Bacterially expressed nucleoprotein of infectious hematopoietic necrosis virus augments protective immunity induced by the glycoprotein vaccine in fish.

The ribonucleoprotein gene of infectious hematopoietic necrosis virus (IHNV) has been expressed in Escherichia coli as a trpE fusion protein. This viral protein does not induce protective immunity to lethal IHNV infection in fish, and virus-neutralizing antibodies do not react with this viral protein. However, when it was administered with a bacterial lysate containing a region of the IHNV glycoprotein, there was enhanced resistance in immunized fish to lethal virus infection.