Effects of vaccination and innate immune defence against recurrence of IPN in salmon carrying IPN virus of different virulence.

There is a need to identify factors that may contribute to the serious infectious pancreatic necrosis (IPN) disease problems in A. salmon post-smolts. It is important to know more about the impact of the widespread carrier state of IPNV in A. salmon, the risk of recurrence of IPN, and the high virulence observed among the IPNV strains isolated from farmed salmon today. We will study in vivo if it is possible by vaccination to eliminate the carrier state, or to protect salmon already persistently infecte d with IPNV against reactivation of IPN and reinfection with IPNV. Whether different virulence affects the ability of IPNV strains to establish persistent infections, and if immune stimulation of the carrier cells may ?cure? the infection will be investig ated in vitro. The ability of some virus to inhibit or delay the innate first line immune defence is also a virulence factor. Several genetically characterized field isolates of IPNV with different virulence isolated during outbreaks, and isolates from asymptomatic carriers will be used in this project. We will study if they differ in susceptibility to antiviral responses in stimulated cell lines, and their ability to activate or evade antiviral responses. Knowledge about IPNV interactions with the host ?s antiviral immune defence is necessary to develop effective prophylactic treatment.