Prion diseases or TSEs (Transmissible Spongiform Encephalopathies) form a biologically unique group of infectious fatal neurodegenerative disorders, which are caused by toxic gain of function in a normal host cell protein (the Prion protein, PrP). The mec ...hanism of disease propagation is well understood and involves the conformational conversion of a normal cell-surface protein (PrPc) into a protease-resistant, Beta-sheet-rich form (PrPSc) that is infectious in the absence of nucleic acid. BSE (Bovine Spongiform Encephalopathy), Scrapie of sheep and goat, CWD (Chronic Wasting Disease) of deer and elk, and human CJD (Creutzfeldt Jakob Disease) are well-known central nervous system degenerative diseases caused by Prion infection. However, some forms of spongiform encephalopathies are commonly associated with inherited mutations at the PrPc coding gene (PrnP), particularly the GSS (Gerstmann-Straussler-Scheinker syndrome) and FFI (Fatal Familial Insomnia), in addition to CJD in humans. Prion diseases have attracted a broad interest because of their unique mechanisms of replication and propagation; however, the underlying pathogenic mechanisms are still highly speculative. Historically, Prion diseases have been characterized neuropathologically by neuronal vacuolation (spongiosis), brisk reactive proliferation of astrocytes and microglia, and by the deposition of amyloid plaques. Prion diseases are manifest as infectious, genetic, and sporadic disorders.
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