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The gut microbiota is now recognized as a key parameter affecting the host’s anti-cancer immunosurveillance and ability to respond to immunotherapy. Therefore, optimal modulation for preventive and therapeutic purposes is very appealing. Diet is one of the most potent modulators of microbiota, and thus nutritional intervention could be exploited to improve host anti-cancer immunity. Here, we show that an inulin-enriched diet, a prebiotic known to promote immunostimulatory bacteria, triggers an enhanced Th1-polarized CD4+ and CD8+ αβ T cell-mediated anti-tumor response and attenuates tumor growth in three preclinical tumor-bearing mouse models. We highlighted that the inulin-mediated anti-tumor effect relies on the activation of both intestinal and tumor-infiltrating ɣδ T cells that are indispensable for αβ T cell activation and subsequent tumor growth control, in a microbiota-dependent manner. Overall, our data identified these cells as a critical immune subset, mandatory for inulin-mediated anti-tumor immunity in vivo, further supporting and rationalizing the use of such prebiotic approaches, as well as the development of immunotherapies targeting ɣδ T cells in cancer prevention and immunotherapy.

International audience

Extracorporeal Photochemotherapy (ECP) is a promising cell therapy currently used in the treatment of T cell-mediated diseases such as Cutaneous T cell lymphoma and GvHD. Conversely to immunosuppressive drugs, ECP appears to induce an immunomodulation specifically directed toward “pathogenic” T cells, without causing generalized immunosuppression. However, its mechanisms of action are not well understood. To gain further insight in these mechanisms, we first characterized the effects of ECP on Monocytes which represent a large proportion of treated cells. ECP induces a slow apoptosis of monocytes while surviving treated cells conserve their functionalities. In GvHD, we show that following ECP, “pathogenic” activated T cells undergo faster apoptosis than “normal” resting T cells. ECP induced apoptosis is immunogenic and activated-treated cells trigger dendritic cell maturation, increasing their capacity to stimulate T cells with a reduced proportion of induced-regulatory T cells. We are developing an in vitro model to identify an anti-clonotypic response which is strongly suggested by our data. Finally, in collaboration with Paediatric oncologists, we participated in the development of a pre-clinical in vitro model validating a less invasive protocol for the technique for treating paediatric GvHD patients. A clinical trial has been started to evaluate this protocol. This work represents a key step in the understanding of the mechanisms of action of ECP and contributes to an improvement of clinical practices and thus, a better patients' quality of life., La photochimiothérapie extracorporelle (PCE) est une thérapie cellulaire prometteuse utilisée avec succès dans le traitement de pathologies impliquant des lymphocytes T (LT) telles que les lymphomes T cutanés et la GvHD. Contrairement aux immunosuppresseurs, la PCE semble induire une immunomodulation dirigée spécifiquement à l'encontre des LT « pathogènes » sans immunosuppression généralisée, cependant son mode d'action reste inconnu. Afin de comprendre ces mécanismes d'action, nous avons caractérisé dans un premier temps l'effet de la PCE sur la fonctionnalité des monocytes présents en forte proportion dans l'échantillon traité. Ils entrent en apoptose lente et les cellules encore vivantes conservent leur propriétés fonctionnelles. Dans la GvHD, nous avons montré qu'après PCE, les LT « pathogènes » activés entraient plus rapidement en apoptose que les LT « normaux » au repos. L'apoptose des LT activés est immunogène et induit la maturation des cellules dendritiques, leur conférant des propriétés de stimulation T plus fortes tout en diminuant la proportion de T régulateurs induits. Nous développons un modèle in vitro afin de mettre en évidence l'induction d'une réponse anti-clonotypique fortement suggérée par nos résultats. Enfin, en collaborant avec des pédiatres oncologues, nous avons participé au développement d'un modèle in vitro pré-clinique validant un protocole allégé de la technique pour le traitement de la GvHD en pédiatrie, conduisant à l'ouverture d'un essai clinique. Nos travaux constituent une étape clé dans la compréhension des mécanismes d'action de la PCE et contribuent à l'amélioration des pratiques cliniques et ainsi de la qualité de vie des patients.

International audience; Background. Graft versus host disease (GvHD) is the main complication after hematopoietic stem-cell transplantation. Extracorporeal photochemotherapy (ECP) is a cell therapy currently used for the treatment of T-cell-mediated diseases and seems as a valuable second-line therapy for patients suffering from steroid-refractory acute or chronic GvHD. ECP induces the apoptosis of treated cells and is believed to elicit a specific immune regulation of alloreactive T cells through repeated apoptotic T-cell infusions. However, its mechanisms of action have not yet been elucidated. In GvHD, alloreactive but not nonalloreactive T cells are continuously activated by their environment. We hypothesized that ECP has a differential apoptotic effect on activated compared with resting T cells. Method. The ECP-induced apoptosis of resting and activated T cells from patients with chronic GvHD was assessed. The kinetic of apoptosis was also evaluated using several triggers of T-cell activation such as mitogenic or antigen-specific activation. The influence of survival cytokines (interleukin-2,-7, and-15) was also evaluated. Results. Activated T cells from patients with chronic GvHD underwent apoptosis faster than resting T cells. This phenomenon was confirmed using mitogenic and antigen-specific activated T cells from healthy donors and cannot be delayed by protective cytokines. Conclusions. ECP induces a faster apoptosis of alloreactive activated T cells than of nonalloreactive resting T cells in GvHD and more generally of activated T cells than of resting T cells. These novel findings provide new insights about the ECP-induced specific control of pathogenic T cells in GvHD.

International audience; Extracorporeal photochemotherapy (ECP) is an autologous cell therapy used for the treatment of diseases involving pathogenic cells: cutaneous T-cell lymphoma, organ rejection and graft versus host disease. During an ECP procedure, patients receive a cellular product consisting of autologous mononuclear cells, containing the pathogenic cells, treated with a photosensitising agent and an UV-A radiation. The aim of the treatment is to induce a specific immune reaction modulating the activity of untreated pathogenic lymphocytes responsible for the disease and therefore an improvement of clinical manifestations. The precise mechanisms of action remain to be defined in humans. Its efficacy coupled with the absence of side effects could lead to decrease the use of immunosuppressive drugs. PCE appears as an immunotherapy using cells modified by photochemistry, which allows specific immune modulation of pathogenic lymphocytes.; La photochimiothérapie extracorporelle (PCE) est une technique de thérapie cellulaire autologue utilisée dans le traitement de pathologies impliquant des lymphocytes pathogènes : lymphomes cutanés à cellules T, rejet d'organe et maladie du greffon contre l'hôte. À chaque séance de PCE, les patients reçoivent un produit cellulaire composé de cellules mononucléées autologues, contenant les cellules pathogènes, traitées par un agent photosensibilisant et un rayonnement UV-A. L'objectif du traitement est d'entraîner une réaction spécifique du système immunitaire modulant l'activité des lymphocytes pathogènes non traités responsables de la pathologie et par conséquent une amélioration des signes cliniques. Les mécanismes d'action précis restent cependant à identifier chez l'homme. Son efficacité associée à l'absence d'effets secondaires peut conduire à diminuer le recours aux immunosuppresseurs. La PCE apparaît donc comme une immunothérapie par cellules modifiées par photochimie qui permet une immunomodulation spécifique de lymphocytes pathogènes.

International audience; BACKGROUND: Extracorporeal photopheresis (ECP) is a powerful therapy currently used to treat various hematological disorders as in graft versus host disease. Clinical data clearly demonstrate its efficacy and immunomodulation toward the pathogenic T cells. However, ECP mechanism of action is still poorly understood. Monocytes represent up to 30% of the total amount of treated cells and are known to play an important role in adaptive immunity. However, data from previous reports analyzing the effect of psoralen and UV-A irradiation (PUVA) on their functions are heterogeneous. In this study, we focused on the effect of PUVA on human monocytes functions in adaptive immunity. DESIGN AND METHODS: Purified human monocytes were treated in vitro by PUVA. We measured their kinetic of apoptosis after the treatment. We also determine whether their phenotype and functionalities were modified. Finally, we assessed the functionalities of PUVA-treated monocytes-derived dendritic cells (DC). RESULTS: PUVA treatment sentenced purified monocytes to die in 6 days and immediately altered their migratory capacities without impairing their ability of endocytosis. It also up-regulated co-stimulatory molecules and production of inflammatory cytokines on activation and consequently stimulated allogeneic or autologous T cells as efficiently as untreated monocytes. Moreover, PUVA-treated monocytes retained their ability to differentiate into fully functional DC that maturated and stimulated T cells as well as normal DC. CONCLUSIONS: Our data demonstrate that monocytes undergo apoptosis and loose a part of their migratory capacity after ECP and the surviving cell functionalities are not impaired, suggesting that monocytes have a minor effect on ECP-mediated immunomodulation.