Protection of rainbow trout against infectious hematopoietic necrosis virus four days after specific or semi-specific DNA vaccination

A DNA vaccine against a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), was shown to provide significant protection as soon as 4 d after intramuscular vaccination in 2 g rainbow trout (Oncorhynchus mykiss) held at 15 degreesC. Nearly complete protection was also observed at later time points (7, 14, and 28 d) using a standardized waterborne challenge model. In a test of the specificity of this early protection, immunization of rainbow trout with a DNA vaccine against another fish rhabdovirus, viral hemorrhagic septicemia virus, provided a significant level of cross-protection against IHNV challenge for a transient period of time, whereas a rabies virus DNA vaccine was not protective. This indication of distinct early and late protective mechanisms was not dependent on DNA vaccine doses from 0.1 to 2.5 mug. (C) 2001 Elsevier Science Ltd. All rights reserved.