RESUMO
Virus-specific CD8+ T cells probably mediate control over HIV replication in rare individuals, termed long-term nonprogressors (LTNPs) or elite controllers. Despite extensive investigation, the mechanisms responsible for this control remain incompletely understood. We observed that HIV-specific CD8+ T cells of LTNPs persisted at higher frequencies than those of treated progressors with equally low amounts of HIV. Measured on a per-cell basis, HIV-specific CD8+ T cells of LTNPs efficiently eliminated primary autologous HIV-infected CD4+ T cells. This function required lytic granule loading of effectors and delivery of granzyme B to target cells. Defective cytotoxicity of progressor effectors could be restored after treatment with phorbol ester and calcium ionophore. These results establish an effector function and mechanism that clearly segregate with immunologic control of HIV. They also demonstrate that lytic granule contents of memory cells are a critical determinant of cytotoxicity that must be induced for maximal per-cell killing capacity.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Citotoxicidade Imunológica , Infecções por HIV/imunologia , HIV-1/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/virologia , Linfócitos T CD8-Positivos/enzimologia , Linfócitos T CD8-Positivos/virologia , Degranulação Celular/imunologia , Grânulos Citoplasmáticos/enzimologia , Grânulos Citoplasmáticos/imunologia , Granzimas/imunologia , Granzimas/metabolismo , Infecções por HIV/virologia , Sobreviventes de Longo Prazo ao HIV , Humanos , Interferon gama/imunologia , Interferon gama/metabolismo , Perforina/imunologia , Perforina/metabolismo , RNA Viral/imunologiaRESUMO
Characterization of lymphocytes including B cells during early versus chronic HIV infection is important for understanding the impact of chronic viremia on immune cell function. In this setting, we investigated B cells before and after reduction of HIV plasma viremia by antiretroviral therapy (ART). At baseline, peripheral blood B-cell counts were significantly lower in both early and chronic HIV-infected individuals compared with uninfected controls. Similar to CD4(+) but not CD8(+) T cells, B-cell numbers in both groups increased significantly after ART. At baseline, B cells of early HIV-infected individuals were composed of a higher percentage of plasmablasts and resting memory B cells compared with chronic HIV-infected individuals whose B cells were composed of a higher percentage of immature/transitional and exhausted B cells compared with their early infection counterparts. At 1 year after ART, the percentage of resting memory B cells remained higher in early compared with chronic HIV-infected individuals. This difference translated into a better functional profile in that memory B-cell responses to HIV and non-HIV antigens were superior in early- compared with chronic-treated HIV infected individuals. These findings provide new insights on B cells in HIV infection and how early initiation of ART may prevent irreversible immune system damage.
Assuntos
Terapia Antirretroviral de Alta Atividade , Linfócitos B/imunologia , Infecções por HIV/imunologia , Memória Imunológica , Viremia/imunologia , Adulto , Linfócitos B/virologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/virologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/virologia , Doença Crônica , Infecções por HIV/tratamento farmacológico , HIV-1/fisiologia , Humanos , Contagem de Linfócitos , Masculino , Pessoa de Meia-Idade , Carga Viral , Viremia/virologia , Adulto JovemRESUMO
Stimulation through TLR represents a new therapeutic approach for enhancing Ab responses to vaccination. Considering that Ab responses are decreased in HIV disease and that B cells express TLR9 and respond to TLR9 agonists, we investigated the responsiveness of B cell subpopulations from HIV-infected and uninfected individuals to the TLR9 agonist CpG oligonucleotide type B (CpG-B) in the presence and absence of BCR ligation and T cell help (CD40L). CpG-B was equally effective in stimulating the proliferation of naive B cells of HIV-infected individuals and HIV-negative individuals, and, when combined with BCR and CD40 ligation, cytokine secretion by naive B cells was also comparable in HIV-infected and uninfected individuals. In contrast, CD27(+) memory/activated B cells of HIV-infected individuals with active disease were less responsive to CpG-B in terms of proliferation and cytokine secretion when compared with CD27(+) B cells of HIV-negative and HIV-infected individuals whose viremia was controlled by antiretroviral therapy. These findings suggest that despite abnormalities in memory B cells of HIV-infected individuals with active disease, naive B cells of HIV-infected individuals, irrespective of disease status, can respond to TLR9 agonists and that the incorporation of such agents in vaccine formulations may enhance their Ab responses to vaccination.
Assuntos
Adjuvantes Imunológicos , Linfócitos B/imunologia , Infecções por HIV/imunologia , Ativação Linfocitária , Oligodesoxirribonucleotídeos/imunologia , Receptor Toll-Like 9/agonistas , Proliferação de Células , Células Cultivadas , Citocinas/imunologia , Citocinas/metabolismo , HIV , Infecções por HIV/virologia , Humanos , Imunoglobulina G/imunologia , Imunoglobulina G/metabolismo , Receptor Toll-Like 9/imunologia , Receptor Toll-Like 9/metabolismoRESUMO
The programmed death (PD)-1 molecule and its ligands (PD-L1 and PD-L2), negative regulatory members of the B7 family, play an important role in peripheral tolerance. Previous studies have demonstrated that PD-1 is up-regulated on T cells following TCR-mediated activation; however, little is known regarding PD-1 and Ag-independent, cytokine-induced T cell activation. The common gamma-chain (gamma c) cytokines IL-2, IL-7, IL-15, and IL-21, which play an important role in peripheral T cell expansion and survival, were found to up-regulate PD-1 and, with the exception of IL-21, PD-L1 on purified T cells in vitro. This effect was most prominent on memory T cells. Furthermore, these cytokines induced, indirectly, the expression of PD-L1 and PD-L2 on monocytes/macrophages in PBMC. The in vivo correlate of these observations was confirmed on PBMC isolated from HIV-infected individuals receiving IL-2 immunotherapy. Exposure of gamma c cytokine pretreated T cells to PD-1 ligand-IgG had no effect on STAT5 activation, T cell proliferation, or survival driven by gamma c cytokines. However, PD-1 ligand-IgG dramatically inhibited anti-CD3/CD28-driven proliferation and Lck activation. Furthermore, following restimulation with anti-CD3/CD28, cytokine secretion by both gamma c cytokine and anti-CD3/CD28 pretreated T cells was suppressed. These data suggest that gamma c cytokine-induced PD-1 does not interfere with cytokine-driven peripheral T cell expansion/survival, but may act to suppress certain effector functions of cytokine-stimulated cells upon TCR engagement, thereby minimizing immune-mediated damage to the host.
Assuntos
Antígenos CD/biossíntese , Proteínas Reguladoras de Apoptose/biossíntese , Interleucina-15/imunologia , Interleucina-2/imunologia , Interleucina-7/imunologia , Interleucinas/imunologia , Ativação Linfocitária/imunologia , Antígenos CD/imunologia , Proteínas Reguladoras de Apoptose/imunologia , Antígeno B7-H1 , Células Cultivadas , Citocinas , Infecções por HIV/tratamento farmacológico , Infecções por HIV/imunologia , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/biossíntese , Peptídeos e Proteínas de Sinalização Intercelular/imunologia , Interleucina-2/uso terapêutico , Proteína 2 Ligante de Morte Celular Programada 1 , Receptor de Morte Celular Programada 1 , Linfócitos T/imunologiaRESUMO
Chronic immune activation in HIV-infected individuals leads to accumulation of exhausted tissue-like memory B cells. Exhausted lymphocytes display increased expression of multiple inhibitory receptors, which may contribute to the inefficiency of HIV-specific antibody responses. Here, we show that downregulation of B cell inhibitory receptors in primary human B cells led to increased tissue-like memory B cell proliferation and responsiveness against HIV. In human B cells, siRNA knockdown of 9 known and putative B cell inhibitory receptors led to enhanced B cell receptor-mediated (BCR-mediated) proliferation of tissue-like memory but not other B cell subpopulations. The strongest effects were observed with the putative inhibitory receptors Fc receptor-like-4 (FCRL4) and sialic acid-binding Ig-like lectin 6 (Siglec-6). Inhibitory receptor downregulation also led to increased levels of HIV-specific antibody-secreting cells and B cell-associated chemokines and cytokines. The absence of known ligands for FCRL4 and Siglec-6 suggests these receptors may regulate BCR signaling through their own constitutive or tonic signaling. Furthermore, the extent of FCLR4 knockdown effects on BCR-mediated proliferation varied depending on the costimulatory ligand, suggesting that inhibitory receptors may engage specific pathways in inhibiting B cell proliferation. These findings on HIV-associated B cell exhaustion define potential targets for reversing the deleterious effect of inhibitory receptors on immune responses against persistent viral infections.
Assuntos
Linfócitos B/imunologia , Linfócitos B/virologia , Infecções por HIV/imunologia , HIV/imunologia , RNA Interferente Pequeno/imunologia , Receptores de Antígenos de Linfócitos B/imunologia , Antígenos CD/imunologia , Linfócitos B/citologia , Proliferação de Células , Quimiocinas/imunologia , Citocinas/imunologia , Humanos , RNA Interferente Pequeno/genética , Receptores de Antígenos de Linfócitos B/genéticaRESUMO
BACKGROUND: Untreated human immunodeficiency virus (HIV) disease leads to abnormalities in all major lymphocyte populations, including CD4(+) T cells, CD8(+) T cells, and B cells. However, little is known regarding the effect of antiretroviral therapy (ART)-induced decrease in HIV viremia on B cell numbers and subpopulations. METHODS: We conducted a longitudinal study to evaluate changes in B cell numbers and subpopulations that occur during the course of 12 months of effective ART in a group of individuals with chronic HIV infection. RESULTS: ART-induced decrease in HIV viremia was associated with a significant increase in B cell counts, similar to increases in CD4(+) T cell counts yet distinct from the lack of increase in CD8(+) T cells. The increase in B cell counts was accompanied by a significant decrease in the frequency of apoptosis-prone B cell subpopulations, namely mature activated and immature transitional B cells, which are overrepresented in untreated HIV disease. The increase in B cell counts was reflected by a significant increase in naive and resting memory B cells, both of which represent populations that are essential for generating adequate humoral immunity. CONCLUSIONS: Normalization of B cell counts and subpopulations may help to explain the improvement in humoral immunity reported to occur after an ART-induced decrease in HIV viremia.
Assuntos
Antirretrovirais/farmacologia , Linfócitos B/virologia , Infecções por HIV/tratamento farmacológico , Subpopulações de Linfócitos/virologia , Viremia/tratamento farmacológico , Adulto , Doença Crônica , Feminino , Infecções por HIV/imunologia , Humanos , Estudos Longitudinais , Contagem de Linfócitos , Subpopulações de Linfócitos/efeitos dos fármacos , Masculino , Viremia/imunologiaRESUMO
Human immunodeficiency virus (HIV) disease leads to impaired B cell and antibody responses through mechanisms that remain poorly defined. A unique memory B cell subpopulation (CD20(hi)/CD27(lo)/CD21(lo)) in human tonsillar tissues was recently defined by the expression of the inhibitory receptor Fc-receptor-like-4 (FCRL4). In this study, we describe a similar B cell subpopulation in the blood of HIV-viremic individuals. FCRL4 expression was increased on B cells of HIV-viremic compared with HIV-aviremic and HIV-negative individuals. It was enriched on B cells with a tissuelike memory phenotype (CD20(hi)/CD27(-)/CD21(lo)) when compared with B cells with a classical memory (CD27(+)) or naive (CD27(-)/CD21(hi)) B cell phenotype. Tissuelike memory B cells expressed patterns of homing and inhibitory receptors similar to those described for antigen-specific T cell exhaustion. The tissuelike memory B cells proliferated poorly in response to B cell stimuli, which is consistent with high-level expression of multiple inhibitory receptors. Immunoglobulin diversities and replication histories were lower in tissuelike, compared with classical, memory B cells, which is consistent with premature exhaustion. Strikingly, HIV-specific responses were enriched in these exhausted tissuelike memory B cells, whereas total immunoglobulin and influenza-specific responses were enriched in classical memory B cells. These data suggest that HIV-associated premature exhaustion of B cells may contribute to poor antibody responses against HIV in infected individuals.
Assuntos
Subpopulações de Linfócitos B/imunologia , Subpopulações de Linfócitos B/virologia , Infecções por HIV/imunologia , Memória Imunológica , Viremia/imunologia , Estudos de Casos e Controles , Anticorpos Anti-HIV/biossíntese , Infecções por HIV/virologia , Humanos , Ativação Linfocitária , Modelos Imunológicos , Fenótipo , Receptores Fc/metabolismo , Viremia/virologia , Replicação Viral/imunologiaRESUMO
Perturbations of B cells in HIV-infected individuals are associated with the overrepresentation of distinct B cell populations. Here we describe high extrinsic CD95 ligand (CD95L)-mediated apoptosis in CD10-/CD21lo mature/activated B cells that likely arise from HIV-induced immune activation. In addition, high intrinsic apoptosis was observed in CD10+ immature/transitional B cells that likely arise as a result of HIV-induced lymphopenia. CD10+ B cells expressed low levels of Bcl-2 and Bcl-xL, consistent with their high susceptibility to intrinsic apoptosis. Higher levels of activated Bax and Bak were induced in CD10+ B cells compared with CD95L-treated CD10- B cells, consistent with the greater involvement of mitochondria in intrinsic vs. extrinsic apoptosis. Of interest, both extrinsic apoptosis in CD95L-treated CD10- B cells and intrinsic apoptosis in CD10+ B cells were associated with caspase-8 activation. Our data suggest that two distinct mechanisms of apoptosis are associated with B cells of HIV-infected individuals, and both may contribute to the depletion and dysfunction of B cells in these individuals.
Assuntos
Apoptose/fisiologia , Linfócitos B/fisiologia , Infecções por HIV/imunologia , Apoptose/imunologia , Linfócitos B/imunologia , Caspase 8/imunologia , Citometria de Fluxo , Humanos , Neprilisina/imunologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteína Killer-Antagonista Homóloga a bcl-2/metabolismo , Proteína X Associada a bcl-2/metabolismo , Proteína bcl-X/metabolismo , Receptor fas/imunologiaRESUMO
Progression of HIV disease is associated with the appearance of numerous B cell defects. We describe herein a population of immature/transitional B cells that is overly represented in the peripheral blood of individuals with advancing HIV disease. These B cells, identified by the expression of CD10, were unresponsive by proliferation to B cell receptor triggering and possessed a phenotype and an Ig diversity profile that confirmed their immature/transitional stage of differentiation. Consistent with an immature status, their lack of proliferation to B cell receptor triggering was reversed with CD40 ligand, but not B cell activation factor. Finally, levels of CD10 expression on B cells were directly correlated with serum levels of IL-7, suggesting that increased levels of IL-7 modulate human B cell maturation either directly or indirectly by means of a homeostatic effect on lymphopenia. Taken together, these data offer insight into human B cell development as well as B cell dysfunction in advanced HIV disease that may be linked to IL-7-dependent homeostatic events.