Vaccination against intracellular bacterial pathogens for aquaculture.

The development of vaccines against bacterial infection in aquaculture has greatly improved fish health and has resulted in increased production volumes. In addition the use of antibiotics in fish farms is significatnly reduced. Unfortunately, some specific bacteria that infect the fish immune cells still prove problematic to vaccinate against, and are resistant to antibiotic treatment. This project has investigate a newly discovered vaccine technology against bacterial infections that still cause major problems in aquaculture. The vaccine is particularly aimed against the disease francisellosis that has been devastating to fish farming based on Atlantic cod in Norway, and tilapia, a fish that is cultured by over 3.5 mill tons/year world wide. In addition, the same technology was tested against the disease Salmon Rickettsial Septicemia (SRS) that has huge impact on culturing of salmonids in Chile. The vaccine tested is based upon a technology known to protect humans against meningitis. In immunization and challenge trails the vaccine technology protects the infection model zebrafish against the various disease. In the large aquaculture fish tilapia, cod and salmonids the vaccine technology is not as efficient. The basis for this observed difference is so far unknown and will be investigated further.

The project will investigate newly discovered vaccine candidates (VC) against infections by two intracellular bacterial pathogens causing major problems in aquaculture, namely Piscirickettsia salmonis and Francisella noatunensis. F. noatunensis sp is one of the main factors hampering the development of fish farming based on Atlantic cod in Norway and is deleterious in tilapia, a fish that is cultured by over 3.5 mill tons/year world wide. P. salmonis infections have been devastating to culturing of salmon ids in Chile. As of today no effective treatments are available against the diseases. One of our VCs has already been tested effective in our newly established Zebrafish infection model system and is ready for vaccine trial experiments in cod. The two oth er candidates need further isolation and characterization before it can be tested in salmonids and tilapia. If the VCs cause immunity in the fish species in question it will have huge market potential for fish vaccine production in which Norway is world l eading. Moreover, the vaccines will improve the health of the fish and will greatly impact the outcome from the fish farming industry based on cod, salmonids and tilapia. The intracellular nature of Francisella and Piscirickettsia have up until now compli cated the development of protective measures much unlike efficient vaccines against important extracellular bacterial infections in salmon based on whole inactivated bacteria injected with oil adjuvants. Live attenuated vaccines, most easily established b y genetically modification, have proved the most efficient against intracellular pathogens. However, the used of GMO for vaccines purposes are highly regulated and restricted. The new non-GMO based discovery described in this project aim to solve this pro blem. Dette vil gi seg utslag i økt vekst for oppdrettsnæringen som igjen vil resultere i høgere og mer effektiv matproduksjon for de viktigste arter innen akvakultur verden over.