Infectious disease that carries no DNA or RNA
Prions are misfolded proteins that coerce normal copies into the same bad shape. Stanley Prusiner coined the name in 1982 for a proteinaceous infectious particle—no nucleic acid inside, yet able to spread fatal brain disease through shape alone.
Unlike viruses, bacteria, or fungi, prions carry no DNA or RNA. They are twisted isoforms of major prion protein (PrP), a natural protein whose job is still unclear. Diseases linked to them include scrapie in sheep, chronic wasting disease in deer, bovine spongiform encephalopathy in cattle, and Creutzfeldt–Jakob disease in people. In mammals they wreck brain or other neural tissue, progress without known effective treatment, and kill. Since 2015 a prion form of alpha-synuclein has also been tied to multiple system atrophy; Alzheimer's, Parkinson's, and ALS show prion-like spread of misfolded protein.
Cellular PrP sits on membranes—platelets are the largest human blood reservoir—with about 209 amino acids and mostly alpha-helix structure. Infectious PrPSc swaps in more beta-sheet, resists proteases, and templates free cellular PrP into the same fold so fibers grow. Amyloid aggregates damage tissue; structural toughness resists ordinary chemical or physical cleanup and raises iatrogenic risk via instruments. Fibril growth plus breakage can explain exponential rise of infectious particles better than a simple one-to-one heterodimer model, which would demand unrealistically huge catalytic power.
Normal PrP function is debated: hints include myelin repair in peripheral nerves, possible long-term memory roles, bone-marrow stem-cell self-renewal, and antiviral innate-immunity effects. Drug models suggest you need not erase every prion—only slow exponential growth—ideally by blocking fibril ends. That framing turns a slow incubation into a therapeutic opening rather than a hopeless wait for total clearance.
Source: Prion
