Genotyper Could Diagnose Patients, Identify New Flu Strains Quickly

With the threat of a flu pandemic looming, researchers are racing to develop tools to help diagnose and identify new flu strains quickly. A portable lab-on-a-chip called the Genotyper, developed by a multidisciplinary team at the University of Michigan, could eventually allow doctors to de-code the genetic makeup of flu viruses in less than two hours.

Ultimately, the Genotyper will be fully portable and could even be connected wirelessly, thus able to track the spread of existing or emerging flu strains around the globe, said Ron Larson, U-M chemical engineering professor and part of the team developing the technology.

The technology originated in the laboratories of Mark Burns and David Burke, engineering professors who sought to develop fast, inexpensive methods for deriving genetic information from humans, and is now being applied to genotyping influenza virus by a team that also includes Larson, and professors Michael Solomon and Oveta Fuller.

The process for identifying the flu type is similar to genetic fingerprinting used in DNA identification. First, the influenza RNA is converted to DNA, using the same biological processes that the HIV virus uses to convert RNA to DNA to replicate itself and elude the immune system. Then, a segment of the DNA is reproduced in a process called PCR, or "polymerase chain reaction," and enzymes are released that "digest," or cut that DNA at certain points.

"The way the gene is cut or not cut depends on which flu gene you have," Larson said. "Once the genes are cut, you can separate them based on size in a gel." The pattern of fragment sizes tells you the locations of the cuts in the DNA, and this provides a "fingerprint" that distinguishes the type of flu.

During that process, the DNA fragments are run though a gel, which, when it is electrically charged, causes the DNA fragments to move at certain speeds depending on size. The short fragments squirt through quickly, the longer ones more slowly, Larson said. The fragments are stained with fluorescent tags, which allow scientists to distinguish one flu strain from the next, or tell if a new strain has emerged.

Different types of DNA strands can be tested and identified using the same device by simply using different reagents. To demonstrate the Genotyper's versatility, researchers did tests on DNA from a human, a mouse, and from a strain of influenza. The entire device would be about as big as a television remote control, Larson said.

The findings are outlined in a paper, Microfluidic Integrated Device for Genetic Analysis, written by an interdisciplinary team whose primary authors include Larson, Burns, Burke, and Fuller.

Source: University of Michigan College of Engineering