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.
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.
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.
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.
"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.
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.
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.
"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.
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 60ºC (140ºF) 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."
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.
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.
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.
The Idaho National Engineering and Environmental Laboratory is operated for the U.S. Department of Energy by Lockheed Martin Idaho Technologies Company.
Materials provided by Idaho National E & E Laboratory. Note: Content may be edited for style and length.
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