Quick identification of avian influenza infection in poultry is critical to controlling outbreaks, but current detection methods can require several days to produce results.
A new biosensor developed at the Georgia Tech Research Institute (GTRI) can detect avian influenza in just minutes. In addition to being a rapid test, the biosensor is economical, field-deployable, sensitive to different viral strains and requires no labels or reagents.
“We can do real-time monitoring of avian influenza infections on the farm, in live-bird markets or in poultry processing facilities,” said Jie Xu, a research scientist in GTRI's Electro-Optical Systems Laboratory (EOSL).
Worldwide, there are many strains of avian influenza virus that cause varying degrees of clinical symptoms and illness. In the United States, outbreaks of the disease – primarily spread by migratory aquatic birds – have plagued the poultry industry for decades with millions of dollars in losses. The only way to stop the spread of the disease is to destroy all poultry that may have been exposed to the virus.
A virulent strain of avian influenza (H5N1) has begun to threaten not only birds but humans, with more than 300 infections and 200 deaths reported to the World Health Organization since 2003. Looming is the threat of a pandemic, such as the 1918 Spanish flu that killed about 40 million people, health officials say.
“With so many different virus subtypes, our biosensor's ability to detect multiple strains of avian influenza at the same time is critical,” noted Xu.
To test the biosensor, the researchers assessed its ability to detect two avian influenza strains that previously infected poultry. The results showed that a solution containing very few virus particles could be detected by the sensor.
Xu tested a third strain of the virus as a control. When the sensor coating was modified to collect only the other two strains, the control strain was not detected even at high concentrations. Results of this study were published online in August in the journal Analytical and Bioanalytical Chemistry and will be included in journal's print edition on October 16. The work was funded by the U.S. Department of Agriculture's (USDA) Agricultural Research Service (ARS) and the Georgia Research Alliance.
“The technology that Georgia Tech developed with our help has many advantages over commercially available tests -- improved sensitivity, rapid testing and the ability to identify different strains of the influenza virus simultaneously,” said David Suarez, a collaborator on the project and research leader of exotic and emerging avian viral diseases in ARS' Southeast Poultry Research Laboratory in Athens, Ga. Suarez is providing antibodies and test samples for GTRI's research.
The biosensor is coated with antibodies specifically designed to capture a protein located on the surface of the viral particle. For this study, the researchers evaluated the sensitivity of three unique antibodies to detect avian influenza virus.
The sensor utilizes the interference of light waves, a concept called interferometry, to precisely determine how many virus particles attach to the sensor's surface. More specifically, light from a laser diode is coupled into an optical waveguide through a grating and travels under one sensing channel and one reference channel.
Researchers coat the sensing channel with the specific antibodies and coat the reference channel with non-specific antibodies. Having the reference channel minimizes the impact of non-specific interactions, as well as changes in temperature, pH and mechanical motion. Non-specific binding should occur equally to both the test and reference channels and thus not affect the test results.
An electromagnetic field associated with the light beams extends above the waveguides and is very sensitive to the changes caused by antibody-antigen interactions on the waveguide surface. When a liquid sample passes over the waveguides, any binding that occurs on the top of a waveguide because of viral particle attachment causes water molecules to be displaced. This causes a change in the velocity of the light traveling through the waveguide.