00:00 / 00:00
Viral structure and functions
Hepatitis B and Hepatitis D virus
Epstein-Barr virus (Infectious mononucleosis)
Herpes simplex virus
Human herpesvirus 6 (Roseola)
Human herpesvirus 8 (Kaposi sarcoma)
Varicella zoster virus
BK virus (Hemorrhagic cystitis)
JC virus (Progressive multifocal leukoencephalopathy)
Poxvirus (Smallpox and Molluscum contagiosum)
Lymphocytic choriomeningitis virus
Hepatitis C virus
West Nile virus
Yellow fever virus
Human parainfluenza viruses
Respiratory syncytial virus
Hepatitis A and Hepatitis E virus
Human T-lymphotropic virus
Eastern and Western equine encephalitis virus
Prions (Spongiform encephalopathy)
0 / 12 complete
0 / 2 complete
Creutzfeldt-Jakob Disease (CJD)
prion disease p. 175
Spongiform encephalopathy can be broken down. Spongiform means sponge like, encephalo- refers to the brain, and -path refers to a disease process.
So spongiform encephalopathy is a disease where the brain tissue degenerates and healthy tissue gets replaced by clusters of tiny liquid filled, thin-walled cavities called cysts, making the brain look like a sponge.
The underlying cause of spongiform encephalopathy is the accumulation of misfolded proteins called prions.
First, let’s review a bit. Proteins are made up of a long string of amino acids, and the exact sequence of these amino acids is called the primary structure.
These long chains of amino acids can fold to form different shapes, like an α-helix which is a right-handed coiled strand and a ß pleated-sheet which is when the chain folds so that segments line up alongside one another.
Each protein can contain multiple α-helices or ß pleated-sheets.
Now, there’s a protein called Prion protein, or Prp, which is encoded by the PrNP gene.
This protein is 253 amino acid long and is made up of mostly α-helices.
It’s most commonly found on the cell membrane of neurons.
Although the function of Prp is unknown, it’s thought that it might play a role in synapses between neurons and the uptake of copper into the cell.
When a prion protein is misfolded, it changes from mostly having α-helices to having a lot of ß pleated-sheets.
This new abnormal protein is called a “prion”.
When the misfolded protein enters the cells of the nervous system and interact with the normal prion protein, it acts as a template and induces misfolding in the normal prion proteins.
These prions are also highly resistant to being broken down by proteases, which are the enzymes that break down abnormal proteins.
As a result, these misfolded prion proteins cannot be easily broken down, they cause normally folded proteins to misfold and become like them, and they have an affinity for the brain - they’re basically like little ß-sheet filled zombies.
Spongiform encephalopathy is a neurodegenerative brain disease caused by the accumulation of misfolded prion proteins. This degeneration gives the brain a spongy appearance, hence its name. Prions can be transmitted by eating infected meat, blood transfusion, corneal transplants, and contaminated surgical instruments. There is no treatment for spongiform encephalopathy and they always result in dementia and eventually death.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.