UASt regulatory sequences drive expression of a protein that is comprised of a Tag:SS(nec) signal peptide, the mature Ovir\PrP peptide (corresponds to amino acid residues 25-233 of GB:AF156185) with the wild-type Ser residue at residue 138, and the Ovir\PrP glycosylphosphatidylinositol anchor signal sequence (amino acids 234-256).