For 400 years, pet shops and bird lovers have been breeding canaries (Serinus canaria) as flashy caged songbirds. Somewhat more recently, coal miners have carried caged canaries down into the shafts as life-saving sentinels.

Canaries breathe faster than humans, so they are the first to detect pockets of deadly carbon monoxide leaking at the coal face. The trapped gas is colorless, odorless and lethal. When the canary stopped singing and died, the suddenly alerted miners dropped their tools and headed headlong for the elevators to the surface.

At the Massachusetts Institute of Technology, the acronym "CANARY" has a more modern and promising meaning. It stands for Cellular Analysis and Notification of Antigen Risks and Yields - as named by molecular technologist Todd Rider at MIT's Lincoln Laboratory in Lexington, Mass. His paper in today's Science, dated July 11, 2003, of which Rider is lead and senior author, bears the title: "A B-cell-based sensor for rapid identification of pathogens."

"We've created a fast, powerful new sensor," Rider told BioWorld Today, "that can identify everything from SARS to bioterrorist agents. Our sensor," he added, "gives cells that comprise the body's first line of defense against viruses and bacteria the ability to glow like jellyfish in the presence of contaminants. We exploited the remarkable ability of some white blood cells to recognize and attack specific pathogens. When the cells connect with the right target microorganisms, their calcium levels rise rapidly and they emit light within seconds of exposure to bacterial and viral targets."

"This report," the Science article explained, "describes a pathogen sensor that achieves an optimal combination and speed and sensitivity through the use of mouse B lymphocytes. These members of the adaptive immune system have evolved to identify pathogens very efficiently. We engineered B-cell lines to express cytosolic acquorin - a calcium-sensitive bioluminescent protein from the Aequoria victoria jellyfish - as well as membrane-bound antibodies specific for pathogens of interest.

"We subsequently transfected the acquorin cells with plasmids containing antibody light- and heavy-chain constant-region genes. These were inserted into the variable regions specific for a particular pathogen," the Science article recounted. "Clones from the second transfection were selected for optimal response to that pathogen. The resulting cells responded to pathogens with excellent speed, sensitivity and specificity."

On Firing Line: Weapons Of Mass Infection

The pathogens of interest that most interested Rider and his co-authors included anthrax, plague, smallpox, equine encephalitis and chlamydia (a sexually transmitted disease). They placed the pathogens being tested in a luminometer container that keeps the cells alive in test tubes. It monitors their light emission in the presence of the respective microorganisms. Completing the portable detection kit is a laptop computer that reads out the cells' responses.

"Especially in the case of bioterrorism," Rider observed, "it's desirable to have something faster and more sensitive." (Their work is funded by DARPA, the Defense Advanced Research Projects Agency, and the U.S. Army Soldier and Biological Chemical Command.)

Rider made the point that CANARY also has potential applications in medical diagnosis. "It can detect pathogenic bacteria," he commented, "viruses, fungi, protozoa and proteins, from samples in a variety of formats. It can test outdoor and indoor air quality for diseases such as Legionnaire's, food safety, and agricultural pathogens such as animal foot-and-mouth disease."

E. coli Reveals Toxic, Nontoxic Strain Differences

"Our testing of Escherichia coli strains," Rider noted, "distinguished pathogenic from nonpathogenic strains of the microbe in a matter of minutes. Specifically, E. coli, which is found in vegetables, fruit and meat products, detected as little as 500 CFU [colony-forming units] per gram in lettuce in less than five minutes.

"These results compare favorably," he continued, "with reports describing the detection of bacteria in food with PCR protocols that take 30 to 60 minutes and achieve a limit of detection of 10 to 10,000 CFU per gram or per milliliter.

"Rapid pathogenic identification methods," Rider emphasized, "are necessary to ensure timely, accurate diagnosis of disease in patients with infections requiring immediate treatment. CANARY can detect as few as 1,000 CFU of Bacillus anthracis spores extracted from seeded nasal swabs. This demonstrates the potential to rapidly screen patients for inhalation anthrax exposure.

"Existing sensors such as immunoassays and PCR," he pointed out, "are based on chemical reactions that can take several hours to work, and require several thousands of particles to detect. In contrast, CANARY could detect as few as 50 colony-forming units of the Yersinia pestis plague bacterium in less than three minutes, which included a concentration step." Similar performances were observed for other cell lines, including one for orthopoxviruses (smallpox).

Rider is sole inventor of the issued U.S. patent covering his biosensor technology. "I am now talking to various industrial and biotech companies," he said, "with a view toward licensing our technology.

"Nature had already designed B cells to detect any bacteria and viruses very rapidly," Rider pointed out, "so rather than come up with an artificial assay," he concluded, "I decided to go with what nature had already created."