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Diseases of Aquatic Organisms

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DAO 38:183-190 (1999)  -  doi:10.3354/dao038183

Naked DNA vaccination of Atlantic salmon Salmo salar against IHNV

Garth S. Traxler1,*, Eric Anderson2, Scott E. LaPatra3, Jon Richard1, Bill Shewmaker3, Gael Kurath4

1Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia V9R 5K6, Canada
2University of Maine, Orono, Maine 04469-5735, USA
3Clear Springs Foods, Inc., Buhl, Idaho 83316, USA
4Western Fisheries Research Center, Seattle, Washington 98115, USA

ABSTRACT: A naked plasmid DNA encoding the glycoprotein (pCMV4-G) of a 1976 isolate of infectious hematopoietic necrosis virus (IHNV) obtained from steelhead Oncorhynchus mykiss was used to vaccinate Atlantic salmon Salmo salar against IHNV. Eight weeks post-vaccination the fish were challenged with a strain of IHNV originally isolated from farmed Atlantic salmon undergoing an epizootic. Fish injected with the glycoprotein-encoding plasmid were significantly (p < 0.05) protected against IHNV by both immersion and cohabitation challenge. Survivors of the first challenges were pooled and re-challenged by immersion 12 wk after the initial challenge. Significant (p < 0.05) protection was observed in all of the previously challenged groups including those receiving the complete vaccine. Fish injected with the glycoprotein-encoding plasmid produced low levels of virus-neutralizing antibodies prior to the first challenge. Neutralizing antibodies increased in all groups after exposure to the IHNV. Passive transfer of pooled sera from pCMV4-G vaccinates and IHN survivors provided relative survivals of 40 to 100% compared to fish injected with sera collected from fish immunized with control vaccines or left unhandled. In this study, DNA vaccination effectively protected Atlantic salmon smolts against challenges with IHNV.

KEY WORDS: DNA · Vaccine · G protein · Atlantic salmon · IHNV

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