Pathogenetic investigations on the enteric nervous system plexuses of Sarda breed sheep with different PrP genotypes following oral experimental scrapie infection

The enteric nervous system (ENS) plays a key role in sheep scrapie, but no information exists on the cytotypes which are involved during infection, nor on the damage of such cells.We investigated the ileal myenteric (MPs) and submucosal plexuses (SMPs) of 32 Sarda breed sheep carrying different PrP genotypes (ARQ/ARQ, ARQ/AHQ, ARQ/ARR, ARR/ARR), which had been orally dosed with scrapie at 8 months of age and euthanized at definite time intervals post-infection (p.i.). PrPScimmunoreactivity (IR), along with neuronal marker Hu C/D, nitric oxide synthase (nNOS), calbindin (CALB), glial fibrillary acidic protein (GFAP) and synaptophysin IR, were evaluated by immunohistochemistry (IHC) and indirect immunofluorescence on paraffin sections andwholemountpreparations. Eight clinically-healthy ARQ/ARQ sheep euthanized at 12-24 months p.i., along with 1 ARQ/ARQ (euthanized at 24 months p.i.) and 3 ARQ/AHQ (euthanized at 35, 36.3 and 39.5 months p.i., respectively) clinically-affected sheep, showed IHC evidence of PrPScin both their brain (obex) and ENS, especially in MPs. PrPScdepositino was compatible with an involvement of enteroglial cells (EGCs) and a dramatic reduction (P value < 0.05) of CALB-IR neurons was observed in the MPs of 6 ARQ/ARQ animals, as compared to normal healthy controls and to infected subjects of different PrP genotypes, which also showed an almost exclusive nuclear IR of these cells.Therefore, EGCs and CALB-IR neurons of ileal ENS plexuses are likely involved in sheep scrapie.