New Blood Test Could Help Diagnose CJD

In a recent study, scientists have used a technique known as protein misfolding cyclic amplification (PMCA) as a way to screen patients’ blood samples for the presence of abnormal prions (PrP^Sc) that would indicate a diagnosis of Creutzfeldt-Jakob disease (CJD).

“Given that PMCA can detect the equivalent of a single particle of PrP^Sc, our findings suggest that PMCA may be useful for noninvasive diagnosis of this disease in presymptomatic individuals, although this possibility needs to be tested,” write Luis Concha-Marambio, BS, from the University of Texas Medical School at Houston, and colleagues.

The authors published the results of their study online in Science Translational Medicine.

Prion diseases comprise a group of infectious and fatal neurodegenerative disorders in which abnormal, misfolded infectious proteins known as prions accumulate in the tissues of infected individuals. These diseases include bovine spongiform encephalopathy (BSE) in cattle, and Creutzfeldt-Jakob disease (CJD) in humans. Variant CJD (vCJD) in humans is associated with consumption of meat from BSE-infected cattle.

However, according to the authors, a regulatory-approved assay for sensitive, objective, and noninvasive diagnosis of CJD is lacking. This is especially concerning because vCJD can be transmitted by blood transfusion, they add.

With this in mind, the researchers aimed to develop a sensitive test to detect abnormal prions in blood samples from patients with vCJD.

They used PMCA technology—a technique that allows the prion replication process to proceed in the laboratory in a similar way to that which occurs in prion disease. This method amplifies even a tiny amount of abnormal prion in a patient’s blood sample, thereby increasing the concentration of the infectious agent to a level that can be detected.

Concha-Marambio and colleagues used this method to analyze blood samples from 14 patients with vCJD patients and 137 patients who did not have the disease (controls).

“Our results showed that PrP^Sc could be detected with 100% sensitivity and specificity in blood samples from vCJD patients,” they write. The test detected the presence of abnormal prion in all blood samples from vCJD patients, but not in any of the blood samples from the control patients.

The authors were also able to detect the abnormal prion in different blood fractions, such as whole blood, plasma, and white blood cells. They also found that even a few microliters of blood were sufficient to detect the abnormal prion after PMCA amplification.

“Our findings, which need to be confirmed in further studies, suggest that our method of detection could be useful for the noninvasive diagnosis of this disease in pre-symptomatic individuals,” says senior author Claudio Soto, MD, also from the University of Texas Medical School at Houston, in a press release on the University of Texas website.

“Early diagnosis would allow any potential therapy to be given before substantial brain damage has occurred. In the case of the blood supply, availability of a procedure to efficiently detect small quantities of the infectious agent would allow removal of blood units contaminated with prions, so that new cases can be minimized substantially,” he concludes.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.