Modulating DNA Methylation in Activated CD8+ T Cells Inhibits Regulatory T Cell–Induced Binding of Foxp3 to the CD8+ T Cell IL-2 Promoter

Abstract

We have previously demonstrated that CD4+CD25+ Treg cells activated during the course of FIV infection suppress CD8+ CTL function in a TGFβ-dependent fashion, inhibiting IFNγ and IL2 production, and inducing G1 cell cycle arrest. Here, we describe the molecular events occurring at the IL2 promoter leading to suppression of IL2 production. These experiments demonstrate that FoxP3 induced by lentivirus-activated Treg cells in the CD8+ target cells binds to the IL2 promoter, actively repressing IL2 transcription. We further demonstrate that the chronic activation of CD8+ T cells during FIV infection results in chromatin remodeling at the IL2 promoter, specifically, demethylation of CpG residues. These DNA modifications occur during active transcription and translation of IL2; however, these changes render the IL2 promoter permissive to FoxP3-induced transcriptional repression. These data help explain, in part, the seemingly paradoxical observations that CD8+ T cells displaying an activation phenotype exhibit altered antiviral function. Further, we demonstrate that blocking demethylation of CpG residues at the IL2 promoter inhibits FoxP3 binding, suggesting a potential mechanism for rescue and / or reactivation of CD8+ T cells. Using the FIV model for lentiviral persistence, these studies provide a framework for understanding how immune activation combined with Treg cell-mediated suppression may affect CD8+ T cell IL2 transcription, maturation, and anti-viral function.

Feline Immunodeficiency Virus Neuropathogenesis: A Model for HIV-Induced CNS Inflammation and Neurodegeneration

“…Among the many achievements, these efforts led to approval of an effective FIV vaccine in 2002. Recent studies have addressed important issues such as mechanisms of FIV transmission, replication and evolution [ 22 , 23 , 24 , 25 , 26 , 27 ], FIV vaccine efficacy [ 28 , 29 ], the role of neutralizing antibodies in disease progression [ 28 , 30 , 31 ], virus assembly and release [ 32 , 33 ], viral latency and eradication strategies [ 34 , 35 , 36 ], development of adjunctive therapies [ 37 , 38 , 39 , 40 ], immunology [ 41 , 42 , 43 , 44 , 45 ], interactions with the microbiome [ 46 , 47 ], development of antiretroviral compounds [ 48 , 49 , 50 ] and development of protocols for assessing feline cognitive function [ 51 , 52 , 53 , 54 ]. Many of these efforts are summarized in this volume and in a review by Bienzle [ 55 ].…”

Epigenetic Modulation of CD8+ T Cell Function in Lentivirus Infections: A Review

“…Our research group has studied the molecular events responsible for CD8 + T cell dysfunction in the FIV model. Data by our lab and others suggest that FIV provirus and infected CD4 + T cells are epigenetically modulated during infection and that epigenetic modulators can be used to reverse these events [ 25 , 115 ]. We have further demonstrated that dysfunctional CD8 + T cells, that evolve during the chronic phase of FIV infection, are epigenetically modulated [ 115 ].…”

“…Our group has previously reported that, in the FIV model, lentivirus activated CD4 + CD25 + Treg cells signal via membrane bound TGF-β/Smad signaling to induce Foxp3 in CD8 + T cell targets [ 113 , 114 ]. We have also demonstrated that Foxp3 mediates antiviral cytokine suppression by directly binding to IL-2, TNF-α and IFN-γ promoter region in the acute and chronic phase of FIV infection [ 107 , 115 , 116 ]. Figure 2 B summarizes our findings demonstrating Treg-mediated CD8 + T cell suppression in the FIV model.…”

“…We have demonstrated that during FIV infection, CD8 + T cells directly interact with lentivirus activated Treg cells via a membrane bound TGF-β mechanism, inducing Foxp3 in these cells [ 113 , 114 ]. We have shown that Foxp3 binds to the IL-2, IFN-γ and TNF-α promoters in CD8 + T cells isolated from FIV-infected cats and that this binding is epigenetically modulated, via DNA de-methylation and histone acetylation ([ 115 , 116 ]; manuscript in preparation). We have also reported the microRNA 10a is upregulated in Foxp3 + Treg cells isolated from FIV-infected cats likely stabilizing Foxp3 expression in Treg cells ex vivo [ 133 ].…”

Micro-RNA 10a Is Increased in Feline T Regulatory Cells and Increases Foxp3 Protein Expression Following In Vitro Transfection

“…Isolation of T-cell populations: Peripheral blood mononuclear cells ( PBMCs ) from FIV + or FIV − cats were surface stained with CD4-APC and CD25-FITC and sorted into CD4 + CD25 − and CD4 + CD25 + T cell populations (>95% purity) as previously reported [ 24 , 25 ].…”