PrionA prion ˈpriːɒn is a misfolded protein that can transmit its misfoldedness to normal variants of the same protein and trigger cellular death. Prions cause prion diseases known as transmissible spongiform encephalopathies (TSEs) that are transmissible, fatal neurodegenerative diseases in humans and animals. The proteins may misfold sporadically, due to genetic mutations, or by exposure to an already misfolded protein. The consequent abnormal three-dimensional structure confers on them the ability to cause misfolding of other proteins.
Major prion protein'Major prion protein' (PrP) is encoded in the human body by the PRNP gene also known as CD230 (cluster of differentiation 230). Expression of the protein is most predominant in the nervous system but occurs in many other tissues throughout the body. The protein can exist in multiple isoforms: the normal PrPC form, and the protease-resistant form designated PrPRes such as the disease-causing PrPSc(scrapie) and an isoform located in mitochondria.
Transmissible spongiform encephalopathyTransmissible spongiform encephalopathies (TSEs) also known as prion diseases, are a group of progressive, incurable, and fatal conditions that are associated with prions and affect the brain and nervous system of many animals, including humans, cattle, and sheep. According to the most widespread hypothesis, they are transmitted by prions, though some other data suggest an involvement of a Spiroplasma infection. Mental and physical abilities deteriorate and many tiny holes appear in the cortex causing it to appear like a sponge when brain tissue obtained at autopsy is examined under a microscope.
Kuru (disease)Kuru is a rare, incurable, and fatal neurodegenerative disorder that was formerly common among the Fore people of Papua New Guinea. Kuru is a form of transmissible spongiform encephalopathy (TSE) caused by the transmission of abnormally folded proteins (prions), which leads to symptoms such as tremors and loss of coordination from neurodegeneration. The term kuru derives from the Fore word kuria or guria ("to shake"), due to the body tremors that are a classic symptom of the disease. Kúru itself means "trembling".
ScrapieScrapie (ˈskreɪpi) is a fatal, degenerative disease affecting the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies (TSEs), and as such it is thought to be caused by a prion. Scrapie has been known since at least 1732 and does not appear to be transmissible to humans. However, new studies suggest a link between scrapie and sporadic CJD. The name scrapie is derived from one of the clinical signs of the condition, wherein affected animals will compulsively scrape off their fleeces against rocks, trees or fences.
Chronic wasting diseaseChronic wasting disease (CWD), sometimes called zombie deer disease, is a transmissible spongiform encephalopathy (TSE) affecting deer. TSEs are a family of diseases thought to be caused by misfolded proteins called prions and include similar diseases such as BSE (mad cow disease) in cattle, Creutzfeldt-Jakob disease (CJD) in humans and scrapie in sheep. In the United States, CWD affects mule deer, white-tailed deer, red deer, sika deer, elk, caribou, and moose. Natural infection causing CWD affects members of the deer family.
Fungal prionA fungal prion is a prion that infects hosts which are fungi. Fungal prions are naturally occurring proteins that can switch between multiple, structurally distinct conformations, at least one of which is self-propagating and transmissible to other prions. This transmission of protein state represents an epigenetic phenomenon where information is encoded in the protein structure itself, instead of in nucleic acids. Several prion-forming proteins have been identified in fungi, primarily in the yeast Saccharomyces cerevisiae.
Gene therapyGene therapy is a medical technology which aims to produce a therapeutic effect through the manipulation of gene expression or through altering the biological properties of living cells. The first attempt at modifying human DNA was performed in 1980, by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989. The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990.
Post-exposure prophylaxisPost-exposure prophylaxis, also known as post-exposure prevention (PEP), is any preventive medical treatment started after exposure to a pathogen in order to prevent the infection from occurring. In 2021, the FDA has approved bamlanivimab/etesevimab for post-exposure prophylaxis against COVID-19. PEP is commonly and very effectively used to prevent the onset of rabies after a bite by a suspected-rabid animal, since diagnostic tools are not available to detect rabies infection prior to the onset of the nearly always-fatal disease.
InfectionAn infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection. Infections can be caused by a wide range of pathogens, most prominently bacteria and viruses. Hosts can fight infections using their immune systems. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response.
