San
Jose, CA (2/11/99)- A new technique based on unique individual antibody
profiles offers an alternative to current DNA fingerprinting methods.The method
is simple to use and has attracted considerable attention from law enforcement.
Researchers at the US Department of Energy's Idaho National Engineering and
Environmental Laboratory have developed a technique called the Antibody Profile
Assay. The test identifies a subset of antibodies unique to each individual,
know as Individual Specific Autoantibodies. The antibodies are not affected
by medicines or disease and appear to be stable during an individual's lifetime.
The antibody profile assay utilizes a complex array of antigens, immobilized
on a membrane "strip", to capture and resolve autoantibodies from samples.
A sample of blood or other body fluid is flushed across the test strip and
the strip is then rinsed with reagents that stain the antibodies. The immunoassay
test displays a permanent "bar code" of antibodies. The test can distinguish
between samples from human, monkey, horse, cow, sheep, goat, swine, dog, cat,
rabbit and guinea pig. Unlike standard DNA testing, the test can even distinguish
between identical twins -- something DNA testing cannot.
"The test itself is very simple to do; the chemistry behind it is not," says
chemical engineer Vicki Thompson. The new test offers a number of advantages
over standard DNA testing, she notes. First, the test can be prepared by someone
with a high school education. Second, the test does not require DNA material,
only bodily fluids. This might be useful in a law enforcement setting. For
example it might identify or exclude a suspect in in a rape case where the
suspect has had a vasectomy, because while there is no DNA in the fluid, there
are antibodies. Speed is another advantage. The new test provides results
in about two hours, while DNA testing can take anywhere from 24 hours to three
weeks. The new assay is also quite a bit cheaper, $20 per test versus $200
to $1,200 for DNA screening.
There are a few problems remaining to be worked out with the new test. In
tests conducted at model crime scenes, the test was able to correctly identify
91% of the samples. This is not specific enough to present in court. Contamination
with bacteria in dirt was one problem. The test also faltered when applied
to blood samples that had been exposed to temperatures above 60ºC.
"The blood samples just get too degraded at high temperatures. We really
don't understand what is happening with the dirt." says Thompson. She and
her colleagues, along with scientists at a California biotech company, are
working to improve the sensitivity and specificity of the test.
The new test is already in use in clinical and reference laboratories. Potential
uses include newborn identification, blood banks, animal identification, pathology
and forensic science.
Thompson presented her results at a conference of the International Society
for Optical Engineering. Her paper will be published in the conference proceedings
called "Enabling Technologies for Law Enforcement and Security".
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