- Canned peas, beans, and human beings
all have something in common -- they can be identified with a bar code.
It takes more than supermarket science to see a human's bar code, however.
The Department of Energy's Idaho National Engineering and Environmental
Laboratory and Miragen, a biotechnology company, are developing a technique
that can display a "bar code" of antibodies that is unique for
each person and may become a powerful new tool for law enforcement.
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- INEEL's chemical engineer Vicki Thompson
presented an overview of her work to date to the International Society
for Optical Engineering (SPIE). Her paper will be published in the conference
proceedings called Enabling Technologies for Law Enforcement and Security
in January.
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- Miragen, based in Irvine, California,
has developed a technique called the Antibody Profile Assay (AbPTM) that
can identify an individual by a subset of normally occurring antibodies
present in his body. These antibodies, called Individual Specific Autoantibodies
(ISA's), are not affected by medicines or illnesses, and with very few
exceptions are stable across a person's lifetime -- just like a fingerprint.
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- The AbPTM technique involves flushing
a sample containing blood (or potentially other bodily fluids) across a
strip of paper lined with bands of specific proteins that the ISA's can
cling to. The paper is then rinsed with reagents that stain the ISA's,
and researchers are able to see which ISA's an individual has. There is
little sample preparation necessary, and the results are in a permanent,
easy-to-read format. The test can even distinguish between identical twins
-- something DNA testing cannot. Until recently, Miragen has marketed the
technique only for medical and agricultural purposes, but researchers at
the INEEL are interested in developing this new technology for law enforcement.
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- "The test itself is very simple
to do; the chemistry behind it is not," says Thompson. Although she
says she doesn't see this technique replacing DNA testing, it does offer
several advantages: One, the test can be prepared by someone with a high
school education. Secondly, the fact that this test does not require DNA
material, only bodily fluids, gives law enforcement a very powerful new
method for proving someone was at a crime scene. This could be very important
in cases of alleged rape where the suspect has had a vasectomy - there
is no DNA in the fluid, but there are antibodies.
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- Also, results from the AbPTM assay are
available in around two hours whereas DNA tests can take anywhere from
24 hours to three weeks. The assay provides an additional method with which
law enforcement personnel can prove identity. This technique, which costs
an estimated $20 per test, is significantly cheaper than DNA testing, which
can range from $200 to $1,200 per test.
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- Thompson is partnering with Miragen through
a cooperative research and development agreement to test the technique's
efficacy against the real-world problems facing law enforcement. Recently,
she provided blood samples from 10 people to the Wyoming State Crime Laboratory.
They agreed to doctor blood samples to simulate crime scene challenges
for Thompson and her team.
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- "They added gasoline to the blood
samples, swabbed the blood off of sidewalks, windshields, and cars, mixed
the samples, and even used animal blood," said Thompson. Surprisingly,
animal blood is often found at crime scenes, and the assay technique must
distinguish between human and animal blood, said Thompson. The Wyoming
lab obtained samples of blood from cats, dogs, sheep, coyotes -- even moose.
"It's not like you often find moose blood at crime scenes," says
Thompson with a laugh, "it was just what was easy for them to obtain."
The Wyoming Lab created a key of what was done to the samples (and who
they belonged to) and sent Thompson 422 sample puzzles to solve.
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- Thompson was able to correctly identify
91% of the samples. The assay technique was less reliable with blood samples
that had been exposed to temperatures above 60*C (140*F) and samples contaminated
with dirt. "The blood samples just get too degraded at high temperatures,"
says Thompson, "and we really don't understand what is happening with
the dirt."
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- Thompson later scooped dirt from outside
her lab and did several new tests. "It seems to make a real difference
in the samples mixed with dirt if it is over 24 hours before we test them
-- that is a lot of time for microbes to work," she says. This is
problematic because microbes are abundant in soils, and not all crimes
scenes are discovered (and their evidence gathered) within 24 hours. Thompson
also decided to make the new test non-responsive to animal antibodies completely.
She changed the reagent wash composition so that only human ISA's are stained
and create a color band, while the animal antibodies are ignored.
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- A success rate of 91% is not good enough
for the courts. "We realized that the technique had to be made more
sensitive," says Thompson. With funding from the INEEL's discretionary
research program, Thompson is improving the test procedure. By using an
additional wash of reagents, she is able to build up more of the reagents
that stain the ISA's on the protein strip -- refining the distinct bands.
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- In 1999, Thompson will test her new process
against more simulated crime scene situations, and work toward statistical
proof that the bar code is truly as unique to each person as a fingerprint.
The validity of the assay has to be statistically proven before the test
results will be widely used in court proceedings.
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