Project description:Chronic viral infections are characterized by a state of CD8 T cell dysfunction termed exhaustion. A better understanding of the mechanisms that regulate CD8 T cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8 T cells. Here we identify a novel population of virus-specific CD8 T cells with a T follicular helper (Tfh)-like signature in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These Tfh-like CD8 T cells expressed the programmed cell death-1 (PD-1) inhibitory receptor but at the same time also expressed co-stimulatory molecules and had a gene signature that was related to CD8 T cell memory precursor cells and hematopoietic stem cells (HSC). These Tfh-like CD8 T cells acted as stem cells during chronic infection undergoing self-renewal and also differentiating into the terminally exhausted CD8 T cells that were present in both lymphoid and non-lymphoid tissues. The Tfh-like CD8 T cells were found only in lymphoid tissues and resided predominantly in the T cell zones along with naïve CD8 T cells. Interestingly, the proliferative burst after PD-1 blockade came almost exclusively from this Tfh-like CD8 T cell subset. Importantly, the transcription factor TCF1 played a cell intrinsic and essential role in the generation of Tfh-like CD8 T cells. Taken together, our study identifies Tfh-like CD8 T cells as the critical subset for maintaining the pool of virus-specific CD8 T cells during chronic infection and as the cells that proliferate after PD-1 blockade. These findings provide a better understanding of T cell exhaustion and have implications towards optimizing PD-1 directed immunotherapy.
Project description:Chronic viral infections are characterized by a state of CD8+ T-cell dysfunction that is associated with expression of the programmed cell death 1 (PD-1) inhibitory receptor. A better understanding of the mechanisms that regulate CD8+ T-cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8+ T cells. Here we identify a population of virus-specific CD8+ T cells that proliferate after blockade of the PD-1 inhibitory pathway in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These LCMV-specific CD8+ T cells expressed the PD-1 inhibitory receptor, but also expressed several costimulatory molecules such as ICOS and CD28. This CD8+ T-cell subset was characterized by a unique gene signature that was related to that of CD4+ T follicular helper (TFH) cells, CD8+ T cell memory precursors and haematopoietic stem cell progenitors, but that was distinct from that of CD4+ TH1 cells and CD8+ terminal effectors. This CD8+ T-cell population was found only in lymphoid tissues and resided predominantly in the T-cell zones along with naive CD8+ T cells. These PD-1+CD8+ T cells resembled stem cells during chronic LCMV infection, undergoing self-renewal and also differentiating into the terminally exhausted CD8+ T cells that were present in both lymphoid and non-lymphoid tissues. The proliferative burst after PD-1 blockade came almost exclusively from this CD8+ T-cell subset. Notably, the transcription factor TCF1 had a cell-intrinsic and essential role in the generation of this CD8+ T-cell subset. These findings provide a better understanding of T-cell exhaustion and have implications in the optimization of PD-1-directed immunotherapy in chronic infections and cancer.
Project description:Chronic viral infections are characterized by a state of CD8 T cell dysfunction termed exhaustion. A better understanding of the mechanisms that regulate CD8 T cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8 T cells. Here we identify a novel population of virus-specific CD8 T cells with a T follicular helper (Tfh)-like signature in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These Tfh-like CD8 T cells expressed the programmed cell death-1 (PD-1) inhibitory receptor but at the same time also expressed co-stimulatory molecules and had a gene signature that was related to CD8 T cell memory precursor cells and hematopoietic stem cells (HSC). These Tfh-like CD8 T cells acted as stem cells during chronic infection undergoing self-renewal and also differentiating into the terminally exhausted CD8 T cells that were present in both lymphoid and non-lymphoid tissues. The Tfh-like CD8 T cells were found only in lymphoid tissues and resided predominantly in the T cell zones along with naïve CD8 T cells. Interestingly, the proliferative burst after PD-1 blockade came almost exclusively from this Tfh-like CD8 T cell subset. Importantly, the transcription factor TCF1 played a cell intrinsic and essential role in the generation of Tfh-like CD8 T cells. Taken together, our study identifies Tfh-like CD8 T cells as the critical subset for maintaining the pool of virus-specific CD8 T cells during chronic infection and as the cells that proliferate after PD-1 blockade. These findings provide a better understanding of T cell exhaustion and have implications towards optimizing PD-1 directed immunotherapy. 8 samples isolated from CD8 T-cells in LCMV clone 13 GK1.5 infected mice (2 naïve, 3 CXCR5+Tim3-, 3 CXCR5-Tim3+) cells were analyzed
Project description:Chronic viral infections are characterized by a state of CD8 T cell dysfunction termed exhaustion. A better understanding of the mechanisms that regulate CD8 T cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8 T cells. Here we identify a novel population of virus-specific CD8 T cells with a T follicular helper (Tfh)-like signature in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These Tfh-like CD8 T cells expressed the programmed cell death-1 (PD-1) inhibitory receptor but at the same time also expressed co-stimulatory molecules and had a gene signature that was related to CD8 T cell memory precursor cells and hematopoietic stem cells (HSC). These Tfh-like CD8 T cells acted as stem cells during chronic infection undergoing self-renewal and also differentiating into the terminally exhausted CD8 T cells that were present in both lymphoid and non-lymphoid tissues. The Tfh-like CD8 T cells were found only in lymphoid tissues and resided predominantly in the T cell zones along with naïve CD8 T cells. Interestingly, the proliferative burst after PD-1 blockade came almost exclusively from this Tfh-like CD8 T cell subset. Importantly, the transcription factor TCF1 played a cell intrinsic and essential role in the generation of Tfh-like CD8 T cells. Taken together, our study identifies Tfh-like CD8 T cells as the critical subset for maintaining the pool of virus-specific CD8 T cells during chronic infection and as the cells that proliferate after PD-1 blockade. These findings provide a better understanding of T cell exhaustion and have implications towards optimizing PD-1 directed immunotherapy.
Project description:We sequenced allele-resolution single-cell transcriptomes from mouse primary fibroblasts and embryonic stem cells with the overall aim to infer transcriptional kinetics for each gene and allele. Inferred transcriptional burst kinetics revealed the genomic encoding of transcriptional burst frequencies and sizes within the genome. Core promoter elements were found to specify burst sizes, whereas burst frequencies were regulated by enhancers. In particular burst frequencies were found to account for cell-type differences in gene expression levels and were also mostly correlating with absolute expression levels in cells. Importantly, the patterns identified were not detectable at the level of mean expression demonstrating the need to investigate transcriptional dynamics at the level of burst kinetics.
Project description:During acute viral infections, naïve CD8+ T cells differentiate into effector CD8+ T cells and, after viral control, into memory CD8+ T cells. Memory CD8+ T cells are highly functional, proliferate rapidly upon reinfection and persist long-term without antigen. In contrast, during chronic infections, CD8+ T cells become “exhausted” and have poor effector function, express multiple inhibitory receptors, possess low proliferative capacity, and cannot persist without antigen. Exhuasted CD8+ T cells can be further segregated by their expression of the inhibitory cell surface receptor PD-1. We performed transcriptional profiling on both PD-1 High and PD-1 Intermediate H2-Db GP33-specific CD8+ T cells. H2-Db GP33-specific CD8+ T cells were sorted from C57BL/6 mice 30 days p.i. with LCMV clone 13. These cells were then segregated by their expression of the inhibitory cell surface receptor PD-1 into PD-1 High and PD-1 Intermediate subpopulations. We performed transcriptional profiling on these subpopulations.
Project description:We used single-cell RNA-sequencing to generate allele-resolution expression levels in individual cells that we used for inference of transcriptional burst kinetics.
Project description:CD8+ T cells in chronic viral infections like HIV develop functional defects such as loss of IL-2 secretion and decreased proliferative potential that are collectively termed exhaustion1. Exhausted T cells express increased levels of multiple inhibitory receptors, such as Programmed Death 1 (PD-1). PD-1 inhibition contributes to impaired virus-specific T cell function in chronic infection because antibody-mediated blockade of its ligand, Programmed Death Ligand 1 (PD-L1) is sufficient to improve T cell function and reduce viral replication in animal models. Reversing PD-1 inhibition is therefore an attractive therapeutic target, but the cellular mechanisms by which PD-1 ligation results in T cell inhibition are not fully understood. PD-1 is thought to limit T cell activation by attenuating T cell receptor (TCR) signaling. It is not known whether PD-1 ligation also acts by upregulating genes in exhausted T cells that impair their function. Here, we analyzed gene-expression profiles from HIV-specific CD8+ T cells in patients with HIV and show that PD-1 coordinately upregulates a program of genes in exhausted CD8+ T cells from humans and mice. This program includes upregulation of basic leucine transcription factor, ATF-like (BATF), a transcription factor in the AP-1 family. Enforced expression of BATF was sufficient to impair T cell proliferation and cytokine secretion, while BATF knockdown reduced PD-1 inhibition. Silencing BATF in CD4+ and CD8+ T cells from chronic viremic patients rescued HIV-specific T cell function. Thus inhibitory receptors can cause T cell exhaustion by upregulating genes â such as BATF â that inhibit T cell function. PD-1 expressing Jurkat cells were cultured for 18 hours with beads coated with antibodies to CD3 and CD28, with our without an antibody to PD-1.