This is mostly a test ;) I want to see if this actually DOES embed the powerpoint into the post, since there isn't an "embed" button on my blogger dashboard that I can see...
Here is the readings for the slides:
I'm going to talk about prions today. First off, there isn't really a consensus in the pronunciation - some say prions and some say "pree-ons" so sorry if I confuse you!
Prions are a misfolded protein found on many cell membranes, particularly nervous system tissue. we aren't sure exactly what is usually does. The normal configuration is referred to as PrPc (cellular). The misfolded configuration PrPsc (scrapie) where the structure alters from alpha helices into beta sheets that pack tightly together into amyeloid aggregates that disrupt the cell function and interfere with tissue function. The ends of the aggregates are fibrils, which contact adjoining prion proteins and trigger this post-translational rearrangement and add them to the aggregate.
Prion-based diseases are not curable and are fatal. Because of the affinity of the prion protein for neural tissue, the diseases are all neurodegenerative. Scrapie has been the bane of livestock farmers since at least the 1700’s, all they really knew was that it was incredibly infectious. Transmissible spongiform encephalopathy, or TSE, also known as mad cow disease, emerged in the 1980’s in Great Britain, where some infected sheep parts were rendered into cattle meal which infected the cows, and when the beef was eaten, it then infected people and eventually was strongly linked to sudden increased emergence of the variant Cruetzfeldt-Jakob disease. Chronic wasting disease, CWD, is the disease affecting
the cervid family – deer, moose, and elk. This was my research focus. There are also other prion based diseases.
CWD was first identified in Colorado in 1967 but now is found in 23 states and Canada, in
wild populations and deer farms. Like other prion-based diseases, CWD has an incubation
time after infection from 18 months to over 20 years. During this phase, the deer may display muscle wasting, excessive salivation, and weight loss. Near the end, the acute clinical phase develops, asts around 2-6 months and includes hyper-excitibility, abnormal behavior, loss of bodily functions, and eventually death.
Transmission - Only cells that can express the PrP protein can become infected. Researchers have studied transmission routes. Plant leaves can become infected from direct contact with prions or plant root uptake from infected soil. After infection, even before the onset of the acute clinical phase, the deer shed infectious prion particles into the environment. Once death occurs, the body contains a large volume of infectious prions that can be carried to water sources via runoff, or contaminate the soil when the body decomposes. Contaminated water can also come from slaughtering facilities. Ecto-parasites such as certain fly larvae and mites can transmit prions from one species to another.
Holcomb et al, 2016, used computer modeling to determine the volume of shedding from infection until death from saliva, urine, and feces. it predicted that one lethal dose around 9 months post-infection increased drastically by 15 months, to over 10 lethal doses.
Prions are notoriously difficult to eradicate from surfaces or to disinfect tissue. The prion in tissue has found to still be viable at 600 degrees Celsius. And of course, removing plants, soil, water, and ecto-parasites from infected pasture, fields, or forests is almost impossible. The World Health Organization recommendations from 1997 only include “Variable or partially effective” methods. I assume if they had better suggestions, they would have updated this information.
But, there are researchers investigating prion treatments. Ding and his associates have done many ozone treatment studies. Because prions will bind to solid organic particles in water, gravity separation to remove these from wastewater, followed by ozone treatment, can neutralize the water to a safe level. Marciniuk is investigating the possibility of developing vaccines for protein aggregate diseases and others that may be similar, including Alzheimer’s, Huntington’s, and Parkinson’s diseases. There are some challenges involved but they are hoping to use the misfolded protein as an antigen. Hou’s research that our immune system uses infectious aggregates very similar to prion-caused aggregates suggest that this kind of infectious protein may be more common in the natural world than we realize.
I would like to raise deer on my farm, that is why I wanted to research this disease, and there are some risks. Unknowingly buying infected breeding stock has the potential to transmit prions via ectoparasites to other animals on my farm or to nearby farms. If contaminated, the pastures would be unusable for any animals raised for consumption (by humans or other animals) for an unknown length of time. Another would be the possible contamination of slaughterhouse facilities and its wastewater, and inability to safely decontaminate them. And, disposal of bodies after death and loss of investment money.