Experiments Raise Hopes for Pre-symptom vCJD Blood Test

Newswise — Writing in the Friday, July 7, 2006, issue of Science magazine, researchers at the University of Texas Medical Branch at Galveston (UTMB) have reported on experiments that soon may help medical science estimate how many people are infected with the human form of mad cow disease, the "silent" phase of which can last up to 40 years.

The blood tests this advance should facilitate also could help prevent accidental transmission via infected blood transfusions and organ transplants of the malformed proteins causing variant Creutzfeldt-Jakob disease (vCJD), the scientists suggested.

In the paper, the investigators describe what they said are the first experiments ever to biochemically detect the malformed proteins during the "silent phase" of the disease—just weeks after lab animals were infected and months before they showed clinical symptoms.

The scientists report that they detected prions—the infectious proteins responsible for such brain-destroying disorders as bovine spongiform encephalopathy (BSE) in cattle and vCJD in humans—in the blood of hamsters in as few as 20 days after the animals had been infected. That discovery occurred about three months before the hamsters began showing clinical symptoms of the disease, the Science paper reports.

To detect the very small quantities of prions found in blood samples, UTMB professor Claudio Soto, assistant professor Joaquin Castilla, and research assistant Paula Saá used a technique known as protein misfolding cyclic amplification (PMCA), invented by Soto's group few years ago, which greatly accelerates the process by which prions convert normal proteins to misshapen infectious forms.

"With this method, for the first time we have detected prions in what we call the silent phase of infection, which in humans can last up to 40 years," said Soto, senior author of the Science paper.

"The concern is that if many people are incubating the disease silently, then secondary transmission from human to human by blood transfusion or surgical procedures could become a big problem," he continued. "This result is an important step toward a practical biochemical test that will determine how common variant CJD is, and keep contaminated blood and organs from spreading it further."

Creating such a test is a high priority for Soto, who is also director of UTMB's George and Cynthia Mitchell Center for Alzheimer's Disease. "We're now working with natural samples, both from humans and cattle but mostly from humans," he said. With an eye toward making a human test commercially available, Soto and UTMB recently formed a startup company, dubbed "Amprion."

"All our effort so far has been to prove the scientific concepts, so we're building this company to go into issues of development, scalability and practicality," Soto said. "We are hopeful that development of this technology into a useful blood test will be a pretty straightforward process."

"Presymptomatic Detection of Prions in Blood," by P. Saa, J. Castilla, and C. Soto at University of Texas Medical Branch in Galveston, TX; P. Saa now at Universidad Autonoma de Madrid in Madrid, Spain.