New Filter Cleans Human Form of Mad Cow Disease from Blood

EAST HILLS, New York, November 1, 2004 (ENS) - Infectious prions that cause the human form of mad cow disease can be removed from blood with a new filter, according to the inventors, the Pall Corporation, based in East Hills. Prions are misshapen proteins that are behind transmissible spongiform encephalopathies - fatal, degenerative diseases affecting the central nervous systems of humans and animals.

The new filtration technology was presented at the annual meeting of the AABB blood banking conference in Baltimore, Maryland last week.

A study of the new filter, the Pall Leukotrap® Affinity Prion Reduction Filter, conducted at a prion research institute in Europe, found that it reduces infectious variant Creutzfeldt-Jakob Disease (vCJD) prions from red blood cell concentrates below the limit of detection of a test known as the Western blot assay.

The problem of prion transmission from human-to-human through a blood transfusion came to public attention in December 2003 when a case of vCJD was identified in the United Kingdom in a person who received a blood transfusion six years earlier from a donor who later died of the disease. Another UK transmission case has also since been identified.

Pall Leukotrap® Affinity Prion Reduction Filter (Photo courtesy Pall Corporation)

The same filter can remove from blood other transmissible spongiform encephalopathies (TSEs) that cause fatal, neurorodegenerative prion diseases in humans and animals, according to Samuel Coker, Ph.D., principal scientist and technical director of Pall Medical, who presented the company's findings at the AABB conference.

Additional research, conducted with the New York Institute of Basic Research, demonstrated that the filter also reduces infectious scrapie prions in blood, Coker said. Scrapie is a TSE that affects the central nervous system of sheep and goats.

Pall expects to launch the new filter in Europe in early 2005 with a Council of Europe mark. It is also developing documentation to meet regulatory requirements for submission to the U.S. Food and Drug Administration in mid-2005.

Additionally, the company is studying the filter as a device to aid in the detection of bovine spongiform encephalopathy (BSE) in cattle before they enter the food supply.

Since vCJD has an unknown, but lengthy, incubation period during which the infected person shows no symptoms, there is no way to know how many people already have the disease and how many could have already transmitted it via blood transfusion.

The transfusion transmissions have spurred increasing concern about the possibility of a second and larger wave of mad cow disease in humans. Public health officials and risk assessment experts believe that the problem is not limited to the UK, where a majority of the early cases of vCJD have been identified, or to Europe, but is a potential global threat that includes the United States and Canada.

Roger Eglin, Ph.D., a consultant microbiologist with the National Transfusion Microbiology Laboratories of the UK National Blood Service, warned of a potential new wave of the human form of mad cow disease at a symposium on transmissible spongiform encephalopathies (TSEs) at the AABB conference.

He was joined by government, public health and blood safety experts from around the globe, who all raised concerns about a second wave of the disease that could be brought about by human-to-human transmission via blood transfusions.

“This may not be a disease in decline, despite the low number of cases today,” said Dr. Eglin. “There is much uncertainty over the number of cases predicted for the UK. Estimates of up to 25,000 total cases have been predicted with an incidence of one in 24,000 of the UK population.”

Structure of a portion of the bovine prion protein, a molecule associated with mad cow disease. (Photo courtesy National Science Foundation)

In March 2004, the UK Department of Health announced that people who had received a blood transfusion in the UK since 1980 would no longer be able to give blood as a precautionary measure against the possible risk of vCJD being transmitted by blood and blood products.

Britain has exported blood products that could be contaminated with the human form of mad cow disease to at least 11 countries, raising fears of further transmission of the deadly condition, the "Times of London" reported on September 27.

The 11 countries are Brazil, Brunei, Dubai, Egypt, India, Ireland, Morocco, Oman, Russia, Singapore and Turkey.

The blood products were donated by nine people who died from vCJD. Of the more than 150 people worldwide who have died of the disease to date, 143 have been from the UK.

David Asher, M.D., chief and supervisory medical officer with the U.S. Food and Drug Administration's Division of Emerging and Transfusion-Transmitted Diseases at the Center of Biologics Evaluation and Research, expressed heightened concern about vCJD transmission by blood due to the two cases in the UK.

Speaking at the AABB symposium, he agreed that a second wave of vCJD is possible and said that the number of people who may be harboring the infection in the UK, 237 per million, is a minimum estimate and may be too low.

The United States has a number of measures in place to protect blood safety, he said, but warned that it is not possible to remove every blood risk by donor deferral.

Still, on October 14, the Food and Drug Administration's TSE Advisory Committee recommended that no additional residency deferrals are necessary in the United States at this time.

“If we attempt to defer every donor who spent time in the UK from 1980 to 1996, the blood donor loss would be enormous,” Dr. Asher explained.

“If exposure to an infectious agent can be stopped, then the disease can be stopped,” he said. “Physical removal of vCJD from blood appears to be the most promising line of attack.”

PALL Chairman and CEO Eric Krasnoff said, “We are moving forward as quickly as possible so that this new technology can be made available worldwide."