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Prions protein expressed in E. coli bacteria. Credit: NIAID.
By the time symptoms of sporadic Creutzfeldt-Jakob disease are generally discovered, death is imminent and inevitable. But, in a new study, researchers at the University of California San Diego School of Medicine and colleagues at the National Institutes of Health and the University of San Francisco have discovered some telling evidence of the infectious agent of the disease in the eyes of deceased patients with CJDs. the eye is a potential source for early detection of CJD and prevention of disease transmission.
Writing in the November 20 issue of the journal mbio, Corresponding Co-Author Christina J. Sigurdson, DVM, Ph.D., professor of pathology at UC San Diego and UC Davis, and her colleagues found high levels of prions in the eyes of 11 deceased patients, all suffering from the MCJs confirmed.
"Nearly half of patients with CJD develop visual disturbances and we know that the disease can be unknowingly transmitted by corneal transplant grafting," Sigurdson said. "But the distribution and levels of prions in the eye were unknown.We answered some of these questions.Our results have implications both for the estimation of the risk of transmission of CJD and on the development of diagnostic tests for prion diseases before the symptoms appear. "
Prions are malformed forms of a normally harmless protein. It is not known why the normal prion protein folds poorly and becomes pathogenic. In humans, prions that accumulate in the brain produce lesions that can lead to rapidly progressive neurodegeneration. Patients usually die in the year following the diagnosis.
Sporadic CJD is the most common form of the disease (85% of cases); the patients have no known risk factor. Hereditary CJD involves a genetic mutation associated with CJD, and about 10 to 15% of CJD cases in the United States are hereditary. In acquired CJD, the disease is spread by exposure to the brain or nervous system tissues, usually through certain medical procedures, such as corneal transplants. In rare cases, people consuming meat from cattle are suffering from a disease similar to CJD called bovine spongiform encephalopathy or "mad cow disease".
Sigurdson, with Corresponding Authors Michael D. Geschwind, MD, Ph.D., Professor of Neurology at the Memory and Aging Center of the University of California at San Francisco, Byron Caughey, Ph.D., at the NIH Rocky Mountain Laboratories, Montana, NIH researchers then used a highly sensitive real-time test, called the RT-QuIC test, developed by Caughey to measure the post-mortem seeding of prions into different tissues of the eye, such as the cornea, the lens, the eye fluid, the retina and the optic nerve. . Prions were found in the eyes of the eleven patients tested for CJD (who had agreed to give their eyes at the time of death), with the highest rates of germs in the retina – in some cases Were slightly lower than those of the brain. Eye analyzes of six control samples without diagnosed CJD were negative for prions.
Ocular tissues tested by earthquake-induced real-time conversion Credit: Ryan Kissinger, NIAID
"Collectively, these results reveal that patients with CJD accumulate prion seeds in the eye, indicating potential diagnostic utility as well as potential biological risk," the authors wrote.
The RT-QuIC test is used by clinicians to diagnose CJD in humans, usually by brushing cerebrospinal fluid and nose. The researchers plan to further evaluate its utility in eye tests and to evaluate the eyes of patients with Alzheimer's disease, Parkinson's disease or Lewy body dementia to determine the presence of aggregated proteins from these conditions.
In the meantime, the authors have recommended that ophthalmic examinations use either single-use instruments or equipment decontamination procedures to eliminate the risk of prion transmission from one patient to another. They also stated that they hoped that these results would encourage further efforts to develop corneal transplant techniques, such as biosynthetic corneas, to eliminate the transmission of iatrogenic diseases. .
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More information:
Christina D. Orrù et al., Prion Seeds distribute in the eyes of patients with sporadic Creutzfeldt-Jakob disease, mbio (2018). DOI: 10.1128 / mBio.02095-18
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