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Title: Heterogeneous infections in fish : transcriptomic studies on the trout immune response to single and co-infections
Author: Gorgoglione, Bartolomeo
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2014
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Organisms are continuously exposed to heterogeneous micro- and macro-parasitic species, hence simultaneous infections often occur in wild and farm environments. This joint project aimed to develop a co-infection model between chronic and acute infections, evaluating their impact on the fish immune system. Proliferative Kidney Disease was studied on farmed rainbow and brown trout during natural seasonal outbreaks, using a parasite gene (Tetracapsuloides bryosalmonae RPL18) as a proxy for assessment of parasite burden. In hosts with elevated susceptibility PKD pathogenesis was shaped by an anti-inflammatory phenotype, a profound B cell/antibody response and dysregulated TH cell-like activity. Pathogen-free brown trout were exposed to Viral Haemorrhagic Septicaemia Virus (comparatively using European VHSV-Ia and North American VHSV-IVb strains) or to the bacterium Yersinia ruckeri. This European native species was highly resistant to the VHSV-IVb strain, which was undetectable in internal organs despite raising a strong antiviral and mucosal immune response. Following VHS and Yersiniosis infection, haemo-lymphopoietic organs were screened by RT-qPCR to assess the specific pathogen burdens and characterise the immune responses elicited. Transcription patterns were analysed for Interferons, CXC chemokines, SOCS (potential disease resistance biomarkers) and genes of the PACAP system. Lastly, PKD-infected brown trout were co-infected with VHSV-Ia, resulting in typical lesions while showing reduced and delayed mortality. PKD+/VHS+ fish were identified by RT-qPCR and histopathology screening. Pro-inflammatory and antimicrobial peptide genes were modulated following virus co-infection when compared to fish with single infection, with an earlier activation of cellular and humoral responses, and a stronger up-regulation of TH1 and antiviral genes. Oligonucleotide microarrays were used to assess the broader immune gene transcription modulation between single- and co-infected fish. Overall, the results suggest that the immune response of brown trout might be enhanced during the PKD/VHS co-infection.
Supervisor: Secombes, C. J. ; Taylor, N. G. H. ; Feist, S. ; Holland, J. W. ; Martin, S. A. M. Sponsor: DEFRA
Qualification Name: Doctor of Philosophy in Biological Sciences Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Trout ; Immune response ; Co-infections ; Proliferative Kidney Disease ; Tetracapsuloides bryosalmonae ; Viral Haemorrhagic Septicaemia ; Yersinia ruckeri ; Gene Screening; Microarrays