We’ve all heard of things that can be harmful to the human body. Things like viruses, bacterium and parasites. But in the recent scientific world, many scientists are beginning looking into prions. What are prions? Prions are misfolded cellular proteins that are infectious and harmful to the body. Unlike the other infectious agents such as viruses, fungus, bacteria and such, prions does not have DNA,s RNAs, or both. They are abnormal proteins that have the ability to convert healthy proteins to diseased ones. And since these misfolded proteins is just an isoform of our healthy proteins. It makes it nearly impossible for the antibodies our system to detect them as ‘foreign’. The first prion is believed to have come from cows that ate feeders with infectious sheep scrapie and crushed up sheep bones back in the 1980s in Great Britian. Once an infectious prion gets into the body it begins to convert good proteins and replicates without being caught by patrolling lymphocytes! Once replication is done, the prions migrate to the nervous system and lymphoid organs. Prion causes deadly diseases such as Bovine Spongiform Encephalopathy (BSE) aka “Mad Cow Disease” and variant Creutzfeldt-Jakob disease (vCJD). Both diseases are brain degenerative diseases. BSE are found in cattle and vCJD are brain damage in humans. Holes are formed in the tissues of the brain that makes it look like a “sponge” and causes loss of emotions, memory, movement, speech, and sight.
How do we acquire these infectious prions? By consuming machine processed meat such as hamburger beef patties, hot dogs, meat on pizza toppings, taco fillings and sausages. America on average consumes 28 billion processed hamburgers a year. The entire world consumes an estimation of 200 billion hamburgers a year. That’s a lot of processed meat! In meat processing plants, the machine typically separates the spinal cord from the meat. However, the meat that gets separated is not always 100% free of nervous tissues. Occasionally, there are still some nervous tissues that tag along. Prions are resistant to chemicals and high pressure and temperature cannot denature the prions, so cooking or boiling the meat will not get rid of it. Having that said, the chance of getting a defective patty is fairly rare. According to U. S. Department of Agriculture, every 4 out of 70 beef patties contain spinal tissue residues and of the 4 patties none were infected with the deadly prion. But that doesn’t mean there won’t be any out there. So the next time you eat a burger, before you bite into that delicious, juicy, charbroiled burger, think twice before you do so.
Cited Sources:
Nuvolone M, Aguzzi A, Heikenwalder M. (2009) FEBS Volume 589, Issue 16, Pages 2674-2684, Protein Folding, Misfolding and Diseases “Cells and Prions: License to replicate”.
http://www.sciencedirect.com/science/article/pii/S0014579309004608
Hu W, Kieseier B, Frohman E, Eagar TN, Rosenberg RN, Hartung HP, Stüve O. (2008) J Neurol Sci. 2008 Jan 15;264(1-2):1-8. Epub “Prion proteins: physiological functions and role in neurological disorders”.
http://www.ncbi.nlm.nih.gov/pubmed/17707411
Hu W, Rosenberg RN, Stüve O. (2007) cta Neurol Scand. 2007 Aug;116(2):75-82. “Prion proteins: a biological role beyond prion diseases”.
http://www.ncbi.nlm.nih.gov/pubmed/17661791
David & Stephen Schmidt (2001) Nutrition Action June 2001 US Edition. “How Now, Mad Cow!”.
http://www.cspinet.org/nah/06_01/#3
Interestingly, it's not just that prions able to fly under the radar of our "patrolling lymphocytes," but antigen-presenting dendritic cells have actually been implicated in the spread of prions to the nervous system.
ReplyDeleteIn mouse, sheep, deer, and cow animal models, the first nervous tissue the abnormal isoform of PrP (prion) can be found in is the enteric nervous system of the gut (1). Dendritic cells located in Peyer’s Patches of the gut seem to be capable of capturing prions (2) and several studies have shown convincing evidence that dendritic cells are involved in the neuroinvasion process. For example, prion-loaded dendritic cells given via an intra-peritoneal injection to mice were enough to induce scrapie (a transmissible spongiform encephalopathy caused by a prion) (3). Also, a temporary depletion of dendritic cells was enough to impair prion neuroinvasion after oral inoculation of mice (4).
The exact mechanism of this neuroinvasion is yet to be understood, but the role of dendritic cells seems to be quite important. It’s unfortunate that a system so intricately designed to protect us actually enables the transmission and spread of these fatal neurodegenerative diseases.
1. Andreoletti O, et al. (2000) Early accumulation of PrP(Sc) in gut-associated lymphoid and nervous tissues of susceptible sheep from a Romanov Xock with natural scrapie. J Gen Virol 81:3115–3126
2. Dorban G, et al. (2007a) Interaction between dendritic cells and nerve Wbres in lymphoid organs after oral scrapie exposure. Virchows Arch 451:1057–1065
3. Aucouturier P, et al. (2001) Infected splenic dendritic cells are sufficient for prion transmission to the CNS in mouse scrapie. J Clin Invest 108:703–708
4. Raymond CR, et al. (2007) In vivo depletion of CD11c+ cells impairs scrapie agent neuroinvasion from the intestine. J Immunol 179:7758–776