Pre-clinical and clinical diagnosis of scrapie by detection of PrP protein in tissues of sheep

Abstract

The usefulness of detecting the scrapie-associated fibrillar protein (PrP) in the lymphoreticular organs of sheep as a diagnostic tool was investigated. The PrP was detected by means of a rabbit-anti-sheep PrP polyclonal antibody by Western blot analysis. PrP was detected in samples from the central nervous system (CNS) of five of six sheep showing clinical signs of natural scrapie infection, in spleen samples from four of the six sheep and in lymph node samples taken from three of the sheep. PrP was detected in the spleen and lymph node samples, but not in the CNS samples from one of the six sheep that was clinically and histopathologically abnormal. This animal appeared to be in the early clinical stage of the disease. A total of 47 clinically normal sheep were examined for the presence of PrP. It was detected in spleen samples from three of the 47 sheep and in lymph node samples from three of the 39 sheep tested. Similarly, PrP was detected in a sample of lymph node obtained surgically from one of three experimentally infected sheep 14 months after inoculation. The PrP-positive sheep and one of the remaining PrP-negative sheep showed clinical signs of scrapie six and five months later respectively. One sheep euthanased 18 months after experimental infection was positive for PrP in the CNS, spleen and lymph node, but five other sheep which were killed or died two, eight, 16, 18 and 21 months after infection were negative or doubtful for the detection of PrP.

Immunohistochemical Detection of Prion Protein in Sheep with Scrapie

“…Both of these possibilities have been suggested by results of other studies that used the western blot method for detection of PrP-res. In these reports, PrP-res was detected in 2 experimentally inoculated sheep before clinical signs or lesions had developed, 16 in 3 sheep that had clinical signs of scrapie with minimal or no histologic lesions, 11 and in 9 sheep that did not meet all of the histopathologic criteria necessary for a positive diagnosis of scrapie. 28 One limitation to the use of histology for scrapie immunoreactivity of PrP-res was preserved in PLP diagnosis is that an accurate interpretation of lesions with 0.125% paraformaldehyde, even after prolonged may be difficult or impossible unless the brain is fixed fixation of the tissue.…”

“…The IHC demonstration of PrP-res in sheep that are clinically and histologically diagnosed with scrapie confirms results of studies on other sheep that compared histopathology and the western blot technique. 16,18,28,32,34 The IHC detection of PrP-res in 4 of 11 sheep that were not confirmed with scrapie by histopathology suggests that the method may be capable of identifying sheep with preclinical scrapie or sheep that develop clinical signs without concurrent development of characteristic histologic lesions. Both of these possibilities have been suggested by results of other studies that used the western blot method for detection of PrP-res.…”

Immunodetection of PrPSc in spleens of some scrapie-infected sheep but not BSE-infected cows.

“…In one mouse model of the disease which was derived from the serial passage of BSE infection in mice, PrP Sc was not detected in the peripheral organs examined until late in the incubation period, if at all (Farquhar et al, 1996). PrP Sc has also been found in brains, spleens and lymph nodes of sheep with natural scrapie (Mohri et al, 1992 ;Race et al, 1992 ;Rubenstein et al, 1987), and in sheep spleens prior to the time when clinical signs were evident (Ikegami et al, 1991 Muramatsu et al, 1994 ;Schreu$ der et al, 1996 ;Skarphedinsson et al, 1994 ;van Keulen et al, 1996).…”

Amino acid polymorphisms of PrP with reference to onset of scrapie in Suffolk and Corriedale sheep in Japan

“…A group of 64 randomly collected, healthy sheep comprising 51 Suffolks among which 36 were confirmed to be negative for PrP s°, 12 Corriedales and 1 cross-breed between Suffolk and Corriedale, 4 apparently healthy 0001-3087 © 1995 SGM (Ikegami et al, 1991) was used for confirmation of the scrapie diagnosis. Isolation of sheep DNA and RFLP analysis of the sheep PrP gene with restriction enzymes EcoRI (Life Technologies) and HindIII (Takara) were carried out as described previously (Muramatsu et al, 1992).…”