Responses of cloned rainbow trout Oncorhynchus mykiss to an attenuated strain of infectious hematopoietic necrosis virus

The objective of this work was to examine the response of homozygous clones of rainbow trout to vaccination by an attenuated strain (Nan Scott Lake; NSL) of infectious hematopoietic necrosis virus (IHNV). Adult rainbow trout of the Hot Creek Strain (YY males maintained in a recirculating system at 12 degrees C) were injected 3 times with 10(5) to 10(7) plaque forming units (pfu) of NSL. Intraperitoneal injections were given at Day 0 and at 2 and 4 mo post-infection. All fish were nonlethally bled at monthly intervals for 18 mo. Serum from each fish was analyzed by the complement-dependent neutralization assay and by western blot against purified NSL virus. The highest virus neutralization titers were detected 4 mo after the first injection, and peaked at 1280. When sera were analyzed by western blot, the predominating responses of the serum from immunized fish on the reduced western blot were against M1, a matrix protein of the virus and to a 90 kDa stress protein. The 90 kDa protein was identified by a monoclonal antibody as a stress protein derived from the CHSE-214 cells in which the purified IHN virus was grown and which associates with the virus during purification.