Prion Disease and infection
July 1 2017 by
Ray Sahelian, M.D.

The gastrointestinal tract plays a central role in the transmissible spongiform encephalopathies. These are human and animal diseases that include bovine spongiform encephalopathy, scrapie and Creutzfeldt-Jakob disease. They are uniformly fatal neurological diseases, which are characterized by ataxia and vacuolation in the central nervous system. See mad cow disease.

Prion disease - Infection
Prion diseases or transmissible spongiform encephalopathies (TSEs) are rare neurodegenerative disorders that can be acquired either by direct transmission, inherited through dominant mutations in the prion protein gene or via an unknown sporadic cause. This latter group constitutes the vast majority of cases. Like many neurodegenerative diseases the hallmarks of oxidative damage can be readily detected throughout the brain of the affected individual. However, unlike most other neurodegenerative diseases, prion diseases are connected with a dramatic loss of antioxidant defence. As abnormal protein accumulates in the diseased brain there is both an increase of oxidative substances and a loss of the defences that keep them in check. In particular the normal cellular prion protein has been shown to be an antioxidant. Conversion of this protein to the protease resistant isoform is accompanied by a loss of this antioxidant activity.
   Findings from an animal study suggest that disease-cause prions can be spread via infected skeletal muscle from deer with chronic wasting disease a wildlife illness related to mad cow disease. Whether CWD can be passed to humans is still unclear.
   Rectal tissue from patients with variant Creutzfeldt-Jakob disease (vCJD) contains prions that can transmit the infection.

Biology (Basel) 2016. Disease Transmission by Misfolded Prion-Protein Isoforms, Prion-Like Amyloids, Functional Amyloids and the Central Dogma. In 1982, the term "prions" (proteinaceous infectious particles) was coined to specify a new principle of infection. A misfolded isoform of a cellular protein has been described as the causative agent of a fatal neurodegenerative disease. At the beginning of prion research scientists assumed that the infectious agent causing transmissible spongiform encephalopathy (TSE) was a virus, but some unconventional properties of these pathogens were difficult to bring in line with the prevailing viral model. The discovery that prions (obviously devoid of any coding nucleic acid) can store and transmit information similarly to DNA was initially even denoted as being "heretical" but is nowadays mainly accepted by the scientific community.

Acta Biochim Biophys Sin (Shanghai). 2013. Recent progress in prion and prion-like protein aggregation. Prion diseases and prion-like protein misfolding diseases involve the accumulation of abnormally aggregated forms of the normal host proteins, such as prion protein and Tau protein. These proteins are special because of their self-duplicating and transmissible characteristics. Such abnormally aggregated proteins mainly formed in neurons, cause the neurons dysfunction, and finally lead to invariably fatal neurodegenerative diseases. Prion diseases appear not only in animals, such as bovine spongiform encephalopathy in cattle and scrapie in sheep, but also in humans, such as Creutzfeldt-Jacob disease, and even the same prion or prion-like proteins can have many different phenotypes. A lot of biological evidence has suggested that the molecular basis for different strains of prions could be hidden in protein conformations, and the misfolded proteins with conformations different from the normal proteins have been proved to be the main cause for protein aggregation. Crowded physiological environments can be imitated in vitro to study how the misfolding of these proteins leads to the diseases in vivo.

Prion protein
Cellular prion protein is a glycophosphatidylinositol anchored protein, of unknown function, found in a number of tissues throughout the body, including several blood components of which platelets constitute the largest reservoir in humans. It is widely believed that a mis-folded, protease-resistant form of prion protein is responsible for the transmissible spongiform encephalopathy group of fatal neurodegenerative diseases.

Prion 2014. The many shades of prion strain adaptation. In several recent studies transmissible prion disease was induced in animals by inoculation with recombinant prion protein amyloid fibrils produced in vitro. Serial transmission of amyloid fibrils gave rise to a new class of prion strains of synthetic origin. Gradual transformation of disease phenotypes and PrPSc properties was observed during serial transmission of synthetic prions, a process that resembled the phenomenon of prion strain adaptation. The current article discusses the remarkable parallels between phenomena of prion strain adaptation that accompanies cross-species transmission and the evolution of synthetic prions occurring within the same host. Two alternative mechanisms underlying prion strain adaptation and synthetic strain evolution are discussed. The current article highlights the complexity of the transmission barrier and strain adaptation and proposes that the phenomenon of adaptation is more common than previously thought.

BSE prion
Bovine spongiform encephalopathy.

Creutzfeldt-Jakob disease
Variant Creutzfeld-Jakob-disease (vCJD), but not bovine spongiform encephalopathy (BSE), can be transmitted to humans. Secondary transmission of vCJD via blood transfusion and other routes is probably possible. The results, which appeared in the March, 2006 online issue of The Lancet Neurology, are concerning because they suggest such infections have a long preclinical phase.

Prion Infection Treatment
A novel formulation of copper and hydrogen peroxide can inactivate infectious prions -- disease-causing proteins responsible for scrapie in sheep, mad cow disease, and the human form of the disease called Creutzfeldt-Jacob disease (CJD), according to Dr. Sylvain Lehmann of Institute de Genetique Humaine du CNRS, Montpelier, France. Using medical instruments contaminated by CJD or other prion diseases is a problem. Very harsh treatment such as use of sodium hydroxide or steam -- not at all compatible with delicate equipment -- may be required for sterilization. The researchers found that their copper-hydrogen peroxide formulation significantly reduced the level of prion protein in tissue samples obtained from prion-infected mouse and human brains. In addition, mice inoculated with scrapie-infected brain tissue survived for a mean of 266 days after injection into the brain with chemical combination, compared with 167 days for infected controls. Journal of Infectious Diseases, 2006.

Questions
Q. Is a prion a virus ?
     A. No, it is not a virus.

Q. Can glandular extracts contain prions?
     A. This is a good question. I don't know if glandulars or glandular extracts could potentially contain prions.

Orf Virus
People who come in close contact with sheep and goats risk contracting orf virus from infected animals. Orf is a virus that leads to skin infection. Orf is not a prion.