|Knowles Jr, Donald|
Submitted to: Haematologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2000
Publication Date: N/A
Interpretive Summary: Scrapie is part of a group of neurodegenerative diseases called transmissible spongiform encephopathies (TSE's). Natural sheep scrapie continues to be spread in flocks in the United States, and the peripheral blood remains one possible source of transmission. Since the normal cellular prion protein (PrPc) is required for disease, the location of PrPc in the peripheral blood of normal and scrapie-infected sheep was examined. PrPc was detected on the cell- surface of peripheral blood mononuclear cells (a type of white blood cell) from normal and scrapie-infected sheep, and it was sensitive to the proteolytic enzymes, PK and PIPLC.
Technical Abstract: Transmissible spongiform encephalopathies (TSEs) like sheep scrapie are characterized by the conversion of a normal, cellular prion protein (PrPc) to an abnormal protease-resistant form (PrPSc). Since PrPc is necessary in the disease process, the presence of PrPc was evaluated in peripheral blood cells of five normal and five scrapie- infected Suffolk sheep. Peripheral blood cells were sorted using flow cytometry and examined for PrP mRNA using RT-PCR. PrP mRNA was detected in peripheral blood mononuclear cells (PBMC) but not in platelets or granulocytes. PBMC were further sorted into T- lymphocytes, B-lymphocytes, and unidentified PBMCs with at least 99.0% purity, and PrP mRNA was detected in all three populations. Consistent with PrP mRNA expression, cell-surface expressed PrPc was detected on PBMC, but was not detected on granulocytes, platelets or erythrocytes. Two-color flow cytometry analysis of PBMC specific phenotypes revealed that regardless of disease, expression of PrPc was significantly higher on B2 positive B-lymphocytes than on CD4, CD8, WC1 positive T-lymphocytes or CD14 positive monocytes. In addition, PrPc expressed on PBMC from normal and scrapie-infected sheep was sensitive to proteinase K (PK) and phosphatidylinositol-specific phospholipase C (PIPLC). These combined results show that regardless of the scrapie-status of the sheep, PrPc is transcribed in resting PBMCs and is expressed as a PK and PIPLC sensitive cell-surface protein on resting PBMCs.