Test developed by University of Maryland School of Medicine researchers also would be the first to protect the nation’s blood supply from deadly prion diseases
Scientists at the University of Maryland School of Medicine in Baltimore have developed a highly sensitive test to detect abnormal prions that cause several incurable diseases, such as Bovine Spongiform Encephalopathy (BSE), known as Mad Cow disease, and Creutzfeldt-Jacob disease (CJD), a fatal neurological disorder in humans. The test is more sensitive than all current tests, giving it the potential to be used to examine the blood of cattle prior to slaughter and test the nation’s blood supply to ensure that it is free from CJD. Results of this study, using a novel new Immuno-PCR technique, are currently available in the online edition of the Journal of Virological Methods and will be published in the July 22, 2005, hardcopy version of the journal.
“For the past four years and in collaboration with scientists from SeraCare, Inc., we’ve been dedicated to developing a blood screening test for both humans and animals to be able to detect prion disease before any symptoms appear,” says Niel Constantine, Ph.D., professor of pathology at the University of Maryland School of Medicine and director of the Clinical Immunology Laboratory at the University of Maryland Medical Center.
“We hope that in the near future this test will be used to screen populations of animals and humans to ensure that they aren’t incubating a prion disease and potentially passing it on to others. Presently, the only way to definitively diagnose these diseases in living humans is with a brain biopsy,” says Dr. Constantine, whose work to develop the test was funded in part by the United States Department of Defense.
Prions are proteins found in the central nervous system of humans and animals. When abnormal prions enter the body, they effectively convert normal prions into abnormal ones. The resulting neurological diseases are untreatable and 100 percent fatal. Prion diseases occur in many animals, including scrapie in sheep, chronic wasting disease in deer and elk and BSE in cows and even in cats. CJD occurs spontaneously in one in about one million people and can be passed genetically. A variant form of CJD caused by ingestion of prions from infected beef has caused over 150 fatal cases in humans worldwide.
According to Dr. Constantine, currently available tests that can detect prions in the brain where levels are most concentrated can’t detect abnormal prions in the blood. “Those tests just aren’t sensitive enough. We’ve devised a technique that can detect ultra-low levels of prion protein and believe it has the sensitivity to detect abnormal prions in blood. Our Immuno-PCR test uses a combination of two highly sensitive techniques to detect protein levels several thousand fold to a million fold lower than the current methods.”
So far, Dr. Constantine and his team have assessed the Immuno-PCR test only in a laboratory setting. Future plans call for testing of blood from small animal models known to be infected with prion disease. After that, they plan to evaluate the test among cattle in Europe and in humans.
The availability of such a blood test could have enormous impact on the cattle industry and the blood donor system. “If the test is effective in being able to detect Mad Cow disease and CJD during the incubation period in advance of symptoms, we will have a much better chance of protecting persons from infected beef and increasing the safety of the blood supply,” says Dr. Constantine.
“Consider that in the United States alone we screen 15 million units of blood a year and there are 100 million head of cattle. Ensuring that beef and blood are safe will save lives and will decrease the concern of the public over this class of fatal diseases,” Dr. Constantine adds.
Co-authors on the study are Janet Barletta, Ph.D., of the United States Food and Drug Administration, Daniel Edelman, Ph.D., of the Department of Pathology, University of Maryland School of Medicine and W.E. Highsmith, Ph.D., of the Department of Laboratory Medicine and Pathology at the Mayo Clinic. The University of Maryland, Baltimore, along with scientists from SeraCare, Inc., have filed for patent protection for the Immuno-PCR test.
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