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EBV infects and immortalizes B cells in vitro and in vivo. It is the causative agent of most immune deficiency–related lymphoproliferative disorders and is associated with various lymphomas. EBV latency III–transformed B cells are known to express two immunosuppressive molecules, IL-10 and PD-L1, two characteristics of regulatory B cells (Bregs). In this study, we show that, in addition to secretion of the Breg immunosuppressive cytokines IL-10, IL-35, and TGF-β1, EBV latency III–transformed B cells were able to repress proliferation of their autologous T cells preactivated by CD2, CD3, and CD28. This inhibitory effect was likely caused by CD4+ T cells because EBV latency III–transformed B cells induced a strong proliferation of isolated autologous CD8 T cells. Indeed, EBV was able to promote expansion of autologous FOXP3+ CD39high CTLA4+, Helios+, GITR+, LAG3+ CD4 T cells (i.e., regulatory T cells [Tregs]). Two types of Tregs were induced: unconventional CD25neg and conventional CD25pos Tregs. These Tregs expressed both the latency-associated peptide (LAP) and the PD-1 receptor, two markers of functional Tregs. Expansion of both Treg subtypes depended on PD-L1, whose expression was under the control of LMP1, the main EBV oncogene. These results demonstrate that, like Bregs, EBV latency III–transformed B cells exhibit strong immunoregulatory properties. These data provide clues to the understanding of how after EBV primo-infection, EBV-proliferating B cells can survive in an aggressive immunological environment and later emerge to give rise to EBV-associated B cell lymphomas such as in elderly patients.

Designing multitarget drugs have raised considerable interest due to their advantages in the treatment of complex diseases such as cancer. Their design constitutes a challenge in antitumor drug discovery. The present study reports a dual inhibition of tubulin polymerization and HDAC activity. On the basis of 1,1-diarylethylenes ( isoCA-4) and belinostat, a series of hybrid molecules was successfully designed and synthesized. In particular compounds, 5f and 5h were proven to be potent inhibitors of both tubulin polymerization and HDAC8 leading to excellent antiproliferative activity.

EBV-immortalized B cells induce a complex immune response such that the virus persists as a clinically silent infection for the lifetime of the infected host. B7-H1, also called PD-L1, is a cosignaling molecule of the B7 family that can inhibit activated T cell effectors by interaction with its receptor PD-1. In this work, we have studied the dependence of B7-H1 on NF-κB and c-Myc, the two main transcription factors in EBV latency III proliferating B cells, on various lymphoblastoid and Burkitt lymphoma cell lines, some of them being inducible or not for the EBV latency III program and/or for c-Myc. We found that B7-H1 repressed killing of EBV-immortalized B cells by their autologous T and NK cells. At the mRNA level, NF-κB was a weak inducer whereas c-Myc was a strong repressor of B7-H1 expression, an effect mediated by STAT1 inhibition. At the protein level, B7-H1 molecules were stored in both degradative and unconventional secretory lysosomes. Surface membrane B7-H1 molecules were constitutively internalized and proteolyzed in lysosomes. The EBV latency III program increased the amounts of B7-H1–containing secretory lysosomes and their export to the surface membrane. By repressing actin polymerization, c-Myc blocked secretory lysosome migration and B7-H1 surface membrane export. In addition to B7-H1, various immunoregulatory molecules participating in the immunological synapse are stored in secretory lysosomes. By playing on actin polymerization, c-Myc could thus globally regulate the immunogenicity of transformed B cells, acting on export of secretory lysosomes to plasma membrane.

International audience; Fluorescent labeled monoclonal antibodies (mAbs) against CD36 are routinely used as monocyte, erythroid, or platelet markers in clinical cytometry. CD36 has recently been proposed by various authors as a valuable marker helping to enumerate leukocyte's subpopulations by flow cytometry. However, it is known that binding of CD36 may induce platelet activation and formation of platelet's rosettes on leukocytes, resulting in false expression of platelet markers on white blood cells. To study this phenomenon, we have combined classical flow cytometry and a new quantitative flow imaging technique with the ImageStream(®) analyzer. We show that CD36 ligation induces activation of platelets with CD62 expression and their adhesion on leukocytes due to CD62 and CD162 interactions. Preincubation of whole blood samples with either anti-CD62 or anti-CD162 antibodies could prevent formation of these rosettes. Our approach also emphasizes the fact that immunomorphological analysis of cell events with ImageStream technology is a useful tool to validate the specificity of marker's labeling or to elucidate incoherent results obtained with classical flow cytometry. We thus propose to prevent false platelet labeling on leukocytes by preincubation with either anti-CD62 or anti-CD162 antibodies when using CD36 mAbs.

International audience; B-cell fate and responses are modulated by soluble mediators and direct cellular interactions. Migration properties also vary during differentiation, commitment and activation. In many cells, modulation of responses to stimuli involves cell surface glycans, whose architecture depends on the simultaneous expression of multiple enzymes. By looking at the glycosylation-related gene expression patterns among B cell populations, we determined in this study that the strongest variations were observed for CSGalNAcT-1 and EXTL1. These are enzymes involved in the biosynthesis of alternative forms of glycosaminoglycans, namely chondroitin sulphate and heparan sulphate respectively. These two enzymes showed inverse fluctuations in progenitors, resting B cells and activated B cells, suggesting a developmentally regulated switch between chondroitin and heparan sulphate synthesis. To explore whether these variations contributed to optimal B cell differentiation, we over-expressed EXTL1 in the B-cell lineage of transgenic mice, yielding a partial differentiation blockade at the pro-B to pre-B transition. In the periphery, this defect was almost fully compensated for in vivo, with normal-size B-cell compartments and normal serum immunoglobulin levels in the transgenic EXTL1 mice. The peripheral B cells from EXTL1 transgenics were only affected with regard to their in vitro responses to polyclonal activation, showing reduced proliferation. Together the data suggest that, despite their low amounts in lymphocytes, the heparan sulphate chains decorating the endogenous glycosaminoglycans appear to be regulators of B-cell physiology.

International audience; A central event in the formation of infectious prions is the conformational change of a host-encoded glycoprotein, PrPC, into a pathogenic isoform, PrPSc. The molecular requirements for efficient PrP conversion remain unknown. Altered glycosylation has been linked to various pathologies and the N-glycans harbored by two prion protein isoforms are different. In order to search for glycosylation-related genes that could mark prion infection, we used a glycosylation-dedicated microarray that allowed the simultaneous analysis of the expression of 165 glycosylation-related genes encoding proteins of the glycosyltransferase, glycosidase, lectin, and sulfotransferase families to compare the gene expression profiles of normal and scrapie-infected mouse brain and spleen. Eight genes were found upregulated in "scrapie brain" at the final state of the disease. In the spleen, five genes presented a modified expression. Three genes were also upregulated in the spleen of infected mice, and two (Pigq and St3gal5) downregulated. All changes were confirmed by qPCR and biochemical analyses applied to Pigq and St3gal5 proteins.

Ursolic acid (UA) is a pentacyclic triterpenoid compound which exists widely in nature and is known to have a pleitropic biological activity profile. For the last few decades, extensive work has been carried out to establish its biological activities and pharmacological actions. It is described as a promising chemopreventive agent with an antiproliferative effect on cancer cells that stems from its ability to induce apoptosis. We investigated and compared the role played by mitochondria during the apoptotic process induced by UA in human HaCaT-derived keratinotic cells and M4Beu human melanoma cells. In both cell lines, UA induced significant caspase-3 activation, the downstream central effector of apoptosis. Subsequent JC-1/TOTO-3 double staining clearly demonstrated that UA induces strong mitochondrial-transmembrane potential collapse in M4Beu cells, while mitochondria from HaCaT-treated cells remain largely unstimulated. This was confirmed by Western blot analysis, which revealed a Bax/Bcl-2-balance change in favor of Bax, the proapoptotic member, in UA-treated M4Beu cells. It can be concluded that UA induces apoptosis in M4Beu through the mitochondrial pathway, while other mechanisms are activated in the case of HaCaT cells.

It is now well-established that P-glycoprotein 170 (P-gp), an efflux pump involved in multidrug resistance (MDR) is overexpressed at the plasma membrane of doxorubicin-resistant K562 leukemia cells. Nevertheless, several results suggested: (i) that P-gp-mediated drug efflux was not the only mechanism involved in resistance; (ii) that intracellular compartments could accumulate the drug, preventing it from reaching its nuclear targets; (iii) that agents able to reverse multidrug resistance may lead to intracellular drug redistribution. We have studied the localization of P-gp in mitochondria as well as its functional properties in this compartment. Using several monoclonal antibodies (MoAbs) directed against different P-gp epitopes, a protein was detected in the cytoplasm of two doxorubicin-resistant K562 sublines and, by confocal laser scanning microscopy, this protein was shown to co-localize in the Golgi apparatus and in mitochondria, in equivalent proportions. Purified mitochondria were isolated from K562 cell variants; the presence of a protein of about 170 kDa and reacting with several anti-P-gp antibodies was assessed in MDR cells by Western blotting and flow cytometry. Functional assays have shown that mitochondrial P-gp was involved in doxorubicin accumulation inside the organelle but not in its efflux, suggesting an orientation of P-gp in the mitochondrial membrane inverse to that observed in the plasma membrane. A potential role for mitochondrial P-gp in MDR cells would be to protect the nucleus from doxorubicin. This is the first demonstration of the presence and functional activity of P-gp in mitochondria of MDR cells.

Background: Age-related changes in the antibody response have been classically associated with alterations in T-cell help, but increasing evidence shows that intrinsic B-cell defects exist. This article analyzes the apoptotic susceptibility of peripheral B-cells in aged and young control mice. Materials and Methods: Freshly isolated lymphocytes from spleen and Peyer's patches (PPs) were labeled for B-cell lineage (B220+ cells) and germinal center B subset (GCs, B220+/PNA+ cells). Alternatively, splenic B-cells purified by MACS were used. Apoptosis was monitored by the Annexin V binding, incorporation of 3,3′-dihexyloxacarbocyanine iodide (DiOC6(3)), propidium iodide (PI) staining, and morphological changes. Moreover, intracellular Bcl-2 expression and Bad phosphorylation status were also analyzed in B-cells. Results: We showed in aging mice an enhanced Annexin V+/PI− cell percentage in splenic B-lymphocytes, which was correlated with a lower ΔΨm. By contrast, no change in apoptosis was observed in compartments known to be enriched in activated B-cells (GCs and PPs). Analysis of Bcl-2 levels revealed no modification. When using B-cells purified by MACS, we strongly confirm data obtained on staining cells. Moreover, enhanced spontaneous apoptosis of splenic B-cells in aged mice was found to be correlated with a reduced phosphorylated Bad expression. Conclusion: Increased apoptosis of resting B-cells in old mice may be determined by an altered Bad phosphorylation, which in turn contributes to cell death by lowering the mitochondrial threshold for apoptosis. © 2006 International Society for Analytical Cytology

The Epstein-Barr virus (EBV) is the first transforming virus discovered in humans. It infects more than 90% of the global adult population, persisting in an episomal form in the memory B-cell compartment throughout the life of the host. During primo-infection and during phases of viral reactivation, immortalized B-cells are in latency III, also called the proliferation program, in which the full range of latency proteins are expressed. In immunocompetent subjects, a balance between virus and host is established, and most infected B-cells are eliminated by the host’s immune system, mainly by cytotoxic T lymphocytes. Deficit of the immune system may lead to lymphomagenesis, such as post-transplantation lymphoproliferative disorders (PTLDs), non-Hodgkin’s (NHL) or Hodgkin’s lymphomas (HL). Previous studies in the lab revealed that the immuno-inhibitor PD-L1/B7-H1/CD274 was overexpressed on the surface of EBV latency III B-cells. Interleukin-10 (IL-10was also secreted by these cells. These features are shared with regulatory B-cells (Bregs). Our objective was to examine the immunomodulatory features of EBV latency III B-cells, in the frame of Bregproperties. We found that EBV latency III B-cells possessed the antigenic determinants common to immature Bregs (CD24High CD38High PD-L1High), associated with overexpression of Breg immunosuppressive cytokines (IL-10, TGF-β1 and IL-35). EBV latency III B-cells led to death of autologous CD4 T-cells, as well as inhibition of CD4 and CD8 T-lymphocyte proliferation, favoring regulatory T-cell (Treg) expansion. We found that this expansion was mediated by the PD-1/PD-L1 axis. This study highlights a new mechanism of EBV for t diversion of the host immune system thereby increasing its oncogenic properties., Le virus d’Epstein-Barr (EBV) est le premier virus transformant à avoir été identifié chez l’Homme. Il infecte plus de 90% de la population adulte mondiale, persistant sous forme épisomale dans le compartiment B mémoire tout au long de la vie de l’hôte. Lors de la primo-infection et lors de phases de réactivation du virus, les cellules B immortalisées sont en programme de latence III, aussi appelée phase de prolifération, où l’ensemble des protéines de latence sont exprimées. Lorsque les hôtes sont immunocompétents, un équilibre entre hôte et virus s’établit et la plupart des cellules B infectées sont éliminées par le système immunitaire de l’hôte, principalement par les lymphocytes T cytotoxiques. En cas de déficit immunitaire, il peut y avoir émergence de lymphomes, tels que les désordres lymphoprolifératifs des patients immunodéprimés (PTLDs), les lymphomes non-Hodgkiniens (LNH) et Hodgkiniens (LH). Les travaux antérieurs du laboratoire ont permis de révéler que l’immuno-inhibiteur PD-L1/B7-H1/CD274 est surexprimé à la surface des lymphocytes B en latence III de l’EBV. L’interleukine-10 (IL-10) est également sécrétée par ces cellules. Ces caractéristiques sont communes aux cellules B régulatrices (Bregs). Le but de ma thèse était d’interroger les caractéristiques immuno-modulatrices des cellules B en latence III de l’EBV, dans le cadre des propriétés des Bregs. Nous montrons que les cellules B en latence III de l’EBV possèdent les déterminants antigéniques communs aux Bregs immatures (CD24High CD38High PD-L1High), associée à une surexpression des cytokines immunosuppressives cardinales des Bregs (IL-10, TGF-β1 et IL-35). Nous montrons que les cellules B en latence III de l’EBV peuvent conduire à la mort des cellules T CD4 autologues, ainsi qu’à l’inhibition de la prolifération des lymphocytes T CD4 et CD8, au profit de l’expansion de lymphocytes T régulateurs (Tregs). Nous avons trouvé que cette expansion est médiée par l’axe PD-1/PD-L1. Ces travaux mettent en évidence un nouveau mécanisme de l’EBV concernant le détournement du système immunitaire de l’hôte, augmentant ses capacités oncogéniques.

Histone deacetylase inhibitors (HDAC) are a promising class of anticancer drugs. They can trigger the apoptotic pathway and are available for treatment of blood disorders. However, the HDACi that target HDAC class II, as vorinostat, also are potential reactivators agents of EBV, a virus that infects latently over 90% of the adult population worldwide and is associated with many type B lymphomas the study of switching between the latent cycle and the lytic cycle of EBV is essential to understand the impact of HDACi when treating B-cell lymphoma associated with EBV (salting risk virions in large quantities during the chemotherapeutic treatment).Our study focused on the effect of vorinostat (25 .mu.M for 48) on tumor B cells infected with EBV: three lines of Burkitt lymphoma (BL2B95.8, BL41B95.8 and P3HR1), three lymphoblastoid cell lines (1602 PRI and RUD) and B95.8 marmoset line in the lytic cycle of the EBV (positive control). We have demonstrated that vorinostat can induce EBV reactivation (P3HR1 and B95.8) or apoptosis (BL41B95.8, BL2B95.8, 1602, PRI and RUD) with a mutual inhibition of these two process. At the molecular level, we have shown that the active vorinostat constitutively and simultaneously initiating transcription factor reactivation MEF2D (by dephosphorylation) and MAP kinase p38 pro-apototique (phosphorylation) following the reduction in the expression of the MAP kinase phosphatase (MPK1) p38 which is a substrate. The pre-treatment with a p38 inhibitor (SB203580) showed that MAP kinase is both involved in the process of EBV reactivation and apoptosis. However, cell lines where p38 activation greatly increases during treatment with vorinostat, come directly into apoptosis, without there may EBV reactivation.Our results suggest that the level of activation of p38 MAP kinase helps regulate the balance reactivation / apoptosis of B cell EBV infected when exposed to an inducing agent for the reactivation, in particular in the case of cells B lymphoma treated with vorinostat. They raise the question of the use of HDACi in the treatment of lymphomas associated with EBV, with the risk of viral reactivation by level of intracellular activation of p38 and the need to simultaneously use an antiviral such as ganciclovir., Les inhibiteurs des histones désacétylase (HDACi) constituent une classe prometteuse de médicaments anticancéreux. Ils peuvent déclencher la voie apoptotique et sont proposés pour le traitement des désordres hématologiques. Cependant, les HDACi qui ciblent les HDAC de classe II, tel que le vorinostat, sont également des agents réactivateurs potentiels de l’EBV, un virus qui infecte de manière latente plus de 90% de la population adulte dans le monde et est associée à de nombreux lymphomes de type B. L’étude de la commutation entre le cycle latent et le cycle lytique de l’EBV est essentielle pour appréhender l’impact des HDACi lors du!traitement des lymphomes B associés à l’EBV (risque du relargage de virions en grande quantité lors des traitements chimio thérapeutiques).Notre étude a porté sur l'effet de vorinostat (25 μM pendant 48h) sur des cellules tumorales B infectées par l’EBV : trois lignées de lymphomes de burkitt (BL2B95.8, BL41B95.8 et P3HR1), trois lignées lymphoblastoides (1602, PRI et RUD) et la lignée B95.8 de marmouset en cycle lytique de l’EBV (contrôle positif). Nous avons mis en évidence que le vorinostat peut induire la réactivation de l’EBV (P3HR1 et B95.8) ou à l’apoptose (BL41B95.8, BL2B95.8, 1602, PRI et RUD) avec une inhibition mutuelle de ces deux processus. Au niveau moléculaire, nous avons pu montrer que le vorinostat active constitutivement et simultanément le facteur de transcription initiateur de la réactivation MEF2D (par déphosphorylation) et la MAP kinase pro-apototique p38 (par phosphorylation) suite à la diminution de l’expression de la MAP kinase phosphatase (MPK1) dont p38 est un substrat. Le pré-traitement avec un inhibiteur de p38 (SB203580) a mis en évidence que cette MAP kinase est à la fois impliquée dans les processus de réactivation de l’EBV et d’’apoptose. Cependant, les lignées cellulaires pour lesquelles l'activation de p38 augmente fortement lors du traitement par le vorinostat, entrent directement en apoptose, sans qu’il puisse y avoir réactivation de l’EBV.Nos résultats suggèrent que le niveau d’activation de la MAP kinase p38 permet de réguler la balance réactivation/apoptose des cellules B infectées par l’EBV lorsqu’elles sont soumises à un agent inducteur de la réactivation, en particulier dans le cas de cellules de lymphomes B traitées par le vorinostat. Ils posent la question de l’utilisation des HDACi lors du traitement des lymphomes associés à l'EBV, avec le risque d’une réactivation virale selon le niveau d’activation intracellulaire de p38 et la nécessité d’utiliser simultanément un anti-viral tel que le ganciclovir.