Focus on the Flu : Diagnosing, Part 2

by National Institute of Health

(Page 10 of 15)

Diagnosing the Flu: Can the 'Flu Chip' Handle the Strain?

Currently, most flu strains go undiagnosed, or are identified in a laboratory miles from any doctor's office. If the strain is diagnosed, the time between a throat swab and a final read-out can be days if not weeks. As the risk of a flu pandemic increases, health care professionals must be able to quickly distinguish one flu strain from another.

Kathy Rowlen, Ph.D., professor of chemistry and biochemistry at the University of Colorado at Boulder, and her research team are out to help. Dr. Rowlen and her colleagues are developing a self-contained kit, smaller than the basic Palm Pilot, which can fully characterize an influenza virus in about an hour or so.

The device, called a "flu chip," is based on DNA microarray technology, a research tool that enables scientists to analyze gene activity in cells and, more recently, to detect pathogens in a sample. Short, specially labeled segments of DNA are robotically placed in rows of microscopic spots on a glass slide. The DNA segments can capture telltale "signatures" of specific flu strains. When the viral RNA from a throat swab meets up with the DNA spots, individual RNA strands will stick like Velcro to the DNA sequences they complement, causing them to glow bright yellow. The resulting pattern of glowing versus dark spots will reveal if it's influenza A, B, or C, and, if it's influenza A, whether the strain is H1N1, H5N2, H7N3, and so on. Such a device could also be used to diagnose SARS and other respiratory diseases.

One of the more important aspects of the flu chip is that it's being developed to be used anywhere in the world, wherever there's a potential outbreak. "The current microarray technology is wonderful in the hands of experienced experts in a very clean environment, but it's not practical for going into the fields in, say, Madagascar," says Dr. Rowlen. "We're designing a technology and methodology that can be used in imperfect conditions."

In 2005, the team tested the chip in labs at the Centers for Disease Control and Prevention (CDC). They determined that it was more than 90 percent accurate in detecting a strain of avian influenza, H5N1, and two common human flu strains, H1N1 and H3N2. "This was the first time a version of the flu chip was tested outside of our lab, and it exceeded our expectations," says Dr. Rowlen.

She added that it is feasible that the flu chip could be widely used under research conditions within a year.

Co-principal investigators on the grant include Dr. Robert Kuchta (University of Colorado), Dr. Nancy Cox (CDC), and Dr. Robin Stears (formerly with Bio-Rad Laboratories, currently with Intel Corporation).

Lab-on-a-Chip Offers Potential for Fast Diagnosis of the Flu

Imagine: A traveler, while en route from China to the United States, comes down with a high fever, severe body aches, and diarrhea, symptoms that resemble those experienced by individuals recently infected with H5N1 avian flu. Is she the next case?

If Ronald Larson, Ph.D., professor of chemical engineering at the University of Michigan, has his way, some day health officials will have an answer roughly an hour after the plane lands.

Dr. Larson and his multidisciplinary research team are developing a small, portable device that can quickly decipher the genetic make-up of any influenza virus. Not only could the instrument, called a Genotyper, help diagnose flu in a patient, it could also be used to quickly ascertain if a new human flu strain has emerged. Further down the road, says Dr. Larson, a network of Genotypers could be wirelessly connected, enabling health officials to track the spread of certain flu strains worldwide.

"We believe it's possible, and our efforts are to further that goal-to make that day come more quickly," he says.

The Genotyper is based on a technology developed by a team led by University of Michigan collaborators Mark Burns, Ph.D., professor of chemical and biochemical engineering, and David Burke, Ph.D., associate professor of human genomics, in which processes conducted in a typical DNA lab are condensed onto one small silicon chip.

About the size of a TV remote control, the Genotyper would employ some of the same techniques used by scientists to determine an organism's genome. When the system is fully functional, a throat swab from the patient will be placed into the device, which removes the sample's genetic material-in the case of flu virus, RNA-converts it into DNA, and copies it many times over.

To determine the flu strain, one version of the device uses "restriction enzymes," enzymes that recognize certain sequences of DNA, clipping the DNA at those sites. Samples that share the same signature sequence as a given flu strain will be clipped at those points; samples that don't will remain intact. (The team is initially focusing on the HA gene, but they eventually hope to include other genes as well.)

The DNA fragments are then run through an electrophoresis gel, which separates them out by size. Small fragments move farther and faster through the gel than large fragments. The resulting fluorescent read-out reveals the sample's genetic make-up. In this way, the researchers can tell if a sample matches a common flu virus strain or pinpoint if the HA gene has deviated from the norm, making the virus potentially more dangerous.

In October 2005, Dr. Larson and his colleagues reported that the device accurately distinguished between two strains of flu by detecting variations in the strains' hemagglutinin gene. The report was published in the journal Lab on a Chip.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.