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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Invasion of Polarized Epithelial Cells by Legionella pneumophila: an Opportunistic Strategy

Tabatabaeiyazdi, Zohreh 27 November 2012 (has links)
Legionella pneumophila (Lp.), the causative agent of Legionnaires’ disease, has been well known for infecting and replicating inside airway macrophages. Previous results from our laboratory indicated that Lp. attaches to non-polarized lung epithelial cells by binding and activating E-cadherin and β1-integrin. However, in the polarized alveolar epithelia these receptors are segregated from the apical cell surface by tight junctions (TJs). Our results showed that Lp. behaves as an opportunistic pathogen that efficiently targets disrupted, but not integrated epithelial cell monolayer. In such conditions, Lp. can reach its host-cell receptors and consequently invade and replicate intracellularly, producing large amount of bacterial progeny. These results and clinical evidence suggest the contribution of damaged airway epithelia to Legionellosis by providing a replication reservoir for the bacteria.
2

Invasion of Polarized Epithelial Cells by Legionella pneumophila: an Opportunistic Strategy

Tabatabaeiyazdi, Zohreh 27 November 2012 (has links)
Legionella pneumophila (Lp.), the causative agent of Legionnaires’ disease, has been well known for infecting and replicating inside airway macrophages. Previous results from our laboratory indicated that Lp. attaches to non-polarized lung epithelial cells by binding and activating E-cadherin and β1-integrin. However, in the polarized alveolar epithelia these receptors are segregated from the apical cell surface by tight junctions (TJs). Our results showed that Lp. behaves as an opportunistic pathogen that efficiently targets disrupted, but not integrated epithelial cell monolayer. In such conditions, Lp. can reach its host-cell receptors and consequently invade and replicate intracellularly, producing large amount of bacterial progeny. These results and clinical evidence suggest the contribution of damaged airway epithelia to Legionellosis by providing a replication reservoir for the bacteria.
3

Infection of human placental cells by Brucella / Infection des cellules placentaires humaines par Brucella

Garcia Mendez, Karellen Beren 14 June 2017 (has links)
Les Brucella sont des bactéries intracellulaires responsables de la brucellose, une zoonose mondiale qui cause des avortements chez les animaux, entrainant d'énormes pertes économiques dans les élevages, et des problèmes de santé de longue durée chez l'Homme. Contrairement aux animaux, il existait jusqu’à présent peu de preuves que les infections à Brucella pouvaient causer des complications obstétriques chez la femme. Des récentes études épidémiologiques ont cependant démontré une augmentation significative des risques de complications (fausses couches, mort in utéro, accouchement prématuré) chez les femmes enceintes infectées par Brucella. De plus, il a été montré que plusieurs espèces zoonotiques de Brucella sont capables d’infecter des cytotrophoblastes (CTB) et des trophoblastes extravilleux (EVT) humains, deux types de cellules ayant des fonctions immunitaires et hormonales essentielles pendant le développement du placenta. Dans ce travail, nous avons étudié les conséquences de l’infection des trophoblastes humains par Brucella, du côté du pathogène mais aussi du côté de l’hôte. Nous avons évalué le comportement intracellulaire de différentes souches de Brucella, représentant différentes espèces, hôtes ou symptômes associés. Nous n'avons trouvé aucune corrélation entre la capacité de réplication dans les trophoblastes et l’association des souches avec des complications obstétricales chez leur hôte respectif. Nous nous sommes également intéressé à des souches récemment isolées chez des babouins, après une infection placentaire ayant causé la mort in utéro de leur fœtus. Nous avons montré que ces souches sont capables d’infecter les trophoblastes humains et affectent certaines de leurs propriétés qui sont essentielles lors du développement placentaire. Nous avons également commencé à caractériser des structures intracellulaires atypiques dans lesquelles Brucella semble pouvoir survivre dans certains trophoblastes. Du côté hôte, nous avons analysé le rôle de la protéine eucaryote CD98hc dans l'infection les trophoblastes. Nous avons montré que CD98hc est importante pour l'infection des trophoblastes humains par Brucella, comme cela avait été montré précédemment dans d'autres types cellulaires, et que l’infection modifie le niveau de cette protéine dans les trophoblastes. L'infection des trophoblastes humains par Brucella pourrait donc altérer leurs fonctions au cours du développement placentaire, entraînant ainsi des complications pendant la grossesse.Les résultats obtenus dans ce travail contribuent à une meilleure compréhension des mécanismes pouvant causer des complications obstétricales chez la femme enceinte infectée par brucella et fournissent des informations importantes pour la prise en charge clinique de la brucellose pendant la grossesse. / Brucella are intracellular bacteria responsible for brucellosis, a worldwide zoonotic disease associated with infectious abortions in animals, which causes huge economical losses in the livestock industry and long lasting health problems in humans. In contrast to animals, evidence of Brucella infections cause obstetric complications in humans is scarce. However, epidemiological studies have shown significant increases in the risk of adverse pregnancy outcomes (miscarriage, stillbirth, preterm delivery) in pregnant women infected with Brucella. Moreover, several zoonotic Brucella species were shown to infect efficiently human cytotrophoblasts (CTB) and extravillous trophoblasts (EVT), two types of cells with essential immune and hormonal functions during placental development. In the present study, we studied the effect of Brucella infection in human trophoblasts, from both the bacterial and the host sides. We evaluated the intracellular behavior of different Brucella strains, representing different species, hosts or associated symptoms. We found no correlation between the bacterial replication rate in trophoblasts and whether the strains were associated with pregnancy complications in their respective host. Importantly, we show that strains isolated from female baboons after stillbirth can infect human trophoblasts and affect some of their properties that are essential during placental development. We also started the characterization of atypical intracellular structures in which Brucella seem to be able to survive in certain types of trophoblasts. From the host side, we analyzed the role of the eukaryotic protein CD98hc in trophoblast infection. We found that CD98hc is important for infection of trophoblasts by Brucella, as shown previously in other cell types, and that infection affects the level of the protein in trophoblasts. Infection of human trophoblasts by Brucella could thus affect their function during placental development, leading to complications in pregnancy.The results obtained in this work contribute to a better understanding of the mechanisms that could lead to obstetric complications in Brucella infected pregnant women and provide important information for the clinical management of brucellosis during pregnancy.

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