific immunoglobulin G, depended on an intact naive repertoire and exclusion of pre-existing memory T cells. In the elderly, T cell expansion from both compartments was severely compromised. Our results reveal that an intrinsic defect of the CD4+ T cell repertoire causes the age-dependent decline of immune-response quality against SARS-CoV-2 and highlight the need for alternative strategies to induce high-quality T cell responses against newly arising pathogens in the elderly.
Assuntos
COVID-19 , SARS-CoV-2 , Idoso , Anticorpos Antivirais , Humanos , Imunidade , Imunoglobulina G , Receptores de Antígenos de Linfócitos T , VacinaçãoRESUMO
Aging is associated with DNA accumulation and increased homeostatic proliferation of circulating T cells. Although these attributes are associated with aging-related autoimmunity, their direct contributions remain unclear. Conventionally, KU complex, the regulatory subunit of DNA-dependent protein kinase (DNA-PK), together with the catalytic subunit of DNA-PK (DNA-PKcs), mediates DNA damage repair in the nucleus. Here, we found KU complex abundantly expressed in the cytoplasm, where it recognized accumulated cytoplasmic DNA in aged human and mouse CD4+ T cells. This process enhanced T cell activation and pathology of experimental autoimmune encephalomyelitis (EAE) in aged mice. Mechanistically, KU-mediated DNA sensing facilitated DNA-PKcs recruitment and phosphorylation of the kinase ZAK. This activated AKT and mTOR pathways, promoting CD4+ T cell proliferation and activation. We developed a specific ZAK inhibitor, which dampened EAE pathology in aged mice. Overall, these findings demonstrate a KU-mediated cytoplasmic DNA-sensing pathway in CD4+ T cells that potentiates aging-related autoimmunity.