Pernicious Prions

Much like there is no effective treatment for prion diseases (see my last blog post), there is no method to diagnose prion diseases early, accurately, and easily. The only way to conclusively diagnose a prion disease is through an invasive brain autopsy after the patient has died. To date, no blood test has been developed to test for non-inherited prion diseases. EEG and MRI are used to assess brain damage caused by prion diseases but are insufficient to diagnose the disease itself. A patient’s clinical symptoms are used to provide a clinical diagnosis, but it is not sufficient for a reliable and valid diagnosis. These non-laboratory-based diagnostic tests are not capable of detecting prion diseases because only trace amounts of prion proteins are found in peripheral tissues and bodily fluids. For these diagnostic tests to detect prion proteins, there would need to be an abundance found in the sample. In the late stages of prion disease, large amounts of prion proteins are found in the central nervous system, but it is not helpful for early diagnosis. While prion diseases are fatal, early diagnosis is important. If prion diseases are detected early, medical management can help slow the progression of the disease and keep the patient safe and comfortable as the disease progresses.

Variant Creutzfeldt-Jakob disease (vCJD) is a rare and fatal prion disease transmitted from cattle to humans. It is also one of the most common forms of prion disease in humans. A significant concern with vCJD is that the number of people infected is unknown. Individuals infected with vCJD can transfer the disease to other people before they become symptomatic. Therefore, developing a diagnostic test to detect vCJD is highly important. The first time that vCJD prion proteins were able to be detected was by blood sample testing in 2011. The blood-based assay test could identify patients with vCJD prion proteins with a sensitivity of 71.4% and a specificity of 100%. The study showed that vCJD prion proteins could be detected in the blood before death. While this was an impressive discovery, the test did not catch about 30% of vCJD cases.

Current research into blood-based prion disease diagnostic tests utilizes protein misfolding cyclic amplification (PMCA). This biochemical assay is sensitive, specific, non-invasive and allows for early detection of prion proteins. PMCA speeds up the replication process of misfolding proteins in an artificial environment, such as in a lab. It does this by incubating abnormal proteins among normal proteins. Abnormal proteins are added to a PMCA substrate with normal proteins during the resting stage. The abnormal proteins begin to spread and change the conformation of the normal proteins (also referred to as conversion). This results in a large chain of abnormal proteins amongst the normal proteins. The large clump of abnormal proteins is broken apart with ultrasound waves during the ultrasound stage. After this, the abnormal proteins are now in smaller chains instead of one large chain of abnormal proteins. There are now many smaller chains available to change the conformation of normal proteins, hence the faster replication process. The replication and ultrasound stages are repeated, eventually generating many misfolded proteins. A depiction of the PMCA process is shown below.

The PMCA technique has applications for prion disease research, specifically to detect prion proteins in tissues and body fluids. Prion disease can be detected using PMCA technology in patients with vCJD through blood, urine, and cerebrospinal fluid. When trace amounts of prion proteins are expected in a sample, PMCA will allow the prion proteins to become abundant enough to be detected using routine methods.

The first study to show this was in 2016 and utilized a blood sample. A blood sample is one of the most non-invasive bodily fluids to be collected with the most abundant prion proteins present. A blood sample has two to three times more prion proteins in it compared to urine. A blood sample of 14 patients with vCJD was compared to 153 subjects with either sCJD, neurodegenerative diseases, non-degenerative neurological diseases, or healthy individuals. It was found that after two rounds of PMCA, the vCJD blood samples showed detectable levels of prion proteins. Even after five rounds of PMCA for the other 153 subjects, there were no detectable levels of prion proteins. This indicates that PMCA has 100% sensitivity and 100% specificity when detecting vCJD through blood samples. The researchers also analyzed blood samples taken from patients in the pre-symptomatic stage of vCJD and the symptomatic stage of PMCA. The PMCA technology will detect the prion proteins in the blood samples during both phases. PMCA will also detect the prion proteins in as little as 0.37 microliters of blood. Overall, the study showed that PMCA technology is an effective solution to testing patients’ blood for prion proteins in a clinical setting. Currently, there is no other validated procedure to detect vCJD in premortem patients. Having the ability to detect vCJD before death will significantly improve a patients quality of life. Many of the early symptoms of vCJD are not characteristic of vCJD. Thus, the ability to distinguish vCJD from other neurodegenerative disorders will improve the well-being and safety of patients. Early diagnosis also allows for public health measures to be put in place before the disease can spread and infect others. It also allows for therapies to be administered to the patient before substantial brain damage has occurred. This study was a crucial step toward diagnosing vCJD in a clinical setting. It also paves the way to develop similar diagnostic techniques for other prion diseases, such as sporadic Creutzfeldt-Jakob disease. Having the ability to diagnose a prion disease is the first step toward eradicating the disease.

Read the full study at the citation below!

For prion disease researcher Sonia Vallabh, her work has particular importance. Several years ago, Sonia’s mother became sick with an unexplainable neurodegenerative condition. Following her mother’s death, doctors discovered her illness was caused by a prion disease, a fatal neurodegenerative disease. After learning that Sonia was a carrier of the mutant prion protein gene, she embarked on finding a treatment for the disease.

There are many views on the most effective treatment avenue for prion diseases. Sonia and her team focus on reducing prion protein levels in the brain by using antisense oligonucleotides (ASO), which are small segments of DNA or RNA that bind to RNA and block protein production. The team’s previous research has shown that prion protein targeting ASO reduces the levels of prion proteins found in an animal’s brain, therefore, extending the animal’s lifetime. Sonia and her team have recently applied this finding to a preclinical study using ASO against prion disease in lab-infected mice. This study examines the efficacy of this potential treatment through varying the dose, prion protein strain, timepoint of treatment, and the quantity of drug administered. The manipulation of all these variables showed that reducing the levels of prion proteins in the brain tripled the survival rate of infected mice. Since their study altered many variables, reducing levels of prion proteins in the brain is effective in many scenarios. The study showed that reducing prion protein levels effectively improves survival rate before symptoms begin and after prion protein clumps have formed in the brain.

Sonia’s work in reducing prion protein levels through oligonucleotides has advanced the field and provided evidence for its potential effectiveness in a clinical setting. With significant findings such as these, it is not hard to imagine a world without prion diseases in the future.

Click the link below to read Sonia's original research study.

You may or may not have heard of prions. Understandably so, as little is known about the neurodegenerative disease-causing proteins, despite 30 years of research. While we know that prions are responsible for mad cow disease, Creutzfeldt-Jakob disease (CJD), Alzheimer's disease, Huntington's disease, and Parkinson's disease, we do not know how to treat prion-related diseases. Prion diseases begin with a cellular prion protein (PrPC) which becomes a scrapie associated prion protein (PrPSc). While the PrPC takes on the shape of a normal protein, the PrPSc is an abnormal protein because it becomes misfolded through a process called conversion (see Figure 1 below). The misfolded form of a protein will infect other proteins around them, eventually leaving the brain full of holes. The victim is left with memory impairment, personality changes, movement difficulty, and eventually, death. The solution to any disease is treatment though, and that is where the field of prion diseases is heading.

Figure 1 - Prion Development

Despite researcher's best efforts, there are no medical drugs or therapies to treat prion diseases. The lack of treatment for prion diseases is due to challenges faced when developing a therapy for prion diseases. One challenge is how to get antibodies to cross the blood brain barrier, which prevents substances from entering the brain. Another challenge is selecting the right choice of drug and antibodies to elicit a correct and effective response to the prion proteins. The prevalence of prion diseases is also a challenge. Since they are not extremely prevalent, it can be difficult to test new treatments and set up clinical trials. Much of the research in this field has been conducted on individuals with Alzheimer's disease because it is more prevalent. Many effective treatments for other diseases, such as small molecules, vaccination, antibodies, peptide aptamers, and nucleic acid-based agents, have been tried and have failed to treat prion diseases. Despite this, there is still hope for new advancements in the field.

Immunotherapy is arguably the most promising treatment solution. Prions cannot be destroyed by our immune system unaided. Since prion proteins are composed of a portion of normal proteins, the prion proteins do not activate an immune response. Prions also do not activate B cells, which are immune response cells that play a crucial role in an immune response. However, if an immune response could be triggered, the prion proteins could be destroyed. Immunotherapy does this by activating an immune response as a treatment. This tactic has been used for other diseases, such as cancer, and has promising outcomes. Immunotherapy is very effective in identifying diseased areas of the body with relatively few side effects. In the context of prion diseases, monoclonal antibodies are being used to target the misfolded portion of the prion protein.

Immunotherapy can target prion diseases for two reasons. One reason is that the shape of the misfolded prion proteins is a well-known disease-causing agent. This makes the misfolded protein easily identifiable by therapeutic agents, which are drugs that aim to have curative or preventative properties targeted towards a disease, because the therapeutic agents can target the disease-causing agent. The second reason is that the misfolding of a protein occurs on the cell's surface. Since the protein is found on the cell surface and not within the cell, this makes the protein easily accessible to therapeutic agents. Active immunization and passive immunization are two types of immunotherapies that could be used for prion diseases.

Active immunization is when the immune system produces antibodies for a disease. It is seen as the most practical approach for animal prion diseases. This type of immunization can take days or weeks to develop, but the effects are longer-lasting. Previous research has shown that active immunization is not as safe as passive immunization because it can cause an inflammatory response in the brain. One study used an AN1792 vaccine on mice with Alzheimer's disease to eliminate the misfolding proteins in the brain but had to be stopped due to negative side effects, such as meningo encephalitis and vasogenic edema, which are infections of the brain. After the clinical trial, though, the mice treated with a vaccine showed a reduction in the abnormal proteins. Active immunization is also tricky because the immune system does not recognize the abnormal protein as foreign. Therefore, no immune response is activated. Current research uses drugs to stimulate immune cells, hoping to induce a response.

Passive immunization is giving antibodies to a person for a disease instead of the antibodies being produced by the person immune system. Unlike active immunization, passive immunization develops immediately, but the effects may only last a few weeks or months. The effects only last a short time because the body does not develop memory for what you are immunized against. Therefore, there is a risk of being reinfected by the same pathogen. It is the most practical approach for human prion diseases, but most of the research currently utilizes animal models. One study used antibodies to target different forms of abnormal proteins in Alzheimer's disease but found negative results. Although the experiment failed, the research still contributed to future methods of prion disease clinical trials. For example, it provided insight into future treatments that may be more effective.

Much of the research talked about has ultimately failed in clinical trials for one reason or another. Without these failures, progress towards a treatment could not be made. Research into immunotherapies for prion diseases are ongoing, as an effective treatment solution has not been found. While much of the research done so far has utilized Alzheimer's disease, the similarities to other prion-related diseases will also benefit from this research. All work in neurodegenerative diseases will advance the therapeutic strategies of prions diseases. Many of the challenges faced will be resolved with advancements in technology and new methods for delivering antibodies to the brain. Until then, science will move forward until an effective treatment for prion diseases has been discovered.

If you are interested in learning more about the treatment of prion diseases, I have conveniently linked some awesome websites below!

https://www.mindsunderground.com/muarticles/prions-disease

https://www.smithsonianmag.com/smart-news/prions-are-fascinating-terrifying-and-still-mysterious-180965125/

For years, the mechanisms behind Alzheimer’s disease were unknown, meaning the treatment for this debilitating disease was unreachable. From failed clinical trials to setbacks at the lab bench, the question of how to treat Alzheimer’s disease seemed unanswerable. Ultimately, the lack of novel techniques required to examine Alzheimer’s disease has been withholding treatment advancements. However, recent work in the field has changed the narrative of this story and put us back on track to finding a treatment for Alzheimer’s disease.

The secret to the question of how to treat Alzheimer’s lies with prions. Prions are misfolding proteins that spread throughout the brain, causing damage to structures and its functions. Prions have been linked to Alzheimer’s in the past, but with little certainty. In the study linked below, researchers developed a method to effectively measure prion forms. This never-before-seen technique has shattered the challenges holding back this field and cleared the path for future research. Lead researchers on this study speculate that through identifying prion forms, drugs can be developed to prevent prions from forming and spreading in the first place or to help eliminate them from the brain. While this work focuses on Alzheimer’s, there is a direct connection to other prion-related diseases.

This is just one small step towards developing effective treatments for prion-related diseases. In light of this ground-breaking research, I will be dedicating my next blog post to tackling the challenges of treating prion-related diseases.

Hi everyone,

My name is Emma. I am currently in my fourth year of a psychology-biology degree. The combination of my psychology-biology degree has enabled me to see the biological and social aspects that describe, predict, explain, and change human behaviour and biological systems. My fascination lies in the realm of Clinical Psychology. Still, during my time at UNB, I have had the opportunity to explore several exciting subjects: neuroscience, mental health, substance use, immunobiology and pathology. Currently, I am completing an Honours thesis examining the relationship between substance use and anxiety sensitivity and the moderating and mediating effects of outcome expectancies and social anxiety on this relationship.

I am passionate about bridging the gap between the scientific community and the public. Getting involved and understanding research can be a daunting challenge. A lot of time and years of experience are required to comprehend discoveries in biology fully. This challenge highlights the need for research to be as available and understandable as possible so more people can benefit from these important advancements. As an aspiring researcher, I hope this class will sharpen my writing and critical thinking skills and make me a more effective information carrier.

With this blog, I hope to achieve several goals. I will take a critical stance on any information I read to provide the utmost accuracy in my reporting. I hope to communicate ground-breaking scientific discoveries in an enjoyable, educational manner for the public.

This term, my blog topic will focus on infectious disease-causing agents, prions. Prions cause normal proteins to fold abnormally in the brain. My curiosity in prions peaked when I learned about their inflicted diseases, such as mad cow disease, chronic wasting disease, and potentially Alzheimer’s, Parkinson’s, and Huntington’s disease. Current research examines the processes of prions and, subsequently, how to prevent them. Hopefully, this research will eventually lead to the treatment of these diseases. My goal is for everyone who reads this blog to walk away with a deeper understanding of prions, the real-world consequences they inflict, and how to prevent them.

I look forward to taking this creative journey with you all!

-Emma Giberson