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Examining the role of type III secretion in the biology and intracellular pathogenesis of Chlamydophila psittaci

(2009)
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Abstract
Chlamydiaceae are Gram-negative obligate intracellular bacteria and are therefore completely dependent on a living host cell to execute their unique biphasic developmental cycle. This is accompanied by a reprogramming of the host cell into a minimized factory efficiently supporting chlamydial replication. Type III secretion could be essential in this process as other Gram-negative bacteria deploy similar secretion mechanisms to subvert the cellular functions of their host to their own benefit. Chlamydophila psittaci primarily infects birds and is horizontally transmitted through aerosols of nasal secretions and feces. Initially, the respiratory tract is infected, from where the disease further spreads leading to a systemic infection. The commercial poultry industry is affected by considerable economic losses, especially when the animals are simultaneously infected with avian pathogenic E. coli, Ornithobacterium rhinotracheale or avian metapneumovirus. Zoonotic transmission occurs in people in close contact with infected birds, the clinical outcome ranging from inapparent to severe flu-like symptoms or pneumonia. In this thesis, we have proven that a functional Type III secretion system is present in Chlamydophila psittaci, involved in the entry and replication of chlamydial organisms. Using a newly developed digital titration assay, lactoferrin and especially ovotransferrin proved their usefulness as anti-chlamydial compounds, of which ovotransferrin is now being tested as a cost-effective prophylactic measure in large scale turkey farms. We have also shown that Chlamydophila psittaci ompA genotype B strains invade, survive and replicate less efficiently in avian monocytes/macrophages compared to genotype A or D strains. Moreover, the induced cytokine responses are less pronounced, thus attracting fewer macrophages from the surrounding tissues. We postulate that mildly virulent strains disseminate less throughout the host, leading to more restricted lesions, hardly affecting the physical condition of the host. In addition, exceptionally high IL-10 and no TGF-β4 responses were observed, probably inducing a deactivation of monocytes/macrophages and inhibiting the pro-inflammatory and Th1 responses, resulting in a less efficient clearance of both Chlamydophila psittaci and subsequent infections. However, Chlamydophila psittaci has not yet revealed all of its secrets and more research is needed to unravel the remaining mysteries in its interaction with both the avian and the human host.
Keywords
Chlamydophila psittaci, Chlamydia, pathogenesis, ovotransferrin

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Citation

Please use this url to cite or link to this publication:

Chicago
Beeckman, Delphine Sylvie Anne. 2009. “Examining the Role of Type III Secretion in the Biology and Intracellular Pathogenesis of Chlamydophila Psittaci”. Ghent, Belgium: Ghent University, Faculty of Bioscience Engineering.
APA
Beeckman, D. S. A. (2009). Examining the role of type III secretion in the biology and intracellular pathogenesis of Chlamydophila psittaci. Ghent University, Faculty of Bioscience Engineering, Ghent, Belgium.
Vancouver
1.
Beeckman DSA. Examining the role of type III secretion in the biology and intracellular pathogenesis of Chlamydophila psittaci. [Ghent, Belgium]: Ghent University, Faculty of Bioscience Engineering; 2009.
MLA
Beeckman, Delphine Sylvie Anne. “Examining the Role of Type III Secretion in the Biology and Intracellular Pathogenesis of Chlamydophila Psittaci.” 2009 : n. pag. Print.
@phdthesis{632491,
  abstract     = {Chlamydiaceae are Gram-negative obligate intracellular bacteria and are therefore completely dependent on a living host cell to execute their unique biphasic developmental cycle. This is accompanied by a reprogramming of the host cell into a minimized factory efficiently supporting chlamydial replication. Type III secretion could be essential in this process as other Gram-negative bacteria deploy similar secretion mechanisms to subvert the cellular functions of their host to their own benefit. Chlamydophila psittaci primarily infects birds and is horizontally transmitted through aerosols of nasal secretions and feces. Initially, the respiratory tract is infected, from where the disease further spreads leading to a systemic infection. The commercial poultry industry is affected by considerable economic losses, especially when the animals are simultaneously infected with avian pathogenic E. coli, Ornithobacterium rhinotracheale or avian metapneumovirus. Zoonotic transmission occurs in people in close contact with infected birds, the clinical outcome ranging from inapparent to severe flu-like symptoms or pneumonia.
In this thesis, we have proven that a functional Type III secretion system is present in Chlamydophila psittaci, involved in the entry and replication of chlamydial organisms. Using a newly developed digital titration assay, lactoferrin and especially ovotransferrin proved their usefulness as anti-chlamydial compounds, of which ovotransferrin is now being tested as a cost-effective prophylactic measure in large scale turkey farms. We have also shown that Chlamydophila psittaci ompA genotype B strains invade, survive and replicate less efficiently in avian monocytes/macrophages compared to genotype A or D strains. Moreover, the induced cytokine responses are less pronounced, thus attracting fewer macrophages from the surrounding tissues. We postulate that mildly virulent strains disseminate less throughout the host, leading to more restricted lesions, hardly affecting the physical condition of the host. In addition, exceptionally high IL-10 and no TGF-β4 responses were observed, probably inducing a deactivation of monocytes/macrophages and inhibiting the pro-inflammatory and Th1 responses, resulting in a less efficient clearance of both Chlamydophila psittaci and subsequent infections.
However, Chlamydophila psittaci has not yet revealed all of its secrets and more research is needed to unravel the remaining mysteries in its interaction with both the avian and the human host.},
  author       = {Beeckman, Delphine Sylvie Anne},
  isbn         = {978-90-5989-294-1},
  keywords     = {Chlamydophila psittaci,Chlamydia,pathogenesis,ovotransferrin},
  language     = {eng},
  pages        = {XI, 262},
  publisher    = {Ghent University, Faculty of Bioscience Engineering},
  school       = {Ghent University},
  title        = {Examining the role of type III secretion in the biology and intracellular pathogenesis of Chlamydophila psittaci},
  url          = {http://lib.ugent.be/fulltxt/RUG01/001/333/040/RUG01-001333040_2010_0001_AC.pdf},
  year         = {2009},
}