Alzheimer's is a Prion Infection

Prion Infections are Transmitted Through Cadaver Tissue Grafts and Surgical Instruments

Many neurodegenerative diseases have been found to be prion infections.^1,2

In this post, we will discuss what prions are, what human neurodegenerative diseases are caused by prions, and how the infections are transmitted.

Prions are proteins that are produced in human cells that become misfolded. The misfolding of the protein does not occur randomly but can only take place when the normal protein is induced to change shape by another misfolded protein. They retain the chemical components of the normal protein and it is only their shape that is abnormal. For this reason, they are able to avoid the host immune system.

Most of what we know about prions is a result of mad cow disease. In mad cow disease, the normal protein is termed PrP. When this protein is in its normal composition and shape, it is identified as PrPC. When this protein becomes folded it is termed PrPsc and becomes pathogenic. PrPsc is the pathogenic form of the protein and is what is considered a prion. Prion is short for proteinaceous infectious particle (Prusiner 1982). In animals, the disease is called bovine spongiform encephalopathy (BSE) or mad cow disease. When this PrPsc infects a human, the disease is called Creutzfeldt-Jakob disease (CJD).

As a result of mad cow disease, prions have been studied extensively and most of our knowledge of prions comes from studying the PrP protein. However, in the last 10 years, scientists have been recognizing the potential for different prions to be the cause of other neurodegenerative diseases in humans. Initially, the term prion was limited to the PrP protein. As a result, scientists began to refer to other proteins suspected of causing neurodegenerative diseases as prion-like proteins. However, recently with the acceptance that prions are the cause of many of our neurodegenerative diseases, scientists have now begun to refer to all these pathogenic proteins as prions.

In 2015, scientists began to consider that many neurodegenerative diseases could be caused by prions. Since that time, prions are now considered to be the cause of the following diseases:

PrP (Prion Protein):
- Diseases: Creutzfeldt-Jakob disease (CJD), variant Creutzfeldt-Jakob disease (vCJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), kuru
Alpha-synuclein prion:
- Diseases: Parkinson’s disease (PD), dementia with Lewy bodies (DLB), multiple system atrophy (MSA)
Tau prion:
- Diseases: frontotemporal dementia (FTD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), chronic traumatic encephalopathy (CTE)
β-amyloid (Aβ) prions and Tau prions:
- Diseases: Alzheimer’s disease

Alzheimer’s is now considered to be caused by two different prions: β-amyloid (Aβ) prions and Tau prions.^3,4

The following graphic shows what these prions do to the human brain affected by Alzheimer’s disease:

In brains affected by Alzheimer’s disease, abnormal levels of the beta-amyloid protein clump together to form plaques (seen in brown) that collect between neurons and disrupt cell function. Abnormal collections of the tau protein accumulate and form tangles (seen in blue) within neuros, harming synaptic communication between nerve cells. Credit National Institute on Aging, NIH.

To date, there have been therapeutic efforts to remove the beta-amyloid plaques and Tau tangles, but this has failed to change the course of the disease. It has been found recently that beta-amyloid and tau prions clump together to form the plaques and tangles which then become insoluble and inactive. The disease progresses as a result of the soluble prions still active in the tissues not the insoluble plaques and tangles that are visible in brain biopsies.

It has only been recently that assays have been developed to accurately test tissues for the presence of prions. In the publication “Alzheimer’s Disease is a ‘Double-Prion Disorder”, the author states:

“In assays comparing the samples from Alzheimer’s patients with those who died of other diseases, prion activity corresponded exactly with the distinctive protein pathology that has been established in each disease: in 75 Alzheimer’s disease brains, both Aß and tau prion activity was elevated; in 11 samples from patients with cerebral amyloid angiopathy (CAA), only Aß prions were seen; and in 10 tau-linked frontotemporal lobar degeneration (FTLD) samples, only tau prions were detected. Another recently developed bioassay for alpha-synuclein prions only found these infectious particles in the seven samples from patients with the synuclein-linked degenerative disorder multiple system atrophy (MSA)”.

With the knowledge that many of our neurodegenerative diseases are caused by prions, we need to discuss how those prions infect humans. Originally, CJD was found to be transmitted to humans through eating prion-infected meat. However, subsequently CJD has also been proven to be transmitted to humans via cadavers. The first known method of transmission was found when human growth hormone was extracted from cadavers and injected into children of short stature. It was found that a group of these patients developed CJD early in adulthood resulting in death. Another method of transmission of CJD was found to be the surgical use of dura matter harvested from cadavers. The dura matter was used for a number of purposes such as vascular repair in different areas of the body and in cranial surgery. The dura matter was processed by a tissue harvesting company and the material was then gamma sterilized.⁵

The cadaver did not have symptoms of CJD. The tissue was harvested from the cadaver in Germany and grafted into various surgical sites in patients in Japan. It was only many years later that the Japanese patients began to develop CJD and the source was traced back to the German cadaver. Tissue samples of the cadaver were found and tested to discover the presence of PrPsc.

Prion disease has been shown to have been transmitted via blood transfusions with the potential of transmission via cadaver bone grafts.^6,7

“Human prion diseases are infectious and invariably fatal neurodegenerative diseases… vCJD has already been transmitted from human to human by blood transfusion, and the number of asymptomatic carriers of vCJD in the U.K. alone is estimated to be 1 in 2000 people.”⁸

Prions are known to be present in the bone of infected patients.

“These findings may explain the presence of blood-borne infectivity in sCJD patients. They also suggest that the distribution of prion infectivity in peripheral tissues in sCJD patients could be wider than currently believed, with potential implications for the iatrogenic transmission risk of this disease.”⁹

Prions have also been found to be present in the skin of infected patients with the conclusion that all tissues contain the infectious prion.¹⁰

In regards to Alzheimer’s disease, 90% of the cases are called sporadic, which means they do not know how they developed the disease. Approximately 5% of the cases have a genetic mutation that predisposes the patient to the disease.

All evidence points to the fact that many of our most feared neurodegenerative diseases are prion infections. We know the time between prion infection and clinical symptoms has been found to be up to 30 years. We know that the overwhelming majority of Alzheimer’s cases are not the result of a genetic mutation. Due to the long latency between infection and symptoms, we know that many, if not most, cadavers that are infected have no symptoms of the disease. We know prions are in blood and tissues of patients who are asymptomatic and that those prions are not inactivated by steam or gamma sterilization methods.

Alzheimer’s is increasing in frequency. In recent years, there has been a significant increase in the number of deaths due to Alzheimer’s disease. These facts point to Alzheimer’s as an infectious disease. However, studies have shown prion diseases are not transmitted by casual contact. The spouses of patients with prion disease do not contract the disease. It is obvious that prions need to be implanted into the patient for the disease to be transmitted and an obvious method of that happening is in health care.

Two proven methods of prion disease transmission are cadaver tissue grafting and surgical instruments. Currently, cadavers are tested for HIV types 1 and 2, HBV, HCV, and Treponema pallidum. What is interesting is that all of these infections are killed by gamma sterilization. Gamma sterilization is specific for destroying nucleic acid that makes up the DNA in cells. However, it does not affect prions. Any cadaver that harbors prions will transmit these prions to your patient and cadavers are not tested for prions.

The other method of transmission that needs to be of concern to dentists is transmission through surgical instruments. Prions adhere tightly to metal surfaces. Simple surgical wires cleaned and sterilized in a hospital have been found to transmit human prion diseases from one surgical patient to another. Because prion disease requires decades between infection and symptoms, many of your healthy patients are likely to be infected with prions that will produce disease later in life. We all think our surgical instruments are clean; however, analysis of surgical instruments that have been cleaned and sterilized remain coated with a layer of proteins from previous surgeries. One study found the average surgical instrument after cleaning and sterilization to be coated with between 21.5 – 54.0 μg of proteins. So, assuming the average surgical instrument is coated with 40 μg of mainly blood plasma proteins with an average size of around 50 kDa, then there are approximately 4.82 x 10¹⁴ or 482,000,000,000,000 proteins on each instrument. In essence, our surgical instruments are coated with a history of proteins from every patient it has contacted.

Prions are remarkably adherent to metal surfaces and very difficult to remove. In our next post, we will provide information on how you can remove prions from your surgical instruments and eliminate the transmission of prion diseases.

Unfortunately, dentistry may be found to be a source of prion infections resulting in the development of neurodegenerative diseases. For the last few years, prion scientists have been warning of the potential for iatrogenic prion transmission in medicine and dentistry. However, the most obvious mode of transmission of prion diseases to our patients is through allografts. A donor does not need to be symptomatic to transmit this disease, so there is no way for you or your patient to know if they are being infected with an allograft. Skin, blood, and bone harbor prions in infected cadavers. Prion disease transmission from an infected cadaver is not just a possibility, but a probability.

Freeze-dried bone allografts have been shown to inhibit bone formation, they produce sclerotic bone, and they are never fully resorbed. The long-term success rate of implants placed in sockets grafted with freeze-dried bone allografts has never been studied. Freeze-dried bone allografts have never been shown to outperform even the oldest synthetic bone grafts, and all studies show modern synthetics significantly outperform allografts. There is no justification for putting our patients at risk of developing a fatal disease when better substitutes are available that have no risk of infection. A doctor is required to inform a patient of the potential risks for all surgical procedures. For a patient to give informed consent, they must be informed that any allograft material can infect them with a mind wasting disease. When other effective materials are available that are proven safe, a patient would never choose a cadaver tissue if they were fully informed. The public is becoming informed of this threat and they will be asking what dentistry is doing to protect them from these diseases. It is dentistry’s responsibility to make the changes now to protect our patients and protect our professional reputation.

For those interested in making the transition from cadaver tissues to science-based bone grafts, it is necessary to understand that you cannot simply swap a cadaver bone graft for a science-based bone graft. Cadaver bone grafts heal differently from science-based bone grafts, and your technique needs to be modified for successful outcomes. Please view the following link and feel free to call SteinerBio with any questions you may have: A Paradigm Shift in Bone Grafting

Our next post will discuss prion biology, how prions are generated, how you can successfully remove prions from surgical instruments, and medications that are available to us today that reduce our own chance of developing Alzheimer’s.

References:

Additional Links

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Prion Infections are Transmitted Through Cadaver Tissue Grafts and Surgical Instruments