Researchers have found abnormal prion protein in the skin of 23 people who died from Creutzfeldt-Jakob Disease (CJD). Meanwhile exposing mice to skin tissue taken from the CJD patients caused them to develop prion disease.

The study has raised questions about the possibility of prion diseases being transmitted during medical procedures that involve the skin, as well as the possibility of using skin samples to detect the diseases.

Creutzfeldt-Jakob disease (CJD)—the human equivalent of mad cow disease—is caused by rogue, misfolded protein aggregates termed prions, which are infectious and cause fatal damages in the patient’s brain. CJD patients develop signature microscopic sponge-like holes in their brains. The initial signs of CJD include memory loss, behavior changes, movement disorder, and vision problems, which usually rapidly progress to death. According to the National Institutes of Health (NIH), 90 percent of CJD patients die within one year of onset, and hundreds of Americans are diagnosed annually. There is no available treatment or cure.

There are numerous types of prion diseases in humans. About 90 percent of CJD cases have a sporadic origin. Inter-personal CJD transmission has occurred after patients were exposed to surgical tools previously contaminated by CJD brain tissues.

In a Science Translational Medicine study published today, Case Western Reserve University School of Medicine researchers found that CJD patients also harbor infectious prions in their skin, albeit at lower levels. In the study, the researchers collected skin samples from 38 patients with assistance from the National Prion Disease Pathology Surveillance Center at Case Western Reserve School of Medicine and measured their prion levels.

Using a highly sensitive in vitro assay developed and conducted by Byron Caughey’s group at the NIH, they detected prion protein aggregates in the skin samples from all of CJD patients. Prion levels were 1,000-100,000 times lower in the skin than in the brain, and only detectable by this extremely sensitive assay. The researchers further demonstrated that such skin prions are infectious, since they are capable of causing disease in humanized mouse models.

“It is well known that CJD is transmissible via surgical or medical procedures involving prion-infected brain tissue. Our finding of infectious prions in skin is important since it not only raises concerns about the potential for disease transmission via common surgeries not involving the brain, but also suggests that skin biopsies and autopsies may enhance pre-mortem and post-mortem CJD diagnosis,” said Wenquan Zou, Associate Professor of Pathology and Neurology and Associate Director of the National Prion Disease Pathology Surveillance Center at Case Western Reserve School of Medicine. Zou led the study involving a consortium of research groups and researchers across Case Western Reserve School of Medicine, University Hospitals Cleveland Medical Center, the NIH, and the People’s Republic of China.

“The level of prion infectivity detected in CJD skin was surprisingly significant, but still much lower than that in CJD brains,” cautioned Qingzhong Kong, Associate Professor of Pathology and Neurology at Case Western Reserve School of Medicine.

“Prion transmission risk from surgical instruments contaminated by skin prions should be much lower than that of instruments contaminated by brain tissue.” In the study, the Kong group assisted by the Zou group demonstrated that CJD patient skin is infectious using humanized transgenic mouse models.

Current diagnostic tools for CJD rely on brain tissue samples collected at either biopsy or autopsy, or cerebral spinal fluid obtained by spinal taps. The new study may lay the foundation for less invasive techniques. “Using the skin instead of brain tissue for post-mortem diagnosis could be particularly helpful in cultures that discourage brain autopsy, such as China and India. These countries have the largest populations with the greatest number of patients, but brain autopsy is often not performed,” said Zou.

“Further investigation is necessary to determine whether extra precautions should be taken during non-neurosurgeries of CJD patients, especially when surgical instruments will be reused,” said Zou. Case Western Reserve School of Medicine researchers plan to further evaluate the potential risk of skin prion transmission through non-neurosurgeries.

The study was conducted by scientists from the National Institute of Allergy and Infectious Diseases (NIAID) and various other collaborating groups.

Generally, people associate prion diseases with the brain, although it has been shown that clusters of the abnormal prion protein, which cause sponge-like holes in the brain, can accumulate in other organs including the liver, spleen, lungs and kidney. It is known that Sporadic CJD, which can be transmitted via invasive medical procedures involving the central nervous system and cornea, but transmission via the skin has not generally been considered a concern. Blood products also pose a rsk of prion transmission.

The authors want to study the risk of surgical instruments becoming contaminated and the risk associated with procedures that involve CJD patients. They also suggest the possibility of using the skin-based diagnostic test for prion diseases in humans and animals.

The medical term for prion disease is transmissible spongiform encephalopathy, which includes ALS, Alzheimer’s disease, Parkinson’s disease, Creutzfeldt-Jakob disease, mad cow disease, chronic wasting disease. The operative word is transmissible. Victims generate a tremendous amount of infectious waste.

The major difference between these forms of neurodegenerative disease is the species under attack and the region of the brain that is under attack. The primary difference between Alzheimer’s disease and Parkinson’s disease, for example, is the region of the brain that is under attack by the pathological protein.

There are proven strategies to help avert neurodegenerative disease, including nutrition, exercise and prion aversion. There is not a cure for prion disease. Preview and order the eBook now to defend yourself and your family.

The post Skin Transmits Prion Disease appeared first on Neuroscience News.

The 1997 Nobel Prize in Physiology or Medicine is awarded to the American Stanley Prusiner for his pioneering discovery of an entirely new genre of disease-causing agents and the elucidation of the underlying principles of their mode of action. Stanley Prusiner has added prions to the list of well known infectious agents including bacteria, viruses, fungi and parasites.

Prions exist normally as innocuous cellular proteins, however, prions possess an innate capacity to convert their structures into highly stable conformations that ultimately result in the formation of harmful particles, the causative agents of several deadly brain diseases of the dementia type in humans and animals.

Prion diseases may be inherited, transmitted, or occur spontaneously.

Regions within diseased brains have a characteristic porous and spongy appearance, evidence of extensive nerve cell death, and affected individuals exhibit neurological symptoms including impaired muscle control, loss of mental acuity, memory loss and insomnia. Stanley Prusiner’s discovery provides important insights that may furnish the basis to understand the biological mechanisms underlying other types of dementia-related diseases, for example Alzheimer’s disease, and establishes a foundation for drug development and new types of medical treatment strategies.

In 1972 Stanley Prusiner began his work after one of his patients died of dementia resulting from Creutzfeldt-Jakob disease (CJD). It had previously been shown that CJD, kuru, and scrapie, a similar disease affecting sheep, could be transmitted through extracts of diseased brains. There were many theories regarding the nature of the infectious agent, including one that postulated that the infectious agent lacked nucleic acid, a sensational hypothesis since at the time all known infectious agents contained the hereditary material DNA or RNA.

Prusiner took up the challenge to precisely identify the infectious agent and ten years later in 1982 he and his colleagues successfully produced a preparation derived from diseased hamster brains that contained a single infectious agent. All experimental evidence indicated that the infectious agent was comprised of a single protein, and Prusiner named this protein a prion, an acronym derived from “proteinaceous infectious particle.” It should be noted that the scientific community greeted this discovery with great skepticism, however, an unwavering Prusiner continued the arduous task to define the precise nature of this novel infectious agent.

Infectious Prions

Where was the gene encoding the prion, the piece of DNA that determined the sequence of the amino acids comprising the prion protein? Perhaps the gene was closely associated with the protein itself as in a small virus? The answers to these questions came in 1984 when Prusiner and colleagues isolated a gene probe and subsequently showed that the prion gene was found in all animals tested, including man. This startling finding raised even more questions. Could prions really be the causative agent of several dementia-type brain diseases when the gene was endogenous to all mammals? Prusiner must have made a mistake!

The solution to this problem became evident with the sensational discovery that the prion protein, designated PrP, could fold into two distinct conformations, one that resulted in disease (scrapie PrP = PrPSc) and the other normal (PrP = PrPc). It was subsequently shown that the disease-causing prion protein had infectious properties and could initiate a chain reaction so that normal PrPc protein is converted into the more stabile PrPSc form. The PrPSc prion protein is extremely stabile and is resistant to proteolysis, organic solvents and high temperatures (even greater than 100^o C).

With time, non-symptomatic incubation periods vary from months to years, the disease-causing PrPSc can accumulate to levels that result in brain tissue damage. In analogy to a well known literary work, the normal PrPc can be compared to the friendly Dr. Jekyll and the disease causing PrPSc to the dangerous Mr. Hyde, the same entity but in two different manifestations.

The long incubation time for prion based disease hampered the initial efforts to purify the prion protein. In order to assess purification schemes Prusiner was forced to use scores of mice and in each experiment wait patiently for approximately 200 days for the appearance of disease symptoms. The purification efforts accelerated when it was demonstrated that scrapie could be transferred to hamsters, animals that exhibited markedly shortened incubation times.

Together with other scientists, Prusiner cloned the prion gene and demonstrated that the normal prion protein was an ordinary component of white blood cells (lymphocytes) and was found in many other tissues as well. Normal prion proteins are particularly abundant on the surface of nerve cells in the brain. Prusiner found that the hereditary forms of prion diseases, CJD and GSS (see the last section), were due to mutations in the prion gene. Proof that these mutations caused disease was obtained when the mutant genes were introduced into the germline of mice. These transgenic mice came down with a scrapie-like disease.

Learn more about Dr. Stanley Prusiner and the Nobel Prize for prion science and prion disease.

In 1992 prion researchers obtained conclusive evidence for the role of the prion protein in the pathogenesis of brain disease when they managed to abolish the gene encoding the prion protein in mice, creating so called prion knockout mice. These prion knockout mice were found to be completely resistant to infection when exposed to disease-causing prion protein preparations. Importantly, when the prion gene was reintroduced into these knockout mice, they once again became susceptible to infection. Strangely enough, mice lacking the prion gene are apparently healthy, suggesting that the normal prion protein is not an essential protein in mice, its role in the nervous system remains a mystery.

Prions accumulate in different regions of the brain

Specific mutations within the prion gene give rise to structurally variant disease-causing prion proteins. These structural prion variants accumulate in different regions of the brain. Dependent upon the region of the brain that becomes infected, different symptoms, typical for the particular type of disease are evident. When the cerebellum is infected the ability to coordinate body movements declines. Memory and mental acuity are affected if the cerebral cortex is infected. Thalamus specific prions disturb sleep leading to insomnia, and prions infecting the brain stem primarily affect body movement.

Prusiner’s pioneering work has opened new avenues for understanding the pathogenesis of more common dementia-type illnesses. For example, there are indications that Alzheimer’s disease is caused when certain, non-prion, proteins undergo a conformational change that leads to the formation of harmful deposits or plaques in the brain. Prusiner’s work has also established a theoretical basis for the treatment of prion diseases. It may be possible to develop pharmacological agents that prevent the conversion of harmless normal prion proteins to the disease-causing prion conformation.

Prions are much smaller than viruses. The immune response does not react to prions since they are present as natural proteins from birth. They are not poisonous, but rather become deleterious only by converting into a structure that enables disease causing prion proteins to interact with one another forming thread-like structures and aggregates that ultimately destroy nerve cells. The mechanistic basis underlying prion protein aggregation and their cummulative destructive mechanism is still not well understood.

In contrast to other infectious agents, prion particles are proteins and lack nucleic acid. The ability to transmit a prion infection from one species to another varies considerably and is dependent upon what is known as a species barrier. This barrier reflects how structurally related the prions of different species are.

Prion Disease In Mammals

Without exception, all known prion diseases lead to the death of those affected. There are, however, great variations in pre-symptomatic incubation times and how aggressively the disease progresses.

Scrapie, a prion disease of sheep, was first documented in Iceland during the 18th century. Scrapie was transferred to Scotland in the 1940s. Similar prion diseases are known to affect other animals, e.g., mink, cats, deer and moose.

Bovine Spongiform Encephalopathy (BSE) – Mad cow disease is a prion disease that has recently received a great deal of publicity. In England BSE was transmitted to cows through feedstuff supplemented with offals from scrapie-infected sheep. The BSE epidemic first became evident in 1985. Due to the long incubation time the epidemic did not peak until 1992. In this year alone roughly 37,000 animals were affected.

Kuru among the Fore-people in New Guinea was studied by Carleton Gajdusek (recipient of the 1976 Nobel Prize in Physiology or Medicine). Kuru was shown to be transmitted in connection with certain cannibalistic rituals and was thought to be due to an unidentified slow virus. The infectious agent has now been identified as a prion. Duration of illness from first symptoms to death: 3 to 12 months.

Gertsmann-Sträussler-Scheinker (GSS) disease is a hereditary dementia resulting from a mutation in the gene encoding the human prion protein. Approximately 50 families with GSS mutations have been identified. Duration of illness from evidence of first symptoms to death: 2 to 6 years.

Fatal Familial Insomnia (FFI) is due to another mutation in the gene encoding the human prion protein. Nine families have been found that carry the FFI mutation. Duration of illness from evidence of first symptoms to death: roughly one year.

Creutzfeldt-Jakob Disease (CJD) affects about one in a million people. In 85-90 percent of the cases it has been shown that CJD occurs spontaneously. Ten to fifteen percent of the CJD cases are caused by mutations in the prion protein gene. In rare instances CJD is the consequence of infection. Previously infections were transmitted through growth hormone preparations prepared from the pituitary gland of infected individuals, or brain membrane transplants. About 100 families are known carriers of CJD mutations. Duration of illness from evidence of first symptoms to death: roughly one year.

Prion disease is now the fastest-growing cause of death in the world. The medical term for prion disease is transmissible spongiform encephalopathy, which includes ALS, Alzheimer’s disease, Parkinson’s disease, Creutzfeldt-Jakob disease, mad cow disease, chronic wasting disease. The operative word is transmissible. Victims generate a tremendous amount of infectious waste.

The major difference between these forms of neurodegenerative disease is the species under attack and the region of the brain that is under attack. The primary difference between Alzheimer’s disease and Parkinson’s disease, for example, is the region of the brain that is under attack by the pathological protein.

There are proven strategies to help avert neurodegenerative disease, including nutrition, exercise and prion aversion. There is not a cure for prion disease. Preview and order the eBook now to defend yourself and your family.

The post Prusiner Earns Nobel Prize For Prion Science appeared first on Neuroscience News.