Chicken antibody against a restrictive epitope of prion protein distinguishes normal and abnormal prion proteins

Recently, we reported the application of a recombinant chicken IgY monoclonal antibody, Ab3–15, against mammalian prion protein (PrP), for the diagnosis of bovine spongiform encephalopathy in cattle. In this study, we have characterized a soluble, single-chain variable fragment (scFv) form of this antibody, sphAb3–15 using brain homogenates from mice. This sphAb3–15 antibody recognized denatured forms of both PrPC and PrPSc, and PrPSc after PK-treatment, on Western blotting. In sandwich ELISAs, on dot blots and by immunoprecipitation, sphAb3–15 efficiently bound to PrP from normal brain homogenates, but weakly bound PrP from scrapie-infected brain homogenates. These results suggest that sphAb3–15 selectively recognizes PrPC under native conditions and that the epitope recognized by sphAb3–15 may undergo conformational changes during the conversion of PrPC into PrPSc.