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Bim-mediated deletion of antigen-specific CD8 T cells in patients unable to control HBV infection.

ABSTRACT: HBV-specific CD8(+) T cells are critical for a successful immune response to HBV infection. They are markedly diminished in number in patients who fail to control the virus, but the mechanisms resulting in their depletion remain ill defined. Here, we dissected the defective HBV-specific CD8(+) T cell response associated with chronic HBV infection by gene expression profiling. We found that HBV-specific CD8(+) T cells from patients with different clinical outcomes could be distinguished by their patterns of gene expression. Microarray analysis revealed that overlapping clusters of functionally related apoptotic genes were upregulated in HBV-specific CD8(+) T cells from patients with chronic compared with resolved infection. Further analysis confirmed that levels of the proapoptotic protein Bcl2-interacting mediator (Bim) were upregulated in HBV-specific CD8(+) T cells from patients with chronic HBV infection. Blocking Bim-mediated apoptosis enhanced recovery of HBV-specific CD8(+) T cells both in culture and directly ex vivo. Consistent with evidence that Bim mediates apoptosis of CD8(+) T cells expressing low levels of CD127 (IL-7R), the few surviving HBV-specific CD8(+) T cells were CD127(hi )and had elevated levels of the antiapoptotic protein Mcl1, suggesting they were amenable to IL-7-mediated rescue from apoptosis. We therefore postulate that Bim-mediated attrition of HBV-specific CD8(+) T cells contributes to the inability of these cell populations to persist and control viral replication.

SUBMITTER: Lopes AR

PROVIDER: S-EPMC2289792 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Functional Exhaustion of HBV-Specific CD8 T Cells Impedes PD-L1 Blockade Efficacy in Chronic HBV Infection.

Project description:BackgroundA functional cure for chronic HBV could be achieved by boosting HBV-specific immunity. In vitro studies show that immunotherapy could be an effective strategy. However, these studies include strategies to enrich HBV-specific CD8 T cells, which could alter the expression of the anti-PD-1/anti-PD-L1 antibody targets. Our aim was to determine the efficacy of PD-L1 blockade ex vivo.MethodsHBV-specific CD8 T cells were characterized ex vivo by flow cytometry for the simultaneous analysis of six immune populations and 14 activating and inhibitory receptors. Ex vivo functionality was quantified by ELISpot and by combining peptide pool stimulation, dextramers and intracellular flow cytometry staining.ResultsThe functionality of HBV-specific CD8 T cells is associated with a higher frequency of cells with low exhaustion phenotype (LAG3-TIM3-PD-1+), independently of the clinical parameters. The accumulation of HBV-specific CD8 T cells with a functionally exhausted phenotype (LAG3+TIM3+PD-1+) is associated with lack of ex vivo functionality. PD-L1 blockade enhanced the HBV-specific CD8 T cell response only in patients with lower exhaustion levels, while response to PD-L1 blockade was abrogated in patients with higher frequencies of exhausted HBV-specific CD8 T cells.ConclusionHigher levels of functionally exhausted HBV-specific CD8 T cells are associated with a lack of response that cannot be restored by blocking the PD-1:PD-L1 axis. This suggests that the clinical effectiveness of blocking the PD-1:PD-L1 axis as a monotherapy may be restricted. Combination strategies, potentially including the combination of anti-LAG-3 with other anti-iR antibodies, will likely be required to elicit a functional cure for patients with high levels of functionally exhausted HBV-specific CD8 T cells.

| S-EPMC8473828 | biostudies-literature

Mathematical models of e-antigen mediated immune tolerance and activation following prenatal HBV infection.

Project description:We develop mathematical models for the role of hepatitis B e-antigen in creating immunological tolerance during hepatitis B virus infection and propose mechanisms for hepatitis B e-antigen clearance, subsequent emergence of a potent cellular immune response, and the effect of these on liver damage. We investigate the dynamics of virus-immune cells interactions, and derive parameter regimes that allow for viral persistence. We modify the model to account for mechanisms responsible for hepatitis B e-antigen loss, such as seroconversion and virus mutations that lead to emergence of cellular immune response to the mutant virus. Our models demonstrate that either seroconversion or mutations can induce immune activation and that instantaneous loss of e-antigen by either mechanism is associated with least liver damage and is therefore more beneficial for disease outcomes.

| S-EPMC3388102 | biostudies-other

Persistent antigen at vaccination sites induces tumor-specific CD8? T cell sequestration, dysfunction and deletion.

Project description:To understand why cancer vaccine-induced T cells often do not eradicate tumors, we studied immune responses in mice vaccinated with gp100 melanoma peptide in incomplete Freund's adjuvant (peptide/IFA), which is commonly used in clinical cancer vaccine trials. Peptide/IFA vaccination primed tumor-specific CD8(+) T cells, which accumulated not in tumors but rather at the persisting, antigen-rich vaccination site. Once there, primed T cells became dysfunctional and underwent antigen-driven, interferon-? (IFN-?)- and Fas ligand (FasL)-mediated apoptosis, resulting in hyporesponsiveness to subsequent vaccination. Provision of CD40-specific antibody, Toll-like receptor 7 (TLR7) agonist and interleukin-2 (IL-2) reduced T cell apoptosis but did not prevent vaccination-site sequestration. A nonpersisting vaccine formulation shifted T cell localization toward tumors, inducing superior antitumor activity while reducing systemic T cell dysfunction and promoting memory formation. These data show that persisting vaccine depots can induce specific T cell sequestration, dysfunction and deletion at vaccination sites; short-lived formulations may overcome these limitations and result in greater therapeutic efficacy of peptide-based cancer vaccines.

| S-EPMC3618499 | biostudies-literature

Cancer-associated fibroblasts induce antigen-specific deletion of CD8 + T Cells to protect tumour cells.

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| S-EPMC5838096 | biostudies-literature

Mast Cells Modulate Antigen-Specific CD8+ T Cell Activation During LCMV Infection.

Project description:Mast cells (MCs), strategically localized at mucosal surfaces, provide first-line defense against pathogens and shape innate and adaptive immune responses. Recent studies have shown that MCs are involved in pathogenic responses to several viruses including herpes simplex viruses, dengue virus, vaccinia virus and influenza virus. However, the underlying mechanisms of MCs in the activation of CD8+ T cells during viral infections are not fully understood. Therefore, we investigate the role of MCs in the development of virus-specific CD8+ T cell responses using the well-characterized murine lymphocytic choriomeningitis virus (LCMV) model and the transgenic MasTRECK mice that contain the human diphtheria toxin receptor as an inducible MC-deficient model. Here, we report that MCs are essential for the activation and expansion of virus-specific CD8+ T cells. After MC depletion and subsequent intradermal LCMV infection, the CD8 + T cell effector phenotype and antiviral cytokine production were impaired at the peak of infection (day 8 p.i.). Importantly, MC-deficient mice were unable to control the infection and exhibited significantly higher viral loads in the spleen and in the ear draining lymph nodes compared to that of wild type control mice. In the absence of MCs, dendritic cell (DC) activation was impaired upon LCMV infection. In addition, type-I interferon (IFN) levels in the serum and in the spleen of MC-deficient mice were reduced during the first days of infection. Interestingly, depletion of MCs after intradermal LCMV infection did not impair virus-specific CD8+ T cell expansion, activation or antiviral cytokine production. In summary, our results indicate that MCs play a pivotal role in the activation and antiviral functions of CD8+ T cells through proper DC activation. A better understanding of the impact of MCs on CD8+ T cell responses is mandatory to improve antiviral immune responses.

| S-EPMC8236703 | biostudies-literature

Model to predict on-treatment restoration of functional HBV-specific CD8+ cell response foresees off-treatment HBV control in eAg-negative chronic hepatitis B.

Project description:BackgroundHepatitis B virus (HBV)-specific CD8+ cell response restoration during nucleos(t)ide analogue (NUC) treatment could lead to off-treatment HBV control in e-antigen-negative chronic hepatitis B (CHBe(-)).AimTo predict this response with variables involved in T-cell exhaustion for use as a treatment stopping tool.MethodsIn NUC-treated CHBe(-) patients, we considered a functional response in cases with HBV-specific CD8+ cells against core and polymerase HBV epitopes able to proliferate and secrete type I cytokines after antigen encounter. We performed a logistic regression model (LRM) to predict the likelihood of developing this response, based on patient age (subrogate of infection length), HBsAg level, NUC therapy starting point and duration (antigenic pressure). We discontinued treatment and assessed HBV DNA dynamics, HBsAg decline and loss during off-treatment follow-up according to LRM likelihood.ResultsWe developed an LRM that predicted the presence of a proliferative type I cytokine-secreting CD8+ cell response, which correlated positively with treatment duration and negatively with treatment initiation after the age of 40 years and with age adjusted by HBsAg level. We observed a positive correlation between LRM probability and intensity of proliferation, number of epitopes with the functional proliferating response and type I cytokine secretion level. Off-treatment, HBsAg loss, HBsAg decline >50% and HBV control were more frequent in the group with >90% LRM probability.ConclusionsShort-term low-level antigen exposure and early long-term NUC treatment influence the restoration of a functional HBV-specific CD8+ cell response. Based on these predictors, a high likelihood of detecting this response at treatment withdrawal is associated with off-treatment HBV control and HBsAg decline and loss.

| S-EPMC9305412 | biostudies-literature

Antigen-specific CD4 T-cell help rescues exhausted CD8 T cells during chronic viral infection.

Project description:CD4 T cells play a critical role in regulating CD8 T-cell responses during chronic viral infection. Several studies in animal models and humans have shown that the absence of CD4 T-cell help results in severe dysfunction of virus-specific CD8 T cells. However, whether function can be restored in already exhausted CD8 T cells by providing CD4 T-cell help at a later time remains unexplored. In this study, we used a mouse model of chronic lymphocytic choriomeningitis virus (LCMV) infection to address this question. Adoptive transfer of LCMV-specific CD4 T cells into chronically infected mice restored proliferation and cytokine production by exhausted virus-specific CD8 T cells and reduced viral burden. Although the transferred CD4 T cells were able to enhance function in exhausted CD8 T cells, these CD4 T cells expressed high levels of the programmed cell death (PD)-1 inhibitory receptor. Blockade of the PD-1 pathway increased the ability of transferred LCMV-specific CD4 T cells to produce effector cytokines, improved rescue of exhausted CD8 T cells, and resulted in a striking reduction in viral load. These results suggest that CD4 T-cell immunotherapy alone or in conjunction with blockade of inhibitory receptors may be a promising approach for treating CD8 T-cell dysfunction in chronic infections and cancer.

| S-EPMC3248546 | biostudies-literature

NIX-Mediated Mitophagy Promotes Effector Memory Formation in Antigen-Specific CD8+ T Cells.

Project description:Autophagy plays a critical role in the maintenance of immunological memory. However, the molecular mechanisms involved in autophagy-regulated effector memory formation in CD8+ T cells remain unclear. Here we show that deficiency in NIX-dependent mitophagy leads to metabolic defects in effector memory T cells. Deletion of NIX caused HIF1α accumulation and altered cellular metabolism from long-chain fatty acid to short/branched-chain fatty acid oxidation, thereby compromising ATP synthesis during effector memory formation. Preventing HIF1α accumulation restored long-chain fatty acid metabolism and effector memory formation in antigen-specific CD8+ T cells. Our study suggests that NIX-mediated mitophagy is critical for effector memory formation in T cells.

| S-EPMC6886713 | biostudies-literature

Siglecs induce tolerance to cell surface antigens by BIM-dependent deletion of the antigen-reactive B cells.

Project description:Infusion of blood cells from a donor can induce humoral tolerance in a recipient and increase the probability of successful organ transplant, a clinical method defined as donor-specific transfusion (DST). Despite the clinical success of DST, the immunological mechanisms by which blood cells displaying a foreign Ag induce tolerance remain poorly understood. Based on recent findings showing that the B cell siglecs, CD22 and Siglec-G, can promote tolerance to Ags presented on the same surface as their ligands, we speculated that the B cell siglecs are key players in tolerance induced by DST. Using a variety of chemical and genetic approaches, we show that the B cell siglecs mediate tolerance to cell surface Ags by initiating an inhibitory signal that culminates in elimination of the Ag-reactive B cell. CD22 and Siglec-G are recruited to the immunological synapse by sialic acid ligands on the Ag-bearing cells, producing a tolerogenic signal involving Lyn and the proapoptotic factor BIM that promotes deletion of the B cell and failure of mice to develop Abs to the Ag upon subsequent challenge. We speculate that this tolerogenic mechanism is a contributing factor in DST and a mechanism of peripheral B cell tolerance to cell surface autoantigens.

| S-EPMC4201975 | biostudies-literature

Selective dependence on IL-7 for antigen-specific CD8 T cell responses during airway influenza infection.

Project description:Interleukin-7 (IL-7) is a cytokine known for its importance in T cell development and survival. How IL-7 shapes CD8 T cell responses during an acute viral infection is less understood. We had previously shown that IL-7 signaling deficient mice have reduced accumulation of influenza-specific CD8 T cells following influenza infection. We sought to determine whether IL-7 affects early CD8 T cell expansion in the mediastinal lymph node and effector function in the lungs. Using IL-7Rα signaling deficient mice, we show that IL-7 is required for a normal sized mediastinal lymph node and the early clonal expansion of influenza-specific CD8 T cells therein. We show that IL-7 plays a cell-intrinsic role in the accumulation of NP366-374 and PA224-233-specific CD8 T cells in the lymph node. We also found that IL-7 shapes terminal differentiation, degranulation and cytokine production to a greater extent in PA224-233-specific than NP366-374-specific CD8 T cells. We further demonstrate that IL-7 is induced in the lung tissue by viral infection and we characterize multiple cellular sources that contribute to IL-7 production. Our findings on IL-7 and its effects on lower respiratory diseases will be important for expanding the utility of therapeutics that are currently available.

| S-EPMC8741933 | biostudies-literature

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