"Effective prophylaxis and treatment for infections caused by biological threat agents (BTA) rely upon early diagnosis and rapid initiation of therapy. However, most methods for identifying pathogens or infectious agents in body fluids and tissues required that the pathogen proliferate to detectable and dangerous levels, thereby delaying diagnosis and treatment," says Rasha Hammamieh, a researcher on the study.

Over the past five years Hammamieh and her colleagues have been studying the host response to BTAs. Upon exposure to a BTA host cells initiate a unique response, turning specific genes on and off. Leukocytes in the bloodstream course throughout the body in a matter of minutes. If they encounter something that is not normally there they make a record in their gene expression.

They first drew blood from healthy donors and screened leukocytes to get a baseline for gene expression in unexposed samples. They then exposed the samples to a number of different pathogens (including BTAs) and bacterial toxins and confirmed their results in animal models.

"We see very specific changes in gene expression that are quite unique to each pathogen as little as 2 hours after exposure. Use of mathematical modeling tools has identified a list of over 300 genes that can discriminate among 8 pathogenic agents with 99 percent accuracy," says Hammamieh. They are also looking for gene expression patterns that could help determine severity of exposure

While the technology for conducting these tests in the field is still in development Hammamieh and her colleagues foresee a day when hand-held devices could be used at the site of a suspected bioterrorism attack to determine who has been exposed within hours instead of days that would be required using traditional culture methods.

"The technology is not there yet, but within 10 years this test could also be done in doctors' offices for a variety of common illnesses, including some types of cancer," says Hammamieh.

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