Prion disease

**Transmissible spongiform encephalopathies** (**TSEs**), dem sanso know as **prion diseases**, be a group of progressive, incurable, den invariably fatal conditions wey be associated plus de degeneration of de nervous system insyd chaw animals, wey dey include humans, cattle, den sheep. Strong evidence dey support de once unorthodox hypothesis wey prion diseases be transmitted by abnormally shaped protein molecules dem know as prions. Prions dey consist of a protein dem call de prion protein (PrP). Misshapen PrP (dem often refer to as PrPSc) dey conveys ein abnormal structure to native PrP molecules by a crystallization-like seeding process. Because de abnormal proteins stick to each oda, den secof PrP be continuously produced by cells, PrPSc wey accumulate insyd de brain, dey harm neurons den eventually dey cause clinical disease.

Prion diseases be marked by mental den physical deterioration wey dey worsen over time. A defining pathologic characteristic of prion diseases be de appearance of small vacuoles insyd various parts of de central nervous system wey dey create a sponge-like appearance wen na brain tissue obtain at autopsy be examined under a microscope. Oda changes insyd affected regions dey include de buildup of PrPSc, gliosis, den de loss of neurons.

Insyd non-human mammals, de prion diseases dey include scrapie insyd sheep, bovine spongiform encephalopathy (BSE) insyd cattle (dem popularly know as "mad cow disease") chronic wasting disease (CWD) insyd deer den elk, den odas. Prion diseases of humans dey include Creutzfeldt–Jakob disease, Gerstmann–Sträussler–Scheinker syndrome, fatal familial insomnia, kuru, den variably protease-sensitive prionopathy. Na dem divide Creutzfeldt-Jakob disease into four subtypes: sporadic (idiopathic) (sCJD), hereditary/familial (fCJD), iatrogenic (iCJD) den variant (vCJD). Dese diseases dey form a spectrum of related conditions plus overlapping signs den symptoms.

Prion diseases be unusual insyd dat dema etiology fi be genetic, infectious, anaa idiopathic. Genetic (inherited) prion diseases dey result from rare mutations insyd PRNP, de gene wey dey codes for PrP (spy Genetics, below). Unlike conventional infectious diseases, wich be spread by agents plus a DNA anaa RNA genome (such as viruses anaa bacteria), prion diseases be transmitted by prions, de active material of wich be solely abnormal PrP. Infection fi occur wen de organism be exposed to prions thru ingestion of infected foodstuffs anaa via iatrogenic means (such as treatment plus biologic material wey na e be inadvertently contaminated plus prions). De variant form of Creutzfeldt–Jakob disease insyd humans be caused by exposure to BSE prions. Whereas de naturally occurring transmission of prion diseases among nonhuman species be relatively common, prion transmission to humans be very rare; rather, de majority of human prion diseases be idiopathic insyd nature (spy Infectivity, below). Sporadic prion diseases dey occur insyd de absence of a mutation insyd de gene for PrP anaa a source of infection.

Although na research show say de infectious capacity of prions be encoded insyd de conformation of PrPSc, e be likely say auxiliary substances contribute to dema formation den/anaa infectivity. Purified PrPC dey appear to be unable to convert to de infectious PrPSc form insyd a protein misfolding cyclic amplification (PMCA) assay unless dem add oda components, such as a polyanion (usually RNA) den lipids. Dese oda components, dem term cofactors, fi form part of de infectious prion, anaa dem fi serve as catalysts give de replication of a protein-only prion. Considering say na de cofactors fi be produced by chemical synthesis instead of dem be sourced solely from infected cases (anaa any animal at all), e be fair to say dat dem no dey form de infectious part of de prion. However, dese catalysts (especially de polyanion) get a tendency to be included insyd de prion aggregate, wich dey make seeding new aggregates easier *in vitro*.

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