Dissertations / Theses: 'Peptides of innate immunity'

1

Sang, Yongming. "Porcine innate antiviral immunity : host defense peptides and toll-like receptors." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/960.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Tollin, Maria. "Antimicrobial peptides and proteins in innate immunity : emphasis on isolation, characterization and gene regulation /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-270-5/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Barassé, Valentine. "Etude de peptides de venin de fourmis : diversité moléculaire et lien avec la fonction immunitaire." Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0111.

Full text

Abstract:

Les venins d’animaux sont des bibliothèques naturelles de composés bioactifs optimisés au cours de l’évolution, appelés toxines. Les venins de nombreux animaux restent néanmoins inexploités, notamment ceux des insectes. Plusieurs études portant sur les venins de fourmis ont révélé que ces venins étaient riches en peptides. La caractérisation du peptidome du venin de Tetramorium bicarinatum a également permis de constater que, malgré la diversité de peptides matures, ces derniers se classent en 3 grandes familles de précurseurs dont certaines ont déjà été décrites chez d’autres hyménoptères. Il est de plus apparu que des gènes codant certains d’entre eux s’expriment en dehors du système vulnérant. Ces résultats posent les questions des mécanismes impliqués dans la diversification des toxines peptidiques de venins de fourmis, ainsi que leur rôle en dehors de la fonction venimeuse. Pour répondre à ces problématiques, la première partie de ce travail de thèse a consisté en la caractérisation via des approches protéotranscriptomiques, des venins de 7 espèces de fourmis appartenant aux différentes tribus phylogénétiques de la sousfamille des Myrmicinae, et du venin d’une espèce appartenant à une sous-famille proche, les Pseudomyrmecinae. Cent toxines peptidiques aux structures variées ont ainsi été identifiées et classées en 8 superfamilles de précurseurs. La seconde partie a consisté en l’exploration du lien entre les toxines peptidiques du venin de T. bicarinatum et son immunité innée via des méthodes de biologie moléculaire et cellulaire. La présence de transcrits codant certains peptides a été vérifiée dans des organes impliqués dans l’immunité innée (i.e. corps gras, tubes digestifs). L’expression des gènes les codant a également été évaluée suite à une infection bactérienne. Il a ainsi été montré que les transcrits codant les peptides de venin sélectionnés sont présents dans les organes testés, et que certains sont produits dans les corps gras en réponse à une infection bactérienne. Ces résultats confirment l’existence d’un lien entre les peptides de venin et l’immunité innée de la fourmi T. bicarinatum, bien que des études complémentaires soient nécessaires
Animal venoms are natural libraries of bioactive compounds, called toxins, which have been finetuned through the course of evolution. However, numerous venomous organisms are still neglected, especially venomous insects. Several studies of ant venoms revealed that they were peptide-rich. Furthermore, the characterization of the ant Tetramorium bicarinatum venom peptidome revealed that, despite the diversity of mature peptides, they belonged to 3 superfamilies of precursors, some of which have already been described in other aculeate hymenoptera. This study also observed that genes encoding some of them were expressed outside the venom apparatus. These results raise questions about the mechanisms involved in the diversification of peptide toxins from ant venoms, as well as their role apart from the venomous function. To address these issues, the first part of this thesis work consisted in the characterization via proteotranscriptomics approaches of 7 venoms from ants belonging to the different phylogenetic tribes of the Myrmicinae subfamily, and of the venom of one species. belonging to a close subfamily, the Pseudomyrmecinae. A total of 100 peptide toxins with various structures were thus identified and classified into 8 precursor superfamilies. The second part explored the link between peptide toxins of T. bicarinatum venom and its innate immunity via molecular and cellular biology methods. The presence of transcripts encoding certain peptides have been verified in organs which are involved in innate immunity of insects (i.e. fat bodies, digestive tracts). The expression of the genes encoding them has also been evaluated following a bacterial infection. It has thus been shown that the transcripts encoding the selected venom peptides are present in the organs tested, and that some are produced in fat bodies in response to a bacterial infection. These results confirm the existence of a link between the venom peptides and the innate immunity of the ant T. bicarinatum, although further studies are needed

APA, Harvard, Vancouver, ISO, and other styles

4

Bergsson, Gudmundur. "Antimicrobial polypeptides and lipids as a part of innate defense mechanism of fish and human fetus /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-546-1/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Edfeldt, Kristina. "Innate immunity in atherosclerosis : signaling pattern recognition receptors and an antimicrobial peptide /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-299-3/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Sonthi, Molruedee. "Structure, polymorphisme et régulation de l'expression de la mytimycine, peptide antifongique de la moule Mytilus." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20105/document.

Full text

Abstract:

Les peptides antimicrobiens sont des éléments clés des mécanismes d'immunité innée développés pour combattre les microorganismes. Parmi ceux-ci, il y a les peptides antifongiques dont l'un, la mytimycine (MytM), avait été partiellement décrite chez la moule Mytilus edulis. Les buts de cette thèse consistaient en la caractérisation complète de la MytM chez M. edulis et chez M. galloprovincialis, ainsi qu'en la compréhension du rôle de ce peptide dans l'immunité de la moule. Les résultats montrent (i) une diversité des séquences nucléotides et en acides aminés en fonction de l'origine géographique des moules, résultant probablement d'une adaptation aux conditions environnementales; (ii) que 2 gènes différents codant la MytM sont simultanément présents dans le génome d'une même moule; (iii) que le niveau d'expression du gène de la MytM dépend de la nature du stimulus, suggérant l'existence de processus de reconnaissance spécifiques; et (iv) que le niveau d'expression du gène de la MytM varie d'une moule à l'autre. En conclusion, la MytM joue un rôle essentiel et spécifique chez la moule. Les données apportées par cette thèse enrichissent notre connaissance sur l'immunité innée des invertébrés
Antimicrobial peptides are crucial elements of the innate immune mechanisms developed to fight microorganisms. Among them are antifungal peptides from which one, named mytimycin (MytM), had been partially reported in the blue mussel, Mytilus edulis. The purposes of this thesis were to fully characterize MytM in M. edulis and M. galloprovincialis and to understand how this peptide participates in mussel immunity. Results showed (i) the diversity of MytM mRNA and translated amino acid sequences according to geographic origin of mussels, probably resulting from adaptation to their environments; (ii) that 2 different MytM genes are simultaneously present in the genome of the same individual mussel; (iii) that expression level of MytM gene depends on the nature of the challenge, suggesting specific recognition processes; and (iv) MytM expression level was different from one mussel to another. In conclusion, MytM appeared to play a prominent and specific role in mussels. The advancement of our works added new data to the knowledge of innate immunity in invertebrates

APA, Harvard, Vancouver, ISO, and other styles

7

Varma, Disha [Verfasser]. "Role of antimicrobial peptides in metabolism and innate immunity in Drosophila melanogaster / Disha Varma." Bonn : Universitäts- und Landesbibliothek Bonn, 2014. http://d-nb.info/1058400495/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Vladimer, Gregory I. "Inflammasomes and the Innate Immune Response Against Yersinia Pestis: A Dissertation." eScholarship@UMMS, 2013. https://escholarship.umassmed.edu/gsbs_diss/649.

Full text

Abstract:

Yersinia pestis, the causative agent of plague, is estimated to have claimed the lives of 30-50% of the European population in five years. Although it can now be controlled through antibiotics, there are still lurking dangers of outbreaks from biowarfare and bioterrorism; therefore, ongoing research to further our understanding of its strong virulence factors is necessary for development of new vaccines. Many Gram-negative bacteria, including Y. pseudotuberculosis, the evolutionary ancestor of Y. pestis, produce a hexa-acylated lipid A/LPS which can strongly trigger innate immune responses via activation of Toll-like receptor 4 (TLR4)-MD2. In contrast, Y. pestis grown at 37ºC generates a tetra-acylated lipid A/LPS that poorly induces TLR4-mediated immune activation. We have reported that expression of E. coli lpxL in Y. pestis, which lacks a homologue of this gene, forces the biosynthesis of a hexa-acylated LPS, and that this single modification dramatically reduces virulence in wild type mice, but not in mice lacking a functional TLR4. This emphasizes that avoiding activation of innate immunity is important for Y. pestis virulence. It also provides a model in which survival is strongly dependent on innate immune defenses, presenting a unique opportunity for evaluating the relative importance of innate immunity in protection against bacterial infection. TLR signaling is critical for the sensing of pathogens, and one implication of TLR4 engagement is the induction of the pro-forms of the potent inflammatory cytokines IL-1β and IL-18. Therefore Y. pestis is able to suppress production of these which are generated through caspase-1-activating nucleotide-binding domain and leucine-rich repeat (NLR)-containing inflammasomes. For my thesis, I sought to elucidate the role of NLRs and IL-18/IL-1β during bubonic and pneumonic plague infection. Mice lacking IL-18 signaling led to increased susceptibility to wild type Y. pestis, and an attenuated strain producing a Y. pseudotuberculosis-like hexa-acylated lipid A. I found that the NLRP12, NLRP3 and NLRC4 inflammasomes were important protein complexes in maturing IL-18 and IL-1β during Y. pestis infection, and mice deficient in each of these NLRs were more susceptible to bacterial challenge. NLRC4 and NLRP12 also directed interferongamma production via induction of IL-18 against plague, and minimizing inflammasome activation may have been a central factor in evolution of the high virulence of Y. pestis. This is also the first study that elucidated a pro-inflammatory role for NLRP12 during bacterial infection.

APA, Harvard, Vancouver, ISO, and other styles

9

Vladimer, Gregory I. "Inflammasomes and the Innate Immune Response Against Yersinia Pestis: A Dissertation." eScholarship@UMMS, 2001. http://escholarship.umassmed.edu/gsbs_diss/649.

Full text

Abstract:

Yersinia pestis, the causative agent of plague, is estimated to have claimed the lives of 30-50% of the European population in five years. Although it can now be controlled through antibiotics, there are still lurking dangers of outbreaks from biowarfare and bioterrorism; therefore, ongoing research to further our understanding of its strong virulence factors is necessary for development of new vaccines. Many Gram-negative bacteria, including Y. pseudotuberculosis, the evolutionary ancestor of Y. pestis, produce a hexa-acylated lipid A/LPS which can strongly trigger innate immune responses via activation of Toll-like receptor 4 (TLR4)-MD2. In contrast, Y. pestis grown at 37ºC generates a tetra-acylated lipid A/LPS that poorly induces TLR4-mediated immune activation. We have reported that expression of E. coli lpxL in Y. pestis, which lacks a homologue of this gene, forces the biosynthesis of a hexa-acylated LPS, and that this single modification dramatically reduces virulence in wild type mice, but not in mice lacking a functional TLR4. This emphasizes that avoiding activation of innate immunity is important for Y. pestis virulence. It also provides a model in which survival is strongly dependent on innate immune defenses, presenting a unique opportunity for evaluating the relative importance of innate immunity in protection against bacterial infection. TLR signaling is critical for the sensing of pathogens, and one implication of TLR4 engagement is the induction of the pro-forms of the potent inflammatory cytokines IL-1β and IL-18. Therefore Y. pestis is able to suppress production of these which are generated through caspase-1-activating nucleotide-binding domain and leucine-rich repeat (NLR)-containing inflammasomes. For my thesis, I sought to elucidate the role of NLRs and IL-18/IL-1β during bubonic and pneumonic plague infection. Mice lacking IL-18 signaling led to increased susceptibility to wild type Y. pestis, and an attenuated strain producing a Y. pseudotuberculosis-like hexa-acylated lipid A. I found that the NLRP12, NLRP3 and NLRC4 inflammasomes were important protein complexes in maturing IL-18 and IL-1β during Y. pestis infection, and mice deficient in each of these NLRs were more susceptible to bacterial challenge. NLRC4 and NLRP12 also directed interferongamma production via induction of IL-18 against plague, and minimizing inflammasome activation may have been a central factor in evolution of the high virulence of Y. pestis. This is also the first study that elucidated a pro-inflammatory role for NLRP12 during bacterial infection.

APA, Harvard, Vancouver, ISO, and other styles

10

Al, souhail Qasim Mohammed. "Characterization, regulation and biophysical studies of immune-related peptides from Manduca sexta." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32618.

Full text

Abstract:

Doctor of Philosophy
Biochemistry and Molecular Biophysics Interdepartmental Program
Michael Kanost
Insects secrete antimicrobial peptides as part of the innate immune response. Most antimicrobial peptides from insects have antibacterial but not antifungal activity. We have characterized an antifungal peptide, diapausin-1 from hemolymph of a lepidopteran insect, Manduca sexta (tobacco hornworm). Diapausin-1 was isolated by size exclusion chromatography from hemolymph plasma of larvae that were previously injected with a yeast, Saccharomyces cerevisiae. Fractions containing activity against S. cerevisiae were analyzed by SDS-PAGE and MALDI-TOF MS/MS and found to contain a 45-residue peptide that was encoded by sequences identified in M. sexta transcriptome and genome databases. A cDNA for diapausin-1 was cloned from cDNA prepared from fat body RNA. Diapausin-1 is a member of the diapausin family of peptides, which includes members known to have antifungal activity. The M. sexta genome contains 14 genes with high similarity to diapausin-1, each with 6 conserved Cys residues. Diapausin-1 was produced as a recombinant protein in Escherichia coli. Purified recombinant diapausin-1 was active against S. cerevisiae, with IC₅₀ of 12 μM, but had no detectable activity against bacteria. Spores of some plant fungal pathogens treated with diapausin-1 had curled germination tubes or reduced and branched hyphal growth. Diapausin-1 mRNA level in fat body strongly increased after larvae were injected with yeast or with Micrococcus luteus. In addition, diapausin-1 mRNA levels increased in midgut and fat body at the wandering larval stage prior to pupation, suggesting developmental regulation of the gene. Our results indicate that synthesis of diapausin-1 is part of an antifungal innate immune response to infection in M. sexta. Biophysical analysis showed that diapausin-1 binds to the β-1,3 glucan component of the S. cerevisiae cell wall. A second insect peptide investigated in this project was M.sexta stress-response peptide 1(SRP1), an immune-related peptide upregulated under different stress conditions including immune-challenge. Preliminary results for NMR structure determination are presented. Most of the amino acid residue spin systems were assigned, and we determined the connectivities of many amino residues as a first step to solve the NMR structure. The circular dichroism spectrum of SRP1 indicates that the peptide lacks alpha-helical structure and may contain beta strands and turns.

APA, Harvard, Vancouver, ISO, and other styles

11

Hamad, Shaimaa Kamal. "Developmental gene expression of host defense peptides in immune organs and the small intestine of turkey poults (Meleagris gallopavo)." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73056.

Full text

Abstract:

Host defense peptides (HDPs) are a large group of small positively charged peptides that play an important role in innate immunity. Their role is more critical at early ages when other components of the immune system have not fully developed. There are three classes of avian HDPs: avian beta defensins (AvBDs), cathelicidins (Cath) and liver-expressed antimicrobial peptide 2 (LEAP-2). The objective was to compare expression of HDPs in male turkey poults at day of hatch (D0), D7, D14, D21 and D28 from the thymus, spleen, bursa, duodenum, jejunum and ileum. The expression of AvBD1, AvBD2, AvBD8, AvBD9, AvBD10, AvBD13, Cath2, Cath3 and LEAP-2 was measured using qPCR (n=6 birds/tissue/age). Data were analyzed by one-way ANOVA and Tukey's test, and significance considered at P ≤ 0.05. AvBDs and Caths exhibited greater expression in immune organs than intestinal tissues, with the greatest expression of AvBDs observed in the spleen. The intestinal tissues showed very low expression of AvBDs except for AvBD10 at D0. Similar to AvBDs, Caths expression in the immune organs was greater than the intestinal tissues with the spleen having the greatest expression among immune organs. Conversely, LEAP-2 showed greater expression in the intestinal tissues than in the immune tissues, which showed very low LEAP-2 expression unlike other HDPs. Understanding the differential expression of HDPs could reveal the innate immune status of poults, and may subsequently allow improvement of their health through appropriate mitigation strategies.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

12

Labed, Sid ahmed. "Caractérisation génétique de l'immunité innée dans l'épiderme de C.elegans." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4050.

Full text

Abstract:

Pour comprendre les mécanismes de l'immunité innée, nous utilisons Caenorhabditis elegans comme un organism model host et coniospora Drechmeria comme un pathogène. D. coniospora adhère à la cuticule de C. elegans pour infecter son épiderme. Le ver répond par une régulation de gènes de défense multiples, y compris des gènes codant pour des peptides antimicrobiens (AMP) comme nlp-29. En utilisant des vers transgéniques portant des constructions rapporteurs fluorescents comme nlp-29p :: gfp, nous pouvons suivre l'expression des gènes in vivo AMP et de chercher des gènes nécessaires à l'induction de gènes AMP à travers les écrans génétiques. Le but de mon projet était de caractériser des mutants qui ont été identifiés dans un nouvel écran génétique saturée, où 57 nouveaux allèles Nipi qui manquent nlp-29 d'induction après l'infection ont été isolés. Adaptation d'une nouvelle cartographie combinée SNP et toute stratégie de séquençage du génome, nous avons pu isoler 15 allèles de gènes nouveaux Nipi déjà connus et 12 allèles de 6 «nouveaux» gènes. Notre travail a confirmé le rôle principal de la MAPK PKCδ/p38 dans la régulation de l'expression nlp-29 AMP après l'infection, ainsi que le facteur de transcription STA-2/STAT et le transporteur SNF-12/SLC6. Nous faire progresser nos connaissances en identifiant NIPI-4 comme un régulateur positif de l'expression des gènes nlp peptide antimicrobien après l'infection. NIPI-4 est un membre de la famille des kinases nématode spécifique et est prévu pour être un pseudokinase. Nous avons montré qu'il agit dans l'épiderme partie aval de la MAPK p38
To understand the mechanisms of innate immunity, we use Caenorhabditis elegans as a model host and Drechmeria coniospora as a fungal pathogen. D. coniospora adheres to the cuticle of C. elegans to infect its epidermis. The worm responds by an up-regulation of multiple defence genes, including genes encoding anti-microbial peptides (AMP) like nlp-29. Using transgenic worms carrying fluorescent reporter constructs like nlp-29p::gfp, we can follow AMP gene expression in vivo and look for genes required for the induction of AMP genes through genetic screens. The aim of my project was to characterize mutants that have been identified in a new saturated genetic screen, where 57 new Nipi alleles that lack nlp-29 induction after infection were isolated. Adapting a new combined SNP mapping and whole genome sequencing strategy we were able to isolate 15 new alleles of previously known Nipi genes and 12 alleles of 6 “new” genes. Our work confirmed the primary role of the PKCδ/p38 MAPK in the regulation of nlp-29 AMP expression after infection, as well as the STA-2/STAT transcription factor and the SNF-12/SLC6 transporter. We further advance our knowledge by identifying NIPI-4 as a positive regulator of nlp antimicrobial peptide genes expression after infection. NIPI-4 is a member of a nematode-specific kinase family and is predicted to be a pseudokinase. We showed that it acts in the epidermis partially downstream of the p38 MAPK. It also controls the constitutive expression of antimicrobial peptide genes of the cnc family that are targets of TGFß regulation. Together these suggested that NIPI-4 acts with STA-2 and SNF-12 to regulate AMP gene expression in the epidermis

APA, Harvard, Vancouver, ISO, and other styles

13

Toubiana, Mylène. "L’immunité innée chez la moule méditerranéenne Mytilus galloprovincialis : de la transmission du signal à la régulation génique." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20201/document.

Full text

Abstract:

La moule de Méditerranée Mytilus galloprovincialis (Mollusque Bivalve), est un animal important tant au niveau écologique qu'économique. Comme tous les invertébrés, elle ne possède qu'un système d'immunité innée pour lutter contre les infections. Cependant, étant constamment exposée à une grande variété de microorganismes invasifs et potentiellement pathogènes, et existant depuis plus de 500 millions d'années, son système immunitaire paraît très efficace. C'est afin de mieux comprendre comment celui-ci fonctionne, que ces travaux concernant la structure des peptides impliqués dans la réponse immunitaire, ainsi que leur régulation, ont été entrepris. Ils ont permis (i) de déterminer que le niveau d'expression constitutive des gènes liés à l'immunité, ainsi que la nature et l'intensité de la régulation de leur expression, sont fortement dépendant de la saison et de l'origine géographique des moules ; (ii) de confirmer le rôle essentiel de la structure tridimensionnelle des peptides antimicrobiens (AMP) dans les activités biologiques ; (iii) de déterminer la structure complète de la mytimycine, peptide strictement antifongique, ainsi que de la cytokine MIF ; (iv) de confirmer l'existence d'un fort polymorphisme des ARNm codant les molécules effectrices de l'immunité au niveau individuel, intra et inter-populationnel ; (v) de déterminer que les niveaux d'expression des gènes liés à l'immunité dépendent des microorganismes injectés, ce qui suggère une reconnaissance/réponse spécifique; (vi) de démontrer l'existence d'une voie de transmission du signal fonctionnelle depuis des récepteurs membranaires de type Toll (TLR) jusqu'au facteur NF-κB, mais pas d'une voie de type IMD. Ainsi, la réponse immunitaire innée de la moule apparait extrêmement complexe, mettant en jeux des effecteurs polymorphes dont l'expression est modulée en fonction de la saison, de l'origine géographique et de façon spécifique en réponse à différents microorganismes. Par contre, la transcription de leurs gènes pourrait être sous le contrôle d'une seule voie de transmission du signal
The Mediterranean mussel, Mytilus galloprovincialis (bivalve, mollusc), is an ecologically and economically essential animal. As other invertebrates, it possesses only an innate immune system to protect itself against infections. However, constantly exposed to a large variety of invasive and potentially pathogen microorganisms, and existing since more than 500 million years, its immune system seems very effective. To improve our understanding on such a system, present works were made concerning the structure and expression regulation of peptides involved in the immune response. They allowed (i) to determine that the constitutive expression levels of genes linked to immunity, as well as the nature and intensity of their expression regulation, are strongly dependent on the season and on the geographical origin of mussels; (ii) to confirm the crucial role of the three-dimensional structure of antimicrobial peptides (AMP) in biological activities; (iii) to determine the complete structure of mytimycine, a strictly antifungal peptide, as well as of cytokine MIF; (iv) to confirm the existence of an extended polymorphism of mRNA coding for the molecular effectors of immunity in individuals, within and between populations; (v) to determine that expression levels of genes linked to immunity are strongly dependent to the injected microorganisms, suggesting a specific recognition/ response; (vi) to demonstrate the existence of a functional signalling pathway from Toll-like receptors (TLR) to NF-κB factor, but not of an IMD-like pathway. In conclusion, the immune response of the mussel appeared extremely complex, involving polymorphic effectors expressed differently according to the season, the geographical origin, and specifically in response to different microorganisms. On the other hand, their gene transcription could be under the control of only one signal transmission pathway

APA, Harvard, Vancouver, ISO, and other styles

14

Menzel, Lorenzo P. "Aspects of the Innate Immune System in the Caribbean Octocoral Swiftia exserta." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/1025.

Full text

Abstract:

The immune systems of cnidaria are important to study for two reasons: to gain a better understanding of the evolution of immune responses, and to provide a basis to partially redress the precipitous world-wide die-offs of reef corals, some of which have been attributed to diseases and stress. Many immune responses share ancient evolutionary origins and are common across many taxa. Using Swiftia exserta, an azooxanthellate ahermatypic local octocoral, as a proxy model organism to study aspects of innate immunity in corals and cnidaria allows us to address both of the reasons listed above while not using endangered species. Utilizing a coral that does not contain symbiotic dinoflagellates (zooxanthellae) simplifies the system by restricting the source of proteins to a single genome. The lack of zooxanthellae in Swiftia exserta also allows the animal’s simple adaptation to lab settings. This study of the innate immune system of an octocoral demonstrates: 1) a novel understanding of the microanatomy of octocoral tissues; 2) that Swiftia exserta has at least two cell types that function as constitutive immunocytes; and 3) the presence of two potent antibacterial peptides, one with a mass between 4694 and 4696 Daltons. My report on the microanatomy of the coenenchyme, the tissue between polyps, advances the understanding of octocoral anatomy by systematically comparing histology sections with electron micrographs. Applying various techniques of enzyme histochemistry, coupled with cryo-preservation, to the coenenchyme I have identified at least two populations of constitutive immunocytes in Swiftia exserta. Two antibacterial proteins are identified by protein purification and antimicrobial testing techniques. The more active protein is partially characterized with modern hyphenated mass-spectrometry techniques, and can be the focus of future study.

APA, Harvard, Vancouver, ISO, and other styles

15

Romoli, Ottavia. "Antimicrobial peptide-mediated immune response in four Bombyx mori strains infected with Gram-positive and -negative pathogens." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424450.

Full text

Abstract:

The domesticated silkworm Bombyx mori is an important organism for its intrinsic economic and biotechnological value, but also for representing a model organism for Lepidoptera genetics. Silkworm strains can be grouped into four geographical types (Japanese, Chinese, European and Tropical) characterized by a different resistance to infections, which is inversely correlated to the silk productivity. The aim of this project was to characterize which are the main elements of the immune response protecting Bombyx mori against pathogen infections, with the final purpose to obtain silkworms enhanced in their pathogen-resistance, but still maintaining good production capabilities. To achieve this objective, two main approaches have been used: 1) the characterization of the humoral immune response to oral infection of four B. mori strains originating from Japan, China, Europe and India, focusing on antimicrobial peptides (AMPs), important effectors of the innate immunity; 2) the production and characterization of transgenic silkworms over-expressing specific AMPs. We first characterized the four strain under germ-free conditions for the structure of their peritrophic membranes and intestinal epithelia, which represent the first barriers for oral infection. Moreover, we evaluated the genetic variability of the four strains at the level of the 21 B. mori AMP genes, identifying several amino acid substitutions in the active portion of peptides. To determine the possible differential sensitivity to microbial attack, we performed infection experiments in which each B. mori line was exposed to two silkworm pathogens, the Gram-positive Enterococcus mundtii or the Gram-negative Serratia marcescens. After a 24h oral infection, the differential response to pathogens of the four strains was determined by comparing 1) the survival profiles, 2) the presence of living pathogen cells in the hemolymph circulation, 3) the expression induction of 9 representative AMP genes in the tissues involved in the immune response (fat bodies and midgut), 4) the in vitro antimicrobial activity of the silkworm hemolymph, 5) the Lysozyme concentration in larvae plasma and 6) the rate of the melanization reaction. Regarding the E. mundtii infection, the European line was found to be the most resistant, followed by the Chinese, the Indian and the Japanese strains. Our data suggest that the key resistance factor might consist in the AMP classes and/or isoforms produced in the European strain at both local and systemic levels. Regarding the S. marcescens infection, the Indian strain was completely resistant, while none of the other three strains survived to the microbial exposure. We found a general correlation between the survival profile and the systemic AMP transcription activation. In fact, the Indian line was the only one which showed a systemic induction of most AMPs and in which no viable bacteria were found in the hemolymph. Further analyses are required to explore whether this strain-specific resistance is due to more efficient mechanisms in the Gram-negative recognition process or in the signal transduction pathway activation. In order to obtain transgenic silkworm strains with enhanced pathogen resistance, we generated three different piggyBac-based constructs to achieve the over-expression of moricin, gloverin2 or cecropinB at the level of fat bodies. Currently, 2 independent lines over-expressing moricin have been obtained and are under evaluation for their resistance to infections.
Il baco da seta, Bombyx mori, oltre a possedere un’importanza economica intrinseca, è ampiamente utilizzato sia come sistema modello per i Lepidotteri, che nel campo delle biotecnologie. In seguito alla domesticazione si sono originati numerosi ceppi, che possono essere classificati sulla base della loro origine geografica in giapponesi, cinesi, europei e tropicali. In genere, i ceppi che provengono dalle aree temperate mostrano una maggiore produttività, ma anche una più alta suscettibilità alle infezioni, mentre i ceppi di origine tropicale risultano essere più resistenti alle infezioni. Lo scopo di questo progetto consisteva nell’identificare quali potessero essere gli elementi chiave della resistenza del B. mori alle infezioni. Il fine ultimo era di creare dei ceppi di baco da seta che fossero più tolleranti ai patogeni, ma che mantenessero comunque buone capacità produttive. Per raggiungere questi obiettivi, sono stati utilizzate due principali strategie: 1) la caratterizzazione della risposta immunitaria indotta da infezioni orali di quattro ceppi di baco da seta originatisi rispettivamente in Giappone, Cina, Europa ed India, ponendo particolare attenzione sui peptidi antimicrobici (AMP), i principali effettori dell’immunità innata; 2) la produzione e la caratterizzazione di linee transgeniche over-esprimenti i geni codificanti gli AMP. In primo luogo abbiamo caratterizzato la morfologia delle membrane peritrofiche e degli epiteli intestinali dei quattro ceppi allevati in condizioni sterili. Queste strutture rappresentano la prima barriera fisica durante le infezioni orali. Successivamente, abbiamo valutato la variabilità genetica dei quattro ceppi a livello dei 21 geni codificanti per gli AMP di B. mori, identificando numerose sostituzioni amminoacidiche nella porzione attiva dei peptidi. Abbiamo quindi sottoposto i quattro ceppi ad infezione orale con due batteri, specifici patogeni del baco da seta: Enterococcus mundtii, Gram-positivo, e Serratia marcescens, Gram-negativo. In seguito ad un’infezione di 24 ore abbiamo valutato la risposta differenziale dei quattro ceppi confrontando: 1) i profili di sopravvivenza, 2) la presenza di cellule batteriche vive nell’emolinfa, 3) l’induzione dell’espressione dei geni codificanti 9 AMP rappresentativi, 4) l’attività antimicrobica dell’emolinfa, 5) la concentrazione del Lisozima nel plasma, 6) la velocità di melanizzazione dell’emolinfa. Per quanto riguarda l’infezione con E. mundtii, il ceppo europeo è risultato essere il più resistente, seguito dal cinese, dall’indiano e dal giapponese. I dati ottenuti indicano che le classi e i tipi di AMP prodotti dal ceppo europeo, sia a livello locale che a quello sistemico, possano essere l’effettiva causa della maggiore resistenza di questo ceppo. A seguito dell’infezione con S. marcescens, il ceppo Indiano si è rivelato essere totalmente resistente a questo patogeno, mentre nessuno degli altri tre ceppi è sopravvissuto all’infezione. Abbiamo trovato una generale correlazione tra il profilo di sopravvivenza e l’attivazione sistemica degli AMP. Infatti nell’emolinfa dei bachi da seta indiani non sono state isolate cellule batteriche di S. marcescens e solamente questo ceppo ha mostrato un’induzione della trascrizione della maggior parte degli AMP. Sono necessarie ulteriori analisi per verificare se il ceppo indiano possieda meccanismi di riconoscimento o vie di trasduzione del segnale più efficaci per questo tipo di infezione. Infine sono stati generati tre differenti costrutti basati sull’elemento trasponibile piggyBac per ottenere ceppi di baco da seta transgenici con una maggiore resistenza alle infezioni. Sono state ottenute due linee indipendenti over-esprimenti il gene per la Moricina. Al momento si stanno caratterizzando queste linee per verificare la loro resistenza alle infezioni.

APA, Harvard, Vancouver, ISO, and other styles

16

Sow, Fatoumata B. "Expression and regulation of the iron regulatory hormone and antimicrobial peptide hepcidin in mycobacteria-infected mice and macrophages." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180299600.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Ulvila, J. (Johanna). "Functional genomic analysis of the Drosophila immune response:identification of genes essential for phagocytosis, viral defense and NF-κB signaling." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514289941.

Full text

Abstract:

Abstract Innate immunity provides the first line of defense against invading, pathogenic microorganisms in all multicellular organisms. The fruit fly Drosophila melanogaster has turned out to be an excellent model organism to elucidate mechanisms of innate immune responses because of the highly conserved intracellular signaling cascades mediating these ancient immune functions in flies and mammals. In the present study, RNA interference (RNAi) -based functional genomics were utilized to identify novel components of Drosophila’s immune reactions. Mediators of bacterial phagocytosis, nuclear factor kappa B (NF-κB) signaling and the antiviral RNAi pathway were screened in hemocyte-like S2 cells. Follow-up studies were executed in mammalian cells as well as in Drosophila larvae and adult flies to gain broader significance for the results. Seven novel components essential for efficient phagocytosis of bacteria were identified. Eater was defined as Drosophila’s most important phagocytic receptor showing novel epidermal growth factor (EGF)-repeat -based microbial recognition properties. Additionally, Abelson interacting protein (Abi), capping protein alpha (cpa), 14-3-3ζ, tousled-like kinase (tlk), CG2765 and CG15609 were determined as intracellular effectors of phagocytosis, the three former ones executing their evolutionarily conserved functions through remodeling of the actin cytoskeleton. Eater, together with Scavenger receptor class C, type I (Sr-CI), was demonstrated to be responsible for double-stranded RNA (dsRNA) uptake into S2 cells and, when ectopically expressed, into mammalian cells via clathrin-mediated endocytosis. Proteasome component Pros45 and RNA helicase Belle were established as mediators of the intracellular RNAi pathway, whereas essential roles in antimicrobial signaling via the immune deficiency (Imd) pathway were addressed for Inhibitor of apoptosis 2 (Iap2) and Tak1-associated binding protein (TAB). Iap2 and TAB were shown to affect nuclear translocation of NF-κB -like transcription factor Relish. The present study identifies several novel mediators of the Drosophila immune response and provides insight into mechanisms of fly host defense. As insects serve as vectors of human diseases (e.g. malaria), knowledge about Drosophila immune mechanisms may help to better understand the transmission and pathogenesis of these diseases and develop treatments to fight these infections. Additionally, knowledge gained from model organisms serves as valuable background information, often conducting human research into new tracks
Tiivistelmä Synnynnäinen immuniteetti on elintärkeä puolustusjärjestelmä taudinaiheuttajia vastaan. Kodeissakin yleinen banaanikärpänen, Drosophila melanogaster, on osoittautunut erinomaiseksi synnynnäisen immuniteetin tutkimusmalliksi, erityisesti teknisesti yksinkertaisen ja eettisesti ongelmattoman geneettisen muunneltavuutensa ansiosta. On myös havaittu, että solunsisäiset, immunologisia signaaleja välittävät mekanismit ovat evoluutiossa hyvin säilyneitä. Hyvin usein samankaltaiset geenituotteet toimivat signaalinsiirtäjinä sekä kärpäsen että ihmisen soluissa. Tämän työn tarkoituksena oli RNA-häirintää (RNAi) sekä muita nykyaikaisia solu- ja molekyylibiologisia tutkimusmenetelmiä hyödyntäen tunnistaa uusia kärpäsen synnynnäiselle immuunipuolustukselle välttämättömiä geenituotteita. Bakteerien fagosytoosille, viruspuolustukselle ja tumatekijä nuclear factor kappa B:n (NF-κB) välittämälle signaloinnille välttämättömiä signalointimolekyylejä pyrittiin identifioimaan laajan mittakaavan RNA-häirintään perustuvilla seuloilla kärpäsen soluissa. Saatujen tulosten merkitystä nisäkkäiden immuunipuolustukselle tutkittiin myös hiiren soluissa. Seitsemän geenituotteen osoitettiin olevan bakteerien fagosytoosille tärkeitä kärpäsen soluissa. Aiemmin tuntematon geenituote, joka nimettiin Eateriksi, osoitettiin kärpäsen tärkeimmäksi bakteereja fagosytoivaksi reseptoriksi. Eaterin solun ulkoisen osan osoitettiin tunnistavan taudinaiheuttajia uudella epidermaalisen kasvutekijän (epidermal growth factor, EGF) kaltaisella toistosekvenssillä. Myös useiden solun tukirankaan, sytoskeletoniin, liittyvien proteiinien (Abi, cpa, 14-3-3ζ) sekä aiemmin vähemmän tunnettujen geenituotteiden (CG2765, CG15609, tlk) osoitettiin osallistuvan bakteerien fagosytoosiin. Näistä kolmen ensinmainitun immunologinen tehtävä havaittiin evoluutiossa säilyneeksi, kärpäsestä hiireen. Eaterin, yhdessä kärpäsen toisen scavenger reseptorin (Sr-CI) kanssa, havaittiin myös toimivan kaksijuosteisen RNA:n (dsRNA) reseptoreina kärpäsen soluissa, mahdollistaen helpon ja tehokkaan RNA-häirinnän. RNA-häirinnän, ja siten mahdollisesti myös viruspuolustuksen, välittäjiksi identifioitiin proteasomin alayksikkö Pros45 ja RNA-helikaasi Belle. Lisäksi Inhibitor of apoptosis 2 (Iap2) ja Tak1-associated binding protein (TAB) todettiin kärpäsen immune deficiency (Imd) signalointireitin komponenteiksi, jotka osallistuvat antimikrobisten peptidien tuotantoon välittämällä NF-κB:n kaltaisen kärpäsen transkriptiotekijän (Relish) siirtymisen tumaan aktivoimaan immuunipuolustusta välittävien geenien ilmentymistä. Tämän tutkimuksen tulokset valottavat banaanikärpäsen immuunipuolustuksen mekanismeja. Koska hyönteiset toimivat monien ihmisten infektiotautien välittäjinä, kärpäsen immuniteetin tuntemus luo mahdollisuuksia kehittää hoitoja näitä tauteja vastaan. Lisäksi malliorganismeista saatu tieto luo uusia teorioita ja näkökulmia, johtaen usein myös lääketieteellistä tutkimusta uusille raiteille

APA, Harvard, Vancouver, ISO, and other styles

18

Young, James L. "Innate Immunity in Type 2 Diabetes Pathogenesis: Role of the Lipopolysaccharide Signaling Cascade: A Dissertation." eScholarship@UMMS, 2008. https://escholarship.umassmed.edu/gsbs_diss/400.

Full text

Abstract:

Once seen as a disease of wealthy nations, type 2 diabetes mellitus is now showing unprecedented growth throughout the world, fueling increases in microvascular and macrovascular complications. A compelling and growing body of evidence suggests that glucose intolerance and insulin resistance, hallmarks of the diabetic patient, may be driven by chronic inflammation. In particular, a predominance of visceral fat has been associated with enhanced inflammatory cytokine secretion that may contribute to enhanced risk of diabetes and comorbid cardiovascular disease in these individuals. As a function of its potency and wide environmental and biological distribution, we hypothesized that bacterial lipopolysaccharide (LPS, also known as endotoxin) may promote adipose inflammation and concomitant metabolic dysfunction. Indeed, expression of the LPS receptor CD14 is enhanced on visceral adipocytes of ob/ob mice, paralleling enhanced IL-6 secretion ex vivo. Furthermore, rosiglitazonefed ob/obmice demonstrated a reduction in CD14 that coordinated with diminished IL-6 secretion, suggesting a basis for the touted anti-inflammatory effects of this commonly employed type 2 diabetes medication. Mice deficient in components of the LPS signaling cascade, namely CD14, TLR4, and MyD88, yielded adipocytes with markedly attenuated IL-6 secretion, corroborating the central importance of LPS in adipocyte inflammation and supporting the role of this signaling pathway in depot-specific inflammation. Despite the prominent role of LPS signaling in adipocyte inflammation, CD14-, TLR4-, and MyD88-deficient mice failed to show resistance to diet induced obesity. Surprisingly, cd14-/- and tlr4-/- mice had marked glucose intolerance without alteration in total weight or adipose accumulation. In contrast, myd88-/- mice revealed minor glucose intolerance only with high fat diet challenge at an advanced age despite being overtly obese. In cd14-/- and tlr4-/-, but not myd88-/-, mice, an exaggerated rebound to hypoglycemia was associated with enhanced norepinephrine secretion, which could be abrogated by the adrenergic β-blocker propranolol. The overlay of these mouse models reveals a divergence of phenotypes that demonstrate LPS signaling disruption may lead to glucose intolerance and insulin resistance in part due to enhanced sympathoadrenal tone, uncovering an essential role of innate immunity in physiological stress and its impact upon glucose homeostasis.

APA, Harvard, Vancouver, ISO, and other styles

19

Borge-Renberg, Karin. "Communicate or die : signalling in Drosophila immunity." Doctoral thesis, Umeå : Univ, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1817.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Ou, Gangwei. "Human intestinal epithelial cells in innate immunity : interactions with normal microbiota and pathogenic bacteria." Doctoral thesis, Umeå : Umeå University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-18388.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Rahabi, Mouna. "Les macrophages dans l'inflammation colique, approches expérimentale et translationnelle : impact des récepteurs Dectine-1 et mannose et des peptides Naticol(r)Gut." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30104.

Full text

Abstract:

La maladie de Crohn (MC) et la rectocolite hémorragique (RCH) sont les deux formes principales des maladies inflammatoires chroniques de l'intestin (MICI) et sont le résultat de réactions inflammatoires excessives au niveau du système digestif. Bien qu'elles partagent certaines caractéristiques, ces deux entités se distinguent par des différences concernant la prédisposition génétique, les facteurs de risque, et les caractéristiques cliniques, endoscopiques et histologiques. Dans un premier temps, nous nous sommes intéressés au rôle des récepteurs lectines de type C dans l'inflammation colique. Nous montrons que dans un contexte de colite, l'absence de Dectine-1 prévient l'inflammation intestinale, tandis que l'absence du récepteur mannose (RM), l'exacerbe. Ceci a été confirmé dans un modèle expérimental d'exposition au DSS sur souris déficientes pour le RM chez qui nous avons relevé une augmentation marquée de l'expression de Dectine-1. Dectine-1 participe au recrutement des monocytes sanguins, précurseurs des macrophages, sur le site inflammatoire de la muqueuse colique et favorise la production d'IL-1ß de façon leucotriène B4- dépendante. Nous associons donc l'inflammation colique à une activation de l'axe Dectine-1/CCL2/LTA4H et à une régulation négative du RM sur les macrophages de patients atteints de MICI. Par ailleurs, la deuxième partie de notre travail montre que les peptides de collagène de poisson, dont les propriétés anti- inflammatoires ont été décrites dans d'autres contextes pathologiques tels que l'arthrite ou les dérégulations métaboliques, ont un effet bénéfique dans un contexte d'inflammation colique. Le Naticol(r)Gut, nom commercial des peptides de collagène de poisson que nous avons étudiés, régule l'inflammation par effet direct sur la polarisation des macrophages coliques vers un phénotype anti-inflammatoire et anti-oxydant. Par conséquent, nous avons montré que l'administration de Naticol(r)Gut module l'équilibre Th1/Th2 des cellules T CD4 en faveur d'une réponse Th2 et limite l'activation des cellules T CD8 cytotoxiques. L'atténuation du statut inflammatoire de l'intestin généré par l'administration de Naticol(r)Gut entraîne une eubiose intestinale subséquente caractérisée par une limitation du développement des espèces pathobiontes au profit des espèces probiotiques. De plus, nous observons des contributions similaires du Naticol(r)Gut dans la restauration du phénotype anti-inflammatoire, anti-oxydant et immuno-tolérant des monocytes humains de sujets atteints de MICI. Ces deux études appuient le rôle crucial que joue la polarisation des macrophages dans la physiopathologie de l'inflammation colique. Enfin, ce dernier travail appuierait l'effet protecteur du RM, récepteur au collagène, dans la colite
Crohn's disease (CD) and ulcerative colitis (UC) are the two main forms of chronic inflammatory bowel disease (IBD) and are the result of excessive inflammatory reactions in the digestive system. Although they share some characteristics, they are distinguished by differences in genetic predisposition, risk factors, and clinical, endoscopic and histological features. First, we have focused on the role of C-type lectin receptors in colonic inflammation. We show that in a colitis context the absence of Dectin-1 prevents intestinal inflammation, while the absence of the mannose receptor (MR) exacerbates it. This was confirmed in an experimental model of DSS exposure in MR-deficient mice in which we found a marked increase in the expression of Dectin-1. Dectin-1 is involved in the recruitment of blood monocytes, precursors of macrophages, to the inflammatory site of the colonic mucosa and promotes the production of IL-1ß in a leukotriene-B4-dependent manner. We therefore associate colonic inflammation with the activation of the Dectin1/CCL2/LTA4H axis and with a negative regulation of MR in macrophages from IBD patients. In addition, the second part of our work shows that fish collagen peptides, whose anti-inflammatory properties have been described in other pathological contexts such as arthritis or metabolic deregulation, have a beneficial effect in a context of colonic inflammation. Naticol(r)Gut, the trade name of the fish collagen peptides we studied, regulates inflammation by direct effect on the polarization of colonic macrophages towards an anti-inflammatory and antioxidant phenotype mediated by the recognition by the MR thereby supporting its protective effect. Therefore, we have shown that Naticol(r)Gut administration modulates the Th1/Th2 balance of CD4 T cells in favor of a Th2 response and limits the activation of cytotoxic CD8 T cells. The attenuation of the intestinal inflammatory status generated by the administration of Naticol(r)Gut subsequently leads to intestinal eubiosis characterized by a limitation of the development of pathobiontic species in favor of probiotic species. In addition, we observe similar contributions of Naticol(r) in restoring the anti-inflammatory, antioxidant and immunotolerant phenotype of human monocytes from subjects with IBD. These two studies support the crucial role of macrophage polarization through the C-type lectin receptors in the pathophysiology of colonic inflammation. Finally, the latter work supports the protective effect of the MR collagen receptor in colitis

APA, Harvard, Vancouver, ISO, and other styles

22

Kim, Young-A. "Hematopoiesis, Kazal Inhibitors and Crustins in a Crustacean." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7123.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Schmitt, Paulina. "Diversité moléculaire des effecteurs antimicrobiens chez l'huître creuse Crassostrea gigas : mise en évidence et rôle dans la réponse antimicrobienne." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20158/document.

Full text

Abstract:

Ce travail a contribué à la compréhension des bases moléculaires de l'immunité de l'huître creuse par la caractérisation la diversité de trois effecteurs antimicrobiens de C. gigas et par l'appréhension du rôle de cette diversité dans les mécanismes de défense. Des analyses phylogénétiques de deux peptides antimicrobiens (AMPs), Cg-Défensines (Cg-Defs) et Cg-Proline rich peptide (Cg-Prp), et d'une protéine de type Bactericidal Permeability Increasing protein, Cg-BPI, nous a permis montrer la grande diversité pour les 2 AMPs, qui est générée par plusieurs mécanismes génétiques et par des pressions de sélection directionnelles, suggèrant une diversité fonctionnelle des variants. L'importance biologique de cette diversité a été étudiée pour trois variants de Cg-Defs. Une forte activité antimicrobienne a été mise en évidence contre les bactéries à Gram positive, mais celle-ci diffère selon les variants. De plus, nous avons démontré que le mécanisme d'action des Cg-Defs contre S. aureus repose sur l'inhibition de la biosynthèse du peptidoglycane par le piegeage de son précurseur, le lipide II. Finalement, l'expression des transcrits et la localisation de ces effecteurs en réponse à une infection par un Vibrio pathogène ont montré un réseau complexe des profils d'expression des différents antimicrobiens, au niveau des populations hémocytaires et des tissus d'huître, suggérant une interaction entre les antimicrobiens du fait de leur colocalization. La combinaison entre les familles ou entre les variants d'une même famille produit de fortes activités synergiques qui élargissent les spectres d'activité. Ainsi, la diversité produit par la coévolution entre hôte et pathogènes pourrait améliorer l'activité des AMPs d'huître, lui conférant une plus grande protection contre les pathogènes de son environnement
This work contributed to the knowledge of the molecular bases of oyster immunity by the characterization of the diversity of three antimicrobials of C. gigas and the understanding of the role played by their diversity in the oyster antimicrobial response. Phylogenetic analyses of two antimicrobial peptides (AMPs), Cg-Defensins (Cg-Defs) and Cg-Proline rich peptide (Cg-Prp), and one Bactericidal Permeability Increasing protein, Cg-BPI, led us to the identification of a high diversity for both AMPs. Further analyses showed that this diversity is generated by gene duplication, allelic recombination and directional selection pressures, suggesting their functional diversification. The biological meaning of AMP diversity was investigated for the three major variants of Cg-Defs, which revealed a strong but variable potency against Gram-positive bacteria. We evidenced that oyster defensins kill S. aureus through binding to the cell wall precursor lipid II, resulting in the inhibition of peptidoglycan biosynthesis. Finally, transcript expression and localization of oyster antimicrobials after a pathogenic infection evidenced a complex network in their expression profiles in hemocyte populations and oyster tissues, suggesting a potential interplay between antimicrobials as a result of their colocalization. Indeed, the combination of oyster antimicrobials produced strong synergistic activities that enlarged their antimicrobial spectra. Thus, the diversity of oyster antimicrobials may provide significant means in acquiring functional divergence, probably concerned in the evolutionary arms race between hosts and their pathogens.From our data, it would provide oysters with a higher protection against the potential pathogens from their environment

APA, Harvard, Vancouver, ISO, and other styles

24

Hartman, Michelle L. "M.tb Killing by Macrophage Innate Immune Mechanisms: A Dissertation." eScholarship@UMMS, 2011. https://escholarship.umassmed.edu/gsbs_diss/606.

Full text

Abstract:

Macrophages infected with a heavy burden of M.tb Erdman undergo a cell death that initially resembles apoptosis but quickly transitions to necrosis. Unlike the previously reported TNF dependent apoptosis induced by avirulent Mycobacterium [1], this form of macrophage cell death is not microbicidal [2]. Microbicidal effects are observed however, when the heavily infected macrophage encounters an uninfected naïve macrophage. My studies describe in part, the crosstalk between the uninfected and infected macrophage that results in the killing of the intracellular M.tb Cell contact between the two cell populations is not necessary for this killing of bacilli to occur and the soluble “signal” of communication between the two cell populations is transferrable, without naïve macrophages present, to newly infected cells also resulting in the reduced viability of the bacilli. We have found that when the IL-1 receptor is absent in the naïve macrophage population that the co-culture antimycobacterial effect is abrogated, suggesting that IL-1 released by the infected dying macrophage is critical for naïve macrophages to respond in a way that results in the decrease in mycobacterial viability. The signaling between the two cell population ultimately converges on activation of iNOS in the infected cell however ROS appears not to be involved.

APA, Harvard, Vancouver, ISO, and other styles

25

St, Pierre Christine A. "Endocytosis, Phagocytosis, and Innate Immune Responses: A Dissertation." eScholarship@UMMS, 2010. https://escholarship.umassmed.edu/gsbs_diss/488.

Full text

Abstract:

In this dissertation, the roles of endocytosis and phagocytosis pathways in a variety of clinically relevant scenarios were examined. These scenarios include antibody-mediated internalization of cell surface proteins, titanium wear-particle uptake in failed joint replacements, and polymeric microparticle uptake and immune responses for drug delivery or adjuvant use. The use of antibodies specific for cell surface proteins has become a popular method to deliver therapeutics to target cells. As such, it is imperative to fully understand the ability of antibodies to mediate internalization and endosomal trafficking of the surface protein that it recognizes, so that drug delivery can be optimized. By comparing the internalization and endosomal localization of two different antibody-bound proteins, the transferrin receptor (TfR) and rabies G, we have found that there is a specific antibody-mediated internalization pathway that occurs when an antibody binds to a cell surface protein. Interestingly, the internalization pathway induced by antibody binding is different than that seen with recycling receptor internalization after ligand binding. This may have broad implications for the future development of antibody-based therapeutics. Joint replacement failure is a major clinical problem. Studies have indicated that a large amount of metal and polyethylene wear debris is found in the synovial membrane and tissue surrounding failed replacements. Through examination of the immune response following uptake of titanium particles, our results suggest that titanium wear-particle induced inflammation and subsequent joint replacement failure may be due to activation of the NLRP3 inflammasome, leading to increased IL-1ß secretion and IL-1 associated signaling. These findings introduce IL-1 as a target for potential therapeutics for patients exhibiting significant inflammation. Polymeric microparticles have been widely used in a variety of therapeutic applications, including drug delivery and vaccine adjuvants. It is essential to understand the ability of such particles to either activate or inhibit an immune response following uptake. Through comparison of particles with varying surface morphology, we have determined that particles with regions of high surface curvature (budding) are more immunogenic than particles with low surface curvature (spherical). Budding particles were more rapidly phagocytosed and induced higher levels of the inflammasome-associated cytokine, IL-1ß, when exposed to mouse macrophages. Additionally, budding particles induced a more rapid neutrophil response in vivo, when compared to spherical particles. These findings have broad implications for the development of future targeting vehicles for delivery of vaccines, drugs, proteins, and siRNA therapeutics.

APA, Harvard, Vancouver, ISO, and other styles

26

Raval, Forum M. "Innate Signaling Pathways in the Maintenance of Serological Memory: A Dissertation." eScholarship@UMMS, 2012. https://escholarship.umassmed.edu/gsbs_diss/635.

Full text

Abstract:

Long-term antiviral antibody responses provide protection from re-infection and recurrence of persistent viruses. Using a polyomavirus (PyV) mouse model, our lab has shown that MyD88-deficient mice generate low levels of virus-specific IgG after the acute phase of infection and that these IgG responses have a skewed isotype distribution with low levels of IgG2a/c. Moreover MyD88-deficient mice have reduced numbers of long-lived plasma cells in the bone marrow. These studies suggest an important role of MyD88-mediated signaling in long-term antiviral responses. Our lab has shown that T cell-deficient mice can also maintain long-term virus-specific IgG responses following PyV infection. The goal of this thesis is to evaluate the role of innate signaling pathways in maintaining serological memory to persistent virus infection and to elaborate on how long-term antiviral responses can be maintained in an immunocompetent or partially immune compromised, T cell-deficient host. Regarding T cell-dependent B cell responses, I set out to investigate the upstream and downstream components of the MyD88-mediated pathways required for normal antibody isotype and long-term humoral responses. IgG2a is a predominant immunoglobulin isotype in most virus infections. Wild type mice, in response to PyV infection, primarily induce antiviral IgG2a with some IgG1. MyD88-deficient mice in response to PyV infection display attenuated levels of virus-specific IgG2a, but normal levels of IgG1. Using Unc93B1 mutant mice (3d mice), which are defective in TLRs 3, 7 and 9 signaling, I show that 3d mice also generated low levels of virus-specific IgG2a following PyV infection. Studies in individual TLR3-/-, TLR7-/- or TLR9-/- mice displayed PyV-specific IgG2a responses similar to wild type responses. TLR7 and TLR9 double deficient mice generated similar skewed antibody isotype responses, where virus-specific IgG2a was reduced compared to wild type mice. This shows that TLR7 and TLR9-MyD88 mediated pathways are important in regulating IgG2a responses during a PyV infection. To investigate what components downstream of MyD88 are involved in mediating IgG2a responses, I worked with IRF5-deficient mice. IRF5 is a transcription factor that is activated upon stimulation of TLR7 or TLR9-MyD88-mediated pathways. Moreover, IRF5-deficient mice cannot generate autoantibodies specifically of the IgG2a isotype in a mouse lupus model, suggesting that IRF5 plays an important function in mediating class switching to IgG2a. In vitro studies where IRF5-/- B cells were stimulated with TLR7 or TLR9 ligands also generated low levels of γ2a germ-line transcripts, suggesting a B cell-intrinsic role for IRF5 in regulating γ2a germ-line transcription. PyV infection of IRF5-deficient mice resulted in similar skewed isotypes as observed in MyD88-deficient and 3d mice. To investigate a B cell-intrinsic role for IRF5 in regulating IgG2a responses in vivo upon PyV infection, I transferred IRF5-/- B cells and WT T cells into RAG KO mice prior to infection and compared the responses of these mice with mice reconstituted with wild type B6 B and T cells. Diminished numbers of IgG2a+ B cells and reduced levels of virus-specific IgG in mice reconstituted with IRF5-/- B cells were seen compared to mice reconstituted with wild type B cells. Regarding the defect in long-term IgG production in MyD88-/- mice upon PyV infection, I conducted studies in IRF5-/-, 3d, single TLR3-/-, TLR7-/-, TLR9-/- and TLR7/9 double deficient mice. These studies reveal an important and redundant role for TLR7- and TLR9-MyD88 signaling in maintaining long-term anti-PyV IgG responses. To determine how MyD88 signaling affects the generation of long-lived plasma cells and memory B cells, I investigated germinal center (GC) responses in MyD88-deficient mice. A defect in GC B cell numbers is observed in MyD88-deficient mice after the acute phase of infection. The GC reaction is essential for the generation and maintenance of long-lived plasma cells and memory B cells. T follicular helper (TFH) cells are absolutely required to generate normal GC. l found reduced numbers of TFH cells in MyD88-deficient mice. Lower numbers of T FH cells suggests that poor T cell help may contribute to the diminished number of GC B cells. However, interaction with B cells is required for the formation of fully differentiated TFH cells. Along with B cell function, MyD88 signaling can affect T cell and dendritic cell function as well. Thus, it is not clear at this point whether the requirement for intact MyD88 signaling for the formation and maintenance of long-term B cell populations is completely B cell-intrinsic. Some viruses can induce T cell-independent B cell responses, perhaps due to their complex arrays of repetitive antigenic epitopes on virions, coupled with the induction of innate cytokines. Nevertheless, T cell help is usually necessary for generating long-term antibody responses in the form of long-lived plasma cells and memory B cells. In contrast, our lab has found that T cell-deficient mice infected with PyV develop long-lasting, protective antiviral IgG responses. I questioned whether these mice could generate TI B cell memory cells or long-lived plasma cells. I show that long-lasting anti-PyV antibody in T cell-deficient mice was not due to the presence of long-lived plasma cells or memory B cell responses. TCRβδ deficient mice, which lack both CD4 and CD8 T cells, had ~10 a times higher virus load persisting in various organs. Therefore, I hypothesized that the high level of persistent PyV antigen, in completely T cell-deficient mice, may activate naïve B cell populations continuously, thereby maintaining the long-lasting IgG responses. Prior to PyV infection, T cell-deficient mice received wild type CD8 T cells, which reduced PyV loads, and this was associated with decreased levels of antiviral serum IgG over time. As in TCRβδ deficient mice, high PyV loads were detected in the bone marrow, which is the site for B cell lymphopoiesis, I questioned how B cells develop in the presence of PyV antigen and still stay responsive to PyV, generating long-term antiviral IgG responses in the periphery. Studies have shown that self-antigens that trigger both B cell receptor signaling and TLR-MyD88 signaling pathways in the bone marrow lead to the breaking of B cell tolerance and production of autoantibody in the periphery. Thus, we hypothesized that high PyV levels in the bone marrow signal through both B cell-receptors and TLRs, allowing continuous antiviral antibody production by B cells. Using mice that are deficient in T cells and MyD88 signaling, I found that PyV-specific TI IgG levels gradually decreased, supporting this hypothesis. Thus, high PyV loads and innate signaling together can break B cell tolerance. During a persistent virus infection this can result in sustaining long-term protective T cell-independent IgG responses.

APA, Harvard, Vancouver, ISO, and other styles

27

Kamar, Rita. "Mécanismes de résistance aux peptides antimicrobiens chez Bacillus thuringiensis : rôle de dltX dans la D-alanylation des acides téichoïques." Electronic Thesis or Diss., Paris, AgroParisTech, 2014. http://www.theses.fr/2014AGPT0029.

Full text

Abstract:

Le groupe Bacillus cereus est très hétérogène du point de vue toxicité et il est difficile de prédire le potentiel pathogène d'une souche. Dans ce travail, nous avons étudié les différents phénotypes de colonisation/adaptation à l'hôte, et analysé la corrélation entre ces phénotypes et les maladies humaines, pour une collection de souches représentatives de la diversité pathologique de B. cereus chez l'homme. L'analyse statistique a révélé des corrélations entre plusieurs phénotypes, et une analyse en composante principale a permis de regrouper les souches en deux sous-populations distinctes. Notre étude a ainsi permis de montrer qu'un ensemble de caractères phénotypiques liés au pouvoir pathogène permet de discriminer les souches présentant un historique en maladies infectieuses des souches sans historique. Nous pensons que ces résultats faciliteront l'identification d'un phénotype ou d’une combinaison de phénotypes qui pourraient être utilisés dans le développement de stratégies de prévention des infections par B. cereus. Le résultat de cette étude suggère que B. cereus n'est pas exclusivement un pathogène opportuniste et pourrait plutôt être considéré comme un véritable agent pathogène en soi.Cependant, la virulence est un phénomène multifactoriel impliquant de nombreux facteurs du côté de l'hôte ainsi que de celui de l'agent pathogène envahisseur. Les peptides antimicrobiens (PAMs) cationiques constituent les principales molécules effectrices de l’immunité innée. La résistance des microorganismes vis à vis de ces composés est donc nécessaire pour qu’ils puissent se développer dans l’hôte et exercer leur pouvoir pathogène. Par conséquent, de nombreuses bactéries pathogènes ont développé des stratégies de résistance impliquant la réduction des charges négatives de l’enveloppe bactérienne, réduisant ainsi l'interaction et la fixation de ces PAMs. L'incorporation de résidus D-alanine aux acides téichoïques (ATs) représente l'un des mécanismes les plus courants de résistance bactérienne qui dépendent de telles modifications. Ce processus de D-alanylation est accompli par les produits des gènes de l’opéron dlt. Celui-ci contient cinq gènes dltXABCD dont les séquences sont très conservées dans la quasi-totalité des bactéries à Gram-positif. La première ORF, dltX, code pour une protéine dont la fonction est inconnue. Le but de la seconde partie de ce travail était donc de déterminer si cette protéine est impliquée dans le processus de D-alanylation chez Bacillus thuringiensis. Pour cela, nous avons procédé à une délétion en phase du gène dltX, qui n’affecte pas l’expression des autres gènes de l'opéron. Les caractéristiques de croissance du mutant dltX et celles de la souche de type sauvage se sont avérées similaires in vitro. Cependant la délétion de dltX affecte considérablement la résistance de B. thuringiensis aux PAMs et atténue significativement sa virulence chez deux espèces d’insectes: Galleria mellonella et Drosophila melanogaster. En outre, une analyse HPLC montre que la paroie du mutant dltX est dépourvue de D-alanine, et la mesure de la mobilité électrophorétique indique que cette absence de D-alanylation est associée à un changement de la charge globale à la surface bactérienne. Des expériences de microscopie électronique à balayage montrent aussi des modifications morphologiques du mutant dltX, ce qui suggère que l'absence de D-alanine affecte également la structure de la paroi cellulaire. Nos résultats montrent que DltX est essentiel pour l'incorporation de la D-alanine aux acides téichoïques. Par ailleurs nous avons également démontré que dltX n’affecte pas l’expression de l’opéron dlt. Par conséquent nos résultats indiquent clairement que DltX joue un rôle direct dans la résistance aux PAMs, contribuant ainsi à la survie et la virulence de B. thuringiensis chez les insectes. Ce travail est le premier qui étudie la participation de dltX dans la D-alanylation des ATs
The Bacillus cereus pathogenic spectrum ranges from strains used as probiotics to human-lethal strains (causing gastrointestinal disorders or local and severe systemic infections). However, prediction of the pathogenic potential of a strain remains difficult. In this work, we studied different phenotypes of colonization/adaptation to the host (adhesion, cytotoxicity, motility, biofilm formation, resistance to antimicrobial peptides and virulence), analyzing the correlation between these phenotypes and human disease in a collection of strains representative of the pathological diversity of B. cereus in humans. Statistical analysis revealed correlations between several phenotypes, and principal component analysis grouped the strains into two distinct subpopulations. We found that strains differed in pathogenic potential and that virulent strains could be differentiated from non-pathogenic strains. We believe that these findings will facilitate the identification of a phenotype or a combination of phenotypes of potential use in the development of effective prevention strategies and/or diagnostic tools for distinguishing between pathogenic and non-pathogenic B. cereus strains. Our result suggests that B. cereus is not an exclusively opportunistic pathogen and could instead be considered a real pathogen per se. However, virulence is a multifactorial phenomenon involving numerous factors from both the host and the invading pathogen. As cationic antimicrobial peptides (CAMPs) are the primary defense mechanism against invading organisms, virulence of pathogens like B. cereus requires bacterial resistance to such compounds. Consequently, many pathogens have developed resistance strategies involving the reduction of the cell envelope negative charge, thereby influencing the binding and interaction of these CAMPs. The incorporation of Dalanine esters into teichoic acids (TAs) represents one of the most common bacterial resistance mechanisms that depend on such charge modifications. That D-alanylation process is accomplished by the gene products of an operon containing five genes, dltXABCD, that is highly conserved among nearly all gram-positive bacteria. The small first ORF, dltX, encodes a protein of unknown function. The aim of the other part of this work was then to establish whether this protein is involved in the D-alanylation process in Bacillus thuringiensis. We therefore constructed an in frame deletion mutant of dltX, without affecting the expression of the other genes of the operon. The growth characteristics of the dltX mutant and those of the wild type strain were similar under standard in vitro conditions. However disruption of dltX drastically impaired the resistance of B. thuringiensis to CAMPs and significantly attenuated its virulence in two insect species: Galleria mellonella and Drosophila melanogaster. Moreover, HPLC studies showed the dltX mutant was devoid of D-alanine, and electrophoretic mobility measurements indicated that the cells carried a higher negative surface charge. Scanning electron microscopy experiments showed morphological alterations of these mutant bacteria, suggesting that depletion of D-alanine from TAs affects cell wall structure. Our findings suggest that DltX is essential for the incorporation of D-alanyl esters into teichoic acids. Moreover, we found that DltX does not affect the expression of the operon. We therefore conclude that dltX is translated into a functional protein that plays a direct biosynthetic, transport or addresser role. Altogether, our results clearly indicate that DltX plays a direct role in the resistance to CAMPs, thus contributing to the survival and virulence of B. thuringiensis in insects. The exact function of that protein remains to be elucidated. This work is the first report examining the involvement of dltX in the Dalanylation of TAs

APA, Harvard, Vancouver, ISO, and other styles

28

Welsby, Iain. "PARP12, a novel interferon stimulated gene potentially involved in the control of protein translation and innate immunity." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209714.

Full text

Abstract:

Poly(ADP-ribose) polymerases belong to a family of proteins with 17 members in human beings. PARP1, the founding member of the family is a protein that synthesizes linear or branched polymers of ADP-ribose on itself or on target proteins. Different members of this family, that do not all possess ADP-ribosyl polymerase activity, are involved in the regulation of various cellular mechanisms. Some members of the family are particularly involved in the positive or negative control of the immune response. PARP1 is a key player in the regulation of inflammation, through its positive control of cell death and of proinflammatory cytokine production. On the other hand, the tankyrases (PARP5a and PARP5b) and PARP14 seem to regulate inflammatory responses in a negative fashion. PARP12 is a poorly characterized member of the family, whose expression is greatly increase following stimulation with type-I interferons, cytokines mainly involved in antiviral defences.

PARP12 is a protein that possesses three main domains: A putative RNA binding N-terminal domain composed of tandem CCCH zinc-fingers, a central WWE domain and a C-terminal PARP catalytic domain. In this work, we have shown that the expression of PARP12 is strictly-dependent on type-I interferons, that it possesses ADP-ribosyl transferase activity and that in can regulate the translation of messenger RNA into proteins. PARP12 can be found in stress granules, sites of storage of untranslated mRNAs, and is capable of directly inhibiting the translation of a reporter mRNA when tethered to it, in a manner dependent on its catalytic activity. Furthermore overexpression of wild-type PARP12, in contrast to overexpression of a mutant with no detectable catalytic activity (PARP12-G575W), leads to a general arrest of most cellular translation.

On the other hand, we have shown that PARP12 can activate the transcription of genes under the control of an NFκB-dependent promoter, especially when its zinc-fingers are deleted or mutated (PARP12ΔZnF). PARP12ΔZnF is located in structures that can enclose TRIF, RIP1, NEMO, p62/SQSTM1 and ubiquitin. These proteins have all possess an important role in the activation of NFκB signalling cascades. Moreover, we have shown that endogenous PARP12 is situated in ALIS (Aggresome-Like Induced Structures) in LPS-stimulated macrophages. These structures have a possible role in the presentation of antigens on class I major histocompatibility complexes, implying that PARP12 may be involved in the regulation of antigen presentation.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO, and other styles

29

Filewod, Niall Christopher Jack. "Immunomodulatory effects of LL-37 in the epithelia." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/927.

Full text

Abstract:

The cationic host defence peptide LL-37 is an immunomodulatory agent that plays an important role in epithelial innate immunity. Previously, concentrations of LL-37 thought to represent levels present during inflammation have been shown to elicit the production of cytokines and chemokines by epithelial cells. To investigate the potential of lower concentrations of LL-37 to alter epithelial cell responses, normal primary keratinocytes and bronchial epithelial cells were treated with pro-inflammatory stimuli in the presence or absence of 1 – 3 μg/ml LL-37. Low, physiologically relevant concentrations of LL-37 synergistically increased IL-8 production by both proliferating and differentiated keratinocytes in response to IL-1β and the TLR5 agonist flagellin, and synergistically increased IL-8 production by bronchial epithelial cells in response to IL-1β, flagellin, and the TLR2/1 agonist PAM3CSK4. Treatment of bronchial epithelial cells with LL-37 and the TLR3 agonist poly(I:C) resulted in synergistic increases in IL-8 release and cytotoxicity. The synergistic increase in IL-8 production observed when keratinocytes were co-stimulated with flagellin and LL-37 was suppressed by pretreatment with inhibitors of Src-family kinase signalling and NF-κB translocation. These data suggest that low concentrations of LL-37 may alter epithelial responses to microbes in vivo. Microarray analysis of keratinocyte transcriptional responses after LL-37 treatment suggest that LL-37 may alter the expression of growth factors and a number of genes important to innate immune responses. LL-37 may thus play a more important role than previously suspected in the regulation of epithelial inflammation; an improved understanding of the mechanisms by which LL-37 alters chemokine responses could lead to the development of novel anti-infective and anti-inflammatory therapeutics.

APA, Harvard, Vancouver, ISO, and other styles

30

Junell, Anna. "Regulation of antimicrobial peptide gene expression in Drosophila melanogaster : involvement of POU and NF-kB/Rel factors in innate immunity /." Stockholm : Department of Molecular Biology and Functional Genomics, Stockholm University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6614.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Masson, Florent. "Régulations immunitaires et cellulaires impliquées dans le maintien et le contrôle des bactéries endosymbiotiques du charançon des céréales du genre Sitophilus spp." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0116/document.

Full text

Abstract:

Plusieurs insectes se développant dans des milieux nutritionnellement déficients vivent en symbiose durable avec des bactéries intracellulaires (endosymbiotes) qui complémentent leur alimentation et améliorent leur pouvoir adaptatif. Alors que ces associations ont été largement étudiées sur les plans physiologiques et évolutifs, peu de travaux se sont consacrés à l’étude des mécanismes impliqués dans la tolérance et le contrôle des endosymbiotes par l’hôte. L’objectif de cette thèse est d’étudier, chez les charançons des céréales du genre Sitophilus, les particularités moléculaires et immunitaires du bactériome, un organe que l’insecte développe pour héberger les symbiotes et les isoler de sa réponse immunitaire systémique. Le bactériome du charançon exprime une réponse immunitaire modulée : des études transcriptomiques ont montré que les effecteurs de l’immunité sont peu exprimés dans cet organe, à l’exception d’un gène codant un peptide antimicrobien, la coléoptéricine A. Cette dernière interagit avec les endosymbiotes et participe à leur confinement intracellulaire. Dans une première partie, j’ai montré avec une approche d’interférence à l’ARN que l’expression du gène colA serait contrôlée par un système original qui impliquerait les gènes relish et tollip. Cette régulation « interne » au bactériome semble assurer le maintien des endosymbiotes et l’homéostasie de l’organe. Afin de comprendre comment le bactériome répond à une infection par les bactéries exogènes, j’ai suivi par RT-qPCR l’expression de gènes effecteurs de l’immunité dans le bactériome après injection systémique de bactéries à Gram positif ou négatif. Ceci a mis en évidence une réponse « externe », induite en cas d’infection, et qui aurait un rôle de protection des endosymbiotes contre les bactéries exogènes. Enfin, je me suis consacré à l’étude des changements de régulation accompagnant le passage du stade larvaire au stade adulte, marqué par une symbiose très dynamique. Le nombre d’endosymbiotes augmente fortement pendant les premiers jours de vie imaginale, puis diminue jusqu’à leur élimination complète par recyclage autophagique. Une analyse RNAseq a permis d’identifier les voies de signalisation dont l’activité accompagne cette dynamique. Une approche de RT-qPCR a également montré que l’immunité du bactériome est maintenue à un faible niveau d’activation pendant tout le processus de recyclage. Ce travail montre qu’au cours de leur évolution, les insectes ont sélectionné plusieurs stratégies pour assurer le maintien et l’ajustement de leur charge endosymbiotique en fonction de leurs besoins physiologiques : une signalisation immunitaire assurerait le confinement intracellulaire des endosymbiotes, et un ensemble de processus cellulaires incluant l’apoptose et l’autophagie semble être en associé aux voies métaboliques pour assurer le contrôle de la dynamique bactérienne et garantir le compromis bénéfice/coût de la symbiose
Many insect species living on nutritionally unbalanced media depend on intracellular mutualistic bacteria, called obligatory endosymbionts, for their development and reproduction. Endosymbionts are housed in specialized host cells called bacteriocytes, that group together to form the bacteriome organ. Although such associations have been widely investigated on a physiological and evolutionary point of view, little is known about the mechanisms involved in the tolerance and the control of endosymbionts by the host. This work aims at deciphering the molecular and immune specificities of the bacteriome using the model system Sitophilus oryzae, the cereal weevil, and its obligate endosymbiont Sodalis pierantonius. The weevil bacteriome expresses a modulated immune response: transcriptomic studies showed that immune effector genes were lowly expressed despite the massive bacterial presence, with the exception of colA, a gene encoding for Coleoptericin A, an antimicrobial peptide. Coleoptericin A interacts with endosymbionts and participates in their intracellular seclusion. In a first chapter, I used RNA interference to demonstrate that colA gene expression may be controlled by an original system involving the genes relish and tollip. This “internal” regulation for endosymbiont control seems to maintain bacteriome homeostasis. In a second chapter, in order to understand how the bacteriome responds to an infection by exogenous bacteria, I followed up by RT-qPCR the expression of immune effector genes in the bacteriome after injection of Gram positive and Gram negative bacteria. This highlighted an “external” immune response, inducible upon infections, which may enable endosymbiont protection against exogenous intruders. In a third and last chapter, I focused on the regulation changes that accompany the switch from the larval stage to the imaginal stage, the latter being characterized by a very dynamic symbiosis. Endosymbiont load drastically increases during the first days of imaginal life, then rapidly decreases until complete elimination of the bacteria by autophagic recycling. RNAseq analysis allowed the identification of signaling pathways linked to this dynamic. A complementary RT-qPCR approach also showed that bacteriome immunity was laid low during the whole recycling process. This work shows that several strategies have been selected during host-symbiont coevolution to ensure the maintenance of the endosymbionts and the adjustment of their population depending on the insects physiological needs: immunity allows the intracellular seclusion in the bacteriocytes, and cell processes including autophagy and apoptosis are associated to metabolic pathways to control the endosymbiotic dynamics and secure the cost and benefit trade-off of symbiosis

APA, Harvard, Vancouver, ISO, and other styles

32

Winkle, Sean M., Andrea L. Throop, and Melissa M. Herbst-Kralovetz. "IL-36γ Augments Host Defense and Immune Responses in Human Female Reproductive Tract Epithelial Cells." FRONTIERS MEDIA SA, 2016. http://hdl.handle.net/10150/617371.

Full text

Abstract:

IL-36 gamma is a proinflamatory cytokine which belongs to the IL-1 family of cytokines. It is expressed in the skin and by epithelial cells (ECs) lining lung and gut tissue. We used human 3-D organotypic cells, that recapitulate either in vivo human vaginal or cervical tissue, to explore the possible role of IL-36 gamma in host defense against pathogens in the human female reproductive tract (FRT). EC were exposed to compounds derived from virus or bacterial sources and induction and regulation of IL-36 gamma and its receptor was determined. Polyinosinic-polycytidylic acid (poly I:C), flagellin, and synthetic lipoprotein (FSL-1) significantly induced expression of IL-36 gamma in a dose-dependent manner, and appeared to be TLR-dependent. Recombinant IL-36 gamma treatment resulted in self amplification of IL-36 gamma and its receptor (IL-36R) via increased gene expression, and promoted other inflammatory signaling pathways. This is the first report to demonstrate that the IL-36 receptor and IL-36 gamma are present in the human FRT EC and that they are differentially induced by microbial products at this site. We conclude that IL-36 gamma is a driver for epithelial and immune activation following microbial insult and, as such, may play a critical role in host defense in the FRT.

APA, Harvard, Vancouver, ISO, and other styles

33

Paquet, Amélie. "Peptides de l’immunité innée (défensines et cathélicidines) : expression dans les contextes d’obésité et de diabète de type 2, et lien avec la régulation fonctionnelle des adipocytes médullaires et l’os." Electronic Thesis or Diss., Littoral, 2024. https://documents.univ-littoral.fr/access/content/group/50b76a52-4e4b-4ade-a198-f84bc4e1bc3c/BULCO/Th%C3%A8ses/MABLab/123427_PAQUET_2024_archivage.pdf.

Full text

Abstract:

L'obésité est un facteur de risque majeur de diabète de type 2 (DT2), favorisés par une inflammation systémique et une résistance à l'insuline. Ces pathologies métaboliques sont associées à une fragilité osseuse augmentant significativement le risque de fracture souvent sans modification de la masse osseuse. Elles s'accompagnent aussi d'un niveau de graisse dans la moelle osseuse (adiposité médullaire (AM)) anormalement élevé et suspectée de jouer un rôle délétère sur l'os. Cependant, les mécanismes responsables de l'accroissement de l'AM et ses conséquences sur l'os sont encore mal définis. Les défensines et la cathélicidine, des peptides antimicrobiens de l'immunité innée dont l'expression est modifiée dans l'obésité et le DT2, semblent influencer la différenciation ostéoblastique de cellules souches squelettiques (CSS). Cette thèse explore les relations entre l'expression du gène de la cathélicidine, la régulation de l'AM, et les altérations osseuses dans les contextes d'obésité et de DT2. La première partie de ce travail a évalué, dans des modèles murins d'obésité (basé sur un régime riche en lipides, High Fat Diet-HFD) et de DT2 (HFD associé à un traitement par streptozotocine-STZ), les relations entre l'expression de la cathélicidine murine (CRAMP : cathelicidin-related antimicrobial peptid), l'AM, la microarchitecture et la fragilité osseuse. Les souris C57BL/6J mâles soumises à un régime HFD développent une obésité hyperinsulinémique, caractérisée par un gain de poids, une hyperglycémie modérée, une intolérance au glucose et une insulino-résistance. Cette obésité a induit une réduction de l'épaisseur trabéculaire et corticale du tibia, associée à une expansion significative de l'AM, sans modification des taux circulants du peptide CRAMP malgré une baisse de l'expression de ses transcripts dans le tissu adipeux viscéral (TAV). Ces observations soulignent un effet de l'insuline sur l'accumulation des adipocytes médullaires (AdMeds). En revanche, le modèle HFD/STZ induit une hyperglycémie et une insulinopénie marquées, caractéristiques d'un DT2, limitant l'expansion des graisses périphériques et médullaires par rapport aux souris HFD. Ces souris diabétiques présentent une fragilité osseuse accrue, avec une réduction du nombre de trabécules de tibia et une baisse de rigidité de l'os cortical fémoral, associées à des taux réduits de CRAMP circulant. Cela suggèrent une corrélation entre la diminution de CRAMP circulant dans le DT2 et une qualité osseuse compromise à l'origine de la fragilité osseuse des souris diabétiques. Dans la deuxième partie de cette thèse, nous avons étudié in vitro l'expression du gène de la cathélicidine humaine (CAMP) dans les AdMeds différenciés à partir de CSS, et sa régulation par divers stimuli métaboliques. Pour la première fois, nous avons détecté l'expression des transcrits de CAMP dans les AdMeds dès le jour 3 de différenciation, avec une augmentation linéaire jusqu'à maturité des AdMeds au jour 21. En présence de fortes concentrations de glucose (11 ou 25 mM), le taux d'ARNm de CAMP est significativement réduit dans les AdMeds, ce qui corrobore la corrélation négative observée entre CRAMP circulant et la glycémie des souris diabétiques. En outre, le traitement des AdMeds différenciés avec du butyrate ou de l'oléate a entraîné une augmentation des ARNm de CAMP, tandis que le propionate a induit un effet inverse. Ces régulations suggèrent que les taux altérés d'acides gras libres dans les contextes d'obésité/DT2 ou de fragilité osseuse peuvent impacter la sécrétion de CAMP dans le plasma et la moelle osseuse. Ce travail de thèse suggère que l'expression systémique de CAMP pourrait constituer un marqueur immuno-métabolique de la fragilité osseuse associée au DT2. D'autres études sont nécessaires pour préciser les mécanismes régulant l'expression de la cathélicidine en contextes d'obésité et de DT2 et mieux comprendre son rôle dans la régulation de l'AM et de la qualité osseuse
Obesity is a major risk factor for developing type 2 diabetes (T2D), the diseases favoured by systemic inflammation and insulin resistance. These metabolic diseases are associated to bone fragility increasing significantly the risk of fracture, often without modification in bone mineral density. Obesity and T2D are also accompanied by an abnormal high level of fat in the bone marrow (bone marrow adiposity (BMA)) which is suspected to exert a deleterious effect on the bone. However, the underlying mechanisms increasing the BMA and its consequences on bone tissue are not fully understood. The defensins and the cathelicidin, the antimicrobial peptides of the innate immunity the expression of which is modified in obesity and T2D, seem to influence the osteoblastic differentiation of skeletal stem cells (SSC). This PhD thesis explores the relationships between the expression of the cathelicidin gene, the regulation of BMA, and the bone alterations in the context of obesity and T2D. The first part of this work evaluated, in murine models of obesity -based on High Fat Diet - HFD) and of T2D (induced by HFD combined with streptozotocin-STZ treatment), the relations between the expression of the murine cathelicidin (CRAMP : cathelicidin-related antimicrobial peptide), the BMA, and bone microarchitecture and fragility. C57BL/6J male mice fed with HFD have developed hyperinsulinemic obesity, characterized by weight gain, a moderate hyperglycaemia, an impaired glucose tolerance with an insulin resistance. This obesity induced decreased trabecular and cortical thickness of the tibia, associated with a significant expansion of BMA, without changes in the circulating levels of the CRAMP peptide despite a decreased expression of its transcripts in visceral adipose tissue (VAT). These findings highlight the role of insulin in the accumulation of bone marrow adipocytes (BMAds). In contrast, the HFD/STZ mice model induces a marked hyperghycemia and insulinopenia, features of T2D, limiting the expansion of both peripheral and marrow fat as compared to the HFD group. The HFD/STZ diabetic mice also exhibit increased bone fragility, as characterized by a reduction in the trabeculae number of the tibia and a decrease of cortical rigidity of the femur, associated with decreased of CRAMP circulating levels. These alterations suggest a correlation between declined serum levels of CRAMP with a compromised bone quality leading to the bone fragility in diabetic mice. In the second part of this thesis, we studied in vitro the expression of the human cathelicidin gene (CAMP) in BMAds differentiated from SSC, as well as its regulation in response to various metabolic stimuli. For the first time to our knowledge, this study detected the expression of CAMP transripts in BMAds as early as the third day of differentiation, with a gradual increase until mature adipocytes on day 21. Under high glucose concentration (11 or 25 mM), the mRNA levels of CAMP are significantly reduced in BMAds, thus corroborating the negative correlation observed between circulating CRAMP and glycaemia in diabetic mice. Furthermore, treatment of differentiated BMAds with butyrate or oleate led to an increase in CAMP transcripts, whereas propionate caused an opposite effect on CAMP expression in vitro. These regulations suggest that abnormal levels of free fatty acids in the contexts of obesity and T2D or of bone fragility, may have effects on plasma and bone marrow levels of CAMP. Although further studies are needed, this thesis work suggests that the systemic expression of CAMP could constitute an immune-metabolic marker of bone fragility related to T2D. Future research is essential to clarify the mechanisms regulating the cathelicidin expression and better understand its role in the regulation of BMA and bone quality in the contexts of obesity and T2D

APA, Harvard, Vancouver, ISO, and other styles

34

Rowe, Daniel C. "Analysis of Toll-Like Receptor 4 Signal Transduction and IRF3 Activation in the Innate Immune Response: A Dissertation." eScholarship@UMMS, 2006. https://escholarship.umassmed.edu/gsbs_diss/163.

Full text

Abstract:

Over the last decade, the innate immune system has been the subject of extensive research. Often overlooked by the robustness and specificity of the adaptive immune system, the innate immune system is proving to be just as complex. The identification of several families of pattern recognition receptors (PRRs) has revealed an ancient yet multifaceted system of proteins that are responsible for initiating host defense. A wide array of pathogens, from virus to bacteria, is detected using this assortment of receptors. One such family, the Toll-like receptors (TLRs), has been at the forefront of this research. To date, 10 TLRs have been described in the human genome. Activation of TLRs leads to the induction of immune-related genes that ultimately control the response of the host. However, the signaling pathways emanating from activated TLRs and other PRRs are not fully understood. In particular, the pathway leading to the activation of interferon regulatory factor 3 (IRF3), a transcription factor crucial for the induction of type I interferon, remains undefined. IRF3 activation occurs as the consequence of viral infection and through the activation of TLRs 3 and 4 by dsRNA and lipopolysaccharide (LPS), respectively. The focus of this research is to describe components of the IRF3 activation pathway, partly through the analysis of TLR signal transduction. IRF3 normally resides in the cytoplasm of cells. Upon infection with certain viruses and bacteria, IRF3 is activated though phosphorylation at its C-terminus. Phosphorylated IRF3 homodimerizes and associates with co-activators CBP-p300. After translocating to the nucleus, the activate IRF3 complex induces the activation of type 1 interferon and interferon related genes. Little is known about the pathways that lead to the activation of IRF3, especially the kinases involved. In this study we report that the non-canonical IкB kinase homologues, IкB kinase epsilon (IKKε) and TANK-binding kinase-1 (TBK1), which were previously implicated in NF-кB activation, are also essential components of the IRF3 signaling pathway. In particular, mouse embryonic fibroblasts from TBK1 deficient mice fail to activate IRF3 in response to both viral infection and stimulation with LPS or poly (IC), a dsRNA analog. Thus, both IKKε and TBK1 play a critical role in innate immunity and host defense. In addition to viral infection, IRF3 activation also occurs via the activation of TLR3 and 4. TLRs signal through a subfamily of Toll-IL-1-Resistance (TIR) domain containing adapter molecules. One such adapter, MyD88, is crucial for all TLRs, with the exception of TLR3. MyD88 participates in a signal transduction pathway culminating in the activation of the transcription factor NF-кB. Studies from MyD88-deficient mice reveal that both TLR3 and 4 still are capable of activating NF-кB, although with slightly delayed kinetics. Another aspect of the MyD88-independent signal transduction pathway is the activation of IRF3. A second TIR domain containing adapter molecule called Mal/Tirap was discovered and originally thought to mediate the MyD88-independent pathway. However, Mal-deficient mice were found to be defective in both TLR2 and 4 mediated NF-кB activation. We hypothesized that other TIR domain containing adapters could mediate this MyD88-independent pathway of TLR3 and 4 leading to the activation of IRF3. Two additional TIR adapters were discovered, TRIF and TRAM. TRIF was shown to mediate TLR3 signal transduction. In this study, we report that both TRIF and TRAM mediate the activation of the MyD88-independent pathway in response to LPS/TLR4 activation. Unlike any of the other known TIR domain containing adapters, TRAM appears to be restricted to the LPS/TLR4 activation pathway while TRIF plays a role in both TLR3 and TLR4 pathways leading to IRF3 target gene expression. Our studies revealed that TRAM could be acting upstream of TRIF in the LPS/TLR4 pathway. To this end, we sought to determine the localization of TRAM within the cell. We found that TRAM localizes to the plasma membrane. TRAM localization is the result of myristoylation since mutation of the predicted myristoylation site (G2A) resulted in the re-distribution of TRAM from the membrane into the cytoplasm. Reconstitution of TRAM-deficient macrophages with TRAM G2A is unable to rescue LPS/TLR4 signal transduction. Thus, myristoylation and membrane association of TRAM are critical for LPS/TLR4 signal transduction. The data generated in this dissertation extends our understanding of the signaling pathways of the innate immune system. Indeed, the molecules and pathways described herein could prove to be beneficial targets for ameliorating symptoms of disease, both autoimmune and pathogen-associated. Finally, the research described here will spur further insight into the complex signaling pathways of a once ignored arm of the immune system.

APA, Harvard, Vancouver, ISO, and other styles

35

Aggarwal, Kamna. "A View of the IMD Pathway from the RHIM." eScholarship@UMMS, 2010. https://escholarship.umassmed.edu/gsbs_diss/463.

Full text

Abstract:

Innate immunity is the first line of defense against invading pathogens. It functions to eliminate pathogens and also to control infections. The innate immune response is also important for the development of pathogen-specific adaptive immune responses. As a result, the study of innate immune signaling pathways is crucial for understanding the interactions between host and pathogen. Unlike mammals, insects lack a classical adaptive immune response and rely mostly on innate immune responses. Innate immune mechanisms have been widely studied in the fruit fly, Drosophila melanogaster. The genetic and molecular tools available in the Drosophila system make it an excellent model system for studying immunity. Furthermore, the innate immune signaling pathways used by Drosophila show strong homology to those of vertebrates making them ideal for studying these pathways. Drosophila immunity relies on cellular and humoral innate immune responses to fight pathogens. The hallmark of the Drosophilahumoral immune response is the rapid induction of antimicrobial peptide genes in the fat body. The production of these antimicrobial peptides is regulated by two immune signaling pathways-Toll and Immune Deficency (IMD) pathways. The Toll pathway responds to many Gram-positive bacterial and fungal infections , while the IMD pathway is potently activated by DAP-type peptidoglycan (PGN) from Gram-negative bacteria and certain Gram-positive bacteria. Two receptors, PGRP-LC and PGRP-LE, are able to recognize DAP-type PGN at the cell surface or in the cytosol, respectively, and trigger the IMD pathway. Upon binding DAP-type PGN, both PGRP-LC and PGRP-LE dimerize/ multimerize and signal to the downstream components of IMD pathway. It is unclear how the receptor activates its downstream components. My work has focused on understanding the molecular events that take place at the receptors following there activation. In these studies I have identified a common motif in the N-terminal domains of both the receptors, known as the RHIM-like domain. The RHIM-like domain is critical for signaling by either receptor, but the mechanism(s) involved remain unclear. IMD, a downstream component of the pathway, associates with both PGRP-LC and -LE but the interaction of PGRP-LC with IMD is not mediated through its RHIM-like domain. Also, mutations affecting the PGRP-LC RHIM-like motif are defective in all known downstream signaling events. However, the RHIM-like mutant receptors are capable of serving as a platform for the assembly of all known components of a receptor proximal signaling complex. These results suggest that another, unidentified component of the IMD signaling pathway may function to mediate interaction with the RHIM-like motif. I performed a yeast two-hybrid screen to identify proteins that might interact with the receptor PGRP-LC through its RHIM- like domain. With this approach, two new components of the IMD pathway were identified. The first component I characterized is called Rudra and it is a critical feedback inhibitor of peptidoglycan receptor signaling. The other factor is known as RYBP, it includes a highly conserved ubiquitin binding motif (NZF), and RNAi studies suggest it is a critical component of the IMD pathway. The identification and characterization of these two new components of the IMD pathway has provided a new insight into the molecular events that take place proximal to the receptor.

APA, Harvard, Vancouver, ISO, and other styles

36

Jiang, Zhaozhao. "Dissecting the Role of Innate Pattern Recognition Receptors and Interferon Regulatory Factor-5 in the Immune Response to Human Metapneumovirus and other Pathogens: A Dissertation." eScholarship@UMMS, 2010. https://escholarship.umassmed.edu/gsbs_diss/510.

Full text

Abstract:

The Innate immune system is the first line of defense against invading microbial pathogens. It is a fast-acting and non-antigen-specific defense system, which employs germline encoded surveillance systems capable of responding to a broad-spectrum of pathogens. The innate immune system involves a variety of immune cells, which express different profiles of surveillance or detection receptors. Upon sensing pathogens, these receptors trigger cell signalling to turn on transcription of inflammatory cytokines, chemokines, anti-microbial peptides and type I Interferons. These effectors have direct effects on the control of pathogen load and also activate the adaptive immune system, which is ultimately required to clear infections. The type I interferons (IFNs) are the principal cytokines strongly induced during infection with viruses and are required for direct control of viral replication and modulation of cells of the adaptive immune response. The signalling pathways induced in order to activate type I IFNs are dependent on the interferon regulatory factors (IRFs). Striving for survival, microbes have evolved various strategies to subvert/impair these critical defense molecules. In this thesis work, I have used Human Metapneumoviruses (HMPVs), a relatively newly described family of paramyxoviruses as model viruses to explore the role of pattern recognition receptors (PRRs) and the IRF family of transcription factors in the innate immune response. These studies revealed that the recognition of HMPV viral pathogen-associated molecular patterns (PAMPs) by immune cells is different in different cell types. Retinoic acid-inducible gene-I (RIG-I), a cytosolic RNA helicases senses HMPV-A1 virus for triggering type I IFN activation by detecting its 5’- triphosphate viral RNA in most human cells, including cell lines and primary monocytes. An exception to these findings was plasmacytoid dendritic cells (PDCs), where Toll-like receptor (TLR)-7 is the primary sensor involved in detecting HMPV viruses. By comparing the innate immune response to two HMPV strains, we found that these two closely related strains had very different immune stimulatory capabilities. HMPV-1A strain triggered type I IFNs in monocytes, PDCs and cells of epithelial origin. In contrast, a related strain, HMPV-B1 failed to trigger IFN responses in most cell types. Our studies suggested that the phosphoprotein (P) of HMPV-B1 could prevent the viral RNA from being detected by RIG-I, thus inhibiting the induction of type I IFN production in most cell type examined. This finding adds to our understanding of the mechanisms by which viruses are sensed by surveillance receptors and also unveils new means of viral evasion of host immune responses. Although IRFs are extensively studied for their role in regulating type I IFN activation, especially in TLR and RIG-I like receptor (RLR) signalling pathways upon viral infection, a clear understanding of how this family of transcription factors contributes to anti-viral immunity was lacking. Studies conducted as part of this thesis revealed that in addition to IRF3 and IRF7, which play a central role in anti-viral immunity downstream of most PRRs (e.g. TLRs, RLRs, DNA sensors), the related factor IRF5 was also an important component of innate anti-viral defenses. Using IRF5-deficient mice we studied in detail the role of IRF5 in coordinating antiviral defenses by examining its involvement in signalling downstream of TLRs. These studies led us to examine the role of IRF5 in the regulation of type I IFNs as well as inflammatory cytokines in different cell types. While most TLRs that induced IFNβ showed normal responses in IRF5-deficient mice, CpG-B-induced IFNβ production in CD11c+CDCs isolated from mouse spleen but not those generated in vitro from bone marrow required IRF5. This was in contrast to responses with lipopolysaccharide (LPS) or polyriboinosinic polyribocytidylic acid (polyIC), ligands for TLR4 and 3, respectively. Moreover, we found that in contrast to IRF3 and/or IRF7, IRF5 was important in coordinating the expression of inflammatory cytokines such as TNFα downstream of some TLRs. In addition to our studies to examine the requirement for IRF5 in TLR signaling, we also showed that muramyl peptide (MDP) from Mycobacterium tuberculosis (Mtb) could activate type I IFNs via IRF5. This was the first evidence linking IRF5 to a non-TLR-driven pathway. IRF5 activation in this case was downstream of a novel nucleotide-binding oligomerization domain containing (NOD)-2/receptor-interacting serine-threonine kinase (RIP)-2 signaling pathway. Collectively, the studies outlined in this thesis have assisted in providing a framework to understand the role of TLRs, RLRs and IRFs in the immune response to paramyxoviruses and have unveiled new mechanisms of activation of the IRFs as well as new mechanisms by which pathogens subvert or evade these important innate defense mechanisms.

APA, Harvard, Vancouver, ISO, and other styles

37

Paquette, Nicholas Paul. "Caspase Mediated Cleavage, IAP Binding, Ubiquitination and Kinase Activation : Defining the Molecular Mechanisms Required for Drosophila NF-кB Signaling: A Dissertation." eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/444.

Full text

Abstract:

Innate immunity is the first line of defense against invading pathogens. Vertebrate innate immunity provides both initial protection, and activates adaptive immune responses, including memory. As a result, the study of innate immune signaling is crucial for understanding the interactions between host and pathogen. Unlike mammals, the insect Drosophila melanogasterlack classical adaptive immunity, relying on innate immune signaling via the Toll and IMD pathways to detect and respond to invading pathogens. Once activated these pathways lead to the rapid and robust production of a variety of antimicrobial peptides. These peptides are secreted directly into the hemolymph and assist in clearance of the infection. The genetic and molecular tools available in the Drosophila system make it an excellent model system for studying immunity. Furthermore, the innate immune signaling pathways used by Drosophilashow strong homology to those of vertebrates making them ideal for the study of activation, regulation and mechanism. Currently a number of questions remain regarding the activation and regulation of both vertebrate and insect innate immune signaling. Over the past years many proteins have been implicated in mammalian and insect innate immune signaling pathways, however the mechanisms by which these proteins function remain largely undetermined. My work has focused on understanding the molecular mechanisms of innate immune activation in Drosophila. In these studies I have identified a number of novel protein/protein interactions which are vital for the activation and regulation of innate immune induction. This work shows that upon stimulation the Drosophila protein IMD is cleaved by the caspase-8 homologue DREDD. Cleaved IMD then binds the E3 ligase DIAP2 and promotes the K63-polyubiquitination of IMD and activation of downstream signaling. Furthermore the Yersinia pestis effector protein YopJ is able to inhibit the critical IMD pathway MAP3 kinase TAK1 by serine/threonine-acetylation of its activation loop. Lastly TAK1 signaling to the downstream Relish/NF-κB and JNK signaling pathways can be regulated by two isoforms of the TAB2 protein. This work elucidates the molecular mechanism of the IMD signaling pathway and suggests possible mechanisms of homologous mammalian systems, of which the molecular details remain unclear.

APA, Harvard, Vancouver, ISO, and other styles

38

Aslam, Rizwan. "Les peptides antimicrobiens dérivés de la chromogranine A et Staphylococcus aureus : de l'analyse de l'interaction hôte-pathogène au développement de revêtement de polymère antimicrobien." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01059511.

Full text

Abstract:

Les chromogranines (Cgs) sont une famille de protéines acides exprimées dans les granules des cellules neuroendocrines et immunitaires. Plusieurs peptides dérivés des Cgs présentent des activités antimicrobiennes. L'objectif de ma thèse est d'évaluer l'interaction hôte-pathogène et ensuite de développer un polymère antimicrobien avec insertion du peptide antimicrobien cateslytin (CTL).Dans une première partie, nous avons évalué l'aptitude de la leukotoxine LukE/D à induire la sécrétion des neutrophiles et rôle des protéases bactériennes à dégrader les peptides dérivés de la CgA. Les neutrophiles activés sécrètent de nombreux composés que nous avons identifiés. De plus, la dégradation des PAMs dérivés de la CgA par les protéases de S.aureus a été déterminée. Sur tous les PAMs testés, CTL est le seul qui tue S.aureus et résister à dégradation. Par ailleurs, CgA et CgB sont dégradés par la protéase Glu-C pour produire de nouveaux fragments sans activité antibactérienne, mais d'activité antifongique.Dans une deuxième partie, nous avons décidé de préparer un revêtement conjugué à CTL. CTL-C est utilisé pour préparer des films avec le dépôt alterné de CHI et HA-CTL-C. Par la suite nous avons synthétisé HAFITC-CTL-C and HAFITC pour analyser leur interaction. HAFITC-CTL-C est rapidement détectable dans le cytoplasme sans provoquer la lyse cellulaire. De plus, les films contenant CTL-C ne sont pas toxiques pour les fibroblastes gingivaux humains.En conclusion, CTL est le seul peptide antimicrobien dérivé de la CgA qui peut tuer S.aureus et résiste à la dégradation protéolytique, ce qui est de bon augure pour de nouvelles études visant à développer des biomatériaux antimcrobiens.

APA, Harvard, Vancouver, ISO, and other styles

39

Schramm, Frédéric. "Inflammation cutanée et borréliose de Lyme : étude in vitro des interactions entre les cellules résidentes de la peau et Borrelia." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00757050.

Full text

Abstract:

Nous avons étudié le rôle de l'immunité innée de la peau lors de la transmission des Borrelia (agent infectieux de la borréliose de Lyme) par son vecteur, une tique dure du genre Ixodes. Nous avons montré que la salive de tique et la protéine salivaire Salp15 inhibent la réaction inflammatoire (production de chimiokines et de peptides antimicrobiens) des kératinocytes induite par Borrelia. Cet effet anti- " alarmine " de la salive de tique contribue probablement à créer un environnement cutané local favorable à la transmission de Borrelia. Nous avons montré que Borrelia induit également au niveau des fibroblastes cutanés la transcription de nombreux gènes proinflammatoires. Nous avons observé un effet toxique direct de la salive de tique sur les fibroblastes cutanés : cet effet dose-dépendant est de nature protéique mais non lié à la protéine Salp15. Ces résultats indiquent que les fibroblastes jouent un rôle important dans l'inflammation cutanée induite par Borrelia.

APA, Harvard, Vancouver, ISO, and other styles

40

Stålhammar, Maria. "Neutrophil Chemotaxis and Respiratory Burst in Term and Preterm Newborn Infants." Doctoral thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305009.

Full text

Abstract:

Neutrophil activation is the most important initial immune defense against invading microbes in newborn infants. The reduced neutrophil migration and uncontrolled regulation of reactive oxygen species (ROS) production observed in neonates, could result in a diminished infectious response or in tissue damage. The aims were to study neutrophil chemotactic response towards IL-8 and fMLP in term neonates; to examine neutrophil receptor expression involved in adhesion, migration, phagocytosis and complement after stimulation with IL-8 and fMLP in term neonates; and to investigate neutrophil production of ROS, induced by PMA and E.coli, after preincubation with IL-8 and fMLP in term and preterm newborn infants. Comparisons were made to neutrophils from healthy adults. Chemotaxis was distinguished from randomly migrating neutrophils, and the neutrophil migration distance and the number of migrating neutrophils per distance was evaluated. Neutrophils were labeled with antibodies to cell surface antigens (CD11b, CD18, CD65, CD15S, CD162, CD44, CD35, CD88, CD181, CD182 and CD64) after stimulation with IL-8 and fMLP. After preincubation of neutrophils with fMLP or IL-8 and stimulation with PMA or E.coli, respiratory burst was detected. The same analyses were also made in preterm infants (median 25+3weeks GA; range 23+0–29+2) within 3 days postnatal age. Neutrophils from neonates exhibited different migratory and receptor responses to IL-8 and fMLP, with a diminished response towards IL-8 in term newborn infants in terms of reduced chemotaxis and modulation of receptors involved in adhesion, chemotaxis, complement and phagocytosis as compared to adults. fMLP reduced PMA- and E.coli-induced respiratory burst in neutrophils from term neonates and adults. The reduced respiratory burst by fMLP may be a mechanism for reducing the detrimental effects of uncontrolled inflammation. Although a similar burst reduction was observed in preterm infants born >25 weeks GA with fMLP, a diminished neutrophil respiratory burst modulation in very preterm infants cannot be excluded and requires further studies at different gestational and postnatal ages.

APA, Harvard, Vancouver, ISO, and other styles

41

Ahrens, S. "Extracellular actin in innate immunity." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1433762/.

Full text

Abstract:

The innate immune system is capable of responding to tissue injury by detecting the abnormal exposure of intracellular, often ubiquitously expressed, molecules referred to as damage-associated molecular patterns (DAMPs). DAMPs are normally sequestered inside healthy cells but become exposed to the extracellular environment upon loss of membrane integrity during cell death. Exposed DAMPs are then recognised by receptors of the innate immune system. One such DAMP receptor is DNGR-1 (CLEC9A), which is expressed on CD8+ DCs, a rare but specialised subset of DCs involved in regulating T cell responses. Loss of DNGR-1 on CD8+ DCs impairs cross-presentation of dead-cell associated antigens to CD8+ T-cells indicating that DNGR-1 couples DAMP recognition to the generation of cytotoxic T cell immune responses. Prior to the work presented in this thesis, the DAMP ligand for DNGR-1 had not been identified. Using a variety of experimental approaches, I demonstrated that this ligand corresponds to filamentous actin (F-actin), a component of the cytoskeleton of all cells. Given its extreme evolutionary conservation, abundance and ubiquitous expression, as well as its association with tissue damage in a range of inflammatory conditions, actin possesses ideal DAMP characteristics. Thus, I further hypothesised that actin may engage receptors other than DNGR-1 and act as a universal and evolutionarily ancient sign of cell damage that is more generally detected by metazoans as a means of inducing sterile inflammation and/or tissue repair. In order to test this hypothesis, I made use of the Drosophila melanogaster model system. I found that actin injection into flies stimulates strong activation of the stress-induced JAK/STAT pathway without triggering immune defence pathways. Given the conservation of innate defence mechanisms in invertebrates and vertebrates, it is tempting to speculate that understanding the recognition of actin in Drosophila melanogaster will provide useful insights into the induction of inflammation in mammals.

APA, Harvard, Vancouver, ISO, and other styles

42

Ramanathan, Balaji. "Innate immunity : receptors and effectors /." Search for this dissertation online, 2004. http://wwwlib.umi.com/cr/ksu/main.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

McAuley, Julie Louise. "MUC1 in innate and adaptive immunity /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19061.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Goritschnig, Sandra. "Protein modification in plant innate immunity." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/30887.

Full text

Abstract:

Plant diseases cause major crop losses worldwide. Crop protection strategies enhancing the plants' own defence mechanisms could be a sustainable solution to ensure future food supply. This thesis describes my research effort to better understand the innate defence mechanisms in plants. Specific resistance responses towards invading pathogens are mediated by Resistance (R) proteins. They recognize pathogen-derived molecules and activate signalling cascades, initiating physiological responses to limit pathogen spread in infected cells while minimizing harmful effects on the rest of the plant. We use the unique gain-of-function R gene snd as a tool to identify components of resistance signalling in Arabidopsis thaliana. In a screen for suppressors of snc7-mediated constitutive resistance, we identified a number of modifier of snd (mos) mutants. My thesis focuses on the identification and characterization of mos5 and mos8. Both mutations partially suppress sndassociated morphological phenotypes and revert susceptibility to virulent pathogens to wild type levels. mos5 contains a deletion in one of two ubiquitin activating enzyme genes in Arabidopsis. The mutation in mos5 lies in a putative binding domain, potentially disrupting interaction with downstream ubiquitin acceptors. The mos5 single mutant displays enhanced susceptibility to virulent bacteria, as well as to bacteria carrying the effector protease AvrRpt2, indicating a role of ubiquitination in both specific and basal resistance. A mutation in the mos5 homolog UBA2 does not affect resistance, however, a double mutant mos5 uba2 is lethal, indicating that the two genes are partially redundant. mos8 is allelic to enhanced response to abscisic acid 1 (eral), which encodes the beta subunit of protein farnesyltransferase. Mutations in the gene are known to affect development and abscisic acid signalling. mos8 displays enhanced susceptibility to virulent and avirulent pathogens and acts additively with NPR1. Defects in geranylgeranylation, a protein modification similar to farnesylation, do not affect resistance responses against virulent or avirulent pathogens. Taken together, my data reveals the importance of post-translational modification of yet to be identified regulatory proteins in plant innate immunity. Further research will aim at unravelling the mechanisms by which mos5 and mos8 affect resistance signalling.
Science, Faculty of
Botany, Department of
Graduate

APA, Harvard, Vancouver, ISO, and other styles

45

Linde, Annika. "Comparative studies on cardiac innate immunity." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/946.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Haghayeghi, Amirhossein. "Pellino function in «Drosophila» innate immunity." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86930.

Full text

Abstract:

The Toll pathway mediates innate immunity, the first line of defense against pathogens in vertebrates and invertebrates. In Drosophila the Toll pathway protects against Gram-positive bacteria and fungi by inducing antimicrobial peptides such as Drosomycin. Pellino is a highly conserved protein which biochemically interacts with Pelle/IRAK, a crucial kinase downstream of Toll. Here we report that the chemically induced Pellino 7T2 mutant does not affect Toll pathway function in early embryonic dorsoventral patterning, but it severely compromises induction of Drosomycin upon infection with Gram-positive Micrococcus luteus. In this study we identify Pellino as a novel component of Toll pathway-mediated innate immunity.
La transduction de signal initiée par Toll active l'immunité innée. Cet événement constitue la première ligne de défense contre des agents pathogènes chez les vertébrés et les invertébrés. Dans la Drosophile, la transduction de signal initiée par Toll protège contre les bactéries Gram-positives et les champignons en induisant la production de peptides antimicrobiens tels que Drosomycin. Pellino est une protéine hautement conservée qui interagit biochimiquement avec Pelle/IRAK, une kinase essentielle activée par Toll. Ici, nous reportons que Pellino 7T2, un mutant chimiquement induit, n'affecte pas la fonction de Toll durant l'établissement de la polarité dorsoventral dans les embryons précoces. Cependant, Pellino affecte l'induction de Drosomycin suite à une infection avec les bacteries Gram-positive Micrococcus luteus. Dans cette étude, nous reportons un nouveau rôle à Pellino, notamment, celui d'un élément de la voie de signal initiée par Toll qui impacte l'immunité innée.

APA, Harvard, Vancouver, ISO, and other styles

47

Truman, William Matthew Donald. "Signalling pathways underylying plant innate immunity." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429264.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Kiritsy, Michael C. "Functional Genomics of Mammalian Innate Immunity." eScholarship@UMMS, 2020. https://escholarship.umassmed.edu/gsbs_diss/1102.

Full text

Abstract:

The breadth of genetic diversity in the mammalian immune response stands out amongst the ubiquity of variation seen in the genome, evidence that microbial infections have been a major driver of evolution. As technology has facilitated an understanding of the etiology of immunological diversity, so too has it enabled the assessment of its varied functions. Functional genomics, with its ability to assess both cause and effect, has revolutionized our understanding of fundamental biological phenomena and recalibrated our hypotheses. We build upon the model of host immunity established by rare genetic variants that are causative of immunodeficiencies, but that incompletely consider the complexities of the genome. To expand our understanding, we performed a series of forward genetic screens to identify regulators of distinct functions of the innate immune system. Our studies discovered genes with novel functions in antigen presentation and immunoregulation, including several involved in central metabolism. Studies in macrophages and dendritic cells identified mitochondrial respiration as a positive regulator of the interferon-gamma response, and cells incapable of respiration failed to activate T cells. Notably, human mutations in several of these genes are responsible for immune dysfunction. In summary, this work uses new methods in genetic engineering to systematically assess the regulation of innate immunity. Our results suggest that variation in these regulatory pathways is likely to alter immunity in states of health and disease. Thus, our work validates a new approach to identify candidate genes relevant to immune dysfunction.

APA, Harvard, Vancouver, ISO, and other styles

49

Dayel, Iman Bin. "Probiotics, innate immunity & ageing (PRIMAGE)." Thesis, University of Reading, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.658873.

Full text

Abstract:

Introduction: Ageing has often been associated with a marked reduction in numbers of bifidobacteria and an increase in numbers of clostridia. In addition, ageing is associated with alterations in immunity and poor response to vaccination. Pre- and probiotics are suggested to restore the gut micro flora ecosystem and modulate immune function. The current study evaluated the influence of a novel probiotic, Bifidobacterium longum by. infantis CCUG 52486, with a potential prebiotic (glucooligosaccharide; GIOS) on the gut microbiota composition and on innate immunity in young (18-35y) and older (60-85y) subjects undergoing influenza vaccination.

APA, Harvard, Vancouver, ISO, and other styles

50

Vajhi, Jafari N. "Defining innate immunity to Clostridium difficile." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1347959/.

Full text

Abstract:

Clostridium difficile is a spore-forming anaerobic bacillus and a leading cause of nosocomial diarrhoea. C. difficile infection occurs often following antibiotic treatment leading to alteration of the gut microbiota enabling C. difficile to thrive and cause a range of symptoms from asymptomatic carriage to severe diarrhoea, PMC and death. C. difficile virulence is associated with production of toxins (A, B and CDT) nonetheless this bacteria harbours an array of other virulence factors. In the present study, C. difficile-mediated innate immunity response was investigated utilising four different strains including: R20291 a hypervirulent strain (A+B+, CDT+), 630 a fully sequenced strain (A+B+) and variant strains M68 and CF5 (A-B+). Initial studies showed that all strains shared comparable survival and sporulation capacity whereas strains R20291, M68, and CF5 achieved similar growth kinetics. R20291 showed significant adherence to IEC and was the most potent strain. 630 and M68 were found to be as cytotoxic leading to significant cell apoptosis, IEC TJ disruption and increased paracellular permeability. In contrast, CF5 had the least effect on cell death and IEC barrier integrity. Although all four strains induced antimicrobial immunity and pro-inflammatory cytokines, CF5 mediated the least pro-inflammatory responses. Similar findings were also found in an ex vivo model of infection utilising human colonic explants. C. difficile strains up-regulated murine DC maturation markers leading to a predominant anti-inflammatory IL-10 secretion, which is known to suppress IL-12 and IL-23 induction although C. difficile may generate a cytokine milieu that favours dual Th1/Th17 immunity. C. difficile toxin mutant strains showed DC activation and cytokine production in a toxin-dependent and independent manner and triggered an ASC-containing inflammasome causing the activation of caspase-1 and release of mature IL-1β. These findings indicated that multiple bacterial factors may play a role in initiating host innate immune responses to C. difficile infection.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Peptides of innate immunity'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles