T and B-lymphocytes play an important role in an adaptive immune response. Communication between these two cells may result in either a humoral immune response or tolerance. Communication between T and B-lymphocytes involves a number of inducible cell surface molecules on both T and B-lymphocytes. It was the aim of this project to gain a greater understanding of the role of CD40 in the dynamic communication that occurs between naïve T-lymphocytes and resting B-lymphocytes during cognate communication. Because in vivo antigen specific T-lymphocytes are at low frequency, it is difficult to examine antigen-specific naïve T-lymphocytes. Thus, an in vitro system employing naïve antigen-specific T cell receptor (TCR) transgenic T cells and small resting B-lymphocytes that did not express CD40 was devised to examine the role of CD40 in cognate communication between naïve T-lymphocytes and resting B-lymphocytes. Upon recognition of antigen on resting B-lymphocytes that expressed CD40, T-lymphocytes proliferated, expressed the activation antigens CD69 and CD25, and remained responsive to subsequent antigen challenge. In the absence of CD40, resting B-lymphocytes did not induce sustained proliferation or sustained expression of the activation markers CD69 and CD25 on naïve T-lymphocytes, and their recovery was decreased compared to naïve T-lymphocytes that recognized antigen on resting B-lymphocytes that expressed CD40. Naïve T-lymphocytes, however, remained responsive to subsequent antigen challenge after recognition of antigen on resting CD40-/- B-lymphocytes. Recognition of antigen on resting CD40-/- B-lymphocytes also resulted in increased recovery and antigen responsiveness of T-lymphocytes when compared to controls without antigen, The role of CD40 in sustaining activation of naïve T-lymphocytes may be unique to resting B-lymphocytes, since proliferation of naïve T-lymphocytes in response to dendritic cells that did not express CD40 was similar to proliferation of naïve T-lymphocytes in response to dendritic cells that expressed CD40. The mechanism by which CD40 sustained activation of naïve T-lymphocytes was investigated by examining the induction of various costimulatory molecules on resting CD40+/- and CD40-/- B-lymphocytes during cognate interaction with naive T-lymphocytes. Induction of B7-1, upregulation of CD44 and ICAM-1, and sustained but not initial induction of B7-2 required that CD40 be expressed on resting B-lymphocytes. Expression of B7-1 and CD44H was not required for proliferation of naïve T-lymphocytes in response to antigen presented on resting B-lymphocytes. However, sustained expression of B7-2 was crucial for proliferation of naïve T-lymphocytes in response to antigen presented on resting B-lymphocytes.

Les myosites sont des maladies auto-immunes, caractérisées par des atteintes musculaires et extra musculaires. Le diagnostic des myosites peut être difficile et nécessite de l’expertise, afin d’éviter l’administration de thérapie inapproprié. Les mécanismes impliqués au cours des myosites sont peu connus. Notre but était de décrire le profil immunitaire des patients, afin d’identifier des biomarqueurs. Nous avons utilisé un panel de 36 marqueurs pour caractériser les PBMC issus de patients actifs (MIs, SAS anti-Jo1, myopathies anti-SRP et anti-HMGCR) et de sujets sains par cytométrie de masse combiné au « barcoding ». Tout d’abord, nous avons mis au point une procédure technique pour la détection simultanée de cibles extracellulaires et intracellulaires. En utilisant différents outils bio-informatiques, nous avons isolé une fréquence de lymphocytes CD8+T-bet+ > 51.5% comme étant un biomarqueur spécifique de la MIs en comparaison aux autres myosites, avec une sensibilité de 94,74% et une spécificité de 88,46%. De plus, nous avons identifié un profil immunitaire CD8+T-bet+ CD57- activé, potentiellement capable de prolifération et de maintien de mécanismes auto-immuns chez les patients atteints de MIs. Chez les patients anti-Jo1, nous avons observé une dérégulation de l’homéostasie des lymphocytes B, caractérisée par une diminution des lymphocytes B mémoires circulants. La présence de ces derniers dans le muscle des patients suggère qu’ils se nichent dans le muscle afin d’éviter l’action des immunosuppresseurs. Ces travaux ont permis l’identification de biomarqueurs et de phénotypes cellulaires potentiellement impliqués au cours de la MIs et du SAS anti-Jo1. / Myositis is an autoimmune disease characterized by muscular and extra-muscular disorders. In the early stages of the disease, the diagnosis of myositis can be misleading and requires expertise, in order to avoid the administration of inappropriate treatment. The mechanisms involved in these diseases are poorly understood. Our aim was to describe the immune profile specific to each patient group, in order to identify biomarkers that may be useful for diagnosis and management of patients. We used a panel of 36 markers by mass cytometry to characterize PBMCs derived from active patients (sIBM, anti-Jo1 ASyS, anti-SRP and anti-HMGCR myopathies) and healthy subjects. First, we developed and optimized a technical procedure for the simultaneous detection of extracellular and intracellular targets by mass cytometry. Using different bioinformatics tools, we isolated a frequency of CD8 +T-bet + cells > 51.5% as a specific biomarker for sIBM compared to other myositis, with a sensitivity of 94.74% and a specificity of 88. , 46%. In addition, we identified an activated CD8 + T-bet + CD57- immune profile, potentially capable of proliferation and the maintenance of autoimmune mechanisms in patients with sIBM. In anti-Jo1 patients, we observed a dysregulation of B cell homeostasis, characterized by a decrease in circulating memory B cells. The presence of the latter in the muscle of patients suggests that they nest in the muscle to avoid immunosuppressants. This work allowed the identification of a biomarker that could enhance the diagnosis of MIs compared to other myositis and the identification of cells potentially involved during sIBM and anti-Jo1 ASyS.

In this thesis I describe an investigation into the function of the protein Icb-1, a homologue of Themis1 in B cells and monocytes. Themis1 is important for T cell positive and negative selections. Yet its function in T cell development is not clear. Although it shows characteristics of an adaptor protein and involvement in TCR-induced signalling, the exact signalling defects in Themis1-/- T cells remain obscure. Icb-1 is similar to Themis1 in sequence, function and binding partners. It has been studied in human tumour and macrophage cell lines, leading to limited conclusions. Its role in B cells has never been published. Given the link with Themis1, it is of great interest to investigate the function of Icb-1. My study has been focused on the comparison between Icb-1 knockout mice with wild-type controls. I characterised the B cell development in Icb-1-/- mice, either naturally born or produced as mixed adult bone marrow chimeras reconstituted from WT and Icb-1-/- donor cells. I examined the possible compensation and redundancy of Themis1 and Icb-1, by characterising Thems1/Icb-1 double knockout mice. The Ig-HEL mouse models were used to examine the change in B cell repertoire due to negative and positive selections. The mice were challenged with SRBCs or NP-CGG to examine the germinal centre response to foreign antigen when Icb-1 is absent. In vitro stimulation of B cells with soluble and membrane-bound antigens was used to investigate early B cell responses in detail and to give insights into the defects found in in vivo challenges. Finally, I examined the BCR-induced phosphorylation of key signalling molecules and Ca2+ flux in splenic B cells. The study revealed largely normal B cell development with subtle selection impairments, but a partially defected B cell immune response to antigens in Icb-1-/- mice. The marginal zone B cell population was enlarged in the absence of Icb-1, while the positive selection of B1 B cells induced by intracellular self-antigen was impaired. The deficient mice showed a reduction in germinal centre B cell generation. The defects are associated with impaired BCR-induced cell signalling to low abundance and/or low avidity antigens. In particular, Ca2+ flux and Erk1/2 phosphorylation were clearly reduced under certain conditions. The results shine a light on the function of protein Icb-1, and also improve our knowledge of Themis1 and the Themis family. They provide a new avenue of investigation into the regulation of BCR signalling, especially in Ca2+ flux induction and Erk1/2 activation. They also provide insight into how differential signalling is controlled within cells during activation and differentiation in response to antigens that vary in terms of affinity, avidity and frequency.

Plusieurs paramètres participent à l'homéostasie du système immunitaire. On peut notamment citer : la production lymphocytaire (les lymphocytes B dans la moelle osseuse ou les lymphocytes T (LyT) dans le thymus), la prolifération et la survie des lymphocytes périphériques et enfin, la compétition entre les différents clones de lymphocytes ou les différentes populations de lymphocytes pour des ressources limitées en particulier les cytokines. Les mécanismes de régulation homéostatique sont différents selon la sous-population de lymphocyte considérée. Dans le cadre de cette thèse, nous avons étudié le rôle de l'interleukine-7 (IL-7) dans l'homéostasie des lymphocytes et plus particulièrement les lymphocytes T ΑΒ. Disposant de souris surexprimant l'IL-7 dans un état lymphopénique plus ou moins sévère, nous avons pu décortiquer les effets de l'IL-7 sur le développement précoce des LyT et leur survie périphérique. L'analyse du développement précoce des lymphocytes n'a pas révélé d'effet notable de la sur-expression de l'IL-7 sur le développement thymique des LyT. En revanche, une expansion considérable des LyT périphériques a été observée. A partir d'expérience de transferts adoptifs, nous avons montré que l'IL-7 favorisait la prolifération et la survie des LyT périphériques. La quantité d'IL-7 disponible module donc le devenir des LyT présents dans les organes lymphoïdes lors d'un épisode lymphopénique.

Cardiovascular disease, often induced by hypertension, represents a serious health threat, is a primary cause of death worldwide, and results in altered cardiovascular function and ECM composition. Hypertension and related cardiovascular diseases are associated with immune dysfunction. This dissertation investigated the role of T-lymphocytes in modulating cardiovascular function and ECM composition as a possible therapeutic for the treatment of cardiovascular disease. Study one investigated the role of TCR peptide in the development of hypertension and subsequent cardiovascular changes in Balb/C mice. The coadminstration of TCR and L-NAME/8% NaCl reduced the effects of L-NAME/8% NaCl, decreasing blood pressure and crosslinked collagen compared to L-NAME/8% NaCl alone. Study two examined the effects of T-lymphocyte function on cardiovascular structure and function. Adoptive transfer of T-lymphocytes from C57BL/6 WT mice into C57BL/6 SCID mice induced changes in the SCID so that it resembled the WT donor, with increased percent crosslinked collagen and LOX activity. Hemodynamics in the SCID recipient resembled that of the WT and were significantly different from the sham injected SCID. Study three combined aspects of both previous studies. T-lymphocytes were adoptively transferred from hypertensive WT donors into naïve SCID recipients, who developed hypertension and cardiovascular function resembling the hypertensive donor, as well as changes in the ECM, including increased collagen crosslinking. Study four investigated the effect of strain specific T-lymphocyte polarization on hypertension induced cardiac ECM remodeling. Balb/C, C57BL/6 WT, and C57BL/6 SCID had divergent responses to L-NAME induced hypertension. Ventricular stiffness increased in Balb/C, decreased in C57 SCID and did not change in C57 WT; LOX activity changed correspondingly in all groups. The final study examined the effect of TCR administration on LOX activity and collagen crosslinking. Th1 polarization increased LOX activity and crosslinked collagen with corresponding changes in cardiovascular function. In conclusion, modulation of T-lymphocyte function alters cardiovascular function and ECM composition in pathologic and non-pathologic conditions. Immune modulation should be further investigated as a therapeutic for cardiovascular disease.

Le but du travail de recherche présenté dans cette thèse était de déterminer les mécanismes impliqués dans le développement de symptômes neurologiques observés dans une lignée de souris transgénique pour l’expression de la molécule B7.2/CD86. La molécule B7.2 est un des ligands du récepteur CD28 qui transmet des signaux intracellulaires nécessaires à la prolifération des lymphocytes T et au développement de leurs fonctions effectrices. Nos travaux démontrent que ces souris développent spontanément une pathologie démyélinisante auto-immune conséquemment à l’expression transgénique de la molécule B7.2 sur les cellules de la microglie du système nerveux central. Les souris affectées présentent une infiltration de lymphocytes T au niveau du système nerveux central et périphérique proximal et cet infiltrat est prédominé par une population de lymphocytes T CD8[indice supérieur +] mémoires/effectrices. Nos études indiquent que la population de lymphocytes T CD8[indice supérieur +] joue un rôle effecteur dans le développement de la pathologie tandis que la population des lymphocytes T CD4[indice supérieur +] la régulent de façon négative. Nos résultats démontrent également que l’activation des cellules de la microglie survient très tôt lors de la pathogenèse et que cette activation des cellules de la microglie ainsi que le processus de démyélinisation sont entièrement dépendants de la signalisation par le récepteur de l’IFNy. Ce modèle de démyélinisation reflète l’émergence de cellules T autoréactives spécifiques au système nerveux à partir d’un répertoire périphérique polyclonal, un processus immunopathogénique qui se produit possiblement durant la pathogenèse de la sclérose en plaques. De plus, il présente certaines caractéristiques pathologiques similaires à celles de la sclérose en plaques tels que le développement spontané du processus de démyélinisation et de dommages aux axones ainsi qu’une connexité avec l’activité de l’IFNy. Plusieurs données de la littérature suggèrent que les lymphocytes T CD8[indice supérieur +] pourraient jouer un rôle dans les maladies auto-immunes affectant le système nerveux, mais la contribution exacte et les mécanismes pathogéniques spécifiques des lymphocytes T CD8[indice supérieur +] ne sont pas encore clairement établis. Le travail de recherche présenté dans cette thèse a donc permis d’établir que la lignée de souris transgénique qui exprime de façon constitutive le ligand de costimulation B7.2/CD86 sur les cellules de la microglie représente un nouveau modèle animal qui permettra d’étudier et de comprendre ces mécanismes pathogéniques spécifiques aux lymphocytes T CD8[indice supérieur +] ainsi que les processus qui régulent la participation des lymphocytes T CD8[indice supérieur +] dans la destruction de la gaine de myéline.

B lymphocytes are an important type of immune cell that contributes to pathogen clearance. When dysregulated, these cells contribute significantly to diseases such as autoimmunity, allergy and B cell cancers. Here we examine an important regulatory circuit that involves the lipid phosphatase SHIP, a key regulator of the PI3K signaling pathway. SHIP was first described as the major effector of inhibitory IgG receptor FcγRIIB, which downregulates B cell antigen receptor (BCR) signaling pathways when co-engaged. However, it is also known to inhibit signaling downstream of several other receptors, both activating and inhibitory. Here we examine the regulation and function of SHIP in B cells, focusing on the inter-related influences of binding partners, tyrosine phosphorylation and subcellular localization dynamics. First, we assess interaction of SHIP to selected candidate binding partners using an in vitro screening approach. The two most robust interactions were further characterized with respect to dissociation constant. These were: a novel interaction between SHIP phospho-Tyr944 and the SH2 domain of Nck, and a known interaction between the SH2 domain of SHIP and FcγRIIB phospho-Y292. Next, we perform the first examination of SHIP Tyr944. We provide evidence that it contributes to interaction with Nck after BCR engagement and is required for inhibition of actin turnover by SHIP. Finally, we perform the first detailed examination of the mechanisms controlling SHIP localization in human B cells stimulated through the BCR with and without co-engagement of FcγRIIB. We discover that SHIP is recruited to the plasma membrane equally in both stimulation contexts, however FcγRIIB co-ligation results in reduced mobility of SHIP molecules at the cell periphery. We identify a novel and essential role for Syk kinase in promoting SHIP membrane localization, tyrosine phosphorylation, and interaction with known binding partner Shc1. Together, these results provide significant and exploitable insight into the molecular control of a clinically important regulator of B cell responses. / February 2017

Lymphocyte activation and trafficking are indispensable to the immune system. CD44, an adhesion molecule, plays important roles in T cell activation, lymphocyte homing/trafficking, and tumor metastasis. Although the functions of CD44 have been shown in T cells and other leukocytes, little is known about its role in B cells. The effects of CD44 cross-linking on murine B cell activation via CD40L/IL-4 was explored using the anti-CD44 mAbs RK3G9 and IM7. Immobilized RK3G9 and IM7 could strongly inhibit B cell proliferation and Ig production, with IgE inhibition being prominent. Soluble anti-CD44 had no effect. The inhibitory effect of RK3G9 was not influenced by addition of anti-FCγRII, indicating no role for the inhibitory receptor. The effects of delayed addition of immobilized anti-CD44 mAbs were studied, and the results indicated no inhibition after 96 hrs of culture. B cells were also activated by either LPS or anti-IgM F(ab')2. While LPS-induced B cell activation was inhibited by immobilized anti-CD44 mAbs, anti-IgM activation was refractory. Interestingly, addition of both anti-IgM and CD40L or LPS resulted in some modulation of the inhibitory activity. Additionally, FACS and Elispot revealed that RK3G9-treated cells had reduced numbers of plasma cells. Taken together, these results suggest that CD44 cross-linking could control polyclonal B cell activation by CD40L, but allow sIgM/CD40L activation to continue.

La transplantation allogénique de cellules souches hématopoïétiques (ASCT) est couramment utilisée pour traiter différents cancers hématologiques. Malheureusement, l’effet bénéfique de cette technique est limité par la réaction du greffon contre l’hôte (GVHD) qui demeure la cause principale de mortalité post-greffe. La GVHD endommage différents organes et retarde la reconstitution immunitaire des lymphocytes T (LT) ce qui augmente les risques d’infection et de rechute. Le développement de nouveaux traitements permettant d’accélérer la reconstitution immunitaire augmenterait donc les chances de survie des patients greffés. Il existe deux façons de régénérer des LT: via la thymopoïèse qui consiste à produire de nouveaux LT, ou par la prolifération homéostatique (PH) qui implique l’expansion rapide des LT matures retrouvés dans le greffon. La PH requiert deux signaux essentiels: l’interleukine-7 (IL-7) et la présentation d’antigènes du soi par les cellules dendritiques (DC) via le complexe majeur d’histocompatibilité (CMH) I pour les LT CD8+ et le CMH II pour les LT CD4+. Dans un contexte d’ASCT, la chimiothérapie et la GVHD endommagent le thymus rendant la thymopoïèse inefficace. Par conséquent, la reconstitution immunitaire repose presque entièrement sur la PH des LT. L’objectif de cette thèse était de comprendre comment la GVHD affecte la reconstitution des LT. Grâce à un modèle murin, nous avons démontré que la PH des LT CD4+ est absente durant la GVHD et ce, dû à de faibles niveaux d’IL-7 et une diminution du nombre de DC. La perte des DC est en grande partie causée par des niveaux réduits de stromal derived factor-1α (SDF-1α) et par l’absence de progéniteurs de DC dans la moelle osseuse des souris en GVHD. Le traitement des souris en GVHD avec du SDF-1α permet d’augmenter le nombre de DC, et lorsqu’administré avec l’IL-7, améliore significativement la PH des LT CD4+. Contrairement aux LT CD4+, l’administration d’IL-7 seule est suffisante pour restaurer la PH des LT CD8+ durant la GVHD et ce, même en absence des DC. Ces différences s’expliquent pour deux raisons : 1) l’expression du CMH I, contrairement au CMH II, n’est pas limitée aux DC mais est également exprimée par les cellules stromales du receveur ce qui est suffisant pour induire la PH des LT CD8+ et 2) les LT CD8+ répondent à des concentrations plus faibles d’IL-7 systémique comparativement aux LT CD4+. En conclusion, l’ensemble de ces résultats permettra de mettre en place des études translationnelles sur le potentiel thérapeutique du SDF-1α et de l’IL-7 dans la reconstitution immunitaire des patients greffés. / Hematological cancers are currently treated with allogeneic hematopoietic stem cell transplantation (ASCT). Unfortunately, graft-versus-host disease (GVHD) greatly limits the health benefits of this procedure, as it is the main cause of mortality post-ASCT. GVHD damages various organs and delays the immune reconstitution of T lymphocytes (TL), which increases the risk of infections and relapse. Thus, developing new treatments modulating the immune reconstitution following ASCT would greatly enhance survival of the transplanted patients. TL can be regenerated by two ways: de novo production of TL by thymopoiesis; or homeostatic proliferation (HP), which consists of rapidly expanding mature TL already present in the graft. HP requires two crucial signals: interleukin-7 (IL-7) and self-antigen presentation by dendritic cells (DC) via the major histocompatibility complex (MHC) I for CD8+ TL and MHC II for CD4+ TL. During ASCT however, chemotherapy and GVHD induce damage to the thymus making thymopoiesis inefficient, and thus immune reconstitution relies almost entirely on HP of TL. The objective of this thesis was to understand how GVHD affects TL reconstitution. Using a mouse model, we demonstrate that CD4+ TL fail to undergo HP when transferred in GVHD hosts due to low levels of IL-7 and reduced numbers of DCs. Moreover, the loss of DCs is mostly caused by reduced levels of Stromal Derived Factor-1 alpha (SDF-1α) and the absence of DC progenitors in the bone marrow of mice suffering from GVHD. Treating GVHD hosts with SDF-1α resulted in increased DC counts and, when administered in combination with IL-7, significantly improved HP of CD4+ TL. Unlike CD4+ TL, administration of IL-7 alone was sufficient to restore HP of CD8+ TL in GVHD mice and this, regardless of the presence of DCs. These differences could be explained by two reasons: 1) MHC I expression is not limited to DCs but is expressed by stromal cells from the recipient, which is sufficient to promote HP in CD8+ TL and 2) CD8+ TL respond to lower doses of systemic IL-7 in comparison to CD4+ TL. In conclusion, these results can lead to future translational studies on the therapeutic potential of SDF-1α and IL-7 in the immune reconstitution of grafted patients.

La détection de lymphocytes T (LT) CD8+ infiltrant les tumeurs (TIL), est généralement associée à un bon pronostic chez des patients atteints du cancer. A l’inverse, l'infiltration des tumeurs par des LT CD4+ régulateurs (Treg), est quant à elle, souvent corrélée à un mauvais pronostic. Plusieurs vaccins « thérapeutiques » capables d’induire des réponses T CD8+ spécifiques d’antigènes tumoraux ont été développés. Cependant, à ce jour, les résultats cliniques obtenus par ces vaccins restent décevants. Dans un premier travail, nous avons développé puis testé un vaccin thérapeutique composé de trois longs peptides synthétiques (LSP) dérivés de la protéine survivine (SVX). La survivine est une protéine surexprimée dans la majorité des cancers humains, mais absente dans les tissus adultes sains, ce qui fait d’elle une cible thérapeutique privilégiée pour les vaccins anti-tumoraux. Nous avons démontré l'efficacité thérapeutique élevée du vaccin SVX contre diverses tumeurs murines. Ceci a été associé à l'induction de réponses T spécifiques de la survivine, un prolongement de la survie et la génération de réponses mémoires antitumorales. De plus, SVX a induit à la fois des LT CD8+ cytotoxiques spécifiques et LT CD4+ auxiliaires de type 1 multifonctionnelles, dans la rate et au sein des tumeurs. Il a aussi induit une diminution des Treg, favorisant ainsi une réponse immunitaire très efficace. Enfin, une étude préliminaire menée chez des patients atteints de différents types de cancers, nous a révélé la présence de taux élevés de précurseurs spontanés de LT spécifiques du vaccin SVX. Ces résultats suggèrent que SVX pourrait potentiellement stimuler l'activation de ces précurseurs spécifiques. Ces résultats constituent une preuve de concept pour amener ce vaccin comme un produit de première génération en essai clinique chez l’homme. Dans le but d’étudier plus en détails la cinétique des réponses immunitaires T spécifiques, associées aux vaccins LSP, nous avons étudié dans un second travail, l’efficacité d’un vaccin LSP dérivé de la protéine Ovalbumine (OVA). Nous avons montré dans plusieurs modèles de tumeurs murines, que la combinaison du vaccin LSP-OVA à un adjuvant approprié, induisait une forte régression de la croissance tumorale, l’expansion des cellules spécifiques T CD4+ et T CD8+ dans les organes lymphoïdes, ainsi que leur migration vers les tumeurs. De plus, le vaccin a induit des cellules T spécifiques fonctionnelles, comme le témoignent les niveaux élevés de cytokines cytotoxiques mesurées. De manière intéressante, le vaccin n’a pas induit de Treg spécifiques d’OVA ou de Treg polyclonaux et ce, malgré la présence de la tumeur. Enfin, lorsque LSP-OVA ne parvenait pas à induire une régression complète de la tumeur, celle-ci était infiltrée par des TIL CD4+ conventionnels et CD8+ exprimant fortement les récepteurs inhibiteurs (PD-1, TIM-3 et TIGIT). Nos résultats suggèrent que pour optimiser ce vaccin LSP, une association à des anticorps bloquant un ou plusieurs de ces récepteurs inhibiteurs, devrait être envisagée. / The presence of tumor-infiltrating CD8+ T lymphocytes (TIL) is generally associated with a good prognosis in cancer patients. Conversely, the infiltration of tumors by CD4+ regulators T cells (Treg), is often associated with poor prognosis. Several "therapeutic" vaccines able to induce tumor-specific CD8+ T cell responses have been developed. However, to date, the clinical results of these vaccines remain insufficient. In a first work, we developed and analyzed the immunogenicity and therapeutic efficacy of a new survivin vaccine (SVX) composed of three long synthetic peptides (LSP) containing several CD4 and CD8 T-cell epitopes. Survivin is over-expressed by most human cancers, but absent in healthy adult tissues, making it an interesting therapeutic target for cancer vaccines. We demonstrated the high therapeutic efficacy of SVX vaccine against various established murine tumor models, associated with its capacity to generate both specific cytotoxic CD8+ and multifunctional Th1 CD4+ T-cell responses but also effective memory T-cell responses for long-term protection against relapses. Treatment with SVX vaccine was also found to strongly increase the tumor infiltration of both CD4+ and CD8+ T cells over Treg cells therefore tipping the balance toward a highly efficient immune response. Finally, a preliminary study in patients with different types of cancer revealed the presence of high levels of SVX-specific spontaneous T-cell precursors. This suggests that SVX can potentially stimulate the activation of these specific precursors. Altogether, our results strongly suggest that SVX is a promising cancer vaccine and warrants its further clinical development. In order to study the kinetics of tumor-specific immune responses associated with LSP vaccines, we studied the efficacy of a LSP vaccine derived from the Ovalbumin (OVA) protein. We showed in two tumor models that the combination of LSP-OVA with a suitable adjuvant induced a strong tumor regression, an important expansion of both OVA-specific CD4+ and CD8+ T cells in the lymphoid organs, as well as their migration to the tumor. In addition, the vaccine induced functional specific T cells, as shown by the high levels of cytotoxic cytokines. Interestingly, the vaccine did not induce either OVA-specific or polyclonal Treg, despite the presence of the tumor. Finally, when LSP-OVA failed to induce a complete depletion of the tumor, we observed an important expression of inhibitory receptors (PD-1, TIM-3 and TIGIT) on conventional CD4+ and CD8+ TIL. Our results suggest that to optimize this LSP vaccine, a combination with one or more immune checkpoint blockade agents should be considered.