Transmissible spongiform encephalopathy pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Unlike other kinds of infectious disease which are spread by microbes, the infectious agent in TSEs is a specific protein called prion protein. Misshaped prion proteins carry the disease between individuals and cause deterioration of the brain. TSEs are unique diseases in that their aetiology may be genetic, sporadic or infectious via ingestion of infected foodstuffs and via iatrogenic means (e.g. blood transfusion) (reviewed in Prusiner, 1991; Collinge, 2001).
Pathophysiology
- Most TSEs are sporadic and occur in an animal with no prion protein mutation.
- Inherited TSE occurs in animals carrying a rare mutant prion allele, which expresses prion proteins that contort by themselves into the disease-causing conformation.
- Transmission occurs when healthy animals consume tainted tissues from others with the disease. In recent times a type of TSE called bovine spongiform encephalopathy (BSE) spread in cattle in an epidemic fashion. This occurred because cattle were fed the processed remains of other cattle, a practice now banned in many countries. The epidemic could have begun with just one cow with sporadic disease.
- Prions cannot be transmitted through the air or through touching or most other forms of casual contact. However, they may be transmitted through contact with infected tissue, body fluids, or contaminated medical instruments.
- Normal sterilization procedures such as boiling or irradiating materials fail to render prions non-infective.
- The degenerative tissue damage caused by human prion diseases (CJD, GSS, and kuru) is characterised by four features: spongiform change, neuronal loss, astrocytosis and amyloid plaque formation.
- These features are shared with prion diseases in animals, and the recognition of these similarities prompted the first attempts to transmit a human prion disease (kuru) to a primate in 1966, followed by CJD in 1968 and GSS in 1981.These neuropathological features have formed the basis of the histological diagnosis of human prion diseases for many years, although it was recognised that these changes are enormously variable both from case to case and within the central nervous system in individual cases.[1].
- Early neuropathological reports on human prion diseases suffered from a confusion of nomenclature, in which the significance of the diagnostic feature of spongiform change was occasionally overlooked. The subsequent demonstration that human prion diseases were transmissible reinforced the importance of spongiform change as a diagnostic feature, reflected in the use of the term "spongiform encephalopathy" for this group of disorders.
References
- ↑ Jeffrey M, Goodbrand IA, Goodsir CM (1995). "Pathology of the transmissible spongiform encephalopathies with special emphasis on ultrastructure". Micron. 26 (3): 277–98. PMID 7788281.