Background: Psychological and physical stress can either enhance or suppress immune functions depending on a variety of factors such as duration and severity of stressful situation. Chronic stress exerts a significantly suppressive effect on immune functions. However, the mechanisms responsible for this phenomenon remain to be elucidated. Autophagy plays an essential role in modulating cellular homeostasis and immune responses. However, it is not known yet whether autophagy contributes to chronic stress-induced immunosuppression. T cell immunoglobulin and mucin domain 3 (Tim-3) has shown immune-suppressive effects and obviously positive regulation on cell apoptosis. Tim-3 combines with Tim-3 ligand galectin-9 to modulate apoptosis. However, its impact on autophagy and chronic stress-induced immunosuppression is not yet identified. Results: We found remarkably higher autophagy level in the spleens of mice that were subjected to chronic restraint stress compared with the control group. We also found that inhibition of autophagy by the autophagy inhibitor 3-methyladenine (3-MA) significantly attenuated chronic stress-induced alterations of pro-inflammatory and anti-inflammatory cytokine levels. We further elucidated that 3-MA dramatically inhibited the reduction of lymphocyte numbers. Moreover, chronic stress dramatically enhanced the expression of Tim-3 and galectin-9. Inhibition of Tim-3 by small interfering RNA against Tim-3 significantly decreased the level of autophagy and immune suppression in isolated primary splenocytes from stressed mice. In addition, α-lactose, a blocker for the interaction of Tim-3 and galectin-9, also decreased the autophagy level and immune suppression. Conclusion: Chronic stress induces autophagy, resulting with suppression of immune system. Tim-3 and galectin-9 play a crucial regulatory role in chronic stress-induced autophagy. These studies suggest that Tim-3 mediated autophagy may offer a novel therapeutic strategy against the deleterious effects of chronic stress on the immune system.

La galectine-9 est une lectine animale principalement exprimée dans un contexte inflammatoire et possédant des propriétés à la fois pro-inflammatoires et immunosuppressives. Elle induit la production de cytokines inflammatoires par les cellules du système immunitaire inné tandis qu’elle induit l’apoptose des lymphocytes Th1 CD4+ et favorise l’expansion des lymphocytes Treg. Les propriétés immunomodulatrices de la galectine-9 dépendent en grande partie de son interaction avec le récepteur TIM-3. Cependant, ces deux molécules interagissent chacune avec d’autres protéines et dans plusieurs contextes la responsabilité de l’interaction galectine-9/TIM-3 n’a pas été formellement démontrée. Le développement d’un anticorps neutralisant les effets de la galectine-9 permettrait de préciser son rôle exact dans ces contextes. Par ailleurs, le blocage des voies de signalisations inhibitrices du système immunitaire est aujourd’hui un enjeu majeur en oncologie, comme le démontre le succès récent de la neutralisation du récepteur inhibiteur CTLA-4 pour le traitement des mélanomes. Nous avons produit de nouveaux anticorps monoclonaux dirigés contre la galectine 9 par immunisation de souris avec la partie C-terminale de la protéine. Parmi ces anticorps, 1G3 permet la détection de la galectine-9 sur coupes de tissus humains d’une manière très sensible et spécifique en immunohistochimie. Son utilisation nous a permis de confirmer l’expression constante et intense de la galectine-9 dans les cellules malignes de carcinome nasopharyngé et la forte expression de la galectine-9 dans les cellules de Kupffer présentes dans les tissus hépatiques infectés par le virus de l’hépatite C. Pour la première fois, nous avons mis en évidence une expression de la galectine-9 dans les leukocytes infiltrant les tissus hépatiques infectés par le virus de l’hépatite B. De plus, nous observons une expression de la galectine-9 dans les hépatocytes infectés par ces deux virus, ce qui n’avait pas été démontré jusqu’à présent. Nous avons également caractérisé les capacités fonctionnelles de nos anticorps lors de tests in vitro. L’anticorps 2E12 bloque la fixation de la galectine-9 au récepteur TIM-3 dans un test acellulaire, neutralise l’apoptose induite par la galectine-9 sur cellules de lymphomes T humaines et réduit considérablement l’augmentation de calcium cytosolique induite par la galectine-9 dans les cellules Jurkat. Ces effets de la galectine-9 sont indépendants de TIM-3 dans ce modèle cellulaire. L’anticorps 2E12 constitue un outil puissant pour étudier les fonctions de la galectine-9 à la fois dépendantes et indépendantes de TIM-3. / Galectin-9 is an animal lectin mainly expressed in an inflammatory context which possesses both pro-inflammatory and immunosuppressive properties. It induces inflammatory cytokines production from innate immunity cells whereas it induces apoptosis of Th1 CD4+ lymphocytes and enhance T regulatory lymphocytes expansion. Galectin-9 immunomodulatory properties depends mostly on its interaction with TIM-3 receptor. However, both molecules interact with other proteins, and in several contexts, galectin-9/TIM-3 interaction responsability has not been formally demonstrated. Development of a galectin-9 neutralizing antibody would allow to determine its precise role in those contexts. Moreover, blocking of immune system inhibition pathways is nowaday a major concern in oncology, as the success of CTLA-4 antagonist used for melanoma treatment recently demonstrated. We have produced new monoclonal antibodies against galectin-9 through immunisation of mice with the C-terminus part of the protein. Among those antibodies, 1G3 allows the detection of galectin-9 on human tissue samples in a very sensitive and specific manner in immunohistochemistry. Using 1G3, we could confirm intense and constant expression of galectin-9 in nasopharyngeal carcinoma malignant cells and its strong expression in Kupffer cells infiltrating hepatitis C-infected liver tissue. For the first time, we demonstrated expression of galectin-9 in leukocytes infiltrating hepatitis B-infected liver tissue. Additionally, we could observe galectin-9 expression in infected hepatocytes for both viruses, which had not been demonstrated until now.We also characterized functional properties of our antibodies during in vitro tests. The 2E12 antibody blocks galectin-9 interaction with TIM-3 in an cell-free assay, neutralizes galectin-9-induced apoptosis of human T lymphomas cells and considerably reduces galectin-9-induced increase of intracellular calcium in Jurkat cells. Those effects are independent of TIM-3 in this cell line model. The 2E12 antibody constitutes a powerful too to study both TIM-3-dependent and TIM-3-independent functions of galectin-9.

La galectine-9 (gal-9) est une lectine multifonctionnelle se liant à des glycoprotéines ou des glycolipides possédant des liaisons β-galactosides. Elle est impliquée dans plusieurs pathologies telles que le carcinome nasopharyngé associé au virus d’Epstein-Barr ou les infections chroniques par les virus des hépatites B et C.La gal-9 possède une activité immunosuppressive prédominante liée notamment à une stimulation de l’expansion et de l’activation des lymphocytes T (LTs) régulateurs. Ses effets sur les LTs conventionnels sont plus complexes : elle induit un phénomène d’apoptose précoce dans une fraction des LTs conventionnels mais aussi une activation et une prolifération dans une autre fraction incluant des LTs CD4+ Th1. D’où la nécessité d’explorer les événements de signalisation déclenchés par la gal-9 exogène dans les LTs humains.Notre recherche a été centrée sur des LTs CD4+ humains provenant de lignées leucémiques ou de PBMCs. Nos résultats montrent que le complexe TCR-CD3 et la kinase Lck sont requis pour la mobilisation de Ca2+ et la production de cytokines dont l’expression est induite en aval par la gal-9 (IL-2 et IFN-γ). A l’inverse, l’apoptose déclenchée par la gal-9 n’est pas réduite lorsque les cellules sont invalidées pour l’un de ces composants. Ces données indiquent que la gal-9 agit sur les LTs par deux voies de signalisation distinctes: l’une mimant l’activation classique du TCR avec une contribution majeure des éléments proximaux du complexe TCR, notamment Lck, et l’autre qui aboutit à l’apoptose des cellules et qui est indépendante de ce complexe.Parallèlement à ce volet fondamental de notre recherche, nous avons caractérisé de nouveaux anticorps monoclonaux (AcM) dirigés contre la gal-9. Ceux-ci neutralisent certains effets de la gal-9 sur les LTs humains tels que l’apoptose. Nous avons défini certaines propriétés immunochimiques de nos AcM en vue de leur utilisation potentielle en thérapeutique. Nous pensons que ces travaux pourraient ouvrir la voie à de nouvelles approches dans le champ actuellement en pleine expansion des thérapeutiques qui visent à une restauration de la réponse immunitaire anti-tumorale. / Galectin-9 (gal-9) is a multifunctional lectin binding some glycoproteins and glycolipids containing β-galactoside-bounds. It is involved in several pathologies such as Epstein-Barr virus-associated nasopharyngeal carcinoma or chronic infections by the hepatitis B and C viruses.Gal-9 has predominant immunosuppressive functions notably supported by its capacity to stimulate the expansion and activation of regulatory T cells. Its effects on conventional T cells are more complex: it induces apoptosis in a fraction of them, but it also activates and stimulates proliferation of another fraction including CD4+ Th1 cells. Hence the need to explore the signaling events triggered by exogenous gal-9 in human T cells.Our study was mainly focused on human CD4+ T cells from leukemic cell lines and PBMCs. We found that the TCR-CD3 complex and the Lck kinase were required for Ca2+ mobilization and subsequent cytokines production (IL-2 and IFN-γ) induced by gal-9 in T cells. By contrast, gal-9-triggered apoptosis was not reduced by the knocking-out of these TCR components. These data demonstrate that gal-9 acts on T cells by at least two distinct pathways: one mimicking the classical activation of the TCR with a mandatory contribution of proximal elements of the TCR complex, especially Lck, and another resulting in apoptosis which is independent of this complex.In parallel to this basic research, we characterized new monoclonal antibodies (mAb) targeting gal-9. We demonstrated that our mAb can neutralize the apoptosis and other gal-9 effects in human T cells and we defined some of their immunochemical properties in view of their potential therapeutic use. We believe that this work could pave the way for new approaches in the rapidly expanding field of therapeutics aiming at a restoration of the anti-tumor immune response.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20251号 / 医博第4210号 / 新制||医||1020(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 妹尾 浩, 教授 湊谷 謙司, 教授 江藤 浩之 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23762号 / 医博第4808号 / 新制||医||1056(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 生田 宏一, 教授 川口 義弥, 教授 上野 英樹 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Hepatitis C Virus (HCV) is a small RNA virus that progresses to chronicity in 50-80% of infected individuals. Direct-acting antivirals (DAAs) are revolutionary treatments for HCV with 90-98% cure rates. However, over time, chronic HCV infections can result in advanced liver disease, including cirrhosis. Patients with advanced fibrosis experience a poor response to vaccination, recurrent infections and increased risk for hepatocellular carcinoma (HCC). These outcomes are, in part, a consequence of immune dysfunction. Increased inhibitory receptor and Galectin-9 (GAL-9) expression is a possible mechanism promoting lymphocyte dysfunction. In this study, blood samples were collected from chronic HCV patients with different degrees of liver fibrosis. I conducted a 13-parameter flow stain on the peripheral blood mononuclear cells (PBMC) of these patients. Next, I measured the expression of inhibitory receptors (PD-1, CTLA-4, LAG-3, TIGIT and TIM-3) and GAL-9 on bulk T cell and NK cells of 15 chronic HCV patients with no to moderate fibrosis (F0-F2) and 15 with advanced fibrosis (F3-F4). To analyze receptor co-expression, I employed t-distributed stochastic neighbor embedding (t-SNE) analysis to dimensionally reduce the multi-parametric data. Notably, I found that F3-F4 patients had higher frequencies of >3 inhibitory receptor co-expression on NK cells. Moreover, t-SNE analysis of bulk T cells revealed that F3-F4 patients manifest a higher frequency of cells in the clusters with CD25+TIGITmed-hi CD4+ T cells and PD-1medLAG-3med-hiGAL-9med-hi CD4+ T cells. t-SNE analysis of NK cells also showed that F3-F4 patients manifest a higher frequency of cells in the cluster with CD25+TIGITmed-hiTIM-3med-hi CD56Dim NK cells and CCR7+ PD-1medLAG-3med-hiGAL-9med-hi CD56Dim NK cells. Lastly, the frequency of cells in these clusters was found to positively correlate with patient’s extent of liver damage. In conclusion, I identified phenotypes of immune dysregulation that could explain the increased susceptibility to infection and HCC in chronic HCV patients with advanced fibrosis. These phenotypes could identify targets for combinatorial checkpoint blockade therapy to potentially improve immune function in these patients.

Cancer is the second most common cause of death in the world, and the number of people with the disease increases each year. The therapy of the disease currently stands on four pillars; surgery, chemotherapy, radiotherapy, and immunotherapy. Through the past few years, immunotherapy has become the fastest developing treatment modality. However, despite its unprecedented efficacy in some patients, the majority of patients still does not respond to the therapy. Therefore, there is a need to investigate the mechanisms that make immunotherapy inefficient. Cell-based cancer immunotherapy is the treatment modality which uses live ex vivo-produced tumor-targeting immune cells to treat cancer. One of the mechanisms that may compromise its therapeutic efficacy is the expression of inhibitory molecules on the surface of the produced immune cells. Tim-3 is the inhibitory molecule which attracts attention in recent years. Tim-3 expression in the tumor cells and the tumor-infiltrating immune cells is often associated with worse prognosis and more aggressive forms of the disease. However, its role in the in vitro or ex vivo-produced immune cells is difficult to predict. In this work, an in vitro study model which is based on in vitro-produced antigen-specific CD8+ T cells with high expression of Tim-3 has been...