Good Morning List Friends,
This morning a news snip in the Food Safety Network "FSnet" out of the
University of Guelph referred to a paper presented yesterday at a
meeting sponsored by the American Chemical Society entitled "Diagnostic
Assays for Prion Diseases" symposium.
The snip referred to a new "conformation-dependent immunoassay (CDI)"
which claims to be 100% accurate, which can be automated and which will
produce results within 5 hours. CDI technology is now licensed to InPro
Biotechnology, Inc., of San Francisco, a company founded by Stanley
Prusiner, the first to discover that abnormal prion proteins can cause
disease, an accomplishment that won him the 1997 Nobel Prize in
Physiology or Medicine. They also report that it has detected prions in
muscle tissue and blood in laboratory mice, so it may be useful in live
animal testing.
The following links are to web sites which have references to the CDI
tests:
1. A fairly extensive report by the American Chemical Socitie's
"Chemical and Engineering News" online, Titled "GUARDING AGAINST MAD COW
DISEASE" The reference to CDI is well down in the article which
includes a pretty good review of the current BSE situation in North
America.
http://pubs.acs.org/email/cen/html/080403103837.html
2. A press release from the University of California San Fransisco UCSF
http://pub.ucsf.edu/today/cache/news/200210212.html
I could not find press release from yesterday's meeting with a Google
search so have no URL link. I have pasted it below if you are
interested. It is probably the most current information on the specific
subject of CDI.
Regards
Ross Gould, P.Ag.
Calgary, Alberta
===============
RESEARCHERS DEVELOP FASTER, MORE ACCURATE TEST FOR MAD COW DISEASE
September 7, 2003
American Chemical Society
NEW YORK � As U.S. consumers seek reassurance that their hamburgers and
steaks are free of deadly mad cow disease, researchers at the University
of
California-San Francisco say they may have found a promising solution.
They've developed a faster, more reliable test for identifying the
disease,
possibly even in living cows. Current tests can only detect the disease
after the cow dies.
The test was described today at the 226th national meeting of the
American
Chemical Society, the world's largest scientific society.
Critics argue that the standard immunoassay tests used to identify the
infectious prion proteins that cause mad cow disease are inadequate for
large scale screening of cattle. The tests can produce false readings
and
may take a week to yield results. A better test is needed, they say.
The new test, which has already undergone animal studies, seems to fit
the
bill. Called the conformation-dependent immunoassay (CDI), it can detect
prion proteins with 100 percent accuracy at much smaller levels than
conventional tests and only takes about five hours to produce results,
according to the UCSF researchers.
Like conventional tests, the new test is designed for detecting prions
in
the brain tissue of cows only upon autopsy. Unlike other tests, however,
the
new test also shows promise for detecting the proteins in muscle tissue
and
even blood while the animal is still alive. If so, it could be used to
identify precisely which animals are infected before they show symptoms
and
could help end the current practice of slaughtering whole herds, the
scientists say.
"This represents a new generation of prion tests," says project leader
Dr.
Jiri G. Safar, M.D., an associate adjunct professor at UCSF. "It is the
most
promising test to date for accurately detecting prion proteins," says
Safar,
a member of the school's Institute of Neurodegenerative Diseases.
He says the test has been used in a field trial to check for signs of
the
disease in the brains of 11,000 slaughtered cows in Spain, the United
Kingdom and Germany. Results were compared to those from standard
immunoassays performed on the same animals. There were no discrepancies
between the tests, he says.
"We had a perfect score. There were no false positives and no false
negatives," says Safar. "We can't afford incorrect conclusions, and we
didn't see that in our tests."
He says that the research group plans to use the test on an even larger
scale among European cattle herds within the next year, checking them
for
signs of the disease upon autopsy. If further tests prove successful, he
hopes it will eventually be used to evaluate dead cows in this country
for
mad cow disease, also known as bovine spongiform encephelopathy, or BSE.
Despite the fact that the CDI test is currently being done in dead
cattle,
Safar says the same test could eventually be used on live animals to
determine the presence of prions. In lab tests, the researcher has used
the
CDI test to detect prions in the muscles of living mice.
The live test could eventually be used to screen patients for the human
form
of mad cow disease, known as variant Creutzfeldt-Jakob disease, which is
thought to be acquired from eating infected beef. A tissue or blood test
for
live animals could be available in a year, says Safar. "We're not quite
there yet," he adds. "We still need to validate the effectiveness of CDI
in
live farm animals."
CDI has other advantages. It is automated, allowing larger numbers of
animals to be screened in a short period. The test can detect up to
eight
different strains of prions, including those that cause scrapie in sheep
and
chronic wasting disease in deer.
With the recent detection of mad cow disease in neighboring Canada and
the
temporary ban on beef imported from that country, critics have stepped
up
their call for better testing. To date, there has never been a case of
mad
cow disease detected in the U.S. Given the flaws of current testing,
however, some experts believe it could be just a matter of time.
Safar's coauthor in this study is Dr. Stanley Prusiner, M.D., a
professor of
neurology and biochemistry at the university and director of its
Institute
for Neurodegenerative Diseases. Prusiner was the first to discover that
abnormal prion proteins can cause disease, an accomplishment that won
him
the 1997 Nobel Prize in Physiology or Medicine.
CDI technology is now licensed to InPro Biotechnology, Inc., of San
Francisco, a company founded by Prusiner.
Funding for this study was provided by grants from the National
Institutes
of Health, the United Kingdom's Department for Environment, Food and
Rural
Affairs and private sources.
The paper on this research, ANYL 12, will be presented at 2:30 p.m. on
Sunday, Sept. 7, at the Javits Convention Center, Room 1A01/1A02, during
the
"Diagnostic Assays for Prion Diseases" symposium.
Jiri G. Safar, M.D., is an associate adjunct professor at the University
of
California-San Francisco and a member of the school's Institute of
Neurodegenerative Disorders.
Stanley B. Prusiner, M.D., is a professor of neurology and biochemistry
at
UCSF and director of its Institute for Neurodegenerative Diseases. He is
the
recipient of the 1997 Nobel Prize in Physiology or Medicine.
Mark T. Sampson
