APR 14, 2016

Improved Detection Of Deadly Prion Diseases

WRITTEN BY: Xuan Pham

Prion diseases are rare and deadly diseases of the brain. Once infected, the prion particles self-propagates and converts other proteins to be malformed, leading to irreversible destruction of brain material. Because the disease is transmissible, most notably from animals to humans, prompt knowledge of possible contamination is vital for public health and food safety. A new test will allow researchers to do this at much greater sensitivity than ever before.

Known formally as transmissible spongiform encephalopathies (TSEs), prion diseases made headlines as the cause of mad cow disease, or bovine spongiform encephalopathy (BSE). The prions are “proteinaceous infectious particles,” which are small proteins that are nearly impossible to destroy, but cause deadly brain-wasting diseases such as Creutzfeldt–Jakob disease (CJD), mad-cow disease, and kuru. Most recently, prion contamination was implicated in Alzheimer’s disease, though this link is still under investigation.

Early detection is important for any disease, but especially for prion cases, where there are yet no cures and contamination could lead to transmission and outbreak. To address this, a team of researchers developed an assay to measure prion protein conversion time – that is, the time a normal protein turns into prion form. The test is called timed amyloid seeding assay (tASA), and detects prion conversion through changes in fluorescence.

In a test using elk brains infected with a form of prion disease called chronic wasting disease (CWD), the team found the tASA detected prions with very high sensitivity. Compared to two other available assays, the tASA “was at least as sensitive as two rodent bioassays and up to 16 times more sensitive than three different TSE rapid tests,” said John Gray, lead study author.

Another advantage of the tASA is its ability to detect prions using a variety of sample types, including blood, urine, and saliva. In human applications, prion detection with this test could bypass invasive procedures to obtain tissue biopsies. "This study should further advance ASAs as recognized prion detection systems. We believe this methodology represents the future for prion diagnostics, especially concerning human health, for example in screening blood donations,” said Gray.

“This study represents an important first step for the tASA diagnostic protocol to gain regulatory approval for its use in TSE surveillance programs targeting CWD in cervids," said Holger Wille, a prominent prion expert at the Centre for Prions and Protein Folding Diseases in Alberta, Canada. "Additional work will also be needed to fine-tune and test tASA for the detection of prions in peripheral organs and environmental samples, which represent a substantial unmet need to track the spread of CWD prions among North America cervids as well as in the environment."

Additional source: MNT