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| The following prion diseases have been identified: |
| PRION DISEASES - INTRODUCTION |
| Prion diseases are known scientifically as transmissible spongiform encephalopathies (TSEs). Theses diseases are a group of rare neurodegenerative disorders that are believed to be caused by abnormal versions of proteins called prion proteins. The word "prion" is short for proteinaceous infectious particle. Normal prion proteins occur in cells naturally and are harmless. Infectious prion proteins are mutated versions of the normal prion proteins that have a different folding structure to them (see Protein Chemistry for more information on structure levels of proteins). Both the normal and the infectious prions are nearly identical. The specific protein from which the infectious prion is made from is termed PrP, which is short for "prion-related protein". Normal prion proteins are naturally found in healthy people and animals and are called PrPc -- the "c" refers to "cellular" PrP. Other PrP proteins, those that are resistant to the enzyme proteases, are found in infected material and are termed PrPsc, where the "sc" was initially derived from the term Scrapie because scrapie is the prototypic TSE. Scientists are still searching to find what actually causes this mutation of folding structure between normal and infectious prions. |
| WAYS PRION DISEASES CAN OCCUR IN HUMANS |
| A human can get a prion disease in three ways: * sporadically * genetically * transmission from infected individuals Sporadic TSEs are the most common form and they occur when a person or animal's normal prions spontaneously change into infectious prions. These infectious prions then induce other normal prions to change into them in a chain-like reaction. Inherited TSEs occur via autosomal dominant genes that can be passed along to offspring by either parent. The PRNP gene holds the instructions for making the normal PrPc prion protein. When this gene becomes mutated, abnormal prions, called PrPsc, are made instead. Transmited TSEs are relatively rare and cannot be transmitted through the air or by any other form of general contact. Like sexually transmitted diseases, TSEs are transmitted by body fluids. Variant form is when an individual consumes beef from cattle infected with BSE. Contact with infected tissue and contaminated medical instruments are considered to be Iatrogenic form. |
| SYMPTOMS OF PRION DISEASES IN HUMANS |
| Symptoms commonly include the following: * personality changes * psychiatric problems such as depression * lack of coordination and/or unsteady gait (ataxia) * involuntary jerking movements (myoclonus) * unusual sensations * insomnia * confusion * memory problems Later stages of the disease cause severe mental impairment and loss of the ability so move or speak. The degenerative tissue damage caused by prion diseases is characterized by: *spongiform change *neuronal loss *astrocytosis *amyloid plaque formation This tissue damage is present in both human and animal prion diseases, which leads scientists to believe there is a closer connection between them. |
| TREATMENTS / VACCINES FOR PRION DISEASES |
| Research led by scientists at the U[niversity] of T[oronto] and Caprion Pharmaceuticals have uncovered the basis for a diagnostic, immunotherapy and vaccine, providing a way to detect and treat the brain-wasting damage of infectious prions like those found in mad cow disease and its human version, Creutzfeldt-Jakob Disease (Diagnosis, treatment, vaccine for mad cow, prion diseases - Medical News Today). Until recent, scientists had found no treatment of vaccine for prion diseases. TSEs progress very rapidly and usually result in death within anywhere from a few months to a few years. The research done at the University of Toronto and Caprion Pharmaceuticals has led to the discovery of a side chain of amino acids that is exposed on the infectious prion but not the normal prion. Antibodies coded for this exposed amino acid sequence has been found to initiate an immune system response that attacks the mutated prions while leaving the normal prions unharmed. |
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| Prion diseases are very difficult to detect until symptoms start to arise, however there are safety measures to follow to keep known infected individuals from transmitting the disease. If an individual has suspected or confirmed having a TSE, has family history of the disease, or any other factor that may lead to any suspicion, he/she should not donate blood, tissue, or organs. TSEs can also be transmitted during a surgical procedure by the use of contaminated instruments or people. Caregivers, health care workers, and undertakers should take special precautions when dealing with patients who have a TSE: * Wash hands and exposed skin before eating, drinking, or smoking. * Cover cuts and abrasions with waterproof dressings. * Wear surgical gloves. * Avoid cutting or sticking themselves with contaminated instruments. * Use face protection if there's a risk of splashing contaminated material. * Soak instruments that have come in contact with the patient in undiluted chlorine bleach for an hour or more, then use an autoclave (pressure cooker) to sterilize them in distilled water for at least one hour at 132 - 134 degrees C. |
| WAYS TO PREVENT PRION DISEASES IN HUMANS |
| DIAGNOSIS OF PRION DISEASES |
| An individual is most often diagnosed with a TSE once he/she starts showing symptoms. Several tests can be run to help determine the presence of the disease. Accurate family histories and a physical examination can provide a correct diagnosis in the early stages of the illness in most people with typical features of the disease. Special analysis of spinal fluid for a protein designated as “14-3-3” that is released from damaged or dying nerve cells can help diagnosis in most patients. This protein is detectable in 90% of individuals infected with Creutzfeldt-Jakob Disease (CJD) - the most common human TSE. Magnetic resonance imaging (MRI) is also used to detect the disease. Increasing the signal seems to "light up" certain parts of one or both sides the brain in 80% of the cases. This procedure was overlooked for years because radiologists typically search for asymetrical (not symmetric) radiological changes. None of these tests can provide accurate diagnosis on their own. However, if a majority of the tests are positive, it is almost certain that a person is infected. |