Expression in Escherichia Coli of an Epitope of the Glycoprotein of Infectious Hematopoietic Necrosis Virus Protects Against Viral Challenge

Plasmid vectors were constructed that expressed an antigenic determinant of the glycoprotein gene of infectious hematopoietic necrosis virus (IHNV) as a fusion protein with the trp E protein of Escherichia coli . Insertion of Sau3AI fragments from the IHNV glycoprotein gene into trp E expression plasmids led to a fusion protein containing a hydrophilic segment of 104 amino acids from the middle portion of the viral glycoprotein. Although this region of the glycoprotein contains three N–linked glycosylation sites and is probably glycosylated in the virus, it is not glycosylated in bacteria. Nonetheless, immunization trials in fish with the crude bacterial lysate containing the fusion protein showed that the trp E–glycoprotein fusion protein produced in bacteria induced protective immunity.