Saprolegnia is a fresh water fish parasite responsible for significant economic losses in the aquaculture industry worldwide. The disease caused by this organism is termed saprolegniosis, being characterized by a mycosis-like infection of gills and fish skin. Without sustainable treatments available for controlling or preventing saprolegniosis, it has become a significant problem especially for salmon farming, frequently affecting the fish after vaccination. Little is known regarding how the fish immune system responds to infection and such information is vital for developing future treatments and preventive measures to saprolegniosis. To study the immune response of Atlantic salmon to Saprolegnia, a detailed immune profile of experimentally infected presmolts was performed by analyzing the expression levels of several immunity-related genes. Infected fish exhibit a very strong inflammatory response while the majority of genes associate with the adaptive immunity were found to be down regulated. The mechanisms behind this response were then investigated: It was discovered that the cell wall of Saprolegnia can be recognized by fish immune cells, triggering an inflammatory response. A protease secreted by the parasite that has the ability to degrade fish antibodies was identified and, for the first time in an oomycete, the production of prostaglandin E2 was characterized, a molecule that was later shown to potentiate inflammatory responses while suppressing host adaptive immunity genes. Lastly two metabolic pathways of the oomycete were explored as novel targets for control, prostaglandin and sterol metabolism by the use of cyclooxygenase and CYP51 inhibitors, respectively.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:635980 |
| Date | January 2014 |
| Creators | Belmonte da Silva, Rodrigo Caetano |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=220447 |
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