NR AXPX
AU King,D.
TI Can Brain Samples with Low PrPsc but High Infectivity be Assayed using Currently Available Diagnostic Kits?
QU International Conference - Prion 2007 (26.-28.9.2007) Edinburgh International Conference Centre, Edinburgh, Scotland, UK - Book of Abstracts: Natural and Experimental Strains P02.14
IA http://www.prion2007.com/pdf/Prion Book of Abstracts.pdf
PT Konferenz-Poster
AB
Background: The conversion of the cellular prion protein PrPc, to an insoluble aggregated isoform PrPsc is taken to be the key process in the pathogenesis of Transmissible Spongiform Encephalopathies (TSEs) which include Bovine Spongiform Encephalopathy (BSE), Scrapie in sheep, Creutzfeld-Jacob disease (CJD) and Gerstmann-Sträussler-Scheinker disease (GSS) in humans. The isoform PrPsc consequently forms the basis for most biochemical diagnostic tests in the identification of these diseases. However studies have shown that high titres of TSE infectivity can be present in brain tissue of animals which show clinical and vacuolar signs of TSE disease, but contain low or undetectable levels of PrPsc (using standard techniques such as immunohistochemistry, or immunoblot of PK treated tissue extract). These data question whether PrPsc is a reliable diagnostics marker.
Aims: Using one particular model system showing low PrPsc but high infectivity we aim to determine whether such tissues will be detected by two leading diagnostic assays namely the TeSeE sheep/goat kit (Bio-Rad) and the IDEXX HerdChek BSE-Scrapie kit (IDEXX laboratories).
Methods: Kits were used following manufacturers instructions but were optimised to account for the small amounts of starting material (50 - 200mg of brain tissue).
Results: Initial studies demonstrated that the IDEXX kit had a higher sensitivity than the TeSeE kit. Both kits were able to detect control tissues from a wide range of strains such as ME7, 139A, 79V, and 79A. For 263K and GSS infected brain however some samples were interpreted as negative. Results were confirmed using an optimised immunoblot from the original starting samples.
Discussion: From the panel of control samples both assays demonstrated reliability where results were reproducible and obtained rapidly. However, certain samples containing extremely low levels of PrPsc failed to be detected by both systems. Reliance on protease resistant PrPsc as a sole measure of infectivity is questionable as previous studies have shown that abnormal isoforms of PrP and TSE infectivity do not correlate and therefore the relationship between PrPsc and infectivity is unclear. The possibility of false positive or false negative results in PrPsc-dependant assays could lead to misdiagnosis of disease.
AD D. King, Roslin Institute (Edinburgh), Diagnostic Approaches to TSEs, UK
SP englisch
PO Schottland