Question
Prions
Answer
Prions are unique infectious agents composed entirely of protein, with no associated nucleic acid — a fundamental departure from all other known infectious agents.
Mechanism: prions are misfolded, abnormal isoforms (PrP^Sc) of a normal host cellular protein (PrP^C), able to directly convert normal PrP^C into more abnormal PrP^Sc through a self-propagating conformational templating mechanism, without requiring nucleic-acid-based replication.
Pathogenesis: accumulated abnormal protein aggregates in neural tissue, resistant to normal degradation, causing progressive neuronal dysfunction/death and characteristic spongiform degeneration, without eliciting an inflammatory/immune response.
Diseases: Creutzfeldt-Jakob disease (CJD) — the most common human prion disease; kuru; Bovine Spongiform Encephalopathy (BSE) and its human counterpart variant CJD; fatal familial insomnia.
Distinctive property: remarkably resistant to conventional sterilization (standard autoclaving, formaldehyde), requiring special decontamination protocols for instruments used on suspected/confirmed cases.