Recombinant vaccines against infectious hematopoietic necrosis virus: Bacterial systems for vaccine production and delivery (Oncorhynchus mykiss, Caulobacter crescentus, Escherichia coli, Yersinia ruckeri)

Several systems were examined for the production and delivery of recombinant vaccines for fish. C. crescentus was employed to produce a fragment of the IHNV glycoprotein. When administered by injection to 0.5 gram rainbow trout (Oncorhynchus mykiss), one of the fusion proteins (184 amino acids of the IHNV glycoprotein fused to 242 amino acids of the C-terminus of the Caulobacter crescentus) protected the fish against lethal challenge with IHNV. Attenuated strains of Yersinia ruckeri were generated using allelic exchange mutagenesis. These strains were characterized in terms of in vitro growth characteristics and invasiveness. Attenuated E. coli and Y. ruckeri were exploited to deliver plasmid DNA to fish cells in vitro; attenuated Y. ruckeri bacteria were examined in vivo as bivalent vaccine delivery vehicles, either through the expression of a fragment of the IHNV glycoprotein or by carrying a plasmid DNA vaccine encoding the complete IHNV glycoprotein. A cell wall deficient strain (11.29Δdap) protected rainbow trout against lethal challenge with pathogenic Y. ruckeri. Gene transfer to fish was not detected by luciferase reporter gene assays. No clear protection from IHNV challenge was observed.