Antigenicity of infectious pancreatic necrosis virus VP2 subviral particles expressed in yeast

Infectious pancreatic necrosis (IPN) virus, the etiologic agent of infectious pancreatic necrosis in salmonid fish, causes significant losses to the aquaculture industry. The gene for the viral capsid protein (VP2) was cloned into a yeast expression vector and expressed in Saccharomyces cerevisae. Expression of the capsid gene in yeast resulted in formation of ∼20 nm subviral particles composed solely of VP2 protein. Anti-IPNV antibodies were detected in rainbow trout vaccinated either by injection of purified VP2-subviral particles (rVP2-SVP) or by feeding recombinant yeast expressing rVP2-SVP. Challenge of rVP2-SVP immunized trout with a heterologous IPNV strain and subsequent viral load determination demonstrated that both injection and orally vaccinated fish had lower IPNV loads than naive or sham-vaccinated fish. This study demonstrates the ability of rVP2-SVPs to induce a specific immune response and the ability of immunized fish to reduce the viral load after an experimentally induced IPNV infection.