Question
Prions
Answer
Prions: infectious, misfolded proteinaceous particles, devoid of any nucleic acid, causing disease by inducing conformational conversion of the normal host cellular prion protein (PrP^C, predominantly alpha-helical) into an abnormal, disease-associated isoform (PrP^Sc, predominantly beta-sheet-rich), which is protease-resistant, aggregation-prone, and accumulates in neural tissue.
Diseases caused: collectively termed transmissible spongiform encephalopathies (TSEs) — in humans, Creutzfeldt-Jakob Disease (CJD) (sporadic, familial, iatrogenic, and variant forms), Kuru, Gerstmann-Sträussler-Scheinker syndrome, and Fatal Familial Insomnia.
Pathology: neuronal loss, spongiform (vacuolar) change, and astrogliosis, without accompanying inflammation.
Key feature: remarkably resistant to standard sterilization/disinfection, requiring special decontamination protocols (prolonged autoclaving with sodium hydroxide pretreatment, or incineration of disposable instruments).
Diagnosis: CSF RT-QuIC assay, CSF 14-3-3 protein, characteristic EEG (periodic sharp-wave complexes) and MRI findings; definitive diagnosis via brain biopsy/autopsy demonstrating spongiform change and PrP^Sc.
Treatment: no effective treatment exists; management is supportive, and the diseases are uniformly fatal.