HTLV-1 propels thymic human T cell development in “human immune system” Rag2-/- gamma c-/- Mice

Alteration of early haematopoietic development is thought to be responsible for the onset of immature leukemias and lymphomas. We have previously demonstrated that TaxHTLV-1 interferes with ß- selection, an important checkpoint of early thymopoiesis, indicating that human T-cell leukemia virus type 1 (HTLV-1) infection has the potential to perturb thymic human αβ T-cell development. To verify that inference and to clarify the impact of HTLV-1 infection on human T-cell development, we investigated the in vivo effects of HTLV-1 infection in a “Human Immune System” (HIS) Rag2-/-γc-/- mouse model. These mice were infected with HTLV-1, at a time when the three main subpopulations of human thymocytes have been detected. In all but two inoculated mice, the HTLV-1 provirus was found integrated in thymocytes; the proviral load increased with the length of the infection period. In the HTLV-1-infected mice we observed alterations in human T-cell development, the extent of which correlated with the proviral load. Thus, in the thymus of HTLV-1-infected HIS Rag2-/-γc-/- mice, mature single-positive (SP) CD4+ and CD8+ cells were most numerous, at the expense of immature and double-positive (DP) thymocytes. These SP cells also accumulated in the spleen. Human lymphocytes from thymus and spleen were activated, as shown by the expression of CD25: this activation was correlated with the presence of tax mRNA and with increased expression of NF-kB dependent genes such as bfl-1, an anti-apoptotic gene, in thymocytes. Finally, hepato-splenomegaly, lymphadenopathy and lymphoma/thymoma, in which Tax was detected, were observed in HTLV-1-infected mice, several months after HTLV-1 infection. These results demonstrate the potential of the HIS Rag2-/-γc-/- animal model to elucidate the initial steps of the leukemogenic process induced by HTLV-1

HTLV-1 propels thymic human T cell development in “human immune system” Rag2-/- IL-2R γc-/- Mice

Alteration of early haematopoietic development is thought to be responsible for the onset of immature leukemias and lymphomas. We have previously demonstrated that TaxHTLV-1 interferes with ß-selection, an important checkpoint of early thymopoiesis, indicating that human T-cell leukemia virus type 1 (HTLV-1) infection has the potential to perturb thymic human αβ T-cell development. To verify that inference and to clarify the impact of HTLV-1 infection on human T-cell development, we investigated the in vivo effects of HTLV-1 infection in a “Human Immune System” (HIS) Rag2-/-γc-/- mouse model. These mice were infected with HTLV-1, at a time when the three main subpopulations of human thymocytes have been detected. In all but two inoculated mice, the HTLV-1 provirus was found integrated in thymocytes; the proviral load increased with the length of the infection period. In the HTLV-1-infected mice we observed alterations in human T-cell development, the extent of which correlated with the proviral load. Thus, in the thymus of HTLV-1-infected HIS Rag2-/-γc-/- mice, mature single-positive (SP) CD4+ and CD8+ cells were most numerous, at the expense of immature and double-positive (DP) thymocytes. These SP cells also accumulated in the spleen. Human lymphocytes from thymus and spleen were activated, as shown by the expression of CD25: this activation was correlated with the presence of tax mRNA and with increased expression of NF-kB dependent genes such as bfl-1, an anti-apoptotic gene, in thymocytes. Finally, hepato-splenomegaly, lymphadenopathy and lymphoma/thymoma, in which Tax was detected, were observed in HTLV-1-infected mice, several months after HTLV-1 infection. These results demonstrate the potential of the HIS Rag2-/-γc-/- animal model to elucidate the initial steps of the leukemogenic process induced by HTLV-1

Evaluation de l activité pro-leucémogène de la protéine TaxHTLV-1 dans les thymocytes immatures humains

Le rétrovirus HTLV-1 est l agent étiologique de la Leucémie T de l Adulte (ATL). La protéine virale Tax participe au processus leucémogène en favorisant la survie et la prolifération des cellules infectées. Cependant, la cellule initiale au sein de laquelle ce processus se met en place reste inconnue. Ces travaux portent sur les effets de Tax dans une population de cellules cibles potentielles, les thymocytes immatures humains au niveau de la sélection b. Ce point de contrôle se caractérise par l expression d un pré-TCR, qui envoie des signaux de survie et de prolifération aux cellules exprimant une chaîne b fonctionnelle. Cette chaîne b est associée à la chaîne invariante pTa et aux molécules du CD3. Nous avons montré que la protéine virale Tax inhibe l activité des protéines E2A sur le promoteur du gène pTa. De plus, Tax inhibe la transcription du gène pTa dans des thymocytes immatures humains fraîchement isolés. Ces résultats suggèrent que les thymocytes ne pourront pas exprimer le pré-TCR requis pour leur survie. Cependant, nous avons également démontré que Tax était capable d activer la transcription des gènes codant pour les sous-unités p50 et p65 du facteur NF- B ainsi que pour les protéines anti-apoptotiques Bfl-1 et BclXL dans les thymocytes immatures. Tax pourrait ainsi pallier l absence du pré-TCR. Par ailleurs, Tax active l expression de l oncogène Tal-1 dans les thymocytes immatures. La perturbation du développement T étant associée au développement de leucémies, l interférence de Tax avec la sélection b pourrait correspondre au premier évènement du processus leucémogène associé à une infection par HTLV-1The HTLV-1 retrovirus is the etiologic agent of Adult T cell Leukaemia (ATL). The viral protein Tax is involved in the leukemic process, favoring the survival and the proliferation of infected T-cells. However, the initial cell that could sustain the leukemic process remains unknown. Herein, we studied the effect of Tax in potential target cells, namely human immature thymocytes undergoing -selection. This checkpoint is characterized by the surface expression of the pre-TCR that allows proliferation and survival of thymocytes expressing a functional beta chain. The pre-TCR is composed of the newly rearranged -chain in association with the pT invariant chain and CD3 molecules. We showed that the viral protein inhibits the transcriptional activity of E2A proteins on the promoter of the pT gene. Furthermore, Tax down-regulates the expression of pT transcripts in freshly isolated human immature thymocytes. These results suggest that Tax prevents the expression of the pre-TCR required for the survival of thymocytes. However, we have also demonstrated in immature thymocytes that Tax triggers the expression of genes coding for the p50 and p65 NF- B subunits, as well as for Bfl-1 and Bcl-Xl anti-apoptotic proteins. Thus, Tax could palliate the absence of pre-TCR signalling. Besides, Tax induces the expression of Tal-1 oncogene in immature thymocytes. Considering that leukemias are induced by disturbances in haematopoietic cells development, the expression of Tax in human immature thymocytes could be a pre-requisite to the emergence of ATL cellsLYON1-BU.Sciences (692662101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Epigenetic and transcriptional regulation of γδ T cell differentiation: Programming cells for responses in time and space

International audienceγδ T cells are major providers of the pro-inflammatory cytokines interferon-γ (IFNγ) and interleukin-17 (IL-17) in protective or pathogenic immune responses. Notably, murine γδ T cells commit to either IFNγ or IL-17 production during development in the thymus, before any subsequent activation in the periphery. Here we discuss the molecular networks that underlie thymic γδ T cell differentiation, as well as the mechanisms that sustain or modify their functional properties in the periphery. We concentrate on recent findings on lymphoid and tissue-resident γδ T cell subpopulations, with an emphasis on genome-wide studies and their added value to elucidate the regulation of γδ T cell differentiation at the transcriptional and epigenetic (chromatin) levels

Human T-Cell Leukemia Virus Type 1 Tax Protein Down-Regulates Pre-T-Cell Receptor Alpha Gene Transcription in Human Immature Thymocytes

The human pre-T-cell receptor alpha (TCRα; pTα) gene encodes a polypeptide which associates with the TCRβ chain and CD3 molecules to form the pre-TCR complex. The surface expression of the pre-TCR is pTα dependent, and signaling through this complex triggers an early αβ T-cell developmental checkpoint inside the thymus, known as β-selection. E2A transcription factors, which are involved at multiple stages of T-cell development, regulate the transcription of the pTα gene. Here we show that the regulatory protein Tax of the human T-cell leukemia virus type 1 (HTLV-1) efficiently suppresses the E47-mediated activation of the pTα promoter. Furthermore, we report that in Tax lentivirally transduced human MOLT-4 T cells, which constitutively express the pTα gene, the amount of pTα transcripts decreases. Such a decrease is not observed in MOLT-4 cells transduced by a vector encoding the Tax mutant K88A, which is unable to interact with p300. These data underline that Tax inhibits pTα transcription by recruiting this coactivator. Finally, we show that the expression of Tax in human immature thymocytes results in a decrease of pTα gene transcription but does not modify the level of E47 transcripts. These observations indicate that Tax, by silencing E proteins, down-regulates pTα gene transcription during early thymocyte development. They further provide evidence that Tax can interfere with an important checkpoint during T-cell differentiation in the thymus

Human Naive and Memory T Cells Display Opposite Migratory Responses to Sphingosine-1 Phosphate

International audienceThe role of sphingosine-1 phosphate (S1P) in leukocyte trafficking has been well deciphered in mice but remains largely unaddressed in humans. In this study, we assessed the ex vivo response to S1P of primary human T cell subsets. We found that tonsil but not blood leukocytes were responsive to S1P gradients, suggesting that T cell responsiveness is regulated during their recirculation in vivo. Tonsil naive T cells were readily chemoattracted by S1P in an FTY720-sensitive, S1PR1-dependent manner. Surprisingly, S1P had the opposite effect on effector memory T cells, resident memory T cells, and recently activated T cells, inhibiting their spontaneous or chemokine-induced migration. This inhibition was also more pronounced for CD4 T cells than for CD8 T cell subsets, and was dependent on S1PR2, as shown using the S1PR2 antagonist JTE-013. S1PR1 was progressively downregulated during T cell differentiation whereas S1PR2 expression remained stable. Our results suggest that the ratio between S1PR1 and S1PR2 governs the migratory behavior of T cell subsets. They also challenge previous models of the role of S1P in lymphocyte recirculation and suggest that S1P promotes retention of memory T cell subsets in secondary lymphoid organs, via S1PR2

The inflammasome adaptor ASC delays UV-induced skin tumorigenesis in Beta HPV38 E6 and E7 Transgenic mice.

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Cutting Edge : adaptive versus innate receptor signals selectively control the pool sizes of murine IFN-γ- or IL-17-producing γβ T cells upon infection

©2010 by The American Association of Immunologists, Inc. All rights reserved.γβ T lymphocytes are commonly viewed as embracing properties of both adaptive and innate immunity. Contributing to this is their responsiveness to pathogen products, either with or without the involvement of the TCR and its coreceptors. This study clarifies this paradoxical behavior by showing that these two modes of responsiveness are the properties of two discrete sets of murine lymphoid γβ T cells. Thus, MyD88 deficiency severely impaired the response to malaria infection of CD27(-), IL-17A–producing γβ T cells, but not of IFN-γ–producing γβ cells. Instead, the latter compartment was severely contracted by ablating CD27, which synergizes with TCRγβ in the induction of antiapoptotic mediators and cell cycle-promoting genes in CD27(+), IFN-γ–secreting γβ T cells. Hence, innate versus adaptive receptors differentially control the peripheral pool sizes of discrete proinflammatory γβ T cell subsets during immune responses to infection.This work was supported by an installation grant from the European Molecular Biology Organization (to B.S.-S.), Grants PTDC/SAU-MII/104158/2008 (to B.S.-S.) and PTDC/SAU-MII/099314/2008 (to J.P.S.) from Fundação para a Ciência e Tecnologia, and the Wellcome Trust (to A.C.H. and M.W.)

Zeb1 represses TCR signaling, promotes the proliferation of T cell progenitors and is essential for NK1.1+ T cell development

International audienceT cell development proceeds under the influence of a network of transcription factors (TFs). The precise role of Zeb1, a member of this network, remains unclear. Here, we report that Zeb1 expression is induced early during T cell development in CD4 − CD8 − double-negative (DN) stage 2 (DN2). Zeb1 expression was further increased in the CD4 + CD8 + double-positive (DP) stage before decreasing in more mature T cell subsets. We performed an exhaustive characterization of T cells in Cellophane mice that bear Zeb1 hypomorphic mutations. The Zeb1 mutation profoundly affected all thymic subsets, especially DN2 and DP cells. Zeb1 promoted the survival and proliferation of both cell populations in a cell-intrinsic manner. In the periphery of Cellophane mice, the number of conventional T cells was near normal, but invariant NKT cells, NK1.1 + γδ T cells and Ly49 + CD8 T cells were virtually absent. This suggested that Zeb1 regulates the development of unconventional T cell types from DP progenitors. A transcriptomic analysis of WT and Cellophane DP cells revealed that Zeb1 regulated the expression of multiple genes involved in the cell cycle and TCR signaling, which possibly occurred in cooperation with Tcf1 and Heb. Indeed, Cellophane DP cells displayed stronger signaling than WT DP cells upon TCR engagement in terms of the calcium response, phosphorylation events, and expression of early genes. Thus, Zeb1 is a key regulator of the cell cycle and TCR signaling during thymic T cell development. We propose that thymocyte selection is perturbed in Zeb1-mutated mice in a way that does not allow the survival of unconventional T cell subsets