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Title: Skeletal and cardiac muscle responses to viral infections in Atlantic salmon : potential nutritional implications
Author: Heidari, Zeynab
ISNI:       0000 0004 5348 4010
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2015
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The dramatic increase in the production of farmed fish in the past few decades has resulted in aquaculture species becoming of huge economic importance. In particular Atlantic salmon, are amongst the most important aquaculture species in temperate latitudes. The aims of this thesis were to identify the relationship between viral infection and responses in the muscle and heart tissue, using both in vivo challenges and in vitro approaches. Salmonid alphavirus (SAV), the aetiological agent of pancreas disease (PD) and piscine reovirus (PRV) the aetiological agent of heart skeletal muscle inflammation (HSMI) are both recognized as serious pathogens of farmed Atlantic salmon. They are chronic viral infections and can result in wasting and muscle catabolism, at present the mechanisms by which pathology occurs is unknown. The relationship between antiviral activity and other physiological parameters especially in skeletal muscle are currently not examined in depth in fish. For PD a challenge experiment was carried out (Chapter 3) and maximum viral load in the muscle tissue was found at 4 weeks post infection which was reduced at 8 weeks and cleared by 12 weeks. Antiviral gene expression and a marker for muscle protein degradation (Atrogin-1) were also found to have peak expression at 4 weeks, this suggested atrogin-1 gene expression might be regulated by immune molecules such as cytokines. To understand this in more detail, I have examined atrogin-1 gene expression response in primary muscle cell culture to key immune modulators (Interleukin-1ß, interferon type 1 and interferon ?) and to the anabolic hormone insulin like growth factor (IGF-1) (chapter 4). A luciferase reporter construct of the atrogin-1 promoter showed that the IL-1ß and interferon type I increased atrogin-1 mRNA expression and reporter activity whereas IGF-1 suppressed atrogin-1 expression. The final chapter examined how dietary changes using a phospholipid rich diet might change the response to a PRV challenge. It was hypothesised that diets rich in marine oils and phospholipids (PL) may help to reduce viral infection and improve recovery of the animals following viral clearance. A microarray analysis approach in heart muscle showed differences in response to infection depending on the diet the fish had been fed. The biggest difference was at 8 wpi with 710 genes expressed at significantly different levels depending on diet. At 8 wpi many genes related to innate immune and adaptive immune responses were different, suggesting that these animals are in the process of clearing the virus. Taken together, these observations increase our understanding of salmon poor growth during viral infection, and will serve as a basis to develop strategies to manage this viral wasting disease.
Supervisor: Not available Sponsor: BioMar ; University of Aberdeen
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Atlantic salmon