November 15, 2006

 

US researchers develop chip to identify bird flu in hours

 

 

Scientists from the University of Colorado at Boulder and the Centers for Disease Control and Prevention in Atlanta have developed a "gene chip" based on a single influenza virus gene that is expected to allow scientists to quickly identify bird flu viruses.

 

Tests show the MChip can determine the type and subtype of human flu influenza in less than seven hours, while current methods require several days, said Kuchta.

 

The team used the gene chip, known as the MChip, to detect H5N1 samples collected over a three-year period from people and animals from all over the world, said Professor Kathy Rowlen of the university's chemistry and biochemistry department.

 

Tests on isolates and patient samples showed that the MChip provided accurate information on flu types and subtyples about 97 percent of the time.

 

The MChip fits on a slide and contains an array of microscopic spots. Genetic bits of information complementary to H5N1 and other flu types and subtypes are placed robotically on the microarray, which is immersed in influenza gene fragments obtained from fluids of infected individuals.

 

RNA fragments from the infected fluid bind to specific DNA segments on the microarray, indicating a match when the virus signature is present.

 

Since the RNA that binds to the microarray also contains a fluorescent dye, such "hits" light up when the chip is inserted into a laser scanner.

 

An automated, artificial "neural network" trained to recognize the distinctive genetic pattern of H5N1 eliminates human error.

 

The MChip is based on a single gene segment with less mutation and thus may not need to be updated as frequently as other diagnostic tests, Rowlen said.

 

Another advantage is that the MChip creates a way to simultaneously screen large numbers of flu samples to learn both the type and subtype of virus present, said Rowlen.

 

The team tested the ability of the MChip to correctly identify 24 different H5N1 viral isolates and distinguish those from seven non-H5N1 viral isolates, according to the study. The MChip accurately identified and gave complete subtype information for 21 out of the 24 strains of H5N1. The test gave no false positives, meaning the chip never indicated the presence of H5N1 when none was present.