Scrapie is a naturally occurring
prion (PrP) disease causing a fatal
neurodegenerative disorder in sheep and goats. Previous studies suggest that
scrapie is transmitted naturally through exposure to the
scrapie agent in wasted placentas of infected ewes. This study determined the distribution and biochemical properties of PrP cellular (PrP-C) and the distribution of PrP
scrapie (PrP-Sc) in reproductive, placental, and selected fetal tissues and fetal fluids in sheep. Glycosylated, N-terminally truncated,
proteinase K-sensitive PrP-C with apparent molecular masses of 23-37 kDa was present in reproductive, placental, and fetal tissues and fetal fluids. PrP-C was low or undetectable in intercotyledonary chorioallantois, amnion, urachus, amniotic fluid, and fetal urine. In pregnant ewes, cotyledonary chorioallantois, allantoic fluid, and caruncular endometrium contained higher levels of PrP-C than did intercaruncular endometrium, myometrium, oviduct, ovary, fetal bladder, or fetal kidney. Caruncular endometrial PrP-C was up-regulated during pregnancy. Despite the wide distribution of PrP-C in reproductive, placental, and selected fetal tissues and fetal fluid, PrP-Sc was detected only in caruncular endometrium and cotyledonary chorioallantois of pregnant
scrapie-infected ewes. The embryo/fetus may not be exposed to
scrapie in utero because it is separated physically from PrP-positive allantois and chorioallantois by PrP-negative amnion.