Measles is one of the most contagious diseases known to mankind. Despite the availability of a safe and effective vaccine, approximately 164,000 measles-related deaths were recorded in 2008. The inherent restricted host tropism of MV means that the development of authentic rodent models will be a valuable research tool in testing new vaccines and antivirals. In addition to the receptor requirement, mouse innate immunity has been shown to inhibit MV growth. In this thesis, the contributions of several key components of the mouse innate immune system on the inhibition of MV replication were examined. The transcription factor interferon regulatory factor 3 (IRF3), which normally plays a key role in mediating innate immune signaling, contributed relatively little in inhibiting MV replication both in vitro and in vivo. In contrast, the JAK/STAT pathway and the double-stranded RNA inducible protein kinase, PKR, played more important roles in controlling virus replication. The resurgence of measles in areas where the virus was once thought to be eradicated makes the development of anti-MV treatments essential. Concurrent to the development of an animal model to better study its pathogenesis, we wanted to look at the effect of MV inhibitors on its replication. The MV fusion inhibitor, carbobenzoxy-D-phenylalanine-L-phenylalanine-glycine (ZfFG), was developed in the past to study fusion; however, its mechanism of action has not yet been elucidated. To examine this, spontaneous ZfFG-resistant mutants were generated and characterized. Mutations were found in the HRB region of the fusion (F) protein, and when these were modeled using published paramyxovirus F crystal structures, data suggested that ZfFG targeted a small pocket present between the head and stalk regions of its pre-fusion conformation. An authentic mouse model of measles developed from findings in this study may allow for in vivo efficacy testing of ZfFG in the future.

Measles is one of the most contagious diseases known to mankind. Despite the availability of a safe and effective vaccine, approximately 164,000 measles-related deaths were recorded in 2008. The inherent restricted host tropism of MV means that the development of authentic rodent models will be a valuable research tool in testing new vaccines and antivirals. In addition to the receptor requirement, mouse innate immunity has been shown to inhibit MV growth. In this thesis, the contributions of several key components of the mouse innate immune system on the inhibition of MV replication were examined. The transcription factor interferon regulatory factor 3 (IRF3), which normally plays a key role in mediating innate immune signaling, contributed relatively little in inhibiting MV replication both in vitro and in vivo. In contrast, the JAK/STAT pathway and the double-stranded RNA inducible protein kinase, PKR, played more important roles in controlling virus replication. The resurgence of measles in areas where the virus was once thought to be eradicated makes the development of anti-MV treatments essential. Concurrent to the development of an animal model to better study its pathogenesis, we wanted to look at the effect of MV inhibitors on its replication. The MV fusion inhibitor, carbobenzoxy-D-phenylalanine-L-phenylalanine-glycine (ZfFG), was developed in the past to study fusion; however, its mechanism of action has not yet been elucidated. To examine this, spontaneous ZfFG-resistant mutants were generated and characterized. Mutations were found in the HRB region of the fusion (F) protein, and when these were modeled using published paramyxovirus F crystal structures, data suggested that ZfFG targeted a small pocket present between the head and stalk regions of its pre-fusion conformation. An authentic mouse model of measles developed from findings in this study may allow for in vivo efficacy testing of ZfFG in the future.

Malgré plusieurs chimiothérapies suivies d’une transplantation et d’une immunothérapie, 40% des patients avec un neuroblastome (NB) à haut risque subissent une progression de la maladie ou une rechute. L’échec de ces traitements est attribué à la présence de cellules initiatrices de tumeur (TIC) qui expriment le marqueur CD133 et qui sont souvent résistantes aux agents chimiothérapeutiques. Les cellules Natural Killer (NK), qui possèdent un effet anti-tumoral, peuvent être utilisées dans le cadre du développement de nouvelles approches immuno-thérapeutiques. Nous posons l’hypothèse que les cellules NK activées éliminent efficacement les TIC et contribuent à la réduction des risques de rechute. De plus, il est possible d’augmenter l’effet anti-tumoral des cellules NK contre le NB. L’activité cytotoxique des cellules NK est augmentée par des cellules dendritiques plasmacytoïdes (pDC) activées. A la suite de la stimulation de leurs récepteurs Toll-like les pDC produisent de grandes quantités d'interféron-alpha (IFN-α). Nous avons étudié les propriétés lytiques des cellules NK contre des lignées cellulaires de NB à la suite de leur activation par l’IFN-α ou des pDC activées. Nos résultats révèlent une augmentation de l’activité cytolytique des cellules NK contre ces lignées en réponse à une stimulation par les pDC activées. De plus, les cellules de NB CD133+ ou celles résistantes à l’immunothérapie dirigée contre le GD2 sont sensibles à la lyse médiée par les cellules NK stimulées par les pDC. Nous avons examiné les mécanismes cellulaires impliqués dans la lyse des cellules de NB. Nous montrons que cette cytotoxicité est médiée en partie par TRAIL induisant l'apoptose et en partie par la libération des granules cytotoxiques. Ainsi, ces résultats permettent de proposer une nouvelle approche immuno-thérapeutique complémentaire au traitement par l’anticorps anti-GD2 pour les patients atteints de NB à haut risque. / Despite aggressive treatment by chemotherapy followed by transplantation and treatment with anti-tumor cell disialoganglioside (GD2) monoclonal antibody, IL-2, GM-CSF and retinoic acid, 40% of patients with high-risk neuroblastoma (NB) still undergo disease progression or relapse. Furthermore, tumor-initiating cells (TIC) expressing the CD133 marker are present in NB tumors and are more resistant to chemotherapy. To evaluate a new immunotherapeutic approach, we took advantage of the anti-tumor effect of Natural Killer (NK) cells. We hypothesized that activated NK cells would be a potent therapeutic strategy to eliminate TIC and reduce relapse of NB. We aimed to establish the best strategy to increase the NK cell mediated cytotoxicity against NB. NK cell cytotoxic activity is increased by cytokines, chemokines and activated plasmacytoid dendritic cells (pDC) which produce high amounts of interferon-alpha (IFN-α) upon Toll-like receptor stimulation. We investigated NK-cell lytic properties against NB cell lines following activation by IFN-α or activated pDC. Our results reveal an increased cytolytic activity of NK cells against NB cell lines after stimulation by activated pDC, CD133+ (TIC) as well as anti-GD2 resistant NB cells are sensitive to NK cell mediated cytotoxicity following stimulation by activated pDC. We also examined the cellular mechanisms involved in NK cell-mediated lysis of NB cell lines. The increased cytotoxicity is partially mediated by TRAIL induced apoptosis and as well as by the release of cytolytic granules. In conclusion, we propose a new immunotherapeutic approach that can be used in combination with the anti-GD2 therapy for the treatment of high-risk NB patients.

Chez la souris, les cellules dendritiques plasmacytoïdes (pDC) et natural killer (NK) contribuent à la résistance contre les infections systémiques par les virus herpétiques tels que le cytomégalovirus murin (MCMV). Les pDC représentent la source majeure d’interférons de type I (IFN-I) lors d’une infection par le MCMV. Cette réponse est dépendante de MyD88 et des récepteurs de type Toll 7 et 9. D’autre part, les cellules NK, qui expriment le récepteur d’activation Ly49H, peuvent détecter et lyser les cellules infectées par le MCMV. La perte de l’une de ces réponses augmente la sensibilité à l’infection. Cependant, la façon dont ces réponses antivirales interagissent est mal connue. Chez l’homme, bien que les réponses dépendantes des IFN-I soient essentielles, MyD88 semble superflu pour l’immunité antivirale. Cependant, les mécanismes susceptibles de compenser l’absence de MyD88 chez l’homme sont inconnus. Il a été supposé que les souris déficientes pour MyD88 ne parvenaient pas à monter de réponse protectrice dépendante des IFN-I lors d’infections par le MCMV. Afin d’évaluer cela, nous avons comparé la résistance de souris déficientes pour MyD88, les récepteurs aux IFN-I (IFNAR) et/ou Ly49H lors de cette infection. La déplétion sélective des pDC ou l’absence de MyD88 diminue drastiquement la production d’IFN-I, mais n’empêche pas l’établissement d’une forte réponse aux IFN-I dans la rate. De plus, l’absence de MyD88, mais pas celle d’IFNAR, peut être compensée par l’activité antivirale des cellules NK dépendant de Ly49H. Par conséquent, chez la souris, MyD88 est redondant pour l’établissement d’une réponse splénique aux IFN-I lors d’une infection systémique par le MCMV. / In mice, plasmacytoid dendritic cells (pDC) and natural killer (NK) cells both contribute to resistance to systemic infections with herpes viruses including mouse Cytomegalovirus (MCMV). pDCs are the major source of type I IFN (IFN-I) during MCMV infection. This response requires pDC-intrinsic MyD88-dependent signaling by Toll-Like Receptors 7 and 9. Provided that they express appropriate recognition receptors such as Ly49H, NK cells can directly sense and kill MCMV-infected cells. The loss of any one of these responses has been reported to increase susceptibility to infection. However, the relative importance of these antiviral immune responses and how they are related remain unclear. In humans, while IFN-I responses are essential, MyD88 appears to be dispensable for antiviral immunity. However, the mechanisms that could compensate MyD88 deficiency in humans have not been elucidated. Moreover, it has been assumed, but not proven, that MyD88-deficient mice fail to mount protective IFN-I responses to systemic herpes virus infections. To address these issues, we compared resistance to MCMV infection between mouse strains deficient for MyD88, the IFN-I receptor (IFNAR) and/or Ly49H. We show that selective depletion of pDC or genetic deficiencies for MyD88 drastically decreased production of IFN-I, but not the protective antiviral responses mediated by these cytokines. Moreover, MyD88, but not IFNAR, deficiency could be compensated by Ly49H mediated antiviral NK cell responses. Thus, contrary to the current dogma, but consistent with the situation in humans, we conclude that, in mice, MyD88 is redundant for splenic IFN-I responses against a systemic herpes virus infection.

La leucémie aiguë à cellules dendritiques plasmacytoïdes (BPDCN) fait partie des cancers incurables pour lesquels les mécanismes impliqués dans la pathogénèse restent inconnus. Dans ce travail, nous avons identifié le gène NR3C1 (5q31), qui code pour le récepteur des glucocorticoïdes (GCR), et un long ARN non-codant inter-génique (appelé ici lincRNA-3q), comme étant des cibles d'altération géniques ou de dérégulation transcriptionnelles dans les BPDCN. La translocation/délétion de NR3C1 est associée avec un temps de survie extrêmement court et des activités anormales du réseau de régulation des gènes GCR, EZH2 et FOXP3. Nous avons découvert que lincRNA-3q code pour une forme nucléaire d'ARN non-codant qui est activé de façon ectopique dans les BPDCN et les AML à haut risque. Dans les cancers myéloïdes, une déplétion de lincRNA-3q induit un arrêt du cycle cellulaire qui coïncide avec la suppression des signatures d'expression génique de E2F1/Rb et des gènes spécifiques aux cellules souches leucémiques. Nos résultats démontrent qu'une inhibition des protéines à bromodomaine BET supprime sélectivement l'expression lincRNA-3q, indiquant une stratégie thérapeutique potentielle pour contrer l'activité oncogénique de cet ARN non-codant. Ce travail défini, un nouveau cadre de recherche pour comprendre la pathogénèse et la résistance au traitement dans les BPDCN. / Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an incurable malignancy for which disease mechanisms are unknown. Here, we identify the NR3C1 gene (5q31), encoding the glucocorticoid receptor (GCR), and a long, intergenic, non-coding RNA gene (named here lincRNA-3q), respectively, as targets for genetic alteration or transcriptional deregulation in BPDCN. NR3C1 translocation/deletion was associated to critically short survival in BPDCN and to abnormal activity of GCR, EZH2, and FOXP3 gene regulatory networks. LincRNA-3q, was found to encode a nuclear, non- coding RNA that is ectopically activated in BPDCN and high-risk AML. Depletion of lincRNA-3q in myeloid cancer cells induced cell cycle arrest, coincident to suppression of E2F1/Rb and leukemia stem cell-specific gene expression signatures. BET bromodomain protein inhibition could selectively suppress lincRNA-3q indicating a treatment strategy for counteracting oncogenic activity of this non- coding RNA. Thus, this work defines a new framework for understanding disease pathogenesis and treatment resistance in BPDCN.