Development of a Bivalent ERM-IPN Vaccine for Protection of Salmonid Fish

The bacterial disease enteric redmouth (ERM) and the viral disease infectious pancreatic necrosis (IPN) can cause high mortalities in salmoid fish. Both diseases are of economic significance to the aquaculture industry. Commercial vaccines consisting of lysed Yersinia ruckeri, the etiological agent of ERM, have been highly effective but viral vaccines for salmonid fish are not yet marketed. The goal of the Phase I research is to develop a bivalent ERM-IPN vaccine using recombinant DNA technology. This novel approach appears promising given the success of the ERM vaccine and that cloned IPN virus (IPNV) proteins expressed in the bacteria Escherichia coli have protected fish against IPN in laboratory trials. Cloning and expression of foreign proteins in Y. ruckeri has not been previously attempted. In the proposed research, two strategies, using an E. coli plasmid and a broad host range plasmid, will be evaluated for obtaining the stable expression of immunogenic IPNV proteins by Y. ruckeri. Subsequently, lysed recombinant Y. ruckeri will be tested as a bivalent vaccine for induction of protection in rainbow trout against ERM and IPNV.