Abstract
Prions are transmissible agents comprised of a misfolded protein PrPSc that is post-translationally derived from the normal isoform PrPC. Prion strains are operationally defined by differences in the distribution and intensity of spongiform degeneration and distribution of PrPSc in the CNS. The mechanism by which prion strains are encoded is not known, however, current evidence suggests that the conformation of PrPSc encodes prion strain diversity. In natural prion disease, more than one prion strain can exist in an individual. Prion strains, when present in the same host, can interfere with each other, a process that can influence the emergence of a dominant strain from a mixture and can occur during prion adaptation following interspecies transmission. The parameters and mechanisms that influence prion strain interference are beginning to be understood.