Community Research and Development Information Service - CORDIS

Development of vaccine for bacterial kidney disease in salmonids

Research has been carried out into the development of a recombinant vaccine against the bacterial kidney disease (BKD) of salmonids. The challenging conditions with Renibacterium salmmoninarum, the BKD causal agent, have been optimised and mortalities in the 60 to 80% range are regularly obtained. This tool allows the study of the level of protection provided by the immunization of the rainbow trout. Passive immunizations were done by injecting artificially challenge fish with serum collected from survivors from BKD outbreaks or experimental challenges. The passive immunization did not confer full resistance to the disease, but an attenuation of the virulence and a delay in the mortality could be observed. BKD is a slowly progressing disease, and there is a several week interval between the administration of the bacterial and the death of the fish. In these conditions the persistence of serum is probably too short to provide good protection. The search for protective antigens has focused on extra-cellular virulence factors. Continuous fermentation has been implemented to provide a regular supply of antigenic material. The fermentation conditions of Renibacterium have been modified to stimulate the expression of virulence factors. 3 proteins have been selected for further study and cloning. The actual expression of these proteins in vivo was confirmed during implantation studies. The Renibacterium cells were placed in dialysis tubing introduced in the peritoneal cavity of fish. After several days, the protein content of the tubing was analysed and confirmed the secretion of the selected antigens.

These antigens were partially purified from culture broth and their immunogenicity is currently under evaluation. In parallel, a complete genomic library of Renibacterium salmoninarum was constructed. The gene encoding for these antigens will be expressed in bacteria for subsequent vaccine development.

Finally 2 new vaccines were produced in yeast. They were potent when administered by injection.

The project is currently on hold and the technology is available for in-sourcing.

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