Model Answer
0 min readIntroduction
Prions are unique infectious agents, distinct from conventional pathogens like bacteria, viruses, fungi, and parasites. The term "prion" stands for "proteinaceous infectious particle," coined by Stanley Prusiner, who received the Nobel Prize in Physiology or Medicine in 1997 for their discovery. Unlike other infectious agents, prions lack nucleic acids (DNA or RNA) and are composed solely of misfolded proteins. These misfolded proteins have the ability to induce normal proteins to adopt the same aberrant conformation, leading to a cascade of misfolding and ultimately causing disease.
Prions: Structure and Mechanism
Prions are infectious isoforms of normal cellular proteins found predominantly in the nervous system. The normal, harmless form is denoted as PrPC (cellular prion protein), while the misfolded, infectious form is PrPSc (scrapie prion protein). PrPSc induces PrPC to convert into PrPSc, leading to aggregation and neuronal damage.
Prions vs. Viruses
The key difference lies in their composition. Viruses contain nucleic acid (DNA or RNA) enclosed within a protein coat, requiring a host cell for replication. Prions, however, are solely protein and replicate by converting normal proteins into the misfolded form.
| Feature | Prions | Viruses |
|---|---|---|
| Composition | Misfolded protein (PrPSc) | Nucleic acid (DNA or RNA) + Protein coat |
| Replication | Conversion of PrPC to PrPSc | Host cell machinery |
| Antibiotic/Antiviral Sensitivity | Resistant | Sensitive to antivirals |
Diseases Caused by Prions
- Animals: Scrapie (sheep), Bovine Spongiform Encephalopathy (BSE or "mad cow disease" in cattle), Chronic Wasting Disease (CWD) in deer and elk.
- Humans: Creutzfeldt-Jakob Disease (CJD), Variant Creutzfeldt-Jakob Disease (vCJD) linked to BSE, Gerstmann-Sträussler-Scheinker syndrome (GSS), Fatal Familial Insomnia (FFI).
Conclusion
Prions represent a unique class of infectious agents, posing significant challenges due to their unconventional nature and resistance to conventional sterilization methods. Their ability to induce protein misfolding and cause devastating neurodegenerative diseases highlights the importance of understanding their mechanisms and developing effective prevention and treatment strategies. Continued research is crucial to combat these rare but invariably fatal conditions.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.