Genetic immunization of rainbow trout (Oncorhynchus mykiss) against infectious hematopoietic necrosis virus.

Plasmid vectors encoding the infectious hematopoietic necrosis virus (IHNV) nucleoprotein or glycoprotein gene under the control of a cytomegalovirus promoter were used to immunize rainbow trout (Oncorhynchus mykiss) against IHNV. The plasmid DNA was injected into the skeletal muscle of rainbow trout fry, and immunization was determined by the detection of virus-neutralizing and enzyme-linked immunosorbent assay antibody activity, and by protection against live virus challenge. Fish injected with the glycoprotein-encoding plasmid pCMV4-G, either alone or in combination with the nucleoprotein-encoding plasmid pCMV4-N, generated glycoprotein-specific and virus-neutralizing antibody responses. The vaccinated fish were also protected from subsequent IHNV challenge. Fish receiving pCMV4-N alone did not produce measurable virus-specific antibody and were killed by IHNV infection. These studies show that DNA vaccination will protect rainbow trout against the lethal effects of IHNV infection.