A new species of cellular prion protein (PrPC) has recently been identified in uninfected human brains using the methods described here. These methods can be used to isolate various PrP species, while some of them are also useful in isolating other misfolded protein aggregates from human brains.
Xiao, X., Yuan, J., Zou, W. Isolation of Soluble and Insoluble PrP Oligomers in the Normal Human Brain. J. Vis. Exp. (68), e3788, doi:10.3791/3788 (2012).