A monoclonal antibody (1D12) defines novel distribution patterns of prion protein (PrP) as granules in nucleus

A monoclonal antibody (mAb) panel to bovine prion protein (PrP) was studied by immunoblotting and immunohistochemistry for scrapie and bovine spongiform encephalopathy. A mAb panel recognized both normal (PrP(C)) and abnormal (PrP(Sc)) isoforms of PrP in murine, ovine and bovine brain tissues. Interestingly, an anti-bovine PrP mAb, 1D12, prepared by immunizing PrP gene-knockout mice with a synthetic polypeptides corresponding to codons 153-166 of the bovine PrP gene showed novel patterns of reactivity for prion-uninfected neuronal cells. An enzyme-linked immunosorbent assay-mapping of the mAb epitopes resulted in a reaction of monoclonal 1D12 to YEDRY and M corresponding to amino acids 156-160 and 165 of bovine PrP. Several patterns of bovine PrP(C) distribution in PrP-deficient neuronal cells (HpL3-4) transfected with bovine PrP were observed after different fixation methods. Stained cell surface was observed after formalin fixation by immunofluorescent assay of 1D12 with confocal microscopy, whereas granules in nucleus were stained after acetone fixation. No reactivity in the nucleus was observed to HpL3-4, or HpL3-4mPrP cells expressing mouse PrP. This is the first paper that has reported the detection of the PrP(C) at both cell surface and nuclei of prion-uninfected cell line.