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Title: Activation and regulation of the innate immune system in response to Ureaplasma infection
Author: De Glanville, Benjamin
ISNI:       0000 0004 5355 2159
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2014
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The bacteria Ureaplasma has long been associated with a wide range of adverse health implications, including preterm birth, preterm premature rupture of the membrane and lung disorders, such as bronchopulmonary dysplasia in neonatal infants, but still, little is known about the pathogenic properties of Ureaplasma and possible direct association with adverse health complications. Estimated prevalence of Ureaplasma colonisation in sexually active adults is between 40 – 80%, therefore further understanding of its pathogenic properties and its ability to initiate an immune response is crucial. Specifically selected human cell-lines were examined in vitro to determine whether an innate immune response could be activated by Ureaplasma infection. If inflammatory immune responses were detected in human cell-lines, pathogenic properties of Ureaplasma would be confirmed, and its role in pregnancy and neonatal complications could be supported. Using a range of techniques, activation of immune response pathways were examined, as too were the production of detrimental pro-inflammatory cytokines that would strengthen the suggested associations of Ureaplasma infection with the above-mentioned complications. Myeloid-derived leukocytic monocytes, human bronchial epithelial cells and human amniotic epithelial cells were examined, as these would be the most relevant cell lines to determine if Ureaplasma could induce preterm birth, preterm premature rupture of the membrane and bronchopulmonary dysplasia. All cell lines studied showed immune response and inflammatory cytokine production after stimulation with Ureaplasma. This supports that Ureaplasma is capable of causing tissue damage in neonatal respiratory tracts that may lead to bronchopulmonary dysplasia and damage to the amniotic and chorion membranes that may lead to preterm premature rupture of the membrane. Ureaplasma was detected at the cell surface of human amniotic epithelial cells (HAECs) by TLR2 and TLR2/6 heterodimers. Results suggest that Ureaplamsma multiple banded antigen (MBA) is the strong ligand for TLR2 and TLR6 and stimulation of HAECs with MBA alone caused an immune response. TLR9 was responsible for the detection of internalised Ureaplasma, which is also able to initiate an immune response and inflammatory cytokine production. v Ureaplasma stimulation results in the production of the inflammatory cytokines TNF-α, IL-8 IL-6 via the NF-κB signaling pathway. Production of the potent inflammatory cytokine IL-1β was also observed, which would suggest the formation of inflammasome complexes. NLRs were investigated to find which NLR inflammasome were activated. It was shown that genetically knocking down NLRP7 significantly reduced the amount of IL-1β that was produced after Ureaplasma stimulation, suggesting that NLRP7 inflammsones are activated by Ureaplasma. Reduction in IL-1β was also observed, but to a lesser extent, when NLRP3 was knocked down. We decided to investigate the role of NLRP7 further and found a novel immune pathway, where NH3 causes activation and formation of the NRLP7 inflammasone. NH3 is produced as a bi-product of urease activity, which an essential process for Ureaplasma. The addition of a potent urease inhibitor to HAECs being stimulated with Ureaplasma significantly reduced the production of IL-1β, strongly supporting that NH3 plays a significant role in the detection of Ureaplasma infection and is responsible for causing the tissue damage that contributes to preterm premature rupture of the membrane leading to preterm birth. This investigation strongly supports that Ureaplasma is responsible for causing preterm birth and health complications in neonates, and that more robust treatment and monitoring of Ureaplasma is required, especially in pregnant women. These undertakings will hopefully reduce the rates of preterm birth and the associated health implications, in addition to reducing rates of bronchopulmonary dysplasia in neonates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR180 Immunology ; RG Gynecology and obstetrics