Scrapie is a
transmissible spongiform encephalopathy (TSE) or
prion disease, which naturally affects sheep and goats. Immunohistochemical
epitope mapping of abnormal PrP accumulations (
PrP(d)) in brain can help in characterizing sheep TSE sources or strains and in identifying potential
bovine spongiform encephalopathy (BSE)
infections of sheep. Natural and experimental TSE
infections of goats were examined to determine whether the
epitope mapping approach could also be applied to aid recognition of BSE
infection in goats. Goats experimentally infected with the SSBP/1 or CH1641 sheep
scrapie strains or with cattle BSE, together with four field cases of natural TSE in goats, were examined immunohistochemically with six different
antibodies. CH1641 and SSBP/1
infections in goats, as in sheep, showed
PrP(d) accumulations which were mainly intracellular. Some differences in targeting, particularly of Purkinje cells, was evident in inter-species comparisons of CH1641 and SSBP/1.
PrP(d) labelling of goat BSE experimental cases showed extensive intracellular and extracellular accumulations, also similar to those in sheep BSE. Intra-neuronal
PrP(d) in both goat and sheep BSE was labelled only by
antibodies recognizing
epitopes located C-terminally of residue His99, whereas in natural sheep TSE sources, and in sheep and goat SSBP/1,
PrP(d) was also detected by
antibodies to
epitopes located between residues Trp93 and His99. Testing of four natural goat TSE samples showed one case in which
epitope mapping characteristics and the overall patterns of
PrP(d) accumulation was identical with those of experimental goat BSE. The four natural goat
scrapie cases examined showed some degree of immunohistochemical phenotype variability, suggesting that multiple strains exist within the relatively small UK goat population.