Cellular prion protein in ovine milk

Cellular prion protein, PrPC, is essential for the development of prion diseases where it is considered to be a substrate for the formation of the disease-associated conformer, PrPSc. In sheep, PrPC is abundant in neuronal tissue and is also found at lower concentrations in a range of non-neuronal tissues, including mammary gland. Here, we demonstrate the presence of soluble PrPC in the non-cellular, non-lipid fraction of clarified ovine milk. Compared with brain-derived PrPC, ovine milk PrPC displays an increased electrophoretic mobility. Ovine milk PrPC is mainly present as three species that differ in the extent of their N-linked glycosylation, with glycoform profiles varying among animals. Similar PrPC species are also present in fresh and commercial homogenised/pasteurised bovine milk, with additional N-terminal PrPC fragments detectable in ruminant milk and commercial milk products.