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During my PhD thesis, I mainly worked on three projects involving mathematical and bioinformatics methods in immuno-oncology. 1) Project 1: development of the SmartFACS deconvolution tool. I developed a deconvolution tool called SmartFACS in collaboration with the Mechanics and Applied Mathematics Department (ULB) and the Immunobiology Laboratory (ULB). The role of this computer program is to estimate the cellular composition of a sample from RNA sequencing data. This tool has been developed in the context of immunology, where it is often of interest to identify immune cells present in the blood or in tumors. At the time this project began, no deconvolution tool for mouse data was yet available, despite the fact that much biomedical research is carried out in mouse models. During my thesis, I therefore decided to develop a tool adapted to mouse data, while trying to improve existing tools for human data by detecting a wider range of immune populations. 2) Project 2: research of clinical biomarkers for anti-PD1 immunotherapy treatment. In collaboration with the Immunobiology group (ULB), I worked on anti-PD1 therapy, which is already used clinically for certain cancers. Unfortunately, the success rate of this treatment is still relatively moderate. This is why the aim of my project was to determine predictive markers of response to anti-PD1 in order to better understand the mechanisms of resistance and find avenues of improvement for this treatment, as well as to better identify responder patients. To achieve these objectives, a mouse model was developed in the Immunobiology Laboratory. This model enabled us to reproduce the dichotomous response observed in the clinic. My work focused on analyzing pre-treatment tumor sequencing data obtained using the mouse model, in order to compare the immune infiltrate of responder and non-responder mice. My data analyses, together with experiments conducted by Jelena Gabrilo, revealed two immune populations important for treatmen, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

Le mélanome est la forme la plus agressive et la plus mortelle des cancers de la peau. Une mutation activatrice dans les gènes BRAF ou NRAS est présente dans 95% des cas de mélanomes humains. L'importance de l'inflammation chronique et du microenvironnement tumoral dans le développement, la progression et le potentiel métastatique de cette maladie est bien établie. Les molécules chimioattractantes comme la chémérine jouent dans ce contexte un rôle clé via le recrutement sélectif de populations leucocytaires spécifiques exprimant le récepteur ChemR23. Lors de ma thèse, nous avons étudié le rôle de la chémérine, dans les différentes étapes de la carcinogenèse. Elle possède des propriétés antitumorales, et notamment dans le mélanome. Cependant, les mécanismes de base de son action in vivo restent à déterminer.Suite aux études sur le modèle murin, nous avons choisi d’utiliser le poisson-zèbre afin d’investiguer in vivo les fonctions de la chémérine dans la biologie du mélanome. En effet, les résultats chez le poisson-zèbre obtenus au sein de notre laboratoire, suggèrent que l'axe chémérine/ChemR23 est hautement conservé à travers le phylum des vertébrés. Pour évaluer les propriétés antitumorales de la chémérine, j’ai utilisé différentes stratégies préalablement établies et validées chez le poisson-zèbre :un modèle mosaïque utilisant le système MiniCoopR exprimant l'oncogène NRASQ61L, un modèle génétique stable de mélanome faisant intervenir l’oncogène BRAF sur fond d’absence d’une protéine p53 fonctionnelle, et un modèle de xénogreffe de tumeurs. Mes analyses comparant l’apparition et la progression tumorale entre des animaux invalidés pour le cluster b de la chémérine ou pour son récepteur cmklr1.1 et leurs contrôles WT démontrent de manière non ambigüe que les propriétés antitumorales du système chémérine/ChemR23 sont conservées chez le poisson-zèbre.En ouvrant la voie à l’utilisation du poisson-zèbre pour l’étude des mécanismes clés par lesquels la chémérine agit sur, Doctorat en Sciences biomédicales et pharmaceutiques (Médecine), info:eu-repo/semantics/nonPublished

The current SARS‐CoV‐2 pandemic is wreaking havoc throughout the world and has rapidly become a global health emergency. A central question concerning COVID‐19 is why some individuals become sick and others not. Many have pointed already at variation in risk factors between individuals. However, the variable outcome of SARS‐CoV‐2 infections may, at least in part, be due also to differences between the viral subspecies with which individuals are infected. A more pertinent question is how we are to overcome the current pandemic. A vaccine against SARS‐CoV‐2 would offer significant relief, although vaccine developers have warned that design, testing and production of vaccines may take a year if not longer. Vaccines are based on a handful of different designs (i), but the earliest vaccines were based on the live, attenuated virus. As has been the case for other viruses during earlier pandemics, SARS‐CoV‐2 will mutate and may naturally attenuate over time (ii). What makes the current pandemic unique is that, thanks to state‐of‐the‐art nucleic acid sequencing technologies, we can follow in detail how SARS‐CoV‐2 evolves while it spreads. We argue that knowledge of naturally emerging attenuated SARS‐CoV‐2 variants across the globe should be of key interest in our fight against the pandemic.

Papillary thyroid carcinoma (PTC) is the most frequent histological subtype of thyroid cancers (TC), and BRAFV600E genetic alteration is found in 60% of this endocrine cancer. This oncogene is associated with poor prognosis, resistance to radioiodine therapy and tumor progression. Histological follow-up by anatomo-pathologists reveals that 2/3 of surgically-removed thyroids do not present malignant lesions. Continued fundamental research into the molecular mechanisms of TC downstream of BRAFV600E remains thus central to better understand the clinical behavior of these tumors. To study PTC, we used a mouse model in which expression of BRAFV600E is specifically switched on in thyrocytes by doxycycline administration. Upon daily intraperitoneal doxycycline injection, thyroid tissue rapidly acquired histological features mimicking human PTC. Transcriptomic analysis revealed major changes in immune signaling pathways upon BRAFV600E induction. Multiplex immunofluorescence confirmed the abundant recruitment of macrophages, among which a population of LYVE-1+/CD206+/STABILIN-1+ was dramatically increased. By genetically inactivating the gene coding for the scavenger receptor STABILIN-1, we showed an increase of CD8+ T cells in this in situ BRAFV600E dependent TC. Finally, we demonstrated the presence of CD206+/STABILIN-1+ macrophages in human thyroid pathologies. Altogether, we revealed the recruitment of immunosuppressive STABILIN-1 macrophages a PTC mouse model and the relevance of these observations in human thyroid tissues.

Glioblastoma is the most common and aggressive brain cancer. The low median survival of patients diagnosed with this disease makes it an unmet medical need. Nowadays, immunotherapeutic treatments have shown remarkable results in some populations of cancer patients but are rather ineffective in improving glioblastoma patients’ outcomes when used in monotherapy. The aim of this Ph.D. thesis is to contribute to the research of glioblastoma treatments by developing combination strategies of drug delivery systems to potentiate immunotherapy efficacy. The strategies used in this work include a DNA vaccine encoding glioblastoma-associated antigens, immune checkpoint blockades, and an immunogenic chemotherapeutic agent delivered locally. Our findings confirm the benefit of combination strategies to improve the immune response and increase the survival of glioblastoma., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2022

The management of dental emergencies is a central and essential issue in the daily practice of dentists. Through two clinical studies, we were able to identify new perspectives: 1/ The strategy of emergency management based on triage with the establishment of recommendations allowed to find an effective compromise between limiting the admission of patients and ensuring the control of their pain and the relief of their symptoms. 2/ More conservative management of irreversible pulpitis. Our data tend to support pulpotomy as an acceptable and more conservative permanent treatment option for irreversible pulpitis of mature molars. Our strategies could be considered as first-line treatments, thus providing additional steps in the therapeutic gradient., (DENT - Sciences dentaires) -- UCL, 2022

Malignant mesothelioma is a disease caused by inhalation of needle-like shaped particles and whose pathogenesis is not yet fully elucidated. A long-lasting general inflammation caused by persistent mesotheliomagenic particles is not sufficient to explain mesothelioma onset. Indeed, challenging data have shown that mesothelioma occurs without chronic inflammation. Our research team previously helped to discover that, beside inflammation, particles such as silica also induce a selective, rapid and sustained accumulation of immunosuppressive cells (regulatory T lymphocytes, myeloid derived suppressive cells and M2/regulatory macrophages) participating to fibrogenesis. To determine whether carcinogenic particles such as asbestos and carbon nanotubes (CNT) also elicit immunosuppressive responses, we investigated the impact of these particles on macrophage turnover, phenotype and immunosuppressive activity. With that purpose, we intraperitoneally injected mesotheliomagenic CNT-7 (needle-like, Mitsui & Co) and non-mesotheliomagenic CNT-T (tangled, Nagoya University) particles in Wistar rats and compared the effects on peritoneal macrophage subpopulations. We showed that macrophages die very rapidly in the attempt to phagocyte mesotheliomagenic CNT. They are later replenished by monocytic-derived small peritoneal macrophages (SPM-like macrophages) possessing comparable immunosuppressive functions and signatures to Tumor-Associated Macrophages (TAM), which infiltrate mesothelioma and block T cell antitumor activities. Early immunosuppressive SPM-like macrophages express and release the shed form of the immunoregulatory syndecan-1 glycoprotein, which could explain the immunosuppression that they exert on T cells. Non-mesotheliomagenic peritoneal responses induced by CNT-T are, in contrast, characterized by a recruitment of self-proliferating large peritoneal macrophages (LPM-like macrophages) that correspond to homeostatic macrophages without immunosuppressive activity. Our o, (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2021

Novel Strategies for Cancer Immunotherapy: Targeting Immune-Mediated Suppressive Mechanisms

Cancer immunotherapies, such as monoclonal antibodies (mAbs) directed against PD-1, aim at boosting immune responses against tumor cells. They have become a standard of care for several types of cancer. However, a majority of patients do not respond to current immunotherapies. Resistance to PD-1 blockade can in part be explained by the action of TGF-b1, an immunosuppressive cytokine activated notably by regulatory T cells (Tregs) via a mechanism that requires protein GARP. We developed antibodies against GARP:TGF-b1 complexes that block TGF-b1 activation by Tregs and we evaluated their anti-tumor efficacy in tumor-bearing mice. We observed that anti-GARP:TGF-b1 mAbs induce the regression of tumors otherwise resistant to anti-PD-1, and we showed that combined blockade of GARP:TGF-b1 and PD-1 can exert anti-tumor activity via multiple modes of action. This may prove important for the selection of cancer patients who could benefit from this novel form of immunotherapy in the clinics., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2021

[EN]It is well illustrated that the generation of Tregs is the main mechanism responsible for maintaining immune tolerance during developmental exposure to non-inherited maternal antigen (NIMA). Moreover, the presence of NIMA-specific Tregs in the uterus of pregnant mice promote reproductive fitness by enforcing maternal tolerance to overlapping paternal antigens expressed by the fetus during next-generation pregnancies. However, the reason why perinatal T cell lineage is biased towards immune tolerance is poorly understood. Due to the fact that terminal deoxynucleotidyl transferase (TdT) is not expressed in neonatal T cells in the mouse, neonatal T cells have a less diverse TCR repertoire. This is known to limit their specificity and to increase their affinity for MHC/peptide complexes. At the start of the present work, we postulated that expressing high affinity TCR might be the reason that forces the development of antigen-specific Tregs in neonates. We undertook our study with the aim to investigate the mechanisms underlying mouse NIMA-specific Treg development in the perinatal period. Using 2W1S-OVA+ heterozygous mouse model in which 2W1S antigen was transformed into surrogate NIMA for half of the offspring, we observed an increased frequency of 2W1S-specific Tregs in NIMA-2W1S-exposed animals. Moreover, we also observed that periphery-derived NIMA-2W1S Tregs had a less diverse TCR repertoire and were phenotypically distinct from thymus-derived SELF-2W1S-specific Tregs. In order to investigate whether the lack of diversity was responsible for the development of neonatal NIMA-specific Tregs, we generated transgenic mice where TdT expression was enforced in T cells before birth. We found that transgenic TdT added clonal TCR diversity but did not prevent the development of T cell clones with neonatal type TCR repertoire and did not modify the frequency of neonatal NIMA-specific Tregs. On the contrary, TdT expression increased significantly generation of SELF-speci, [FR]Il est bien illustré que la génération périnatal de Treg est le principal mécanisme responsable du maintien de la tolérance immunitaire fœtale qui se développe suite à l'exposition aux antigènes maternels non-hérités (NIMA). De plus, la présence de Tregs spécifiques des NIMA dans l'utérus des femmes enceintes favorise la capacité de reproduction en renforçant la tolérance maternelle aux mêmes antigènes paternels exprimés par le fœtus pendant les grossesses de prochaine génération. Cependant, la raison pour laquelle la lignée des cellules T fœtales est biaisée en faveur de la tolérance immunitaire est mal comprise. Chez la souris, en raison du manque d'expression de la désoxynucléotidyl transférase terminale (TdT), les cellules T néonatales ont un répertoire de TCR moins diversifié. Ceci est connu pour limiter leur spécificité et augmenter leur affinité pour les complexes CMH / peptide. Au début du présent travail, nous avons émis l'hypothèse que l'expression de TCRs de haute affinité pourrait être la raison qui force le développement de Treg spécifiques chez les nouveau-nés. Nous avons plus particulièrement entrepris notre étude dans le but d'étudier les mécanismes sous-jacents au développement de Tregs spécifiques des NIMA chez la souris pendant la période périnatale. En utilisant le modèle de souris hétérozygotes pour 2W1S-OVA+ dans lequel l'antigène 2W1S a été transformé en NIMA pour la moitié de la progéniture, nous avons observé une fréquence accrue de Tregs spécifiques de 2W1S chez les animaux exposés au NIMA. De plus, nous avons également observé que les Treg NIMA-2W1S dérivés de la périphérie avaient un répertoire de TCRs moins diversifié et étaient phénotypiquement distincts des Tregs spécifiques de SELF-2W1S dérivés du thymus. Afin de déterminer si le manque de diversité était responsable du développement de Tregs néonataux spécifiques de NIMA, nous avons généré des souris transgéniques où l'expression de TdT était appliquée dans les cellules T avant l, Doctorat en Sciences biomédicales et pharmaceutiques (Médecine), info:eu-repo/semantics/nonPublished

The current SARS-CoV-2 pandemic is wreaking havoc throughout the world and has rapidly become a global health emergency. A central question concerning COVID-19 is why some individuals become sick and others not. Many have pointed already at variation in risk factors between individuals. However, the variable outcome of SARS-CoV-2 infections may, at least in part, be due also to differences between the viral subspecies with which individuals are infected. A more pertinent question is how we are to overcome the current pandemic. A vaccine against SARS-CoV-2 would offer significant relief, although vaccine developers have warned that design, testing and production of vaccines may take a year if not longer. Vaccines are based on a handful of different designs (i), but the earliest vaccines were based on the live, attenuated virus. As has been the case for other viruses during earlier pandemics, SARS-CoV-2 will mutate and may naturally attenuate over time (ii). What makes the current pandemic unique is that, thanks to state-of-the-art nucleic acid sequencing technologies, we can follow in detail how SARS-CoV-2 evolves while it spreads. We argue that knowledge of naturally emerging attenuated SARS-CoV-2 variants across the globe should be of key interest in our fight against the pandemic.

Regulatory T cells (Treg) are a suppressive subset of helper T cells that controls immune responses using a variety of mechanisms. Despite initially being thought of as a homogenous population, Treg cells were recently found to adapt their function to their environment and acquire specialized phenotypes depending on their tissue of residence. The molecular mechanisms underlying this functional and tissular adaptation remain to be fully elucidated.In the course of this work, we studied the role of transcription factor c-Maf in the differentiation and the function of Treg cells. For this, we used a murine model invalidated for c-Maf specifically in Treg cells. Transcription factor c-Maf is preferentially expressed by intestinal Treg cells, particularly among the RORγt+ Treg subset, which controls immune responses directed towards the gut microbiota. We have shown that the differentiation of RORγt+ Treg cells results from the integration of multiple environmental signals, highlighting the plasticity of Treg specialization. Furthermore, we have shown that c-Maf is required for the differentiation of RORγt+ Treg cells as well as the expression of the anti-inflammatory cytokine IL-10 by intestinal Treg cells, thus endowing Treg cells with the ability to control homeostatic Th17 responses in the intestine. Mice deficient for c-Maf in Treg cells exhibit an exacerbated Th17 response and spontaneously develop colitis. However, c-Maf-deficient mice develop fewer polyps in a model of colitis-associated colon cancer. This suggests that c-Maf expression in Treg cells plays a beneficial role on intestinal homeostasis at steady state, but is detrimental in a tumoral context.Our results allow a better understanding of the mechanisms involved in the specialization of intestinal Treg cells. The knowledge of these mechanisms is crucial for the identification of new therapeutic targets in the context of inflammatory bowel disease and colon cancer., Doctorat en Sciences, info:eu-repo/semantics/nonPublished

Targeting GARP on human Tregs: a novel approach for the immunotherapy of cancer?

Until now, DNA vaccination against cancer failed to demonstrate a relevant activity in clinic or in a therapeutic setting in preclinical models. This thesis shows two strategies to improve DNA vaccine activity. The first is the optimization of the plasmid itself, by codon optimization and a rational antigen choice. The second is the combination of the vaccines with other complementary therapies: 1) Immune checkpoint blockade in P815 mastocytoma. 2) Oncolytic virus in B16F1 melanoma. 3) Tumor resection in orthotopic GL261 glioblastoma. The common outcome was the dramatic increase in survival in the combination group, explained by the presence of active and antigen-specific T cells in the tumor. Hence, vaccine optimization and rational combined therapies overcome the current limitations of DNA vaccines. This work opens the way to new therapies for the treatment of cancer patients., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2019

One of the immunosuppressive pathways acting in the tumor microenvironment relies on the degradation of tryptophan (Trp) into kynurenine (Kyn), orchestrated by two distinct enzymes: indoleamine 2,3-dioxygenase (IDO1) and tryptophan 2,3 dioxygenase (TDO). Local tryptophan depletion combined with kynurenine production strongly impair cellular immunity and make IDO1 and TDO endowing immunosuppressive properties. Like IDO1, TDO is considered as a relevant drug target to improve the efficacy of cancer immunotherapy. However, its role in various immunotherapy settings has not been fully characterized. Here we report that the small molecule inhibitor of TDO (PF06845102/EOS200809) modulates kynurenine and tryptophan concentration in the plasma, liver and tumor and increases the ability of checkpoint inhibitor anti-CTLA4 to induce rejection of CT26 tumors expressing TDO. To better characterize TDO as a therapeutic target, we also used TDO-KO mice. These mice have drastically increased levels of tryptophan in the blood, because they cannot degrade dietary tryptophan. In the MC38 colon carcinoma mouse model, we found that anti-tumor activity of immune checkpoint inhibitors anti-CTLA4 or anti-PD1 was higher in TDO-KO compared to the wild-type mice. Because these MC38 tumors did not express TDO, we related this improved immune response to the high systemic levels of tryptophan in TDO-KO mice. In agreement with this hypothesis, the effect of anti-PD1 was abolished in TDO-KO mice fed with a tryptophan-low diet that normalized their blood tryptophan level. Moreover, treatment of mice with an IDO1 inhibitor improved the efficacy of anti-PD1 in wild-type but not in TDO-KO mice. Since MC38 tumors express IDO1, its immunosuppressive activity limits the efficacy of anti-PD1 treatment in wild-type mice but appears to be overcome in TDO-KO mice due to the high levels of tryptophan. In addition, TDO-KO mice were more resistant to liver metastases than their wild-type counterpart. These res, (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2019

Targeting GARP on human Tregs: a novel approach for the immunotherapy of cancer?

Les bases scientifiques de l’immunothérapie du cancer.

Les cellules T régulatrices dérivées du thymus (nTreg) sont essentielles pour le maintien de la tolérance périphérique et la prévention des maladies auto-immunes. La caractérisation de ces cellules ainsi que la compréhension de leurs modes d’action sont deux étapes importantes afin de pouvoir les utiliser en thérapie. Nous avons montré que les nTreg sont une population de cellules très hétérogènes. Grâce à deux marqueurs associés au métabolisme de l’ATP, le CD26 et le CD39, et au marqueur de maturation CD45RA, nous avons séparé les nTreg en 5 populations distinctes, chacune représentant un stade de maturation différent. Les facteurs micro-environnementaux dictent cette maturation ainsi que les différentes fonctions des nTreg. En effet, chaque population a une production cytokinique et une activité suppressive qui lui est propre et qui dépend du micro-environnement. De plus, la distribution de ces différentes populations reste stable chez un individu mais elle est variable d’un individu à l’autre. D’un point de vue clinique, nous avons observé une accumulation des cellules mémoires matures et des nTreg « anormaux » CD25- ou CD127+ dans les maladies inflammatoires chroniques. Le profil CD39/CD26 des nTreg pourrait donc représenter un biomarqueur sanguin pour le suivi de ces maladies. La fonction et le nombre des nTreg sont diminués dans de nombreuses maladies auto-immunes et allo-immunes. Le transfert adoptif de ces cellules semble donc être une stratégie thérapeutique prometteuse. Cependant, l’expansion des nTreg est compliquée en raison de leur faible proportion dans le sang et de leur instabilité fonctionnelle dans certaines conditions. La génération d’iTreg stables et suppressifs est donc essentielle. Nous avons décrit un nouveau protocole permettant de générer des iTreg à partir de cellules T naïves, avec une forte activité suppressive peu importe le contexte. L’utilisation du PGE2 et de la rapamycine, en plus du TGFb et de l’IL-2 utilisé classiquement pour génér, Doctorat en Sciences biomédicales et pharmaceutiques (Médecine), info:eu-repo/semantics/nonPublished

Les lymphocytes T (LT) CD8+ sont les médiateurs clés de la réponse immunitaire adaptative dirigée contre les pathogènes intracellulaires et les cellules tumorales. Lors d’une infection ou d’une immunisation, ils sont activés en réponse à leur antigène spécifique, prolifèrent et se différencient en cellules effectrices. Les LT CD8+ effecteurs participent à l’élimination du pathogène grâce à leurs fonctions cytotoxiques et à la production de cytokines. Les cellules activées subissent ensuite une phase de contraction à l’issue de laquelle ne subsistera qu’une petite population hétérogène de cellules mémoires qui contribuera à la protection à long terme de l’organisme lors d’infections ultérieures par le même pathogène. Les LT CD8+ peuvent également acquérir un phénotype de cellule mémoire dans des conditions physiologiques en l’absence de reconnaissance antigénique. Ces LT CD8+ mémoires non conventionnels peuvent apparaître dans le thymus (“LT CD8+ mémoires innés thymiques” (TIM) ou en périphérie (“LT CD8+ mémoires virtuels” (VM)). Ces sous-populations de LT CD8+ mémoires conventionnels et non conventionnels peuvent être activés sans reconnaissance antigénique par des cytokines inflammatoires, acquérir des fonctions cytotoxiques et produire des quantités importantes d’IFNγ. Elles contribuent ainsi à la première ligne de défense de l’organisme au même titre que d’autres cellules de l’immunité innée comme les cellules NK, NKT et γδ. Le programme transcriptionnel impliqué dans ces processus de différenciation alternative est mal connu. Eomesodermin (Eomes), un facteur de transcription apparenté à T-bet, joue un rôle central dans l’acquisition du phénotype mémoire et dans la fonction de ces cellules. Cependant, malgré le rôle crucial d’Eomes dans ce contexte, les signaux responsables de son induction et du maintien de son expression ne sont pas clairement établis. Dans ce travail, nous avons montré que les voies de signalisation induites par les interférons (IFN) de type I, Doctorat en Sciences médicales (Médecine), info:eu-repo/semantics/nonPublished

DNA vaccination against cancer has become a promising strategy for inducing a specific and long-lasting antitumor immunity. However, DNA vaccines fail to generate potent immune responses when used as a single therapy. To enhance their activity into the tumor, a DNA vaccine against murine P815 mastocytoma was combined with antibodies directed against the immune checkpoints CTLA4 and PD1. The combination of these two strategies delayed tumor growth and enhanced specific antitumor immune cell infiltration in comparison to the corresponding single therapies. The combination also promoted IFNg, IL12 and granzyme B production in the tumor microenvironment and decreased the formation of liver metastasis in a very early phase of tumor development, enabling 90% survival. These results underline the complementarity of DNA vaccination and immune checkpoint blockers in inducing a potent immune response, by exploiting the generation of antigen-specific T cells by the vaccine and the ability of immune checkpoint blockers to enhance T cell activity and infiltration in the tumor. These findings suggest how and why a rational combination therapy can overcome the limits of DNA vaccination but could also allow responses to immune checkpoint blockers in a larger proportion of subjects.

The DA strain of Theiler’s virus has a remarkable ability to evade the immune response of the host and to cause persistent infections of the central nervous system. During the chronic phase of infection, the virus is primarily detected in microglial cells, infiltrating macrophages and oligodendrocytes in the white matter of the spinal cord. The non-structural L* protein encoded by Theiler's virus was shown to enhance viral replication in macrophages in vitro and to be required for the establishment of persistent infections. Previous work in our lab revealed that L* directly interacts with RNase L and thereby inhibits the activity of this antiviral enzyme. Interestingly, RNase L antagonism by L* is a highly species-specific process; indeed, L* inhibits mouse RNase L but not its orthologues from other tested species. On the one hand, we characterized further the molecular mechanisms of RNase L antagonism by the Theiler’s virus L* protein. We identified a novel strategy of RNase L inhibition in which, upon binding to ankyrin repeats 1 and 2 of the mouse RNase L, L* competitively inhibits 2-5A binding to RNase L. Using chimeric MHV viruses expressing L*, we demonstrated that L* is able to counteract RNase L activity in vivo, in infected mice. On the other hand, we took advantage of the species-specificity of L* activity to identify the natural host of Vilyuisk human encephalitis virus (VHEV). VHEV was isolated from mice that were inoculated with CSF from a patient suffering from chronic encephalitis. It is therefore unclear whether the virus derives from the human sample or from the mice used to isolate the virus. We observed that L* of VHEV specifically binds to and inhibits mouse but not human RNase L, thereby showing that VHEV is of mouse origin and suggesting that it is a contaminant that originated from the mice that were used to inoculate the human sample., (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2017

While patient selection and clinical management have reduced high-dose IL-2 (HDIL2) immunotherapy toxicities, the immune mechanisms that underlie HDIL2-induced morbidity remain unclear. Here we show that dose-dependent morbidity and mortality of IL-2 immunotherapy can be modeled in human immune system (HIS) mice. Depletion of human T cell subsets during the HDIL2 treatment reduces toxicity, pointing to the central function of T cells. Preferential expansion of effector T cells secondary to defective suppressive capacity of regulatory T (Treg) cells after HDIL2 therapy further underscores the importance of Treg in the maintenance of immune tolerance. IL-2 toxicity is induced by selective depletion or inhibition of Treg after LDIL2 therapy, and is ameliorated in HDIL2-treated HIS mice receiving the PIM-1 kinase inhibitor, Kaempferol. Modeling IL-2 pathophysiology in HIS mice offers a means to understand the functions of effector and regulatory T cells in immune-mediated toxicities associated with cancer immunotherapy.