Search

Special AT‐binding protein 1 (SATB1) is a chromatin‐binding protein that has been shown to be a key regulator of T‐cell development and CD4+ T‐cell fate decisions and function. The underlying function for SATB1 in peripheral CD8+ T‐cell differentiation processes is largely unknown. To address this, we examined SATB1‐binding patterns in naïve and effector CD8+ T cells demonstrating that SATB1 binds to noncoding regulatory elements linked to T‐cell lineage–specific gene programs, particularly in naïve CD8+ T cells. We then assessed SATB1 function using N‐ethyl‐N‐nitrosourea‐mutant mice that exhibit a point mutation in the SATB1 DNA‐binding domain (termed Satb1m1Anu/m1Anu). Satb1m1Anu/m1Anu mice exhibit diminished SATB1‐binding, naïve, Satb1m1Anu/m1Anu CD8+ T cells exhibiting transcriptional and phenotypic characteristics reminiscent of effector T cells. Upon activation, the transcriptional signatures of Satb1m1Anu/m1Anu and wild‐type effector CD8+ T cells converged. While there were no overt differences, primary respiratory infection of Satb1m1Anu/m1Anu mice with influenza A virus (IAV) resulted in a decreased proportion and number of IAV‐specific CD8+ effector T cells recruited to the infected lung when compared with wild‐type mice. Together, these data suggest that SATB1 has a major role in an appropriate transcriptional state within naïve CD8+ T cells and ensures appropriate CD8+ T‐cell effector gene expression upon activation. [ABSTRACT FROM AUTHOR]

SH1 is the only reported isolate of a spherical halovirus, a dominant morphotype in hypersaline lakes. The virus lytically infects the haloarchaeon Haloarcula hispanica, and carries a 30.9 kb linear dsDNA genome that, in a previous study, was proposed to contain 56 protein-coding genes, probably organized into between four and eight operons. In the present study, these predictions were directly tested by determining the orientations and lengths of virus transcripts using systematic RT-PCR and primer extension. Seven major transcripts were observed that together covered most of the genome. Six transcripts were synthesized from early in infection (1 h post-infection; p.i.) onwards, while transcript T6 was only detected late in infection (5-6 h p.i.). No transcripts were detected in the inverted terminal repeat sequences or at the extreme right end of the genome (ORFs 55-56). Start points for the major transcripts were mapped by primer extension and corresponded closely to the 5' termini determined by RT-PCR. Between 1 and 4 h p.i., transcripts usually terminated not far beyond the end of their last coding ORF, but late in infection, transcripts from the same promoters often terminated at more distal points, resulting in much of the genome being transcribed from both strands. Since many of these transcripts are complementary, RNA-RNA interactions are likely, and may play a role in regulating viral gene expression. Puromycin blockage of post-infection protein synthesis significantly altered the levels of certain virus transcripts, indicating that de novo protein synthesis is essential for the correct regulation of SH1 gene expression.

There is continued interest in developing novel vaccine strategies that induce establish optimal CD8+ cytotoxic T lymphocyte (CTL) memory for pathogens like the influenza A viruses (IAVs), where the recall of IAV-specific T cell immunity is able to protect against serologically distinct IAV infection. While it is well established that CD4+ T cell help is required for optimal CTL responses and the establishment of memory, when and how CD4+ T cell help contributes to determining the ideal memory phenotype remains unclear. We assessed the quality of IAV-specific CD8+ T cell memory established in the presence or absence of a concurrent CD4+ T cell response. We demonstrate that CD4+ T cell help appears to be required at the initial priming phase of infection for the maintenance of IAV-specific CTL memory, with "unhelped" memory CTL exhibiting intrinsic dysfunction. High-throughput RNA-sequencing established that distinct transcriptional signatures characterize the helped vs. unhelped IAV-specific memory CTL phenotype, with the unhelped set showing a more "exhausted T cell" transcriptional profile. Moreover, we identify that unhelped memory CTLs exhibit defects in a variety of energetic pathways, leading to diminished spare respiratory capacity and diminished capacity to engage glycolysis upon reactivation. Hence, CD4+ T help at the time of initial priming promotes molecular pathways that limit exhaustion by channeling metabolic processes essential for the rapid recall of memory CD8+ T cells. [ABSTRACT FROM AUTHOR]

Numerous studies have focused on the molecular regulation of perforin (PFP) and granzyme B (GZMB) expression by activated cytotoxic T lymphocytes (CTLs), but little is known about the molecular factors that underpin granzyme A (GZMA) expression. In vitro activation of naïve CD8+ T cells, in the presence of IL-4, enhanced STAT6-dependent GZMA expression and was associated with GATA3 binding and enrichment of transcriptionally permissive histone posttranslational modifications (PTMs) across the Gzma gene locus. While GZMA expression by effector influenza A virus specific CTLs was also associated with a similar permissive epigenetic signature, memory CTL lacked enrichment of permissive histone PTMs at the Gzma locus, although this was restored within recalled secondary effector CTLs. Importantly, GZMA expression by virus-specific CTLs was associated with GATA3 binding at the Gzma locus, and independent of STAT6-mediated signaling. This suggests regulation of GZMA expression is underpinned by differentiation-dependent regulation of chromatin composition at the Gzma locus and that, given GATA3 is key for CTL differentiation in response to infection, GATA3 expression is regulated by a distinct, IL-4 independent, signaling pathway. Overall, this study provides insights into the molecular mechanisms that control transcription of Gzma during virus-induced CD8+ T-cell differentiation. [ABSTRACT FROM AUTHOR]

A cardinal feature of adaptive, cytotoxic T lymphocyte (CTL)-mediated immunity is the ability of naïve CTLs to undergo a program of differentiation and proliferation upon activation resulting in the acquisition of lineage-specific T cell functions and eventual establishment of immunological memory. In this review, we examine the molecular factors that shape both the acquisition and maintenance of lineage-specific effector function in virus-specific CTL during both the effector and memory phases of immunity. [ABSTRACT FROM AUTHOR]

Although the importance of genome organization for transcriptional regulation of cell-fate decisions and function is clear, the changes in chromatin architecture and how these impact effector and memory CD8 + T cell differentiation remain unknown. Using Hi-C, we studied how genome configuration is integrated with CD8 + T cell differentiation during infection and investigated the role of CTCF, a key chromatin remodeler, in modulating CD8 + T cell fates through CTCF knockdown approaches and perturbation of specific CTCF-binding sites. We observed subset-specific changes in chromatin organization and CTCF binding and revealed that weak-affinity CTCF binding promotes terminal differentiation of CD8 + T cells through the regulation of transcriptional programs. Further, patients with de novo CTCF mutations had reduced expression of the terminal-effector genes in peripheral blood lymphocytes. Therefore, in addition to establishing genome architecture, CTCF regulates effector CD8 + T cell heterogeneity through altering interactions that regulate the transcription factor landscape and transcriptome., Competing Interests: Declaration of interests A.W.G. is a member of the scientific advisory board of ArsenalBio. S.J.T. is a member of the scientific advisory board for Medicago, Inc., QC, Canada. No funding from Medicago or ArsenalBio was provided for this work., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Naive CD8 + T cell activation results in an autonomous program of cellular proliferation and differentiation. However, the mechanisms that underpin this process are unclear. Here, we profile genome-wide changes in chromatin accessibility, gene transcription, and the deposition of a key chromatin modification (H3K27me3) early after naive CD8 + T cell activation. Rapid upregulation of the histone demethylase KDM6B prior to the first cell division is required for initiating H3K27me3 removal at genes essential for subsequent T cell differentiation and proliferation. Inhibition of KDM6B-dependent H3K27me3 demethylation limits the magnitude of an effective primary virus-specific CD8 + T cell response and the formation of memory CD8 + T cell populations. Accordingly, we define the early spatiotemporal events underpinning early lineage-specific chromatin reprogramming that are necessary for autonomous CD8 + T cell proliferation and differentiation., Competing Interests: Declaration of interests S.R. is currently the founder/chief scientific officer of EpiAxis Therapeutics. This manuscript received no funding from EpiAxis for this work. S.J.T. is a member of the scientific advisory board for Medicago, Inc., QC, Canada. This manuscript received no funding from Medicago for this work., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Interactions with the microbiota influence many aspects of immunity, including immune cell development, differentiation, and function. Here, we examined the impact of the microbiota on CD8 + T cell memory. Antigen-activated CD8 + T cells transferred into germ-free mice failed to transition into long-lived memory cells and had transcriptional impairments in core genes associated with oxidative metabolism. The microbiota-derived short-chain fatty acid (SCFA) butyrate promoted cellular metabolism, enhanced memory potential of activated CD8 + T cells, and SCFAs were required for optimal recall responses upon antigen re-encounter. Mechanistic experiments revealed that butyrate uncoupled the tricarboxylic acid cycle from glycolytic input in CD8 + T cells, which allowed preferential fueling of oxidative phosphorylation through sustained glutamine utilization and fatty acid catabolism. Our findings reveal a role for the microbiota in promoting CD8 + T cell long-term survival as memory cells and suggest that microbial metabolites guide the metabolic rewiring of activated CD8 + T cells to enable this transition., (Copyright © 2019 Elsevier Inc. All rights reserved.)

There is continued interest in developing novel vaccine strategies that induce establish optimal CD8 + cytotoxic T lymphocyte (CTL) memory for pathogens like the influenza A viruses (IAVs), where the recall of IAV-specific T cell immunity is able to protect against serologically distinct IAV infection. While it is well established that CD4 + T cell help is required for optimal CTL responses and the establishment of memory, when and how CD4 + T cell help contributes to determining the ideal memory phenotype remains unclear. We assessed the quality of IAV-specific CD8 + T cell memory established in the presence or absence of a concurrent CD4 + T cell response. We demonstrate that CD4 + T cell help appears to be required at the initial priming phase of infection for the maintenance of IAV-specific CTL memory, with "unhelped" memory CTL exhibiting intrinsic dysfunction. High-throughput RNA-sequencing established that distinct transcriptional signatures characterize the helped vs. unhelped IAV-specific memory CTL phenotype, with the unhelped set showing a more "exhausted T cell" transcriptional profile. Moreover, we identify that unhelped memory CTLs exhibit defects in a variety of energetic pathways, leading to diminished spare respiratory capacity and diminished capacity to engage glycolysis upon reactivation. Hence, CD4 + T help at the time of initial priming promotes molecular pathways that limit exhaustion by channeling metabolic processes essential for the rapid recall of memory CD8 + T cells., Competing Interests: The authors declare no conflict of interest.