Mother to fry, successful transfer of immunity against infectious haematopoietic necrosis virus infection in rainbow trout.

We have tested whether immunity can be transferred from a mother fish to its fry. Rainbow trout mother fish were inoculated against infectious haematopoietic necrosis virus (IHNV) by intraperitoneal injection of a fragment of the IHNV glycoprotein spanning amino acids 31 to 310. This protein fragment was obtained by isolating the specific cDNA from Japanese IHNV strain HV7601 and expressing it in Escherichia coli. Fry from immunized and control fish were exposed to IHNV at various intervals after hatching, and their mortality monitored. Survival of the fry of immunized fish was significantly greater when exposure to virus occurred 7 days after hatching, and some immunity appeared to persist until at least 25 days after hatching.