Real-time PCR was utilised to measure the expression of several host immune genes in response to experimental infection with either ISAV or infectious pancreatic necrosis virus (IPNV). Probes targeting transcripts produced during type I and type II interferon (IFN) responses demonstrated these viruses induced both responses and peaked by day 6 post infection. The high mortality in ISAV infected fish highlighted the ineffective nature of the response and suggested the virus possesses IFN antagonistic capabilities to circumvent the host defence mechanisms. Viral proteins were studied using transfection-based methodologies to elucidate potential IFN antagonist capabilities with emphasis on the 7i protein as a putative analogue to the non-structural (NS1) protein of influenza. Results of two independent assays demonstrated the 7i protein caused a reduction induction of the interferon stimulated gene, Mx. In addition, RNA binding experiments suggested the 7i protein also possessed an RNA binding function. A surveillance programme with analysis by real-time PCR and sequencing looking for the presence of the putatively avirulent ISAV HPR0 strain, which contains an extra long highly polymorphic region (HPR) with the haemagglutinin-esterase (HE), was performed to demonstrate the extent of this strains presence in Scottish marine Atlantic salmon stocks. A transfection-based system combined with haemadsorption studies was utilised to examine differences in receptor binding and esterase activity of HE proteins obtained from an HPR0 type, a pathogenic virus and a specific combination of the two. The HPR0 HE protein was shown to be functional with respect to both receptor binding and esterase activity although no difference in function could be attributed to the presence of the full-length HPR in comparison to a protein from a pathogenic variant. This suggests the phenotypic variation of HPR0 may lie in another aspect of the viral life cycle.

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Jan. 5, 2009). With: Expression kinetics of interferon and interferon-induced genes in Atlantic salmon (Salmo salar) following infection with infectious pancreatic necrosis virus and infectious salmon anaemia virus / A.J.A McBeath ... et al. Fish and shellfish immunology 2007: 22, 230-241. With: Identification of an interferon anatagonist protein encoded by segment 7 of infectious anaemia virus / Alastair J.A. McBeath ... et al. Virus research 2006: 115, 176-184. With: Surveillance for infectious salmon anaemia virus HPRO in marine Atlantic salmon farms across Scotland / A.J.A. McBeath, N. Bain, M. Snow. Diseases of aquatic organisms (in press). With: Presence of a full length highly polymorphic region (HPR) in the ISAV haemagglutinin-esterase does not affect the primary functions of receptor binding and esterase activity/ Alastair McBeath ... et al. Includes bibliographical references.