Profiling of signal transduction in human memory T cells

Résumé pour un large public: La vaccination a eu un impact énorme sur la santé mondiale. Mais, quel est le principe d'un vaccin? Il est basé sur la 'mémoire immunologique', qui est une particularité exclusive des systèmes immunitaires des organismes évolués. Suite à une infection par un pathogène, des cellules spécialisées de notre système immunitaire (les lymphocytes) le reconnaissent et initient une réaction immunitaire qui a pour but son élimination. Pendant cette réaction se développent aussi des cellules, appelées cellules lymphocytaires mémoire, qui persistent pour longue durée et qui ont la capacité de stimuler une réaction immunitaire très efficace immédiatement après une seconde exposition à ce même pathogène. Ce sont ces cellules mémoires (lymphocytes B et T) qui sont à la base de la 'mémoire immunologique' et qui sont stimulées lors de la vaccination. Chez l'homme, deux populations distinctes des lymphocytes T mémoires ont été identifiées: les cellules centrales (CM) et effectrices (EM) mémoires. Ces populations sont fonctionnellement hétérogènes et exercent des rôles distincts et essentiels dans l'immunité protectrice. Typiquement, les cellules effectrices mémoires sont capables de tuer immédiatement le pathogène tandis que les cellules centrales mémoires sont responsables d'initier une réponse immunitaire complète. Pourtant, les mécanismes biochimiques qui contrôlent les fonctions de ces cellules ont été jusqu'à présent peu étudiés à cause de la faible fréquence de ces cellules et de la quantité limitée de tissus humains disponibles pour les analyses. La compréhension de ces mécanismes est cruciale pour la réalisation de vaccins efficaces et pour le développement de nouveaux médicaments capables de moduler la réponse immunitaire lymphocytaire. Dans cette thèse, nous avons d'abord développé et amélioré une technologie appelée 'protéine array en phase inverse' qui possède un niveau de sensibilité beaucoup plus élevé par rapport aux technologies classiquement utilisées dans l'étude des protéines. Grâce à cette technique, nous avons pu comparer la composition protéique du système de transmission des signaux d'activation des cellules CM et EM humaines. L'analyse de 8 à 13 sujets sains a montré que ces populations des cellules mémoires possèdent un système de signalisation protéique différent. En effet, les cellules EM possèdent, par rapport aux cellules CM, des niveaux réduits d'une protéine régulatrice (appelée c-Cbl) que nous avons démontré comme étant responsable des fonctions spécifiques de ces cellules. En effet, en augmentant artificiellement l'expression de cette protéine régulatrice dans les cellules EM jusqu'au niveau de celui des cellules CM, nous avons induit dans les cellules EM des capacités fonctionnelles caractéristiques des cellules CM. En conclusion, notre étude a identifié, pour la première fois chez l'homme, un mécanisme biochimique qui contrôle les fonctions des populations des cellules mémoires. Résumé en Français: Les cellules mémoires persistent inertes dans l'organisme et produisent des réactions immunitaires rapides et robustes contre les pathogènes précédemment rencontrés. Deux populations distinctes des cellules mémoires ont été identifiées chez l'homme: les cellules centrales (CM) et effectrices (EM) mémoires. Ces populations sont fonctionnellement hétérogènes et exercent des rôles distincts et critiques dans l'immunité protectrice. Les mécanismes biochimiques qui contrôlent leurs fonctions ont été jusqu'à présent peu étudiés, bien que leur compréhension soit cruciale pour le développement des vaccins et des nouveaux traitements/médicaments. Les limites majeures à ces études sont la faible fréquence de ces populations et la quantité limitée de tissus humains disponibles. Dans cette thèse nous avons d'abord développé et amélioré la technologie de 'protéine array en phase inverse' afin d'analyser les molécules de signalisation des cellules mémoires CD4 et CD8 humaines isolées ex vivo. L'excellente sensibilité, la reproductibilité et la linéarité de la détection, ont permis de quantifier des variations d'expression protéiques supérieures à 20% dans un lysat équivalent à 20 cellules. Ensuite, grâce à l'analyse de 8 à 13 sujets sains, nous avons prouvé que les cellules mémoires CD8 ont une composition homogène de leur système de signalisation tandis que les cellules CD4 EM expriment significativement de plus grandes quantités de SLP-76 et des niveaux réduits de c-Cbl, Syk, Fyn et LAT par rapport aux cellules CM. En outre, l'expression réduite du régulateur négatif c-Cbl est corrélée avec l'expression des SLP-76, PI3K et LAT uniquement dans les cellules EM. L'évaluation des propriétés fonctionnelles des cellules mémoires a permis de démontrer que l'expression réduite du c-Cbl dans les cellules EM est associé à une diminution de leur seuil d'activation. En effet, grâce a la technique de transduction cytosolique, nous avons augmenté la quantité de c-Cbl des cellules EM à un niveau comparable à celui des cellules CM et constaté une réduction de la capacité des cellules EM à proliférer et sécréter des cytokines. Ce mécanisme de régulation dépend principalement de l'activité d'ubiquitine ligase de c-Cbl comme démontré par l'impact réduit du mutant enzymatiquement déficient de c-Cbl sur les fonctions de cellules EM. En conclusion, cette thèse identifie c-Cbl comme un régulateur critique des réponses fonctionnelles des populations de cellules T mémoires et fournit, pour la première fois chez l'homme, un mécanisme contrôlant l'hétérogénéité fonctionnelle des ces cellules. De plus, elle valide l'utilisation combinée des 'RPP arrays' et de la transduction cytosolique comme outil puissant d'analyse quantitative et fonctionnel des protéines de signalisation. Summary : Memory cells persist in a quiescent state in the body and mediate rapid and vigorous immune responses toward pathogens previously encountered. Two subsets of memory cells, namely central (CM) and effector (EM) memory cells, have been identified in humans. These subsets display high functional heterogeneity and assert critical and distinct roles in the control of protective immunity. The biochemical mechanisms controlling their functional properties remain so far poorly investigated, although their clarification is crucial for design of effective T-cell vaccine and drug development. Major limitations to these studies lie in the low frequency of memory T cell subsets and the limited amount of human specimen available. In this thesis we first implemented the innovative reverse phase protein array approach to profile 15 signalling components in human CD8 and CD4 memory T cells isolated ex vivo. The high degree of sensitivity, reproducibility and linearity achieved, allowed an excellent quantification of variations in protein expression higher than 20% in as few as 20-cell equivalent per spot. Based on the analysis of 8 to 13 healthy subjects, we showed that CD8 memory cells have a homogeneous composition of their signaling machinery while CD4 EM cells express statistically significant increased amounts of SLP-76 and reduced levels of c- Cbl, Syk, Fyn and LAT as compared to CM cells. Moreover, in EM but not CM cells, reduced expression of negative regulator c-Cbl correlated with the expression of SLP-76, PI3K and LAT. Subsequently, we demonstrated that the higher functional properties and the lower functional threshold of EM cells is associated with reduced expression of c-Cbl. Indeed, by increasing c-Cbl content of EM cells to the same level of CM cells using cytosolic transduction, we impaired their proliferation and cytokine production. This regulatory mechanism was primarily dependent on c-Cbl E3 ubiquitin ligase activity as evidenced by the weaker impact of enzymatically deficient c-Cbl C381A mutant on EM cell functions. Together, these results identify c-Cbl as a critical regulator of the functional responses of memory T cell subsets and provides, for the first time in humans, a mechanism controlling the functional heterogeneity of memory CD4 cells. Moreover it validates the combined use of RPP arrays and cytosolic transduction approaches as a powerful tool to quantitatively analyze signalling proteins and functionally assess their roles.

Additive effects of HLA alleles and innate immune genes determine viral outcome in HCV infection.

BACKGROUND: Chronic HCV infection is a leading cause of liver-related morbidity globally. The innate and adaptive immune responses are thought to be important in determining viral outcomes. Polymorphisms associated with the IFNL3 (IL28B) gene are strongly associated with spontaneous clearance and treatment outcomes. OBJECTIVE: This study investigates the importance of HLA genes in the context of genetic variation associated with the innate immune genes IFNL3 and KIR2DS3. DESIGN: We assess the collective influence of HLA and innate immune genes on viral outcomes in an Irish cohort of women (n=319) who had been infected from a single source as well as a more heterogeneous cohort (Swiss Cohort, n=461). In the Irish cohort, a number of HLA alleles are associated with different outcomes, and the impact of IFNL3-linked polymorphisms is profound. RESULTS: Logistic regression was performed on data from the Irish cohort, and indicates that the HLA-A*03 (OR 0.36 (0.15 to 0.89), p=0.027) -B*27 (OR 0.12 (0.03 to 0.45), p=<0.001), -DRB1*01:01 (OR 0.2 (0.07 to 0.61), p=0.005), -DRB1*04:01 (OR 0.31 (0.12 to 0.85, p=0.02) and the CC IFNL3 rs12979860 genotypes (OR 0.1 (0.04 to 0.23), p<0.001) are significantly associated with viral clearance. Furthermore, DQB1*02:01 (OR 4.2 (2.04 to 8.66), p=0.008), KIR2DS3 (OR 4.36 (1.62 to 11.74), p=0.004) and the rs12979860 IFNL3 'T' allele are associated with chronic infection. This study finds no interactive effect between IFNL3 and these Class I and II alleles in relation to viral clearance. There is a clear additive effect, however. Data from the Swiss cohort also confirms independent and additive effects of HLA Class I, II and IFNL3 genes in their prediction of viral outcome. CONCLUSIONS: This data supports a critical role for the adaptive immune response in the control of HCV in concert with the innate immune response.

Epithelial sodium transport and its control by aldosterone: the story of our internal environment revisited.

Transcription and translation require a high concentration of potassium across the entire tree of life. The conservation of a high intracellular potassium was an absolute requirement for the evolution of life on Earth. This was achieved by the interplay of P- and V-ATPases that can set up electrochemical gradients across the cell membrane, an energetically costly process requiring the synthesis of ATP by F-ATPases. In animals, the control of an extracellular compartment was achieved by the emergence of multicellular organisms able to produce tight epithelial barriers creating a stable extracellular milieu. Finally, the adaptation to a terrestrian environment was achieved by the evolution of distinct regulatory pathways allowing salt and water conservation. In this review we emphasize the critical and dual role of Na(+)-K(+)-ATPase in the control of the ionic composition of the extracellular fluid and the renin-angiotensin-aldosterone system (RAAS) in salt and water conservation in vertebrates. The action of aldosterone on transepithelial sodium transport by activation of the epithelial sodium channel (ENaC) at the apical membrane and that of Na(+)-K(+)-ATPase at the basolateral membrane may have evolved in lungfish before the emergence of tetrapods. Finally, we discuss the implication of RAAS in the origin of the present pandemia of hypertension and its associated cardiovascular diseases.

Fluorine MR Imaging of Inflammation in Atherosclerotic Plaque in Vivo.

PURPOSE: To preliminarily test the hypothesis that fluorine 19 ((19)F) magnetic resonance (MR) imaging enables the noninvasive in vivo identification of plaque inflammation in a mouse model of atherosclerosis, with histologic findings as the reference standard. MATERIALS AND METHODS: The animal studies were approved by the local animal ethics committee. Perfluorocarbon (PFC) emulsions were injected intravenously in a mouse model of atherosclerosis (n = 13), after which (19)F and anatomic MR imaging were performed at the level of the thoracic aorta and its branches at 9.4 T. Four of these animals were imaged repeatedly (at 2-14 days) to determine the optimal detection time. Repeated-measures analysis of variance with a Tukey test was applied to determine if there was a significant change in (19)F signal-to-noise ratio (SNR) of the plaques and liver between the time points. Six animals were injected with a PFC emulsion that also contained a fluorophore. As a control against false-positive results, wild-type mice (n = 3) were injected with a PFC emulsion, and atherosclerotic mice were injected with a saline solution (n = 2). The animals were sacrificed after the last MR imaging examination, after which high-spatial-resolution ex vivo MR imaging and bright-field and immunofluorescent histologic examination were performed. RESULTS: (19)F MR signal was detected in vivo in plaques in the aortic arch and its branches. The SNR was found to significantly increase up to day 6 (P < .001), and the SNR of all mice at this time point was 13.4 ± 3.3. The presence of PFC and plaque in the excised vessels was then confirmed both through ex vivo (19)F MR imaging and histologic examination, while no signal was detected in the control animals. Immunofluorescent histologic findings confirmed the presence of PFC in plaque macrophages. CONCLUSION: (19)F MR imaging allows the noninvasive in vivo detection of inflammation in atherosclerotic plaques in a mouse model of atherosclerosis and opens up new avenues for both the early detection of vulnerable atherosclerosis and the elucidation of inflammation mechanisms in atherosclerosis.

No development of hypertension in the hyperuricemic liver-Glut9 knockout mouse.

Urate is the metabolic end point of purines in humans. Although supra-physiological plasma urate levels are associated with obesity, insulin resistance, dyslipidemia, and hypertension, a causative role is debated. We previously established a mouse model of hyperuricemia by liver-specific deletion of Glut9, a urate transporter that provides urate to the hepatocyte enzyme uricase. These LG9 knockout mice show mild hyperuricemia (120 μmol/l), which can be further increased by the urate precursor inosine. Here, we explored the role of progressive hyperuricemia on the cardiovascular function. Arterial blood pressure and heart rate were periodically measured by telemetry over 6 months in LG9 knockout mice supplemented with incremental amounts of inosine in a normal chow diet. This long-term inosine treatment elicited a progressive increase in uricemia up to 300 μmol/l; however, it did not modify heart rate or mean arterial blood pressure in LG9 knockout compared with control mice. Inosine treatment did not alter cardiac morphology or function measured by ultrasound echocardiography. However, it did induce mild renal dysfunction as revealed by higher plasma creatinine levels, lower glomerular filtration rate, and histological signs of chronic inflammation and fibrosis. Thus, in LG9 knockout mice, inosine-induced hyperuricemia was not associated with hypertension despite partial renal deficiency. This does not support a direct role of urate in the control of blood pressure.

Frequent users of the emergency department in a universal health coverage system : a randomized controlled trial of a case-management intervention

BACKGROUND: Frequent emergency department users represent a small number of patients but account for a large number of emergency department visits. They should be a focus because they are often vulnerable patients with many risk factors affecting their quality of life (QoL). Case management interventions have resulted in a significant decrease in emergency department visits, but association with QoL has not been assessed. One aim of our study was to examine to what extent an interdisciplinary case management intervention, compared to standard emergency care, improved frequent emergency department users' QoL. METHODS: Data are part of a randomized, controlled trial designed to improve frequent emergency department users' QoL and use of health-care resources at the Lausanne University Hospital, Switzerland. In total, 250 frequent emergency department users (≥5 attendances during the previous 12 months; ≥ 18 years of age) were interviewed between May 2012 and July 2013. Following an assessment focused on social characteristics; social, mental, and somatic determinants of health; risk behaviors; health care use; and QoL, participants were randomly assigned to the control or the intervention group (n=125 in each group). The final sample included 194 participants (20 deaths, 36 dropouts, n=96 in the intervention group, n=99 in the control group). Participants in the intervention group received a case management intervention by an interdisciplinary, mobile team in addition to standard emergency care. The case management intervention involved four nurses and a physician who provided counseling and assistance concerning social determinants of health, substance-use disorders, and access to the health-care system. The participants' QoL was evaluated by a study nurse using the WHOQOL-BREF five times during the study (at baseline, and at 2, 5.5, 9, and 12 months). Four of the six WHOQOL dimensions of QoL were retained here: physical health, psychological health, social relationship, and environment, with scores ranging from 0 (low QoL) to 100 (high QoL). A linear, mixed-effects model with participants as a random effect was run to analyze the change in QoL over time. The effects of time, participants' group, and the interaction between time and group were tested. These effects were controlled for sociodemographic characteristics and health-related variables (i.e., age, gender, education, citizenship, marital status, type of financial resources, proficiency in French, somatic and mental health problems, and behaviors at risk).

Two cilengitide regimens in combination with standard treatment for patients with newly diagnosed glioblastoma and unmethylated MGMT gene promoter: results of the open-label, controlled, randomized phase II CORE study.

BACKGROUND: Survival outcomes for patients with glioblastoma remain poor, particularly for patients with unmethylated O(6)-methylguanine-DNA methyltransferase (MGMT) gene promoter. This phase II, randomized, open-label, multicenter trial investigated the efficacy and safety of 2 dose regimens of the selective integrin inhibitor cilengitide combined with standard chemoradiotherapy in patients with newly diagnosed glioblastoma and an unmethylated MGMT promoter. METHODS: Overall, 265 patients were randomized (1:1:1) to standard cilengitide (2000 mg 2×/wk; n = 88), intensive cilengitide (2000 mg 5×/wk during wk 1-6, thereafter 2×/wk; n = 88), or a control arm (chemoradiotherapy alone; n = 89). Cilengitide was administered intravenously in combination with daily temozolomide (TMZ) and concomitant radiotherapy (RT; wk 1-6), followed by TMZ maintenance therapy (TMZ/RT→TMZ). The primary endpoint was overall survival; secondary endpoints included progression-free survival, pharmacokinetics, and safety and tolerability. RESULTS: Median overall survival was 16.3 months in the standard cilengitide arm (hazard ratio [HR], 0.686; 95% CI: 0.484, 0.972; P = .032) and 14.5 months in the intensive cilengitide arm (HR, 0.858; 95% CI: 0.612, 1.204; P = .3771) versus 13.4 months in the control arm. Median progression-free survival assessed per independent review committee was 5.6 months (HR, 0.822; 95% CI: 0.595, 1.134) and 5.9 months (HR, 0.794; 95% CI: 0.575, 1.096) in the standard and intensive cilengitide arms, respectively, versus 4.1 months in the control arm. Cilengitide was well tolerated. CONCLUSIONS: Standard and intensive cilengitide dose regimens were well tolerated in combination with TMZ/RT→TMZ. Inconsistent overall survival and progression-free survival outcomes and a limited sample size did not allow firm conclusions regarding clinical efficacy in this exploratory phase II study.

The role of Notch receptor signaling in T helper 17 cell differentiation

Antigenic recognition by naive CD4+ T cells induces their proliferation and differentiation into functionally distinct T helper (Th) cell. Each CD4+ Th cell subset expresses specific transcription factors and produces signature cytokines that coordinate immune responses against encountered pathogens. Among the factors influencing CD4+ Th cell differentiation, Notch signaling pathway has been reported to play a role in the differentiation and function of multiple CD4+Thcell subsets. Notch signaling is an evolutionarily conserved cell-to-cell signaling cascade involved in many cell fate decision processes. How Notch signaling modulates the differentiation of CD4+ Th cell subsets and whether Notch signaling alone is sufficient or not for the differentiation of CD4+ Th cells is still a matter of debate. Th17 cells are a distinct subset of CD4+ Th cells. They play a role in the control of extracellular bacterial and fungal infections and may lead to inflammatory and autoimmune diseases if not properly regulated. Th17 cells are defined by the expression of RAR-related orphan receptor (ROR)a and RORyT transcription factors and their secretion of IL-17A, IL-17F cytokines. The involvement of Notch signaling in Th17 cell differentiation has mostly been studied in vitro. However, neither the experimental conditions when Notch signaling might be involved in Th17 cell differentiation in vitro and in vivo nor the precise role of Notch in this process remain clear. To better define how Notch signaling impacts Th17 differentiation, we used mice with T cell specific ablation of Notchl and Notch2 (N1 N2ACD4Cre) or of Notch transcriptional repressor RBP- JK (RBP-J ACD4Cre). We show that impaired Notch signaling in T cells, when TCR activating signal were reduced, increased RORyT and IL-17 mRNA levels during in vitro Th17 cell differentiation. Following immunization with OVA in CFA, an adjuvant that induces mostly Th17 cell response, increased IL-17A mRNA and intracellular IL-17A levels were observed in draining lymph nodes of Notch-deficient CD4+T cells. Our data suggest that Notch limited Th17 cell differentiation. Despite high levels of IL-17 mRNA and intracellular IL-17 proteins observed in Notch-deficient T cells, their release of Th17 cytokines ex vivo was markedly decreased, indicating a role for Notch signaling. During the second part of this thesis, we observed that the impact of Notch on Th17 cell differentiation and effector functions was context-dependent using different in vivo experimental models, in which Th17 cells and IL-17A were reported to contribute in the disease development. Collectively, our data reveal that Notch signaling controls the fine-tuning of Th17 cell differentiation and effector functions by limiting their differentiation but promoting selectively cytokine release through Notch-dependent mechanisms that still need to be defined. -- Lors d'une réponse immunitaire et grâce à la reconnaissance antigénique, les lymphocytes CD4+ T naïfs prolifèrent, puis se différencient en CD4+ T auxiliaires ("T helper" ou Th) fonctionnellement distincts. Chaque sous-population de lymphocytes CD4+ T auxiliaires exprime des facteurs de transcription et des cytokines spécifiques qui coordonnent la réponse immunitaire contre les pathogènes rencontrés. Parmi les facteurs influençant la différenciation des lymphocytes CD4+ T auxiliaires, la voie de signalisation Notch a été identifiée comme ayant un rôle dans la différenciation et la fonction des différents sous-types de cellules CD4+ T auxiliaires. La voie de signalisation Notch est une voie évolutivement conservée, qui est impliquée dans la signalisation entre les cellules et dans de nombreux processus de décisions cellulaires. La manière dont la voie de signalisation Notch régule la différenciation des lymphocytes CD4+ T en sous-types de cellules CD4+ auxiliaires, mais également la question de savoir si la voie de signalisation Notch est capable ou non d'induire la différenciation des cellules CD4+T auxiliaires, restent à débattre. Les cellules T auxiliaires 17 (Th17) sont un sous-type distinct de cellules CD4+T. Elles jouent un rôle important dans la défense immunitaire contre des pathogènes tels que les bactéries extracellulaires et les champignons. Une dérégulation de la réponse des cellules Th17 peut conduire à des inflammations mais également à des maladies auto-immunes. Les cellules Th17 sont définies par l'expression de leurs facteurs de transcription RAR-related orphan receptor (ROR)a, RORyT et par la sécrétion de cytokines comme IL-17A, IL-17F. Le rôle de la voie de signalisation Notch dans la différenciation des cellules Th17 a principalement été démontré in vitro. Malgré tout, ni les conditions expérimentales dans lesquelles cette voie pourrait être impliquée dans la différenciation des cellules Th17 in vitro et in vivo, mais également ni la fonction exacte de Notch dans ces processus, ne sont des questions résolues. Afin de mieux définir comment la voie de signalisation Notch est impliquée dans la différenciation des cellules Th17, nous avons utilisé des souris avec une déficience spécifique dans les cellules T des récepteurs Notchl et Notch2 (N1N2ACD4Cre) ou du répresseur transcriptionnel de Notch RBP-JK (RBP-J ACD4Cre). Nous avons montré que lorsque la voie de signalisation Notch est déficiente, les niveaux d'ARN messager (ARNm) de RORyT et de IL-17A sont augmentés dans les cellules Th17 pendant la différenciation in vitro, en présence de niveaux réduits des signaux activant les cellules T CD4+. Une augmentation dans les niveaux d'ARNm de IL-17A et de IL-17A intracellulaire au niveau protéinique a été observée dans les cellules T CD4+ Notch déficientes, au niveau des ganglions drainants après immunisation avec l'OVA dans le CFA, un adjuvant induisant une réponse des cellules Th17. Nos résultats suggèrent que Notch pourrait réguler négativement l'expression de IL-17A au niveau transcriptionnel mais également protéinique. Malgré une augmentation de IL-17A au niveau de l'ARNm et protéinique dans les cellules CD4+ T Notch déficientes, paradoxalement la sécrétion de IL-17A mais également de cytokines associées aux fonctions effectrices des cellules Th17 sont profondément diminuées 6X vivo, suggérant un rôle de la voie de signalisation Notch dans ce processus. Dans la deuxième partie de ce travail de thèse, nous avons observé que l'impact de Notch dans la différenciation des cellules Th17 et dans leurs fonctions effectrices était dépendant du contexte dans d'autres modèles expérimentaux in vivo, où les cellules Th17 et l'IL-17A ont été identifiées comme ar-.riCociêSM dans le développement ds la pathologie. En résumé, nous avons montré que la voie de la signalisation Notch contrôle la régulation précise de la différenciation des cellules Th17 en limitant leur différenciation, mais en promouvant sélectivement leur relâchement en cytokines associés aux cellules Th17 par l'intermédiaire de mécanismes dépendant de Notch, qui restent toujours à déterminer. -- Lors d'une réponse immunitaire et grâce à la reconnaissance antigénique, les lymphocytes CD4+ T naïfs prolifèrent, puis se différencient en CD4+ T auxiliaires ("T helper" ou Th) fonctionnellement distincts. Chaque sous-population de lymphocytes T auxiliaires exprime des facteurs de transcription et des cytokines spécifiques qui coordonnent une réponse immunitaire contre différents pathogènes. Les mécanismes liés à la différenciation des lymphocytes CD4+ T auxiliaires sont complexes et régulés. Une mauvaise régulation de la différenciation des lymphocytes CD4+ T auxiliaires peut conduire à des maladies auto-immunes, mais également à des processus inflammatoires. Parmi les facteurs influençant la différenciation des lymphocytes T auxiliaires, la voie de signalisation Notch a été identifiée comme ayant un rôle dans la différenciation et la fonction des différents sous-types de cellules CD4+ T auxiliaires. La voie de signalisation Notch est une voie évolutivement conservée, qui est impliquée dans la signalisation entre les cellules, mais également dans de nombreux processus de décisions cellulaires. Quelle est l'implication de la voie de signalisation Notch dans la différenciation des lymphocytes CD4+ en sous-types de cellules CD4+T auxiliaires et comment cette voie agit dans ce processus, sont des questions débattues. Les cellules T auxiliaires 17 (Th17) sont une sous-population distincte de lymphocytes CD4+. Elles jouent un rôle important dans la défense immunitaire contre les bactéries extracellulaires et les champignons. Une dérégulation de la réponse des cellules Th17 a été associée à des maladies auto-immunes et à l'inflammation. Les cellules Th17 sont définies par l'expression du facteur de transcription RAR-related orphan receptor (ROR)yT et des cytokines comme IL-17A, IL-17F. Le rôle de la voie de signalisation Notch dans la différenciation des cellules Th17 a été principalement démontré dans des études expérimentales in vitro. Malgré tout, les conditions expérimentales exactes dans lesquelles la voie de signalisation de Notch pourrait être impliquée dans la différenciation des cellules Th17, mais également le rôle de Notch dans ce processus ne sont pas encore clairement élucidés. Afin de mieux définir comment la voie de signalisation Notch est impliquée dans la différenciation des cellules Th17, nous avons utilisé des souris avec une déficience spécifique dans les cellules T des récepteurs Notchl et Notch2 (N1 N2ACD4Cre) ou du répresseur transcriptionnel de Notch RBP-JK (RBP-JACD4CRE). Nous avons montré que lorsque la voie de signalisation Notch est déficiente, les niveaux d'ARN messager (ARNm) de RORyT et de IL-17 sont augmentés dans les cellules Th17 pendant leur différenciation in vitro. Cet effet de Notch sur la transcription apparaît être facultatif lorsque les conditions environnementales sont en excès in vitro. Après immunisation avec un adjuvant qui induit principalement une réponse des cellules Th17, nous avons observé que les niveaux de ARNm de IL-17A et aussi de IL-17A intracellulaire au niveau protéinique étaient augmentés dans les ganglions drainants dans les cellules CD4+ Notch déficientes. Ces résultats suggèrent que Notch pourrait réguler négativement l'expression de IL- 17 au niveau transcriptionnel mais également protéinique. Malgré des niveaux plus élevés de IL- 17 ARNm et aussi IL-17A intracellulaire dans les cellules T Notch déficientes, le relâchement en cytokines Th17 est profondément diminué indiquant un rôle de la voie de signalisation Notch dans ces processus de sécrétion. Dans la deuxième partie de cette thèse, nous avons observé que le rôle de Notch dans ia différenciation dss cellules Ti,17 et dans leurs fonctions effectrices était dépendant du contexte dans d'autres modèles expérimentaux, qui ont été rapportés comme une réponse induisant des cellules Th17. En résumé, nos données montrent que la voie de la signalisation Notch contrôle la régulation précise de la différenciation des cellules Th17 en limitant leur différenciation mais en promouvant sélectivement le relâchement en cytokines associées aux cellules Th17 par des mécanismes dépendant de Notch qui restent toujours à déterminer. Par conséquent, l'inhibition de la voie de signalisation Notch pourrait être utilisée dans des situations inflammatoires ou d'auto-immunité où la réponse des cellules Th17 est exacerbée.

Three essays in behavioral and experimental economics

The present PhD dissertation consists of three papers, organized in chapters, in the field of behavioral economics. This discipline studies economic behavior of individuals subject to limitations, such as bounded self-interest and bounded willpower. The behavior studied in the present thesis ranges from the complex decision to register as an organ donor, decision¬making in the presence of uncertainty and the decision to give money to a charitable organization. The first chapter aims at testing the effectiveness of an active-decision (AD) mechanism on the decision to become an organ donor in Switzerland, using field experiments. We found that stimulating participants' reflection on the topic of organ donation had a negative effect on the decision to become an organ donor. Moreover, a non-binding commitment nudge reduces putting off the decision, but does not lead to donation rates higher than in the control group. The results suggest that AD may be far more limited than previously thought and raise doubts about the efficacy of engaging potential donors to reflect on the topic of organ donation. Beyond carrying for others, behavioral economics also recognizes that individuals do not evaluate outcomes in absolute terms but rather by comparing them to some reference levels, called reference points. Above the reference points, economic outcomes are perceived as gains, while below these levels the same outcomes are felt as losses. The last two chapters analyze the importance of reference points in the evaluation of economic outcomes. Using a laboratory experiment where subjects played two consecutive lotteries, Chapter 2 studies the speed of adjustment of the reference point. We find that varying the probability of winning the first lottery has no effect on subjects' risk behavior regarding the second lottery. This result indicates a very fast adjustment of the reference point to the latest information. Chapter 3 investigates whether reference points are relevant for charitable preferences. Using actual donation decisions of participants in a laboratory experiment, the results suggest that reference points are not crucial for shaping charitable giving. -- Cette thèse de doctorat consiste en trois articles, organisés en chapitres, dans le domaine de l'économie comportementale. Cette discipline étudie le comportement d'agents économiques sujets à des limitations, telles qu'un égoïsme limité et une volonté limitée. Le comportement étudié dans cette thèse va de la décision complexe de devenir donneur d'organes, la prise de décision en présence d'incertitude à la décision de donner de l'argent à une oeuvre caritative. Le premier chapitre vise à tester l'efficacité d'un mécanisme de « décision active » (active decision, AD) sur la décision de devenir donneur d'organes en Suisse, et ce en recourant à deux expériences hors-laboratoire. Les résultats montrent que stimuler la réflexion des participants sur le don d'organes a un effet négatif sur la décision de devenir donneur. De plus, un mécanisme qui encourage les participants à prendre une décision sur le champ réduit la tendance à procrastiner, mais ne mène pas à un taux de donneurs plus élevé par rapport à un groupe de contrôle. Les résultats suggèrent que le mécanisme AD est bien plus limité que ce qui a été supposé jusqu'à maintenant. De plus, ils suscitent le doute quant à l'efficacité de stimuler la réflexion de potentiels donneurs sur le sujet du don d'organes. En plus de se soucier des autres, l'économie comportementale admet également que les individus n'évaluent pas les résultats de façon absolue, mais en comparant ceux-ci à des niveaux de références, souvent appelés points de référence. Au-dessus de ces points de référence, les résultats sont perçus en tant que gains, tandis qu'en-dessous ces mêmes résultats sont considérés comme des pertes. Les deux derniers chapitres analysent l'importance des points de référence dans diverses situations. A l'aide d'une expérience en laboratoire dans laquelle les participants participent à deux loteries consécutives, le chapitre 2 étudie la vitesse d'ajustement du point de référence. Le résultat montre que varier la probabilité de gagner la première loterie n'a aucun effet sur le comportement en matière de risques concernant la deuxième loterie. Cela indique un ajustement très rapide du point de référence. Le chapitre 3 vise à déterminer si les points de référence ont un rôle majeur concernant les préférences caritatives. Les données relatives aux décisions de don des participants d'une expérience en laboratoire montrent que les points de référence n'influencent pas significativement le don caritatif.

Induction chemoradiation in stage IIIA/N2 non-small-cell lung cancer: a phase 3 randomised trial.

BACKGROUND: One of the standard options in the treatment of stage IIIA/N2 non-small-cell lung cancer is neoadjuvant chemotherapy and surgery. We did a randomised trial to investigate whether the addition of neoadjuvant radiotherapy improves outcomes. METHODS: We enrolled patients in 23 centres in Switzerland, Germany and Serbia. Eligible patients had pathologically proven, stage IIIA/N2 non-small-cell lung cancer and were randomly assigned to treatment groups in a 1:1 ratio. Those in the chemoradiotherapy group received three cycles of neoadjuvant chemotherapy (100 mg/m(2) cisplatin and 85 mg/m(2) docetaxel) followed by radiotherapy with 44 Gy in 22 fractions over 3 weeks, and those in the control group received neoadjuvant chemotherapy alone. All patients were scheduled to undergo surgery. Randomisation was stratified by centre, mediastinal bulk (less than 5 cm vs 5 cm or more), and weight loss (5% or more vs less than 5% in the previous 6 months). The primary endpoint was event-free survival. Analyses were done by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00030771. FINDINGS: From 2001 to 2012, 232 patients were enrolled, of whom 117 were allocated to the chemoradiotherapy group and 115 to the chemotherapy group. Median event-free survival was similar in the two groups at 12·8 months (95% CI 9·7-22·9) in the chemoradiotherapy group and 11·6 months (8·4-15·2) in the chemotherapy group (p=0·67). Median overall survival was 37·1 months (95% CI 22·6-50·0) with radiotherapy, compared with 26·2 months (19·9-52·1) in the control group. Chemotherapy-related toxic effects were reported in most patients, but 91% of patients completed three cycles of chemotherapy. Radiotherapy-induced grade 3 dysphagia was seen in seven (7%) patients. Three patients died in the control group within 30 days after surgery. INTERPRETATION: Radiotherapy did not add any benefit to induction chemotherapy followed by surgery. We suggest that one definitive local treatment modality combined with neoadjuvant chemotherapy is adequate to treat resectable stage IIIA/N2 non-small-cell lung cancer. FUNDING: Swiss State Secretariat for Education, Research and Innovation (SERI), Swiss Cancer League, and Sanofi.

Ability of physicians to diagnose influenza and usefulness of a rapid influenza antigen test in febrile returning travelers: A randomized controlled trial.

BACKGROUND: Fever is a frequent cause of medical consultation among returning travelers. The objectives of this study were to assess whether physicians were able to identify patients with influenza and whether the use of an influenza rapid diagnostic test (iRDT) modified the clinical management of such patients. METHODS: Randomized controlled trial conducted at 2 different Swiss hospitals between December 2008 and November 2012. Inclusion criteria were 1) age ≥18 years, 2) documented fever of ≥38 °C or anamnestic fever + cough or sore throat within the last 4 days, 3) illness occurring within 14 days after returning from a trip abroad, 4) no definitive alternative diagnosis. Physicians were asked to estimate the likelihood of influenza on clinical grounds, and a single nasopharyngeal swab was taken. Thereafter patients were randomized into 2 groups: i) patients with iRDT (BD Directigen A + B) performed on the nasopharyngeal swab, ii) patients receiving usual care. A quantitative PCR to detect influenza was done on all nasopharyngeal swabs after the recruitment period. Clinical management was evaluated on the basis of cost of medical care, number of X-rays requested and prescription of anti-infective drugs. RESULTS: 100 eligible patients were referred to the investigators. 93 patients had a naso-pharyngeal swab for a PCR and 28 (30%) swabs were positive for influenza. The median probability of influenza estimated by the physician was 70% for the PCR positive cases and 30% for the PCR negative cases (p < 0.001). The sensitivity of the iRDT was only 20%, and specificity 100%. Mean medical cost for the patients managed with iRDT and without iRDT were USD 581 (95%CI 454-707) and USD 661 (95%CI 522-800) respectively. 14/60 (23%) of the patients managed with iRDT were prescribed antibiotics versus 13/33 (39%) in the control group (p = 0.15). No patient received antiviral treatment. CONCLUSION: Influenza was a frequent cause of fever among these febrile returning travelers. Based on their clinical assessment, physicians had a higher level of suspicion for influenza in PCR positive cases. The iRDT used in this study showed a disappointingly low sensitivity and can therefore not be recommended for the management of these patients. TRIAL REGISTRATION: ClinicalTrials.gov NCT00821626.

The caspase-3-p120-RasGAP module generates a NF-κB repressor in response to cellular stress.

The nuclear factor κB (NF-κB) transcription factor is a master regulator of inflammation. Short-term NF-κB activation is generally beneficial. However, sustained NF-κB might be detrimental, directly causing apoptosis of cells or leading to a persistent damaging inflammatory response. NF-κB activity in stressed cells needs therefore to be controlled for homeostasis maintenance. In mildly stressed cells, caspase-3 cleaves p120 RasGAP, also known as RASA1, into an N-terminal fragment, which we call fragment N. We show here that this fragment is a potent NF-κB inhibitor. Fragment N decreases the transcriptional activity of NF-κB by promoting its export from the nucleus. Cells unable to generate fragment N displayed increased NF-κB activation upon stress. Knock-in mice expressing an uncleavable p120 RasGAP mutant showed exaggerated NF-κB activation when their epidermis was treated with anthralin, a drug used for the treatment of psoriasis. Our study provides biochemical and genetic evidence of the importance of the caspase-3-p120-RasGAP stress-sensing module in the control of stress-induced NF-κB activation.

Longitudinal monitoring of endogenous steroids in human serum by UHPLC-MS/MS as a tool to detect testosterone abuse in sports.

The detection of testosterone abuse in sports is routinely achieved through the 'steroidal module' of the Athlete Biological Passport by GC-MS(/MS) quantification of selected endogenous anabolic androgenic steroids (EAAS) from athletes' urines. To overcome some limitations of the "urinary steroid profile" such as the presence of confounding factors (ethnicity, enzyme polymorphism, bacterial contamination, and ethanol), ultrahigh performance liquid chromatography (UHPLC) measurements of blood concentrations of testosterone, its major metabolites, and precursors could represent an interesting and complementary strategy. In this work, two UHPLC-MS/MS methods were developed for the quantification of testosterone and related compounds in human serum, including major progestogens, corticoids, and estrogens. The validated methods were then used for the analyses of serum samples collected from 19 healthy male volunteers after oral and transdermal testosterone administration. Results from unsupervised multiway analysis allowed variations of target analytes to be assessed simultaneously over a 96-h time period. Except for alteration of concentration values due to the circadian rhythm, which concerns mainly corticosteroids, DHEA, and progesterone, significant variations linked to the oral and transdermal testosterone administration were observed for testosterone, DHT, and androstenedione. As a second step of analysis, the longitudinal monitoring of these biomarkers using intra-individual thresholds showed, in comparison to urine, significant improvements in the detection of testosterone administration, especially for volunteers with del/del genotype for phase II UGT2B17 enzyme, not sensitive to the main urinary marker, T/E ratio. A substantial extension of the detection window after transdermal testosterone administration was also observed in serum matrix. The longitudinal follow-up proposed in this study represents a first example of 'blood steroid profile' in doping control analysis, which can be proposed in the future as a complement to the 'urinary module' for improving steroid abuse detection capabilities.

Screening of mental health and substance users in frequent users of a general Swiss emergency department.

BACKGROUND: The objectives of this study were to determine the proportions of psychiatric and substance use disorders suffered by emergency departments' (EDs') frequent users compared to the mainstream ED population, to evaluate how effectively these disorders were diagnosed in both groups of patients by ED physicians, and to determine if these disorders were predictive of a frequent use of ED services. METHODS: This study is a cross-sectional study with concurrent and retrospective data collection. Between November 2009 and June 2010, patients' mental health and substance use disorders were identified prospectively in face-to-face research interviews using a screening questionnaire (i.e. researcher screening). These data were compared to the data obtained from a retrospective medical chart review performed in August 2011, searching for mental health and substance use disorders diagnosed by ED physicians and recorded in the patients' ED medical files (i.e. ED physician diagnosis). The sample consisted of 399 eligible adult patients (≥18 years old) admitted to the urban, general ED of a University Hospital. Among them, 389 patients completed the researcher screening. Two hundred and twenty frequent users defined by >4 ED visits in the previous twelve months were included and compared to 169 patients with ≤4 ED visits in the same period (control group). RESULTS: Researcher screening showed that ED frequent users were more likely than members of the control group to have an anxiety, depressive disorder, post-traumatic stress disorder (PTSD), or suffer from alcohol, illicit drug abuse/addiction. Reviewing the ED physician diagnosis, we found that the proportions of mental health and substance use disorders diagnosed by ED physicians were low both among ED frequent users and in the control group. Using multiple logistic regression analyses to predict frequent ED use, we found that ED patients who screened positive for psychiatric disorders only and those who screened positive for both psychiatric and substance use disorders were more likely to be ED frequent users compared to ED patients with no disorder. CONCLUSIONS: This study found high proportions of screened mental health and/or substance use disorders in ED frequent users, but it showed low rates of detection of such disorders in day-to-day ED activities which can be a cause for concern. Active screening for these disorders in this population, followed by an intervention and/or a referral for treatment by a case-management team may constitute a relevant intervention for integration into a general ED setting.

Decreased Brain Levels of Vitamin B12 in Aging, Autism and Schizophrenia.

Many studies indicate a crucial role for the vitamin B12 and folate-dependent enzyme methionine synthase (MS) in brain development and function, but vitamin B12 status in the brain across the lifespan has not been previously investigated. Vitamin B12 (cobalamin, Cbl) exists in multiple forms, including methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), serving as cofactors for MS and methylmalonylCoA mutase, respectively. We measured levels of five Cbl species in postmortem human frontal cortex of 43 control subjects, from 19 weeks of fetal development through 80 years of age, and 12 autistic and 9 schizophrenic subjects. Total Cbl was significantly lower in older control subjects (> 60 yrs of age), primarily reflecting a >10-fold age-dependent decline in the level of MeCbl. Levels of inactive cyanocobalamin (CNCbl) were remarkably higher in fetal brain samples. In both autistic and schizophrenic subjects MeCbl and AdoCbl levels were more than 3-fold lower than age-matched controls. In autistic subjects lower MeCbl was associated with decreased MS activity and elevated levels of its substrate homocysteine (HCY). Low levels of the antioxidant glutathione (GSH) have been linked to both autism and schizophrenia, and both total Cbl and MeCbl levels were decreased in glutamate-cysteine ligase modulatory subunit knockout (GCLM-KO) mice, which exhibit low GSH levels. Thus our findings reveal a previously unrecognized decrease in brain vitamin B12 status across the lifespan that may reflect an adaptation to increasing antioxidant demand, while accelerated deficits due to GSH deficiency may contribute to neurodevelopmental and neuropsychiatric disorders.