The Prion

Abstract

Transmissible spongifonn encephalopathies (TSE) have been documented in livestock for centuries but the nature of the putative causative agent as a contagious, mutant form of a host-encoded protein is a very recent discovery whose nuances remain unclear. In its normal conformation, the Prion is believed to be a short-lived uptake protein ubiquitous in nervous tissues.In contrast ,the mutant Prion usually has an identical primary structure , but has a radically different tertiary and quaternary structure that confers on it unusual stability and resistance to the normal post-translational reactions. Most importantly, the mutant protein binds to the normal Prion protein and alters its conformation to the mutant form. Transmission of TSE from host to host has been observed to occur primarily through ingestion of infected tissue and introduction of the mutant Prion to nervous tissue in the mouth, such as the cranial nerves serving the tongue. It is believed that the mutant Prion is transported within the parenchyma via highly motile microglia. The latent damage from eventual accumulation of mutant Prion is the result of the host's immune response to the protein that involves inflammatory TNF-alpha and IL-1 alpha and beta, among others. Clinical symptoms, however , presented well after the host's immune response resulted in spongiform changes to nervous tissue. Fortunately, there currently exists promising research that seeking to explain natural immunity to TSE and apply it to unaffected individuals.