A normal prion protein ($$PrP^C$$) in a cell can be converted into its infectious, misfolded rogue form ($$PrP^{Sc}$$) due to a genetic mutation or spontaneous event. Once formed, the rogue prion protein ($$PrP^{Sc}$$) interacts with and stimulates normal endogenous $$PrP^C$$ proteins to misfold, leading to the accumulation of plaque-like aggregates in nervous tissue.

Prion Misfolding and Disease Onset

Symptoms of transmissible spongiform encephalopathies (TSE) include severe brain damage, loss of motor coordination, dementia, and mental impairment. As the disease rapidly progresses, affected individuals become completely unable to move or speak, eventually leading to death.

Signs and Symptoms of Transmissible Spongiform Encephalopathies

Prions are acellular, infectious protein particles that do not contain DNA or RNA, cause transmissible spongiform encephalopathies, and are excluded from the tree of life. They are exceptionally small, measuring approximately $${}1/10$$ the size of a typical virus, and are extremely resistant to heat, chemicals, and radiation. Currently, there is no treatment or cure for prion infections.

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Transmissible spongiform encephalopathies (TSEs) are rare, fatal degenerative disorders of the brain and nervous system caused by prions. The accumulation of abnormal rogue prion proteins destroys brain cells, creating sponge-like holes in the brain tissue. This results in severe brain damage, rapid cognitive decline, loss of motor control, and ultimately death within months or years, for which there is no cure.

Transmissible Spongiform Encephalopathies

- Opportunistic pathogen
- Primary pathogen

Types of Pathogens

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Creutzfeldt-Jakob disease (CJD) is an extremely rare and universally fatal transmissible spongiform encephalopathy (TSE) caused by prions. Diagnosed in only about $${}300$$ patients in the United States each year, the disease induces rapid cognitive decline. There is currently no approved treatment, and roughly $${}90\%$$ of affected individuals succumb to the disease within $${}1$$ year of diagnosis.

Creutzfeldt-Jakob Disease (CJD)

Scrapie is a fatal, degenerative disease in sheep caused by prions.

Scrapie

Prions

A primary pathogen can cause disease in a host regardless of the host’s microbiota or immune system.

Primary Pathogen

An opportunistic pathogen can only cause disease in situations that compromise the host’s defenses, such as skin, immune system, or normal microbiota.

Opportunistic Pathogens

Nonliving disease agents are acellular pathogens, such as viroids, virusoids, and prions, that are entirely distinct from viruses. These agents consist solely of RNA or proteins, yet they share the viral ability to self-propagate by utilizing host cell machinery to cause disease.

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