SCRAPIE INFECTIVITY AND PROTEINASE K-RESISTANT PRION PROTEIN IN SHEEPPLACENTA, BRAIN, SPLEEN, AND LYMPH-NODE - IMPLICATIONS FOR TRANSMISSION AND ANTEMORTEM DIAGNOSIS

Probable transmission of bovine spongiform encephalopathy to humans ha s focused intense interest on all of the transmissible spongiform ence phalopathies (TSEs) and how they spread. In all TSEs, an abnormal dise ase-associated, proteinase K-resistant protein referred to as PrP-res or PrPSc accumulates in brain. In some species, PrP-res accumulates in other tissues as well. Sheep placenta, brain, spleen, and lymph node were analyzed in detail for PrP-res and infectivity. Both were detecte d in all brain and spleen samples and in placenta and lymph nodes of 8 0% of the scrapie-infected sheep. A perfect correlation was observed b etween infectivity and PrP-res detection. These results substantiate t he probability that placenta plays an important role in natural transm ission of scrapie, suggest that analysis of placenta for PrP-res could be the basis for an antemortem test for sheep scrapie, and show that PrP-res, scrapie infectivity, and scrapie disease are closely associat ed.