The prion is apparently immortal; it won't die. It laughs off high pressurized, superheated steam in the hospitals autoclaves used to sterilize medical instruments.
Hit it with hours of hard radiation and it just smiles. Bury it for decades, soak it in formaldehyde for months, freeze it for years, or zap it in a 700 degree fiery furnace and it still survives.
Prions infected humans from cannibalism in New Guinea and they infected sheep and cattle in the UK when farm animals were fed the remains of their brothers and sisters. Then it infected humans across Europe when they ate the meat from those animals.
Then it infected a lady gardener, a vegetarian, who used bone meal made from infected animals to fertilize her roses and breathed in microscopic prion particles which were transmitted to her brain. It turns out that one didn't actually have to eat the meat of infected animals, breathing it would do the trick.
In one sense, the prion is payback to humans from animal factory beef and mutton.
It plain language, spongiform encephalopathy is a disease that leaves holes in the brain. This is what the prion does and it is not a nice way to die; yet death is always the end result.
In New Guinea the disease was called Kuru. The progression was generally the same, beginning with an unsteady gait that lasted about a month. Then came a month of tremors accompanied by slow, continuous writhing movements of the hands and feet (athetosis), and blurred speech. The third month involved total incapacitation with the inability to swallow or move.
Death came by either starvation or thirst; or maybe sooner due to pneumonia or gangrenous bedsores from lying in their own filth, unable to move. The worst part was that the victim was aware of their suffering, being conscious and alert although unable to speak.
Richard Rhodes book, Deadly Feasts, is a must read; your life could depend on it. Please click the link above or the book image to buy it now.
So far we have been using the word "prion" rather loosely and generically. To be precise, there are two forms of protein that make up the Prion Protein, PrP.
It is "common" because it is found throughout the bodies of humans and
animals and is not infectious. Its structure is well defined.
The infectious prion shows abnormal folding patterns and has the ability to resist the enzymes that break down protein.
TSE is an umbrella term covering all the known prion diseases. It is found in quite a few animals including sheep (scrapie), cattle (bovine spongiform encephalopathy mad-cow disease), and also hits mink, cats, dogs, ostrich, various antelope species, deer and moose.
In humans it covers all the forms of CJD or Creutzfeldt-Jakob disease, the very rare Gerstmann-Straussler-Scheinker syndrome (GSS) and the even more rare Fatal familial insomnia. There is also the ground zero cases of Kuru in New Guinea among the practicing cannibals of years ago.
Early investigators compared human Kuru with sheep scrapie and found astonishing similarities, giving a number of clues. In both Kuru and scrapie the following was noted:
The fact that there is no inflammation response in indicative that the body's immune system doesn't recognize the prion as an invader or the immune response is so small as to be negligible.
The more likely scenario is that the misfolded protein is one of the body’s own proteins that has been highjacked and altered. Thus the body assumes it is an indigenous protein and presents no threat.
The video below from YouTube shows an animation of how an infectious prion might replicate itself by capturing and transforming a normal protein into its "clone".
Another thing about human prion diseases is the long time from infection to manifestation of symptoms which means that the incubation period could be years or even decades.
Since animals are typically slaughtered at market weight or when they become sick, the long incubation period was easy to overlook in livestock.
It has been proven that spongiform encephalopathies can be transmitted between species, from animal to human and furthermore, the means of transmission are numerous.
Humans can acquire it from eating meat, by receiving a transplant from an infected donor, from working around infected animals or possibly by breathing it in via direct transmission from the olfactory organ to the hippocampus, that part of the brain that interprets smells.
It sounds easy to say that the transmission modes have been proven but it was an extremely long, hard road getting there.
One major breakthrough was showing that TSE could be transferred from humans to chimps.
Another big step was that transmission of CJD from human to human was confirmed in cases of human growth hormone harvested from the pituitaries of cadavers given to young children; it was seen in a cornea transplant from an undiagnosed CJD cadaver and it was seen in transplanted dura matter used for patching after brain surgery.
Finally someone was able to put a face on the infective agent. Patricia Merz was a researcher looking into brain diseases in young children. After teaching herself how to use an electron microscope and how to stain sample tissue for viewing by the microscope she made an amazing discovery.
In 1978 she was working with an English colleague and examining some of his sheep scrapie specimens and saw something that looked like "sticks" scattered among cell debris; they had the appearance of short, broken lengths of twisted thread, fibrils as it were.
She also observed that as the disease progressed, they increased in quantity. After seeing the same fibrils in the spleen of infected guinea pigs and human CJD subjects she realized that she was looking at the infectious agent itself. Patricia Merz labeled it scrapie associated fibrils (SAF).
Photo left: Prion at 100,000 times magnification showing threadlike fibrils, courtesy NIAID-RML.
Another researcher, Stanley Prusiner, had been studying scrapie and concluded that he knew enough about the scrapie agent to publish a paper in April 1982. He titled the paper "Novel Proteinaceous Infectious Particles Cause Scrapie".
Playing on the name proteinaceous infectious particle, he christened the agent "prion". Prusiner is widely credited with discovering the prion although Patricia Merz arguably beat him by at least four years.
In April 1985, a dairy cow made history in Britain. She was acting very strangely, exhibiting odd movements, wasting away, behaving differently, losing motor control in its hind legs and eventually was killed.
Its condition was misdiagnosed and she went to the rendering plant where it was made into commercial meat-and-bone meal. Seven more cows succumbed over the next 18 months and by 1986 there were cases in herds in widely separated counties.
Based on the spongiform damage and astrogliosis, the star shaped glial cells, they designated it as bovine spongiform encephalopathy (BSE). By the end of 1987, it had spread to herds throughout England and Wales.
By the end of 1988, there were 2,185 reported cases of BSE, almost certainly very under reported. Actually it was criminally underreported since by February 1995 the cases had risen to 143,109.
Through exhaustive investigation and process of elimination, the source was determined to be meat-and-bone meal that was fed to dairy herds but not usually beef cattle. Beef cattle are fed grass, hay or alfalfa while growing then fattened with grains such as corn or soy.
Dairy cows require a fortified diet in order to maximize their milk production and since not much soy or corn was grown in the UK, meat-and-bone meal was the added protein of choice.
Worldwide, cattle, sheep, pigs and chickens are routinely fed the cooked and dried remains of dead animals, including downer cattle and dead sheep of undiagnosed disease.
Beef cattle are often fed meat-and-bone meal during the finishing phase just before slaughter and calves are fed the meal to maximize their growth. Thus food animals are turned into cannibals in the interest of more and cheaper meat and milk and higher corporate profits.
When dairy cows have reached the end of their milk production they are slaughtered and made into hamburger or chopped for meat pies in England. Even cattle brains used to go into hamburger, thankfully no longer. Nevertheless, every part of both beef and dairy cattle is eaten; recycled back into the next generation of food animals or processed into commercial products.
Some of those commercial products were pet food and it turned out that cats could get TSE as well as sheep, cattle, mink and deer. In May 1990 a pet cat started acting strangely, very similar to sheep with scrapie or the failing hind legs of downer cattle. It was euthanized and diagnosed as spongiform encephalopathy.
Typical of a government bureaucrat, the chief veterinary officer dismissed it, after all, he said there was no evidence that the condition is transmissible nor is there any known connection with the other animal encephalopathies.
He opined that this was only one cat death in 7 million UK cats. Over the next four years, 62 other pet cats died of TSE however no one will ever know how many unreported cats used up their nine lives. Finally the government admitted that it was likely contaminated pet food that did them in.
While all this was going on, a variety of zoo animals were dying of strange spongiform encephalopathies. How odd that they also had meat-and-bone meal incorporated into their feed.
Then the unthinkable happened; people started dying from mad cow disease. In 1993, two dairy farmers died from CJD. Their deaths were dismissed as being within the normal statistical incidence of CJD. Then a fifteen year old girl came down with it and died. Her parents were consoled by a government investigator who told them to keep quiet about it; "Think about the economy, think about the Common Market".
Next, in March, 1994, a sixteen year old Muslim girl who liked hamburgers died of TSE. Then it was an 18 year old schoolboy who had often visited his aunt's farm in his early years and would have drank lots of unpasteurized milk and been in close proximity with the cows.
By the start of 1996, in addition to these cases, seven other young people had died of TSE.
All of these cases had something in common...their brain samples were different from the CJD cases previously seen. The stains of these brain slices showed very large amyloid plaques spread throughout the brain, not just the cerebellum.
Unlike the smaller CJD plaques, these were surrounded by a destructive halo of spongiform holes. These exhibited the diagnostic signs of the Kuru spongiform that had killed the cannibals in New Guinea.
What did the British government do? Well, Prime Minister, John Major, emphatically claimed that human beings do not get mad cow disease.
The Spongiform Encephalopathy Advisory Committee (SEAC), set up to advise the government on BSE, tried to suppress any announcement of this new form of CJD, saying the scientists could be wrong.
Nevertheless, Secretary of State for Health, Stephen Dorrell, went public on March 20th, 1996. In front of the House of Commons, he informed the country that BSE had in all likelihood spread to humans from eating beef.
Next France, then Switzerland reported TSE cases. The source of all these infections became very uncertain. Since meat-and-bone meal had been routinely fed to pigs, chickens and dairy cattle, the source could very well be pork, bacon, leather, butter, milk and chicken-pot-pies.
Pigs and chickens did not exhibit any symptoms because they were usually slaughtered well before the time that incubation symptoms could appear.
The bottom line is that humans contract spongiform encephalopathies from eating infected animal products and animals contract TSE from eating animal protein from other animals.
It is possible that even vegetarians could be at risk in that when meat-and-bone meal is fed to chickens or hogs, it goes through them so fast and their manure is routinely spread on growing crops to be absorbed by food plants.
There is evidence that minute, nanosized particles of the infectant can be inhaled and carried to the brain to start its incubation period.
Currently CJD cases and other TSE's are closely monitored and the new cases seem to be holding steady. The big question however is what will happen in the next decade or two when those infected 20, 30 and 40 years ago start reaching the end of their infections incubation period. Industrial animal factories are still feeding hogs, chickens and cattle ruminant protein.
Governments don't seem to get it. The British government chose to protect its livestock industry over the protection of its citizens and in the US, the USDA is following a similar path based on denial, cover-ups and measures designed to protect large scale CAFO operations to the peril of the industries consumers.
According to Dr. John Collinge, a neurologist at St. Mary's Hospital in London, there are two PrP genes, M and V, and we inherit one from each parent. Therefore it is possible to have an MM or VV or MV combination.
In fact Dr. Collinge claims that 38% of us have MM, 51% are MV and 11% are VV. His experiments showed that the BSE agent can infect all three gene combinations. He noted that since only the MMs have reached the stage of showing symptoms in people, there could be two remaining waves of infection when the VV and MV start dying.
It is still possible that the actual trigger of infection will prove to be viral which would be a great embarrassment to both the 1997 Nobel Medical Assembly at the Karolinska Institute in Stockholm and Stanley Prusiner to whom they awarded the Nobel honor.
Ongoing research, particularly by Laura Manuelides may yet uncover the elusive virus. In the meantime, Prusiner and others still contend that the prion is able to reproduce without the use of nucleic acid to convey the information needed to reproduce.
This would make the prion totally unique in nature and there are many voices stating that non-nucleic reproduction is an absolute impossibility.
The significance is that if the virus is found, then the door is opened to create a protective vaccine. Until then the beat goes on.
Farmers are still incorporating composted, fermented manure into their cattle feed. About 3 billion pounds of waste blood from slaughterhouses is still allowed to be mixed in with animal feed.
Even though the FDA prohibited the use of most animal protein in the manufacture of feed for cattle, sheep and goats back in 1997, it excluded blood, blood products, gelatin, milk and milk products, pig and horse protein and restaurant and institutional plate waste.
According to Richard Rhodes in Deadly Feasts, CJD is the human manifestation of BSE and nothing that the rendering plants or slaughterhouses can do will reliably make the infectious prion or virus, whichever it turns out to be, safe for consumption.
It is a certainty that the U.S. will have to deal with mad cow prion; the only questions are when and how the government and factory farm system will deal with it. History indicates that the initial reaction will be to downplay the danger, protect the industry and keep the status quo.
The foregoing has dealt with domestic livestock with no thought given to animals in the wild. In 1967 all that changed when a prion disease was found in captive deer in U.S. research centers and started showing up in wild herds in 1980.
From the symptoms and progression of the disease it was christened "chronic wasting disease" or just CWD. There are differences between mad cow disease and CWD but the similarities are what makes it a very scary proposition.
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CWD seems to favor deer such as whitetails, mule deer, elk and moose that reside in Wyoming, Colorado, Utah, Kansas, Nebraska, West Texas and Southern New Mexico plus smaller occurances in 10 other states. Two Canadian provinces have reported cases as well.
Symptoms manifest with gradual lose of weight, repetitive behaviors, listless zombielike movements, excessive drooling and urination. Once symptoms appear, death follows in a few months and is always fatal.
One major and very frightening difference between CWD and mad-cow disease is that mad-cow only appears in the nervous system (brain and spinal cord) but CWD the mis-folded protein is systemic. It is found in the animals saliva, blood, bones, feces, urine and muscle tissue.
The implications are that CWD could be spread through indirect contact such as animals sharing a salt lick, drinking out of the same water pool, or licking or grooming an infected herd member.
So far there is no evidence that CWD has or can jump from animal to human and that transmission between animal species is difficult. Nevertheless, the threat is serious and research is proceeding at a rapid pace. The real threat to date seems to be economic where deer hunting brings in millions of dollars to a state.
There are still many, many ongoing research programs in the field of transmissible spongiform encephalopathies and we will close by mentioning two; one having to do with detection, the other with prevention.
From the NIH NIAID website we learn that "miniscule amounts of infectious prions found outside the brain can be detected by current diagnostic tests, but these methods lack the speed and convenience needed for routine use.
Other quicker approaches aren't sensitive enough to detect low levels of infection. A research team led by Dr. Byron Caughey of NIH's National Institute of Allergy and Infectious Diseases (NIAID) has been working to develop a better method for quickly detecting small amounts of prions.
The researchers described their new method called real-time quaking-induced conversion, or RT-QuIC, in the December 2, 2010, online edition of PLoS Pathogens. RT-QuIC is about 50-200 times faster and much less expensive than animal bioassays that detect similarly small amounts of disease-causing prions.
RT-QuIC takes advantage of the ability of tiny amounts of prions to seed the misfolding of normal prion proteins in a test tube. The method involves testing a range of dilutions to see at what point the sample loses its seeding activity.
The scientists tested tissue samples from infected deer and sheep and were able to distinguish infected animals from normal ones in 2 days or less. They were also able to detect prions in nasal washes from infected hamsters."
Concerning prevention, from PhysOrg.com, we read that "antibodies that stick to a brain prion protein called PrP could be the key to treating prion diseases like variant CJD and preventing people accidentally exposed to prions from going on to develop the fatal brain disease.
Using a precise visualization technique, called X-ray crystallography, carried out at the Synchrotron Radiation Source (SRS) at the Science and Technology Facilities Councils (STFC) Daresbury Laboratory in Cheshire, scientists have identified an antibody that has the best ability to bind to PrP in the brain.
Experiments using cells in the laboratory and in mice have suggested it could stop prion infection in its tracks.
Photo left: Crystallographic structure of prion protein
Neither of these items concerning detection or prevention has been applied to humans but great discoveries usually start with the ubiquitous lab mouse, hamster or guinea pig.
One other diagnostic approach that is still way in the future is eyedrops that may be used to identify amyloids. Amyloids are sticky plaques of protein that mark several degenerative neural diseases such as Alzheimer's, Parkinson's and prion diseases.
It turns out that amyloids accumulate in the eyes as well as the brain. So currently in development is eye drops containing flourescent substances that cause the amyloid plaques to glow with different colors depending on the type of plaque.
At least the research is ongoing.
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