ABSTRACT
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.
Subject(s)
CD8-Positive T-Lymphocytes/cytology , CD8-Positive T-Lymphocytes/immunology , Cell Differentiation/immunology , Epigenesis, Genetic , Immunologic Memory/immunology , Yellow Fever Vaccine/immunology , Animals , CD8-Positive T-Lymphocytes/metabolism , Cell Differentiation/genetics , Cell Proliferation , Chromatin/genetics , Chromatin/metabolism , DNA Methylation , Deuterium , Gene Expression Profiling , Half-Life , Humans , Immunologic Memory/genetics , Lymphocyte Count , Mice , Radioisotope Dilution Technique , Transcription, Genetic , Yellow Fever/immunology , Yellow Fever/virology , Yellow fever virus/immunologyABSTRACT
Infection of the central nervous system (CNS) by murine polyomavirus (MuPyV), a persistent natural mouse pathogen, establishes brain-resident memory CD8 T cells (bTRM) that uniformly and chronically express programmed cell death protein 1 (PD-1) irrespective of the expression of αE integrin CD103, a TRM cell marker. In contrast, memory antiviral CD8 T cells in the spleen are PD-1-, despite viral loads being similar in both the brain and spleen during persistent infection. Repetitive antigen engagement is central to sustained PD-1 expression by T cells in chronic viral infections; however, recent evidence indicates that expression of inhibitory receptors, including PD-1, is part of the TRM differentiation program. Here we asked whether PD-1 expression by CD8 bTRM cells during persistent MuPyV encephalitis is antigen dependent. By transferring MuPyV-specific CD8 bTRM cells into the brains of naive mice and mice infected with cognate epitope-sufficient and -deficient MuPyVs, we demonstrate that antigen and inflammation are dispensable for PD-1 maintenance. In vitro and direct ex vivo analyses indicate that CD103- MuPyV-specific CD8 bTRM retain functional competence. We further show that the Pdcd-1 promoter of anti-MuPyV bTRM cells is epigenetically fixed in a demethylated state in the brain. In contrast, the PD-1 promoter of splenic antiviral memory CD8 T cells undergoes remethylation after being demethylated during acute infection. These data show that PD-1 expression is an intrinsic property of brain TRM cells in a persistent CNS viral infection.
Subject(s)
Brain/immunology , CD8-Positive T-Lymphocytes/immunology , Polyomavirus Infections/immunology , Polyomavirus/physiology , Programmed Cell Death 1 Receptor/metabolism , Adoptive Transfer , Animals , Brain/virology , CD8-Positive T-Lymphocytes/virology , Cell Differentiation , Cells, Cultured , Epigenesis, Genetic , Epitopes, T-Lymphocyte/immunology , Female , Gene Expression Regulation , Immunologic Memory , Mice , Mice, Inbred C57BL , Mice, Knockout , Programmed Cell Death 1 Receptor/genetics , Viral LoadABSTRACT
During chronic infection, virus-specific CD8+ cytotoxic T lymphocytes (CTLs) progressively lose their ability to mount effective antiviral responses. This "exhaustion" is coupled to persistent upregulation of inhibitory receptor programmed death-1 (PD-1) (Pdcd1)-key in suppressing antiviral CTL responses. Here, we investigate allelic Pdcd1 subnuclear localization and transcription during acute and chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. Pdcd1 alleles dissociate from transcriptionally repressive chromatin domains (lamin B) in virus-specific exhausted CTLs but not in naive or effector CTLs. Relative to naive CTLs, nuclear positioning and Pdcd1-lamina dissociation in exhausted CTLs reflect loss of Pdcd1 promoter methylation and greater PD-1 upregulation, although a direct correlation is not observed in effector cells, 8 days post-infection. Genetic deletion of B lymphocyte-induced maturation protein 1 (Blimp-1) enhances Pdcd1-lamina dissociation in effector CTLs, suggesting that Blimp-1 contributes to maintaining Pdcd1 localization to repressive lamina. Our results identify mechanisms governing Pdcd1 subnuclear localization and the broader role of chromatin dynamics in T cell exhaustion.
Subject(s)
Lymphocytic Choriomeningitis , Lymphocytic choriomeningitis virus , Mice, Inbred C57BL , Programmed Cell Death 1 Receptor , T-Lymphocytes, Cytotoxic , Animals , Programmed Cell Death 1 Receptor/metabolism , Programmed Cell Death 1 Receptor/genetics , Lymphocytic choriomeningitis virus/immunology , Mice , Lymphocytic Choriomeningitis/immunology , Lymphocytic Choriomeningitis/virology , T-Lymphocytes, Cytotoxic/immunology , T-Lymphocytes, Cytotoxic/metabolism , Cell Nucleus/metabolism , Positive Regulatory Domain I-Binding Factor 1/metabolism , Positive Regulatory Domain I-Binding Factor 1/genetics , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/metabolism , Chronic Disease , Promoter Regions, Genetic/genetics , Genetic LociABSTRACT
Prolonged exposure of CD8+ T cells to their cognate antigen can result in exhaustion of effector functions enabling the persistence of infected or transformed cells. Recent advances in strategies to rejuvenate host effector function using Immune Checkpoint Blockade have resulted in tremendous success towards the treatment of several cancers. However, it is unclear if T cell rejuvenation results in long-lived antitumor functions. Emerging evidence suggests that T cell exhaustion may also represent a significant impediment in sustaining long-lived antitumor activity by chimeric antigen receptor T cells. Here, we discuss current findings regarding transcriptional regulation during T cell exhaustion and address the hypothesis that epigenetics may be a potential barrier to achieving the maximum benefit of T cell-based immunotherapies.