Codon changed immobilization antigen (iAg), a potent DNA vaccine in fish against Cryptocaryon irritans infection

► Codon changed iAg (optiAg) expressed in both prokaryotic and eukaryotic cell systems. ► In vitro immunological data confirmed that optiAg retained the native confirmation. ► iAg is immunogenic due to the protection it conferred to the immunized fish. ► iAg can be a potent DNA vaccine in fish against infection by C. irritans.