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1.
Mol Cell ; 75(6): 1229-1242.e5, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31377117

RESUMO

Interferon gamma (IFN-γ), critical for host defense and tumor surveillance, requires tight control of its expression. Multiple cis-regulatory elements exist around Ifng along with a non-coding transcript, Ifng-as1 (also termed NeST). Here, we describe two genetic models generated to dissect the molecular functions of this locus and its RNA product. DNA deletion within the Ifng-as1 locus disrupted chromatin organization of the extended Ifng locus, impaired Ifng response, and compromised host defense. Insertion of a polyA signal ablated the Ifng-as1 full-length transcript and impaired host defense, while allowing proper chromatin structure. Transient knockdown of Ifng-as1 also reduced IFN-γ production. In humans, discordant expression of IFNG and IFNG-AS1 was evident in memory T cells, with high expression of this long non-coding RNA (lncRNA) and low expression of the cytokine. These results establish Ifng-as1 as an important regulator of Ifng expression, as a DNA element and transcribed RNA, involved in dynamic and cell state-specific responses to infection.

2.
Bull Math Biol ; 81(7): 2553-2568, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31165405

RESUMO

A major question in immunology is what role antigen load plays in determining the size of the CD8 immune response. Is the amount of antigen important during recruitment, proliferation, and/or memory formation? Animal studies have shown that antigen is only strictly required early during activation of T cells, but the importance of antigen at later timepoints is unclear. Using data from 24 volunteers infected with the yellow fever vaccine virus (YFV), we analyzed the dependence of T cell proliferation upon viral load. We found that volunteers with high viral load initially have greater T cell responses, but by 28 days post-vaccination those with lower viral load are able to 'catch-up.' Using differential equation modeling we show that this pattern is consistent with viral load only affecting recruitment (i.e., programmed proliferation) as opposed to affecting recruitment and proliferation (i.e., antigen-dependent proliferation). A quantitative understanding of the dependence of T cell dynamics on antigen load will be of use to modelers studying not only vaccination, but also cancer immunology and autoimmune disorders.

3.
Clin Infect Dis ; 69(2): 348-351, 2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-30668661

RESUMO

An immunocompetent adult received corticosteroids for chest pain, which later was clinically found to be herpes zoster (HZ). She developed severe disease and rapid viral dissemination that elicited an exceptionally strong varicella zoster virus-specific B-cell and CD8 T-cell response. Clinicians should consider atypical HZ presentation prior to corticosteroid administration.

4.
Nat Commun ; 10(1): 196, 2019 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-30643116

RESUMO

In response to viral infection, CD8+ T cells undergo expansion and differentiate into distinct classes of effector cells. After clearance of the virus, a small population of long-lived memory cells persists. Comprehensive studies have defined the protein-coding transcriptional changes associated with this process. Here we expand on this prior work by performing RNA-sequencing to identify changes in long noncoding RNA (lncRNA) expression in human and mouse CD8+ T cells responding to viral infection. We identify hundreds of unannotated lncRNAs and show that expression profiles of both known and novel lncRNAs are sufficient to define naive, effector, and memory CD8+ T cell subsets, implying that they may be involved in fate decisions during antigen-driven differentiation. Additionally, in comparing mouse and human lncRNA expression, we find that lncRNAs with conserved sequence undergo similar changes in expression in the two species, suggesting an evolutionarily conserved role for lncRNAs during CD8+ T cell differentiation.


Assuntos
Linfócitos T CD8-Positivos/imunologia , Diferenciação Celular/genética , Coriomeningite Linfocítica/imunologia , RNA Longo não Codificante/metabolismo , Subpopulações de Linfócitos T/imunologia , Animais , Linfócitos T CD8-Positivos/metabolismo , Diferenciação Celular/imunologia , Sequência Conservada/genética , Sequência Conservada/imunologia , Conjuntos de Dados como Assunto , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Humanos , Memória Imunológica/genética , Ativação Linfocitária/genética , Coriomeningite Linfocítica/virologia , Vírus da Coriomeningite Linfocítica/imunologia , Camundongos , Camundongos Endogâmicos C57BL , RNA Longo não Codificante/imunologia , RNA Longo não Codificante/isolamento & purificação , Análise de Sequência de RNA , Sintenia/imunologia , Subpopulações de Linfócitos T/metabolismo , Transcriptoma/imunologia
5.
Cell Rep ; 25(8): 2148-2162.e5, 2018 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-30463012

RESUMO

Induction of protective vaccine responses, governed by the successful generation of antigen-specific antibodies and long-lived memory T cells, is increasingly impaired with age. Regulation of the T cell proteome by a dynamic network of microRNAs is crucial to T cell responses. Here, we show that activation-induced upregulation of miR-21 biases the transcriptome of differentiating T cells away from memory T cells and toward inflammatory effector T cells. Such a transcriptome bias is also characteristic of T cell responses in older individuals who have increased miR-21 expression and is reversed by antagonizing miR-21. miR-21 targets negative feedback circuits in several signaling pathways. The concerted, sustained activity of these signaling pathways in miR-21high T cells disfavors the induction of transcription factor networks involved in memory cell differentiation. Our data suggest that curbing miR-21 upregulation or activity in older individuals may improve their ability to mount effective vaccine responses.

6.
J Clin Invest ; 128(7): 2763-2773, 2018 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-29781814

RESUMO

Vaccine responses vary by geographic location. We have previously described how HIV-associated inflammation leads to fibrosis of secondary lymph nodes (LNs) and T cell depletion. We hypothesized that other infections may cause LN inflammation and fibrosis, in a process similar to that seen in HIV infection, which may lead to T cell depletion and affect vaccine responses. We studied LNs of individuals from Kampala, Uganda, before and after yellow fever vaccination (YFV) and found fibrosis in LNs that was similar to that seen in HIV infection. We found blunted antibody responses to YFV that correlated to the amount of LN fibrosis and loss of T cells, including T follicular helper cells. These data suggest that LN fibrosis is not limited to HIV infection and may be associated with impaired immunologic responses to vaccines. This may have an impact on vaccine development, especially for infectious diseases prevalent in the developing world.

7.
Bull Math Biol ; 80(1): 46-63, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29110131

RESUMO

Does target cell depletion, innate immunity, or adaptive immunity play the dominant role in controlling primary acute viral infections? Why do some individuals have higher peak virus titers than others? Answering these questions is a basic problem in immunology and can be particularly difficult in humans due to limited data, heterogeneity in responses in different individuals, and limited ability for experimental manipulation. We address these questions for infections following vaccination with the live attenuated yellow fever virus (YFV-17D) by analyzing viral load data from 80 volunteers. Using a mixed effects modeling approach, we find that target cell depletion models do not fit the data as well as innate or adaptive immunity models. Examination of the fits of the innate and adaptive immunity models to the data allows us to select a minimal model that gives improved fits by widely used model selection criteria (AICc and BIC) and explains why it is hard to distinguish between the innate and adaptive immunity models. We then ask why some individuals have over 1000-fold higher virus titers than others and find that most of the variation arises from differences in the initial/maximum growth rate of the virus in different individuals.


Assuntos
Modelos Imunológicos , Vacina contra Febre Amarela/efeitos adversos , Febre Amarela/etiologia , Doença Aguda , Imunidade Adaptativa , Humanos , Imunidade Inata , Conceitos Matemáticos , Vacinação/efeitos adversos , Vacinas Atenuadas/efeitos adversos , Carga Viral , Febre Amarela/imunologia , Febre Amarela/virologia , Vírus da Febre Amarela/imunologia
8.
Nature ; 552(7685): 362-367, 2017 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-29236685

RESUMO

The differentiation of human memory CD8 T cells is not well understood. Here we address this issue using the live yellow fever virus (YFV) vaccine, which induces long-term immunity in humans. We used in vivo deuterium labelling to mark CD8 T cells that proliferated in response to the virus and then assessed cellular turnover and longevity by quantifying deuterium dilution kinetics in YFV-specific CD8 T cells using mass spectrometry. This longitudinal analysis showed that the memory pool originates from CD8 T cells that divided extensively during the first two weeks after infection and is maintained by quiescent cells that divide less than once every year (doubling time of over 450 days). Although these long-lived YFV-specific memory CD8 T cells did not express effector molecules, their epigenetic landscape resembled that of effector CD8 T cells. This open chromatin profile at effector genes was maintained in memory CD8 T cells isolated even a decade after vaccination, indicating that these cells retain an epigenetic fingerprint of their effector history and remain poised to respond rapidly upon re-exposure to the pathogen.


Assuntos
Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/imunologia , Diferenciação Celular/imunologia , Epigênese Genética , Memória Imunológica/imunologia , Vacina contra Febre Amarela/imunologia , Animais , Linfócitos T CD8-Positivos/metabolismo , Diferenciação Celular/genética , Proliferação de Células , Cromatina/genética , Cromatina/metabolismo , Metilação de DNA , Deutério , Perfilação da Expressão Gênica , Meia-Vida , Humanos , Memória Imunológica/genética , Contagem de Linfócitos , Camundongos , Técnica de Diluição de Radioisótopos , Transcrição Genética , Febre Amarela/imunologia , Febre Amarela/virologia , Vírus da Febre Amarela/imunologia
9.
J Infect Dis ; 215(12): 1862-1872, 2017 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-28863472

RESUMO

A nurse who acquired Lassa virus infection in Togo in the spring of 2016 was repatriated to the United States for care at Emory University Hospital. Serial sampling from this patient permitted the characterization of several aspects of the innate and cellular immune responses to Lassa virus. Although most of the immune responses correlated with the kinetics of viremia resolution, the CD8 T-cell response was of surprisingly high magnitude and prolonged duration, implying prolonged presentation of viral antigens. Indeed, long after viremia resolution, there was persistent viral RNA detected in the semen of the patient, accompanied by epididymitis, suggesting the male reproductive tract as 1 site of antigen persistence. Consistent with the magnitude of acute T-cell responses, the patient ultimately developed long-term, polyfunctional memory T-cell responses to Lassa virus.


Assuntos
Anticorpos Antivirais/sangue , Linfócitos T CD8-Positivos/imunologia , Imunidade Celular , Febre Lassa/imunologia , Vírus Lassa/imunologia , Vírus Lassa/isolamento & purificação , Adulto , Amidas/uso terapêutico , Antígenos Virais/imunologia , Antivirais/uso terapêutico , Ensaio de Imunoadsorção Enzimática , Humanos , Switching de Imunoglobulina/genética , Febre Lassa/sangue , Ativação Linfocitária , Masculino , Pirazinas/uso terapêutico , Ribavirina/uso terapêutico , Viremia/sangue
10.
Proc Natl Acad Sci U S A ; 114(19): 4993-4998, 2017 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-28446615

RESUMO

Exhausted T cells in chronic infections and cancer have sustained expression of the inhibitory receptor programmed cell death 1 (PD-1). Therapies that block the PD-1 pathway have shown promising clinical results in a significant number of advanced-stage cancer patients. Nonetheless, a better understanding of the immunological responses induced by PD-1 blockade in cancer patients is lacking. Identification of predictive biomarkers is a priority in the field, but whether peripheral blood analysis can provide biomarkers to monitor or predict patients' responses to treatment remains to be resolved. In this study, we analyzed longitudinal blood samples from advanced stage non-small cell lung cancer (NSCLC) patients (n = 29) receiving PD-1-targeted therapies. We detected an increase in Ki-67+ PD-1+ CD8 T cells following therapy in ∼70% of patients, and most responses were induced after the first or second treatment cycle. This T-cell activation was not indiscriminate because we observed only minimal effects on EBV-specific CD8 T cells, suggesting that responding cells may be tumor specific. These proliferating CD8 T cells had an effector-like phenotype (HLA-DR+, CD38+, Bcl-2lo), expressed costimulatory molecules (CD28, CD27, ICOS), and had high levels of PD-1 and coexpression of CTLA-4. We found that 70% of patients with disease progression had either a delayed or absent PD-1+ CD8 T-cell response, whereas 80% of patients with clinical benefit exhibited PD-1+ CD8 T-cell responses within 4 wk of treatment initiation. Our results suggest that peripheral blood analysis may provide valuable insights into NSCLC patients' responses to PD-1-targeted therapies.


Assuntos
Anticorpos Monoclonais Humanizados/administração & dosagem , Anticorpos Monoclonais/administração & dosagem , Linfócitos T CD8-Positivos/imunologia , Carcinoma Pulmonar de Células não Pequenas , Proliferação de Células/efeitos dos fármacos , Neoplasias Pulmonares , Ativação Linfocitária/efeitos dos fármacos , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Linfócitos T CD8-Positivos/patologia , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/imunologia , Carcinoma Pulmonar de Células não Pequenas/patologia , Feminino , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/imunologia , Neoplasias Pulmonares/patologia , Masculino , Nivolumabe
11.
Cancer Immunol Immunother ; 66(1): 45-50, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27771741

RESUMO

INTRODUCTION: The increased availability of immunotherapeutic agents for the treatment of a wide array of cancer in the general oncology practice setting will reveal rare and unique toxicities. MATERIALS AND METHODS: The mechanism of cardiac allograft rejection in the context of PD-1 antibody therapy was explored in a patient with cutaneous squamous cell cancer complicating long-standing cardiac allograft. Immune cell infiltrate in the myocardium and peripheral blood lymphocyte repertoire were assessed using myocardial biopsy and temporal analysis of peripheral blood samples. The efficacy of high-intensity immunosuppression to reverse graft rejection was explored. RESULTS: Endomyocardial biopsy showed acute moderate diffuse cellular rejection with a predominant population of CD3+, CD8+ and CD4+ infiltrating lymphocytes; peripheral blood circulating lymphocytes showed a high frequency of proliferating and activated CD8+ T cells expressing PD-1 compared to a normal control. There was no difference in the activation and proliferation of CD4+ T cells compared to a normal control. Cardiac function improved following high-intensity immunosuppression and patient survived for up to 7 months after discontinuation of nivolumab. CONCLUSIONS: Immune checkpoint inhibitors should be avoided in allograft recipients but high-intensity immunosuppression is effective to salvage allograft rejection induced by these agents.


Assuntos
Anticorpos Monoclonais/efeitos adversos , Carcinoma de Células Escamosas/tratamento farmacológico , Rejeição de Enxerto/induzido quimicamente , Transplante de Coração/efeitos adversos , Neoplasias/imunologia , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Neoplasias Cutâneas/tratamento farmacológico , Aloenxertos , Anticorpos Monoclonais/administração & dosagem , Carcinoma de Células Escamosas/imunologia , Rejeição de Enxerto/imunologia , Transplante de Coração/métodos , Humanos , Imunoterapia/efeitos adversos , Imunoterapia/métodos , Masculino , Pessoa de Meia-Idade , Nivolumabe , Receptor de Morte Celular Programada 1/imunologia , Neoplasias Cutâneas/imunologia , Imunologia de Transplantes
12.
J Virol ; 90(24): 11259-11278, 2016 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-27707928

RESUMO

Epidemiological studies suggest that India has the largest number of dengue virus infection cases worldwide. However, there is minimal information about the immunological responses in these patients. CD8 T cells are important in dengue, because they have been implicated in both protection and immunopathology. Here, we provide a detailed analysis of HLA-DR+ CD38+ and HLA-DR- CD38+ effector CD8 T cell subsets in dengue patients from India and Thailand. Both CD8 T cell subsets expanded and expressed markers indicative of antigen-driven proliferation, tissue homing, and cytotoxic effector functions, with the HLA-DR+ CD38+ subset being the most striking in these effector qualities. The breadth of the dengue-specific CD8 T cell response was diverse, with NS3-specific cells being the most dominant. Interestingly, only a small fraction of these activated effector CD8 T cells produced gamma interferon (IFN-γ) when stimulated with dengue virus peptide pools. Transcriptomics revealed downregulation of key molecules involved in T cell receptor (TCR) signaling. Consistent with this, the majority of these CD8 T cells remained IFN-γ unresponsive even after TCR-dependent polyclonal stimulation (anti-CD3 plus anti-CD28) but produced IFN-γ by TCR-independent polyclonal stimulation (phorbol 12-myristate 13-acetate [PMA] plus ionomycin). Thus, the vast majority of these proliferating, highly differentiated effector CD8 T cells probably acquire TCR refractoriness at the time the patient is experiencing febrile illness that leads to IFN-γ unresponsiveness. Our studies open novel avenues for understanding the mechanisms that fine-tune the balance between CD8 T cell-mediated protective versus pathological effects in dengue. IMPORTANCE: Dengue is becoming a global public health concern. Although CD8 T cells have been implicated both in protection and in the cytokine-mediated immunopathology of dengue, how the balance is maintained between these opposing functions remains unknown. We comprehensively characterized CD8 T cell subsets in dengue patients from India and Thailand and show that these cells expand massively and express phenotypes indicative of overwhelming antigenic stimulus and tissue homing/cytotoxic-effector functions but that a vast majority of them fail to produce IFN-γ in vitro Interestingly, the cells were fully capable of producing the cytokine when stimulated in a T cell receptor (TCR)-independent manner but failed to do so in TCR-dependent stimulation. These results, together with transcriptomics, revealed that the vast majority of these CD8 T cells from dengue patients become cytokine unresponsive due to TCR signaling insufficiencies. These observations open novel avenues for understanding the mechanisms that fine-tune the balance between CD8-mediated protective versus pathological effects.


Assuntos
Linfócitos T CD8-Positivos/imunologia , Citotoxicidade Imunológica , Vírus da Dengue/efeitos dos fármacos , Subpopulações de Linfócitos T/imunologia , Transcriptoma/imunologia , ADP-Ribosil Ciclase 1/genética , ADP-Ribosil Ciclase 1/imunologia , Adolescente , Anticorpos/farmacologia , Antígenos CD28/antagonistas & inibidores , Antígenos CD28/genética , Antígenos CD28/imunologia , Complexo CD3/genética , Complexo CD3/imunologia , Linfócitos T CD8-Positivos/efeitos dos fármacos , Linfócitos T CD8-Positivos/virologia , Proliferação de Células/efeitos dos fármacos , Criança , Pré-Escolar , Vírus da Dengue/genética , Vírus da Dengue/crescimento & desenvolvimento , Vírus da Dengue/metabolismo , Feminino , Regulação da Expressão Gênica , Antígenos HLA-DR/genética , Antígenos HLA-DR/imunologia , Humanos , Imunidade Celular , Índia , Lactente , Interferon gama/genética , Interferon gama/imunologia , Ionomicina/farmacologia , Masculino , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/imunologia , Cultura Primária de Células , RNA Helicases/genética , RNA Helicases/imunologia , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , Serina Endopeptidases/genética , Serina Endopeptidases/imunologia , Transdução de Sinais , Subpopulações de Linfócitos T/efeitos dos fármacos , Subpopulações de Linfócitos T/virologia , Acetato de Tetradecanoilforbol/farmacologia , Proteínas não Estruturais Virais/genética , Proteínas não Estruturais Virais/imunologia
13.
Proc Natl Acad Sci U S A ; 113(10): 2702-7, 2016 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-26908875

RESUMO

Significantly higher levels of plasma CXCL13 [chemokine (C-X-C motif) ligand 13] were associated with the generation of broadly neutralizing antibodies (bnAbs) against HIV in a large longitudinal cohort of HIV-infected individuals. Germinal centers (GCs) perform the remarkable task of optimizing B-cell Ab responses. GCs are required for almost all B-cell receptor affinity maturation and will be a critical parameter to monitor if HIV bnAbs are to be induced by vaccination. However, lymphoid tissue is rarely available from immunized humans, making the monitoring of GC activity by direct assessment of GC B cells and germinal center CD4(+) T follicular helper (GC Tfh) cells problematic. The CXCL13-CXCR5 [chemokine (C-X-C motif) receptor 5] chemokine axis plays a central role in organizing both B-cell follicles and GCs. Because GC Tfh cells can produce CXCL13, we explored the potential use of CXCL13 as a blood biomarker to indicate GC activity. In a series of studies, we found that plasma CXCL13 levels correlated with GC activity in draining lymph nodes of immunized mice, immunized macaques, and HIV-infected humans. Furthermore, plasma CXCL13 levels in immunized humans correlated with the magnitude of Ab responses and the frequency of ICOS(+) (inducible T-cell costimulator) Tfh-like cells in blood. Together, these findings support the potential use of CXCL13 as a plasma biomarker of GC activity in human vaccine trials and other clinical settings.


Assuntos
Biomarcadores/sangue , Quimiocina CXCL13/sangue , Quimiocina CXCL13/imunologia , Centro Germinativo/imunologia , Animais , Estudos de Coortes , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Infecções por HIV/sangue , Infecções por HIV/imunologia , Humanos , Linfonodos/imunologia , Macaca , Camundongos Endogâmicos C57BL , Vacinação
14.
Proc Natl Acad Sci U S A ; 112(15): 4719-24, 2015 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-25775592

RESUMO

Four Ebola patients received care at Emory University Hospital, presenting a unique opportunity to examine the cellular immune responses during acute Ebola virus infection. We found striking activation of both B and T cells in all four patients. Plasmablast frequencies were 10-50% of B cells, compared with less than 1% in healthy individuals. Many of these proliferating plasmablasts were IgG-positive, and this finding coincided with the presence of Ebola virus-specific IgG in the serum. Activated CD4 T cells ranged from 5 to 30%, compared with 1-2% in healthy controls. The most pronounced responses were seen in CD8 T cells, with over 50% of the CD8 T cells expressing markers of activation and proliferation. Taken together, these results suggest that all four patients developed robust immune responses during the acute phase of Ebola virus infection, a finding that would not have been predicted based on our current assumptions about the highly immunosuppressive nature of Ebola virus. Also, quite surprisingly, we found sustained immune activation after the virus was cleared from the plasma, observed most strikingly in the persistence of activated CD8 T cells, even 1 mo after the patients' discharge from the hospital. These results suggest continued antigen stimulation after resolution of the disease. From these convalescent time points, we identified CD4 and CD8 T-cell responses to several Ebola virus proteins, most notably the viral nucleoprotein. Knowledge of the viral proteins targeted by T cells during natural infection should be useful in designing vaccines against Ebola virus.


Assuntos
Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Ebolavirus/imunologia , Doença pelo Vírus Ebola/imunologia , Imunidade Celular/imunologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Ebolavirus/metabolismo , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Doença pelo Vírus Ebola/sangue , Doença pelo Vírus Ebola/virologia , Humanos , Imunidade Humoral/imunologia , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Imunofenotipagem , Interferon gama/imunologia , Interferon gama/metabolismo , Ativação Linfocitária/imunologia , Células Precursoras de Linfócitos B/imunologia , Células Precursoras de Linfócitos B/metabolismo , Fator de Necrose Tumoral alfa/imunologia , Fator de Necrose Tumoral alfa/metabolismo , Proteínas Virais/imunologia , Proteínas Virais/metabolismo
15.
Proc Natl Acad Sci U S A ; 112(10): 3050-5, 2015 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-25713354

RESUMO

CD8 T cells are a potent tool for eliminating intracellular pathogens and tumor cells. Thus, eliciting robust CD8 T-cell immunity is the basis for many vaccines under development. However, the relationship between antigen load and the magnitude of the CD8 T-cell response is not well-described in a human immune response. Here we address this issue by quantifying viral load and the CD8 T-cell response in a cohort of 80 individuals immunized with the live attenuated yellow fever vaccine (YFV-17D) by sampling peripheral blood at days 0, 1, 2, 3, 5, 7, 9, 11, 14, 30, and 90. When the virus load was below a threshold (peak virus load < 225 genomes per mL, or integrated virus load < 400 genome days per mL), the magnitude of the CD8 T-cell response correlated strongly with the virus load (R(2) ∼ 0.63). As the virus load increased above this threshold, the magnitude of the CD8 T-cell responses saturated. Recent advances in CD8 T-cell-based vaccines have focused on replication-incompetent or single-cycle vectors. However, these approaches deliver relatively limited amounts of antigen after immunization. Our results highlight the requirement that T-cell-based vaccines should deliver sufficient antigen during the initial period of the immune response to elicit a large number of CD8 T cells that may be needed for protection.


Assuntos
Linfócitos T CD8-Positivos/imunologia , Carga Viral , Vacina contra Febre Amarela/imunologia , Estudos de Coortes , Perfilação da Expressão Gênica , Humanos , Vírus da Febre Amarela/genética , Vírus da Febre Amarela/imunologia , Vírus da Febre Amarela/isolamento & purificação
16.
MBio ; 6(1)2015 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-25604792

RESUMO

UNLABELLED: Severe malarial anemia (SMA) in semi-immune individuals eliminates both infected and uninfected erythrocytes and is a frequent fatal complication. It is proportional not to circulating parasitemia but total parasite mass (sequestered) in the organs. Thus, immune responses that clear parasites in organs may trigger changes leading to anemia. Here, we use an outbred-rat model where increasing parasite removal in the spleen escalated uninfected-erythrocyte removal. Splenic parasite clearance was associated with activated CD8(+) T cells, immunodepletion of which prevented parasite clearance. CD8(+) T cell repletion and concomitant reduction of the parasite load was associated with exacerbated (40 to 60%) hemoglobin loss and changes in properties of uninfected erythrocytes. Together, these data suggest that CD8(+) T cell-dependent parasite clearance causes erythrocyte removal in the spleen and thus anemia. In children infected with the human malaria parasite Plasmodium falciparum, elevation of parasite biomass (not the number of circulating parasites) increased the odds ratio for SMA by 3.5-fold (95% confidence intervals [CI95%], 1.8- to 7.5-fold). CD8(+) T cell expansion/activation independently increased the odds ratio by 2.4-fold (CI95%, 1.0- to 5.7-fold). Concomitant increases in both conferred a 7-fold (CI95%, 1.9- to 27.4-fold)-greater risk for SMA. Together, these data suggest that CD8(+)-dependent parasite clearance may predispose individuals to uninfected-erythrocyte loss and SMA, thus informing severe disease diagnosis and strategies for vaccine development. IMPORTANCE: Malaria is a major global health problem. Severe malaria anemia (SMA) is a complex disease associated with partial immunity. Rapid hemoglobin reductions of 20 to 50% are commonly observed and must be rescued by transfusion (which can carry a risk of HIV acquisition). The causes and risk factors of SMA remain poorly understood. Recent studies suggest that SMA is linked to parasite biomass sequestered in organs. This led us to investigate whether immune mechanisms that clear parasites in organs trigger anemia. In rats, erythropoiesis is largely restricted to the bone marrow, and critical aspects of the spleen expected to be important in anemia are similar to those in humans. Therefore, using a rat model, we show that severe anemia is caused through CD8(+) T cell-dependent parasite clearance and erythrocyte removal in the spleen. CD8 activation may also be a new risk factor for SMA in African children.


Assuntos
Anemia/imunologia , Linfócitos T CD8-Positivos/imunologia , Eritrócitos/citologia , Malária Falciparum/complicações , Fagocitose , Plasmodium falciparum/fisiologia , Baço/imunologia , Anemia/etiologia , Anemia/metabolismo , Anemia/fisiopatologia , Animais , Morte Celular , Eritrócitos/metabolismo , Eritrócitos/parasitologia , Hemoglobinas/metabolismo , Humanos , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Ratos , Baço/parasitologia
17.
Eur J Immunol ; 43(12): 3219-32, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24030473

RESUMO

CD4(+) T follicular helper (TFH) cells are central for generation of long-term B-cell immunity. A defining phenotypic attribute of TFH cells is the expression of the chemokine R CXCR5, and TFH cells are typically identified by co-expression of CXCR5 together with other markers such as PD-1, ICOS, and Bcl-6. Herein, we report high-level expression of the nutrient transporter folate R 4 (FR4) on TFH cells in acute viral infection. Distinct from the expression profile of conventional TFH markers, FR4 was highly expressed by naive CD4(+) T cells, was downregulated after activation and subsequently re-expressed on TFH cells. Furthermore, FR4 expression was maintained, albeit at lower levels, on memory TFH cells. Comparative gene expression profiling of FR4(hi) versus FR4(lo) Ag-specific CD4(+) effector T cells revealed a molecular signature consistent with TFH and TH1 subsets, respectively. Interestingly, genes involved in the purine metabolic pathway, including the ecto-enzyme CD73, were enriched in TFH cells compared with TH1 cells, and phenotypic analysis confirmed expression of CD73 on TFH cells. As there is now considerable interest in developing vaccines that would induce optimal TFH cell responses, the identification of two novel cell surface markers should be useful in characterization and identification of TFH cells following vaccination and infection.


Assuntos
Regulação da Expressão Gênica/imunologia , Receptores de Superfície Celular/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , 5'-Nucleotidase/biossíntese , 5'-Nucleotidase/genética , 5'-Nucleotidase/imunologia , Doença Aguda , Animais , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/imunologia , Regulação da Expressão Gênica/genética , Proteína Coestimuladora de Linfócitos T Induzíveis/biossíntese , Proteína Coestimuladora de Linfócitos T Induzíveis/genética , Proteína Coestimuladora de Linfócitos T Induzíveis/imunologia , Camundongos , Camundongos Transgênicos , Receptor de Morte Celular Programada 1/biossíntese , Receptor de Morte Celular Programada 1/genética , Receptor de Morte Celular Programada 1/imunologia , Proteínas Proto-Oncogênicas c-bcl-6 , Receptores CXCR5/biossíntese , Receptores CXCR5/genética , Receptores CXCR5/imunologia , Receptores de Superfície Celular/biossíntese , Receptores de Superfície Celular/genética , Linfócitos T Auxiliares-Indutores/citologia , Linfócitos T Auxiliares-Indutores/metabolismo , Viroses/genética , Viroses/imunologia , Viroses/metabolismo
18.
Curr Opin Virol ; 3(3): 371-6, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23747121

RESUMO

Memory T cells generated from acute infection or vaccination have the potential to provide the host with life-long immunity against re-infection. Protection by memory T cells is achieved through their acquired ability to persist at anatomical sites of the primary infection as well as maintaining a heightened ability to recall effector functions. The maintenance of CD8 and CD4 T cell function in a state of readiness is key to life-long immunity and manifest through changes in transcriptional regulation. Yet, the ability to identify poised transcriptional programs at the maintenance stage of the response is lacking from most transcriptional profiling studies of memory T cells. Epigenetic profiling allows for the assessment of transcriptionally poised (promoters that are readily accessible for transcription) states of antigen-specific T cells without manipulation of the activation state of the cell. Here we review recent studies that have examined epigenetic programs of effector and memory T cell subsets. These reports demonstrate that acquisition of epigenetic programs during memory T cell differentiation to acute and chronic infections is coupled to, and potentially regulate, the cell's recall response. We discuss the usefulness of epigenetic profiling in characterizing T cell differentiation state and function for preclinical evaluation of vaccines and the current methodologies for single locus versus genome-wide epigenetic profiling.


Assuntos
Epigênese Genética , Memória Imunológica , Linfócitos T/imunologia , Vacinas/imunologia , Regulação da Expressão Gênica , Humanos
19.
J Immunol ; 191(2): 540-4, 2013 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-23772031

RESUMO

Ag-specific CD8 T cells play a critical role in controlling HIV infection but eventually lose antiviral functions in part because of expression and signaling through the inhibitory programmed death-1 (PD-1) receptor. To better understand the impact of prolonged TCR ligation on regulation of PD-1 expression in HIV-specific CD8 T cells, we investigated the capacity of virus-specific CD8 T cells to modify the PD-1 epigenetic program after reduction in viral load. We observed that the transcriptional regulatory region was unmethylated in the PD-1(hi) HIV-specific CD8 T cells, whereas it remained methylated in donor-matched naive cells at acute and chronic stages of infection. Surprisingly, the PD-1 promoter remained unmethylated in HIV-specific CD8 T cells from subjects with a viral load controlled by antiviral therapy for >2 y or from elite controllers. Together, these data demonstrate that the epigenetic program at the PD-1 locus becomes fixed after prolonged exposure to HIV virus.


Assuntos
Linfócitos T CD8-Positivos/imunologia , Metilação de DNA , Infecções por HIV/imunologia , Receptor de Morte Celular Programada 1/genética , Receptor de Morte Celular Programada 1/metabolismo , Terapia Antirretroviral de Alta Atividade , Linfócitos T CD8-Positivos/metabolismo , Infecções por HIV/tratamento farmacológico , Infecções por HIV/virologia , HIV-1/imunologia , Humanos , Regiões Promotoras Genéticas , Transcrição Genética , Carga Viral
20.
Immunity ; 38(4): 805-17, 2013 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-23583644

RESUMO

CD4(+) T follicular helper (Tfh) cells provide the required signals to B cells for germinal center reactions that are necessary for long-lived antibody responses. However, it remains unclear whether there are CD4(+) memory T cells committed to the Tfh cell lineage after antigen clearance. By using adoptive transfer of antigen-specific memory CD4(+) T cell subpopulations in the lymphocytic choriomeningitis virus infection model, we found that there are distinct memory CD4(+) T cell populations with commitment to either Tfh- or Th1-cell lineages. Our conclusions are based on gene expression profiles, epigenetic studies, and phenotypic and functional analyses. Our findings indicate that CD4(+) memory T cells "remember" their previous effector lineage after antigen clearance, being poised to reacquire their lineage-specific effector functions upon antigen reencounter. These findings have important implications for rational vaccine design, where improving the generation and engagement of memory Tfh cells could be used to enhance vaccine-induced protective immunity.


Assuntos
Linfócitos T CD4-Positivos/imunologia , Coriomeningite Linfocítica/imunologia , Vírus da Coriomeningite Linfocítica/imunologia , Subpopulações de Linfócitos T/imunologia , Células Th1/imunologia , Transferência Adotiva , Animais , Antígenos Virais/imunologia , Diferenciação Celular , Linhagem da Célula , Células Cultivadas , Metilação de DNA/imunologia , Epigênese Genética/imunologia , Granzimas/genética , Memória Imunológica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptores CXCR5/metabolismo , Transcriptoma
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