Les nouveau-nés, dont le système immunitaire adaptatif est encore en développement sont souvent plus sensibles aux infections que les adultes. L’immunité innée constitue la première ligne de défense de l’organisme contre les agents pathogènes et en particulier les cellules Natural Killer (NK), via leur fonction cytotoxique et leur production d’interféron-gamma (IFN-?). Dans le but de pouvoir étudier, à terme, l’implication des cellules NK des ovins nouveau-nés dans un contexte infectieux, nous avons mis en place une stratégie permettant d’isoler et de caractériser ces cellules pour la première fois. En attendant que cette méthode soit mise au point, nous avons recherché les particularités des cellules NK des nouveau-nés chez les bovins pour lesquels un anticorps dirigé contre le récepteur NKp46 spécifique des cellules NK est disponible. Nous avons observé que, bien que moins nombreuses dans le sang périphérique, les cellules NK des nouveau-nés prolifèrent rapidement, sont totalement fonctionnelles et répondent fortement (cytotoxicité et production d’IFN-?) après culture en présence d’IL-15 et lors de la stimulation du récepteur NKp46 (Elhmouzi-Younes et al., 2009b). Nous avons pu caractériser les cellules NK ovines, parmi les cellules mononuclées du sang périphérique, en mettant en place une méthode basée sur l’utilisation d’anticorps dirigés contre le marqueur CD14, spécifique des monocytes, et le récepteur CD16 exprimé par les cellules NK et les monocytes. Les cellules CD16+/CD14- présentent toutes les caractéristiques morphologiques, phénotypiques et fonctionnelles fondamentales des cellules NK (Elhmouzi-Younes et al., 2009a). / Neonates are often more susceptible to infections than adults, due to their adaptive immune system still in development. Natural Killer (NK) cells are key cells of the innate immune system which provide early resistance to infections through their cytotoxic properties and production of interferon-gamma (IFN-?). In order to study the involvement of NK cells from ovine neonates during an infection we developed, a method to isolate and characterize these cells for the first time. While this method was developed, we investigated the peculiarities of bovine neonate NK cells as an antibody directed against the NKp46 receptor specific of bovine NK cells is available. On the one hand, we found that although less numerous in peripheral blood, neonate NK cells proliferated actively, were totally functional and highly responsive (cytotoxicity and IFN-? production) to IL-15 and to NKp46 receptor stimulation (Elhmouzi-Younes et al., 2009b). On the other hand, we characterized ovine NK cells, among peripheral blood mononuclear cells, after developing a strategy based on the use of antibodies against the CD14 marker, specific of monocytes, and the CD16 receptor expressed by NK cells and monocytes. We found that CD16+/CD14- cells present all the morphological, phenotypical and functional characteristics of NK cells (Elhmouzi-Younes et al., 2009a).

Long double-stranded RNA (dsRNA) is a unique structure formed during viral replication or transcription of repetitive elements. Mammalian cells evolved several mechanisms how to respond to dsRNA. dsRNA can be engaged in one of three pathways: interferon response, RNA editing, and RNA interference (RNAi). RNAi is evolutionary conserved effect of dsRNA, which results in sequence-specific messenger RNA degradation. However, in mammals, RNAi is functional only in mouse oocytes, which express truncated version of Dicer (DicerO ). In somatic cells, dsRNA triggers sequence-independent interferon pathway. The main aim of this Master's thesis was to examine how specific double-stranded RNA-binding proteins (DRBPs) influence distribution of long dsRNA into RNAi and sequence-independent pathways. We used a luciferase-based reporter RNAi assay to monitor sequence-specific and sequence-independent effects of dsRNA co-expressed with selected DRBPs. Our results suggest that none of the tested DRBPs is sufficient to stimulate RNAi in somatic cells. Interestingly, the overexpression of either TARBP2 or PACT suppressed RNAi in cells expressing DicerO . Moreover, microRNA pathway, which employs the same protein factors as RNAi, is not inhibited by TARBP2 or PACT. Therefore, we propose that DRBPs overexpression...

1 / Fatma Aboulnasr

No description available.

Résumé Les cellules dendritiques plasmacytoïdes (pDCs) sont considérées comme quantitativement et qualitativement supérieures aux autres types cellulaires pour la synthèse des interférons (IFNs) de type I lors d’une infection virale. Plusieurs observations viennent supporter cette désignation. Tout d’abord, elles expriment un éventail très large des sous-types d’IFN-alpha en comparaison aux autres types cellulaires. Par ailleurs, elles possèdent la capacité de détecter la présence des virus via leurs TLR7 et TLR9, reconnaissant respectivement l’ARN ou l’ADN d’origine virale. Enfin, elles expriment de manière constitutive dans leur cytoplasme le facteur de transcription IRF-7 qui permet une synthèse rapide et robuste des IFNs de type I en réponse à l’infection. Dans un précédent travail, il a été montré que les pDCs néonatales présentent un défaut majeur de synthèse d’IFN-alpha en réponse aux CpG ODNs, ligands du TLR9. Nous avons ensuite étendu notre étude des pDCs néonatales en les stimulant avec le R-848, ligand du TLR7, mais également en présence de virus tels que HCMV et HSV. Dans ces conditions également, la synthèse de l’IFN-alpha est déficiente dans les pDCs du nouveau-né. Nous avons également observé une déficience de production de l’IFN-beta suite à une stimulation via les ligands TLR7 et TLR9, tant au niveau protéique que de l’expression de l’ARN messager. Par ailleurs, la synthèse des cytokines/chimiokines inflammatoires par les pDCs du sang de cordon ainsi que leur maturation, fonctions dépendantes du facteur NF-kappaB, sont également diminuées en comparaison aux pDCs adultes, suite à une stimulation en présence du CpG ODN ou du R-848. L’ensemble de ces données nous a amené à étudier de manière plus précise les voies de signalisation des pDCs néonatales suite à leur activation. Tout d’abord, nous avons observé que les taux d’expression des TLR7 et 9 tout comme le taux basal d’IRF-7 sont équivalents dans les pDCs néonatales et les pDCs adultes. Ensuite, grâce à la technique d’ImageStream (Amnis corporation), nous avons pu quantifier la translocation nucléaire des facteurs de transcription IRF-7 et de NF-kappaB dans les pDCs activées. Nous avons ainsi pu observer que la translocation de NF-kappaB est comparable dans les pDCs adultes et néonatales en réponse aux ligands TLR7 ou TLR9. Par contre, elle est déficiente lors d’une stimulation par HSV. La translocation du facteur IRF-7, quant à elle, est significativement déficiente en réponse au CpG ODN et au virus HSV dans les pDCs néonatales. Nous proposons que le défaut de translocation d’IRF-7 mis en évidence dans les pDCs néonatales pourrait en partie expliquer la déficience de synthèse des IFNs de type I de ces cellules et fournir une base moléculaire à la plus grande susceptibilité du nouveau-né vis-à-vis des infections virales.

Submitted by Tatiana Silva (tsilva@icict.fiocruz.br) on 2012-12-27T18:20:32Z No. of bitstreams: 1 leonardo_r_b_silva_ioc_bcm_0018_2009.pdf: 8200271 bytes, checksum: dac54c11ebb687bfa547ddb706d42283 (MD5) / Made available in DSpace on 2012-12-27T18:20:32Z (GMT). No. of bitstreams: 1 leonardo_r_b_silva_ioc_bcm_0018_2009.pdf: 8200271 bytes, checksum: dac54c11ebb687bfa547ddb706d42283 (MD5) Previous issue date: 2009 / Fagócitos mononucleares são células alvo para micobactérias patogênicas como M. tuberculosise M. leprae. Essas micobactérias têm a capacidade de modular os mecanismos microbicidas dos macrófagos, sobreviver e replicar nessas células. Contudo o mecanismo molecular envolvido nesta desativação não é totalmente compreendido. Dados do nosso laboratório têm demonstrado que o M. lepraeé capaz de induzir a expressão do fator de crescimento semelhante a insulina I um hormônio com efeito anti-apoptotico ecom atividade de proliferação – em Células de Schwann humanas. Recentemente, foi relatado que IGF-I é capaz de inibir a expressão da enzima óxido nítrico sintase induzível (iNOS) e conseqüentemente a produção de óxido nítrico em macrófagos induzido por Leshimania amazonensis. Baseado nestes dados, nós temos investigado o envolvimento do IGF-I na desativação dos macrófagosobservada na infecção micobacteriana. Com este propósito, macrófagos murinos da linhagem RAW 264.7 foram estimulados ou não com M. lepraee a expressão de IGF-I foi monitorada através de RT-PCR quantitativo e ensaio imunoenzimático específico, ELISA. Duas outras espécies de micobactérias, M. bovisBCG e M. smegmatis, respectivamente, uma cepa atenuada de M. bovise uma micobactéria não-patogênica, foram testadas para comparação. O estímulo com M. lepraeou BCG, em contraste com M. smegmatis, regulou positivamente a expressão de RNAm para IGF-I e aumento significantemente os níveis daproteína quando comparado com a cultura controle. Além disso, nós também investigamos o efeito do IGF-I na produção de NO e na expressão de iNOS induzida por micobactérias em macrófagos RAW 264.7. A produção de NO foi monitorada pela determinação da concentração de nitrito no sobrenadante em meio de cultura, utilizando reagente de Griess e a expressão de iNOS monitorada por Western Blot. M. lepraefoi um fraco estimulo para indução de iNOS. Em contraste, BCG e M. smegmatis induziram a expressão e, como conseqüência, uma significantiva produção de NO em macrófagos RAW. Interessantemente, células pré-tratadas com IGF-I mostraram uma significantiva redução na produção denitrito após a estímulo com micobactérias, o que correlacionou com uma regulação negativa da expressão de iNOS. Além disso, IGF-I foi capaz de reduzir parcialmente a produção de NO induzida por IFN-γrecombinante. Esses resultados sugerem que o IGF-Ipode contribuir para a persistência micobacteriana no hospedeiro, modulando negativamente a resposta imune inata durante a infecção. / Mononuclear phagocytes are target cells for pathogenic mycobacteria such as Mycobacterium tuberculosisand Mycobacterium leprae. These bacteria are able to subvert macrophage microbicidal mechanisms and survive and replicate within these cells. However, the molecular mechanisms involved in this deactivation remain incompletely understood. We have previously described that M. leprae induces the expression of insulin-like growth factor I (IGF-I) – an hormone with anti- apoptotic and proliferation activities– in human Schwann cells. Recently it has been reported that IGF-I can inhibit inducible nitric oxide synthase (iNOS) expression and consequently nitric oxide (NO) production in macrophages infected with Leishmania amazonensis. Based on these data, we have investigated the potential involvement of IGF-I on macrophage deactivation observed during mycobacterial infection. For this purpose, RAW 264.7 murine macrophages were treated or not with M. lepraeand the expression of IGF-I was monitored by quantitative RT-PCR and specific sandwich ELISA. Two other species of mycobacteria, M. bovisBCG and M. smegmatis, respectively, an attenuated strain of M. bovisand a nonpathogenic mycobacterium, were tested forcomparison. M. lepraeor BCG treatment, in contrast to M. smegmatis, positively regulated the expression of IGF-I by RAW cells when compared withcontrol cultures. Furthermore, we also investigated the effect of IGF-I on mycobacterium-induced iNOS expression and NO production in RAW 264.7 macrophages. NO production was evaluated by determination of nitrite concentration in the culture media using the Griess reagent and iNOS expression was monitored by Western Blot. M. leprae was a weak stimulus for iNOS induction. In contrast, BCG and M. smegmatis induced iNOS expression and, as a consequence, significan levels of NO production in RAW macrophages. Interestingly, IGF-Ipre-treated cells showed a significant reduction in nitrite production after infection with mycobacteria that correlated with the down regulation of iNOS expression. Moreover, IGF-I was able to partially reduce NO production induced by recombinant interferon-gamma. Taken together, these results suggest that IGF-I may contribute to mycobacterium persistent in the host by down modulating host innate response during infection.

Indiana University-Purdue University Indianapolis (IUPUI) / The function(s) of the intracellular form of HBeAg, previously reported as the preCore protein intermediate (p22) without the N-terminal signal peptide, remains elusive. Here, we propose to elucidate the translocation of p22 during its formation from endoplasmic reticulum (ER) to cytosol, how it differs from core in its inability to form a capsid and the biological functions of cytoplasmic and nuclear p22. Firstly, we have identified that a portion of p22, after the cleavage of its signal peptide in ER, is released back into the cytosol through an ERAD-independent mechanism, as neither wildtype nor dominant-negative p97 affected the ER-to-cytosol translocation of p22 or ER-Golgi secretion of HBeAg. Secondly, despite sharing the same sequence with core protein except for the extended 10 amino acid precore region at the N-terminus, we observed that p22 wildtype and C-7Q mutant are unable to form a capsid. Thirdly, we report that p22 but not the secreted HBeAg significantly reduced interferon stimulated response element (ISRE) activity and expression of interferon stimulated genes (ISGs) upon interferon-alpha (IFN- α) stimulation. Furthermore, in line with this, RNA-seq analysis of ISG induction profile from IFN-α treated patients showed that HBeAg(+) patients exhibited reduced and weak antiviral ISG upregulations compared to HBeAg(-) patients. Further, mechanistic study indicated that while p22 did not alter the total STAT1 or p-STAT1 levels in IFN-α treated cells, it blocked the nuclear translocation of p-STAT1 by interacting with karyopherin α1, indicating that the cytoplasmic p22 may impede JAK-STAT signaling to help the virus evade host innate immune response and cause resistance to IFN therapy in patients. Additionally, nuclear p22 and nuclear core were found to interact with the promoter regions (ISRE – containing) of ISGs, suggesting a new mechanism of inhibition of ISG expression upon stimulation. Finally, we found that the nuclear p22 can bind to cccDNA minichromosome and affects cccDNA maintenance and/or transcription. Thus, our results indicate that there is a novel ER sorting mechanism for the distribution of the intracellular and secretory HBeAg, and the intracellular HBeAg may contribute to HBV persistence by interfering with IFN-α elicited JAK-STAT signaling and regulating cccDNA metabolism.

Aging is amongst the strongest risk factors for neurodegenerative disease and elevated Type I interferon (IFN) signaling has been associated with both normal aging and central nervous system (CNS) diseases. Type I IFN is normally produced by nucleated cells in response to the detection of viral pathogen associated molecular patterns (PAMPs) by pathogen recognition receptors (PRRs). More recently it has been appreciated that Type I IFNs are also produced in response to endogenous stimuli, in the absence of viral pathogens. While Type I IFN signaling has been shown to be elevated in human and murine brains during normal aging, the underlying cause was unknown. Here we demonstrate by flow cytometry that aging results in increased size and numbers of mitochondria in the murine brain. Despite identifying increased mitochondrial number and mitochondrial DNA content, we found no change to mitochondrially-encoded transcripts, suggesting either deficits in mitophagy or augmented biogenesis due to insufficient oxidative phosphorylation. Interestingly, mitochondrial numbers correlated with elevated Type I IFN signaling in aging, linking mitochondria to the age-dependent innate immune response in the CNS. Using genetically engineered mice, we excluded roles for two critical innate immune pathways, STING and IRAK4, in the age-dependent increase in Type I IFN signaling in the brain. Notably, we subsequently identified a mitochondrially restricted innate immune protein, mitochondrial antiviral signaling (MAVS) as an essential molecular mediator of the age-dependent Type I IFN response; MAVS deficiency in aged mice restored Type I IFN signaling in the CNS to the levels observed in adult wildtype mice. Further, using intracerebroventricular (icv) administration of antisense oligonucleotides (ASO) as an orthogonal approach, we reduced MAVS transcript and protein expression within the CNS and thereby reduced Type I IFN signaling. Our data demonstrate a specific and selective role of MAVS expression in the CNS in Type I IFN signaling in aging. To investigate the relationship between mitochondrial aging and MAVS activation, we isolated cytoplasmic and mitochondrial RNA from young and aged animals as MAVS is most studied for its response to RNA ligands. Upon transfection into reporter cells, we found that mitochondrial RNA, but not cytoplasmic RNA, from both young and aged mice was sufficient to induce Type I IFN reporter activity in a MAVS-dependent manner. Furthermore, we attempted to mimic the increase of mitochondria observed in the aging CNS by transferring mitochondria from young and aged animals to recipient cells. Mitochondrial transfer also induced MAVS-dependent Type I IFN signaling in wildtype, but not MAVS null, mouse embryonic fibroblasts (MEFs). Collectively, our findings suggest that the accumulation of mitochondria in aging serves as a robust source of MAVS pathway ligands and implicate a novel link between mitochondrial aging and MAVS-mediated innate immune signaling in the CNS.

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Each year, 7.9 million babies are born with birth defects. Seventy percent of those could be prevented, ameliorated, or repaired; yet 3.2 million children still die by the age of three (March of Dimes Global Report 2006). We have found that non-specific maternal immune stimulation with the cytokine interferon-gamma (IFN-gamma) can successfully ameliorate some of these defects in the C57BL/6N mouse model. We have observed a reduction in the distal limb malformations syndactyly, polydactyly, and webbing by 47%, 100%, and 63% respectively when IFN-gamma is given 2 days prior to MNU administration. We have also observed that IFN-gamma works at the placental level to protect against MNU-induced damage. Trophoblast loss and associated cytokine alterations occur in gestation day (GD) 14 placenta following GD9 MNU exposure, showing that fetal-maternal communication can be hindered due to MNU. In the labyrinthine layer of the placenta, we observed multifocal fibrinous necrosis of endothelial cells due to MNU, however IFN-gamma almost completely protected the trophoblast and endothelial cells when given to the dam as an immune stimulant. To determine the genes participating in these processes, gene microarray studies were conducted. Hepatocyte growth factor (HGF), interleukin 1 beta (IL1Β), and insulin-like growth factor 2 (IGF2) were elucidated as genes that were significantly expressed in GD12 placenta. These genes are similar in that they are all connected to the Jak-Stat signaling pathway. These findings provide a possible mechanism for birth defect reduction by maternal immune stimulation with IFN-gamma in MNU-challenged mice. / Master of Science