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Gene chip test identifies bird flu strains
2006-11-13
A new "gene chip" test can quickly and cheaply identify different influenza strains, allowing doctors to easily tell who has H5N1 avian influenza and who has everyday flu, U.S. researchers said on Monday. They said their new test, using a gene chip device called an MChip, correctly identified 21 out of 24 different H5N1 flu strains seen in people, birds and cats and never gave a false positive, meaning it never indicated an infection was due to H5N1 when it was not. "This new technology, once manufactured and distributed, could have the potential to revolutionize the way laboratories test for influenza," said Dr. Nancy Cox, director of the influenza division of the U.S. Centers for Disease Control and Prevention. "The MChip could enable more scientists and physicians, possibly even those working in remote places, to more quickly test for H5N1 and to accurately identify the specific strain and its features." The H5N1 avian influenza virus now rarely infects people but experts fear a pandemic if it mutates into a form that passes easily from person to person. Since 2003 the virus has swept through birds in Asia, Europe and Africa. People in close contact with infected birds can become ill and the virus has infected 258 people and killed 153 of them, according to the World Health Organization. Now, people suspected of having an H5N1 infection get a rapid flu test that tells only whether they are infected with an influenza A strain. A sample must be sent to a designated WHO laboratory that then tests for H5N1 genetic material -- a process that can take two weeks. This lengthy process worries flu experts, who say an on-the-spot test is vital if the first outbreak of a pandemic strain of flu is to be caught in time to control it. STABLE GENE A team at the University of Colorado at Boulder and the CDC developed the new test based on a single influenza virus gene that mutates less frequently than other flu genes. Gene chips are now commonly used in many labs, and consist of a silicon or glass plate covered with rows of spots of genetic material -- DNA or RNA -- that react when brought into contact with desired substances. The researchers used their MChip to test H5N1 samples collected over a three-year period from people and animals around the world. They will describe their work in the December 15 issue of the American Chemical Society journal Analytical Chemistry. "Our tests show the MChip can determine the type and subtype of human flu influenza in less than seven hours, in contrast to current methods to identify the type and subtype of flu that require several days," Colorado University's Robert Kuchta said in a statement. Discussions are under way to commercialize the MChip, which costs less than $10 to make, said chemistry professor Kathy Rowlen, who led the study, funded by the National Institutes of Health. "One of our goals has been to address the needs of developing nations by providing an inexpensive field-portable test kit for the World Health Organization for global screening of respiratory illnesses," Rowlen said. The gene chip test lights up with a series of fluorescent spots. To automate recognition of the patterns and reduce the risk of human error the researchers developed an artificial neural network trained to recognize the distinctive pattern indicative of H5N1.
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