Real-time quaking-induced conversion (RT-QuIC) is a highly sensitive assay for prion detection. [1] It is nearly 100% specific for the diagnosis of Creutzfeldt-Jakob disease. [2]
The "quaking" in the name of the technique refers to the fact that samples in the RT-QuIC assay are literally subjected to shaking. This action breaks apart aggregates of prion protein (PrP) that are then further incubated, amplifying the amount of misfolded PrP to detectable levels. [3] [4]
It is "an early, rapid and specific assay for prion diseases". It can sample multiple sample types, such as cerebrospinal fluid (CSF), brain, lymph nodes, blood, muscle, and skin, and so it is applicable to scrapie in sheep, chronic wasting disease (CWD) in cervids, bovine spongiform encephalopathy (BSE) in cows and sporadic Creutzfeldt–Jakob disease in humans, amongst others. [5]
The RT-QuIC assay uses in excess recombinantly produced normally folded prions, often a truncated Syrian Hamster protein, amino acids 90-231. Samples suspected of containing misfolded prions are added, leading to misfolding and aggregation of normally folded prions. These protein aggregates can be detected by thioflavin T visible spectrum fluorescence detection. [6] [7] [8] The Centers for Disease Control and Prevention includes a positive RT-QuIC result in its diagnostic criteria for the probable diagnosis of sCJD. [9]
RT-QuIC assays can also be used to test for scrapie, BSE, and CWD. Various procedures can improve sensitivity and specificity. Iron oxide metal extraction (IOME) uses the natural metal affinity of the prion protein; a sample is incubated with magnetic beads, which bind to the prion protein. The prion-rich bead fraction is subsequently harvested and tested. [10]
Commonly tested tissues are brain homogenates and lymph tissues; however, prions have also been detected in skin and blood samples. [11] [12] [13] Certain tissues can be difficult to test for prions. For example, blood samples tend to have low levels of circulating intracellular prions and have inhibitors of the assay. [14]
Creutzfeldt–Jakob disease (CJD), also known as subacute spongiform encephalopathy or neurocognitive disorder due to prion disease, is a fatal neurodegenerative disease. Early symptoms include memory problems, behavioral changes, poor coordination, and visual disturbances. Later symptoms include dementia, involuntary movements, blindness, weakness, and coma. About 70% of people die within a year of diagnosis. The name "Creutzfeldt–Jakob disease" was introduced by Walther Spielmeyer in 1922, after the German neurologists Hans Gerhard Creutzfeldt and Alfons Maria Jakob.
A prion is a misfolded protein that induces misfolding in normal variants of the same protein, leading to cellular death. Prions are responsible for prion diseases, known as transmissible spongiform encephalopathy (TSEs), which are fatal and transmissible neurodegenerative diseases affecting both humans and animals. These proteins can misfold sporadically, due to genetic mutations, or by exposure to an already misfolded protein, leading to an abnormal three-dimensional structure that can propagate misfolding in other proteins.
Fatal insomnia is an extremely rare neurodegenerative prion disease that results in trouble sleeping as its hallmark symptom. The majority of cases are familial, stemming from a mutation in the PRNP gene, with the remainder of cases occurring sporadically. The problems with sleeping typically start out gradually and worsen over time. Eventually, the patient will succumb to total insomnia, most often leading to other symptoms such as speech problems, coordination problems, and dementia. It results in death within a few months to a few years, and there is no known disease-modifying treatment.
Transmissible 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. The disorders cause impairment of brain function which may result in memory loss, personality changes, and abnormal or impaired movement which worsen over time.
Chronic 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 in cattle, Creutzfeldt–Jakob disease (CJD) in humans, and scrapie in sheep. Natural infection causing CWD affects members of the deer family. In the United States, CWD affects mule deer, white-tailed deer, red deer, sika deer, elk, bison, squirrels, antelope, caribou, and moose. The transmission of CWD to other species such as squirrel monkeys and humanized mice has been observed in experimental settings.
Pentosan polysulfate, sold under the brand name Elmiron among others, is a medication used for the treatment of interstitial cystitis. It was approved for medical use in the United States in 1996.
Protein misfolding cyclic amplification (PMCA) is an amplification technique to multiply misfolded prions originally developed by Soto and colleagues. It is a test for spongiform encephalopathies like chronic wasting disease (CWD) or bovine spongiform encephalopathy (BSE).
Astemizole was a second-generation antihistamine drug that has a long duration of action. Astemizole was discovered by Janssen Pharmaceutica in 1977. It was withdrawn from the market globally in 1999 because of rare but potentially fatal side effects.
The major prion protein (PrP) is encoded in the human body by the PRNP gene also known as CD230. Expression of the protein is most predominant in the nervous system but occurs in many other tissues throughout the body.
Laura Manuelidis is a physician and neuropathologist at Yale University.
Variant Creutzfeldt–Jakob disease (vCJD), formerly known as New variant Creutzfeldt–Jakob disease (nvCJD) and referred to colloquially as "mad cow disease" or "human mad cow disease" to distinguish it from its BSE counterpart, is a fatal type of brain disease within the transmissible spongiform encephalopathy family. Initial symptoms include psychiatric problems, behavioral changes, and painful sensations. In the later stages of the illness, patients may exhibit poor coordination, dementia and involuntary movements. The length of time between exposure and the development of symptoms is unclear, but is believed to be years to decades. Average life expectancy following the onset of symptoms is 13 months.
Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is an incurable and invariably fatal neurodegenerative disease of cattle. Symptoms include abnormal behavior, trouble walking, and weight loss. Later in the course of the disease, the cow becomes unable to function normally. There is conflicting information about the time between infection and onset of symptoms. In 2002, the World Health Organization suggested it to be approximately four to five years. Time from onset of symptoms to death is generally weeks to months. Spread to humans is believed to result in variant Creutzfeldt–Jakob disease (vCJD). As of 2018, a total of 231 cases of vCJD had been reported globally.
The National Prion Clinic (UK) is part of the University College London Hospitals NHS Foundation Trust. Its aim is to diagnose and treat patients with any form of human prion disease (Creutzfeldt-Jakob disease, CJD). In addition, the clinic facilitates research in diagnostics and therapeutics, organises clinical trials, and counsels those with an increased genetic risk of the disease.
Variably protease-sensitive prionopathy (VPSPr) is a sporadic prion protein disease first described in an abstract for a conference on prions in 2006, and this study was published in a 2008 report on 11 cases. The study was conducted by Gambetti P., Zou W.Q., and coworkers from the United States National Prion Disease Pathology Surveillance Center. It was first identified as a distinct disease in 2010 by Zou W.Q. and coworkers from the United States National Prion Disease Pathology Surveillance Center.
Surround optical-fiber immunoassay (SOFIA) is an ultrasensitive, in vitro diagnostic platform incorporating a surround optical-fiber assembly that captures fluorescence emissions from an entire sample. The technology's defining characteristics are its extremely high limit of detection, sensitivity, and dynamic range. SOFIA's sensitivity is measured at the attogram level (10−18 g), making it about one billion times more sensitive than conventional diagnostic techniques. Based on its enhanced dynamic range, SOFIA is able to discriminate levels of analyte in a sample over 10 orders of magnitude, facilitating accurate titering.
Frank O. Bastian is an American physician and neuropathologist, who previously worked at Louisiana State University, moved to a university in New Orleans in 2019. He specializes in the transmissible spongiform encephalopathies (TSEs), which include, but are not limited to, Bovine spongiform encephalopathy (BSE) "Mad cow disease" in cattle, scrapie in sheep and goats, and Creutzfeldt–Jakob disease (CJD) in humans.
Michael D. Geschwind is a professor of neurology at the UCSF Memory and Aging Center (MAC), specializing in neurodegenerative disorders.
The United Kingdom was afflicted with an outbreak of Bovine spongiform encephalopathy, and its human equivalent variant Creutzfeldt–Jakob disease (vCJD), in the 1980s and 1990s. Over four million head of cattle were slaughtered in an effort to contain the outbreak, and 178 people died after contracting vCJD through eating infected beef. A political and public health crisis resulted, and British beef was banned from export to numerous countries around the world, with some bans remaining in place until as late as 2019.
Michael Coulthart is a Canadian microbiologist who is employed as the head of the Canadian Creutzfeldt–Jakob Disease Surveillance System (CJDSS) within the Public Health Agency of Canada (PHAC), which terms CJD a zoonotic and infectious disease. In 2006, a working group named "classic CJD" as well as Variant Creutzfeldt–Jakob disease as two notifiable diseases. It is unknown whether PHAC tracks in an official capacity other transmissible spongiform encephalopathies (TSE), but Coulthart is on the Advisory Committee of the Center for Infectious Disease Research and Policy for Chronic Wasting Disease of cervidae.
The Creutzfeldt-Jakob Disease Surveillance System (CJDSS) is a unit of the Public Health Agency of Canada. It studies the various variants of Creutzfeldt-Jakob Disease, and at least as of 2017, assisted "with DNA sequencing, autopsy and case confirmation". As of 2014, the CJDSS conducted "prospective national surveillance for all types of human prion disease in Canada. The main purposes of the CJDSS [were then] to better understand the epidemiology of human prion diseases, to improve the options available for their rapid and accurate diagnosis, and ultimately to protect the health of Canadians by reducing risks of prion disease transmission."
Adapted from:
a) Global surveillance, diagnosis, and therapy of human transmissible spongiform encephalopathies: Report of a WHO consultation, February 1998, Geneva, Switzerland;
b) Zerr et al. 2009
c) National CJD Research & Surveillance Unit. Protocol: Surveillance of CJD in the UK. Item c accessed 15 Aug 2018.