Enhanced expression of the Erns protein of classical swine fever virus in yeast and its application in an indirect enzyme-linked immunosorbent assay for antibody differentiation of infected from vaccinated animals

•The production of yeast-expressed Erns (yErns) was enhanced by codon optimization.•An indirect ELISA (iELISA) based on yErns was developed and evaluated.•The iELISA could discriminate CSFV-infected from rAdV-SFV-E2-vaccinated animals (DIVA).•The iELISA was specific and sensitive, representing a promising DIVA test.