Real-time quaking-induced conversion (RT-QuIC) is a highly sensitive assay for

prion Prions are misfolded proteins that have the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals. It ...

detection. __TOC__

Technique

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. It is "an early, rapid and specific assay for prion diseases". It can sample multiple sample types, such as

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

(CSF),

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

lymph nodes A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

, and

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

, and so it is applicable to

scrapie Scrapie () 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 ...

in sheep,

chronic wasting disease 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 dis ...

(CWD) in cervids,

bovine spongiform encephalopathy 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 t ...

(BSE) in cows and sporadic

Creutzfeldt–Jakob disease Creutzfeldt–Jakob disease (CJD), also known as subacute spongiform encephalopathy or neurocognitive disorder due to prion disease, is an invariably fatal degenerative brain disorder. Early symptoms include memory problems, behavioral changes, ...

in humans, amongst others. 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 Thioflavins are fluorescent dyes that are available as at least two compounds, namely Thioflavin T and Thioflavin S. Both are used for histology staining and biophysical studies of protein aggregation. In particular, these dyes have been used sin ...

visible spectrum

fluorescence detection A fluorometer, fluorimeter or fluormeter is a device used to measure parameters of visible spectrum fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters ar ...

. The

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...

includes a positive RT-QuIC result in its diagnostic criteria for the probable diagnosis of sCJD. RT-QuIC assays can also be used to test for scrapie, BSE, CWD, and sCJD. 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.Denkers, N. D., Henderson, D. M., Mathiason, C. K. & Hoover, E. A. Enhanced prion detection in biological samples by magnetic particle extraction and real-time quaking-induced conversion. J. Gen. Virol. 97, 2023–2029. https://doi.org/10.1099/jgv.0.000515 (2016) Commonly tested tissues are brain homogenates and lymph tissues, however prions have been detected in skin and blood samples.Mammana, A., Baiardi, S., Rossi, M., Franceschini, A., Donadio, V., Capellari, S., Caughey, B. and Parchi, P. (2020), Detection of prions in skin punch biopsies of Creutzfeldt–Jakob disease patients. Ann Clin Transl Neurol, 7: 559-564. https://doi.org/10.1002/acn3.51000Concha-Marambio L, Pritzkow S, Moda F, et al. Detection of prions in blood from patients with variant Creutzfeldt-Jakob disease. Sci Transl Med. 2016;8(370):370ra183. doi:10.1126/scitranslmed.aaf6188Orrú CD, Yuan J, Appleby BS, Li B, Li Y, Winner D, Wang Z, Zhan YA, Rodgers M, Rarick J, Wyza RE, Joshi T, Wang GX, Cohen ML, Zhang S, Groveman BR, Petersen RB, Ironside JW, Quiñones-Mateu ME, Safar JG, Kong Q, Caughey B, Zou WQ. Prion seeding activity and infectivity in skin samples from patients with sporadic Creutzfeldt-Jakob disease. Sci Transl Med. 2017 Nov 22;9(417):eaam7785. doi: 10.1126/scitranslmed.aam7785. PMID: 29167394; PMCID: PMC5744860 Certain tissues can be difficult to test for prions. For example, blood samples tend to have low levels of circulating intracellular prions, as well as inhibitors.Prion Disease Blood Test Using Immunoprecipitation and Improved Quaking-Induced Conversion, Christina D. Orrú, Jason M. Wilham, Lynne D. Raymond, Franziska Kuhn, Björn Schroeder, Alex J. Raeber, Byron Caughey mBio May 2011, 2 (3) e00078-11; DOI: 10.1128/mBio.00078-11

References

{{reflist Prions Transmissible spongiform encephalopathies Neurodegenerative disorders Rare infectious diseases Wikipedia neurology articles ready to translate Rare diseases 2011 in biology Japanese inventions

Technique

See also

References