Meeting the Need for Rapid Microbiology
Abstract & Commentary
Synopsis: Genetically engineered B lymphocytes were used for rapid detection and identification of pathogens, a methodology with potential use in diagnostics, biowarfare defense, and biomonitoring of food and water.
Source: Rider TH, et al. A B cell-based sensor for rapid identification of pathogens. Science. 2003;301:213-215.
There is no doubt that bioterrorism has spurred new science. One of the fields that has been affected acutely is the identification of biowar pathogens. Speed and accuracy of identification are crucial if there are to be effective public notification and specific implementation defense strategies.
Many labs have focused on rapid pathogen identification. In this report published in Science, Rider and colleagues at MIT present an ingenious method termed CANARY—cellular analysis and notification of antigen risks and yields.
First the lab produced a way for B cells to respond to specific pathogens. Plasmids were transfected into a B-cell line, M12g3R, and these plasmids encoded constant regions for light and heavy chains and also a variable region specific for the specific pathogen. These cells were able to respond to pathogens like Yersinia pestis with speed, sensitivity, and specificity. As few as 50 colony-forming units were detected within 3 minutes. When 200 CFU were used, the probability of detection was 99%. Other pathogens detected included orthopoxviruses and Venezuelan equine virus.
When a pathogen like E coli 0157 was spiked onto lettuce, as few as 500 CFU were detected within 5 minutes. Such a reaction would compare favorably with a PCR reaction reported for E coli. These detector B cells are quite hardy, with a shelf life of 2 days at room temperature, 2 weeks when refrigerated, and indefinitely when frozen.
Comment by Joseph F. John, Jr., MD
Leave it to those crafty engineers at MIT to come up with CANARY. Here they take B cells that will glow when the pathogen in question tickles a pathogen’s surface protein. Quite tricky indeed!
Technology like this linked to cellular detection will have to compete with DNA chip technology, the latter of which potentially could identify thousands of pathogens on the same chip. The advantage of the cell-based technology is that it may be less complex than the chips and more specific.
Rider et al have produced B-cell lines whose expressed antibodies are specific at a subspecies and perhaps a strain level. Trials comparing this method with direct PCR methods could be conducted during specific outbreaks; for example, an E coli 0157 outbreak in a meat processing plant.
Another advantage to a cell system like the one described here is that direct tissue analysis may be possible. Besides the immediate need for identification of biowar agents (the work was sponsored by the Department of Defense), any surgical sample could theoretically be directly examined for specific pathogens like Bacteroides and Pseudomonas.
It will be interesting to see if the industry has enough economic incentive to develop this discovery.
Dr. John is Chief, Medical Subspecialty Services, Ralph H. Johnson Veterans Administration Medical Center; Professor of Medicine, Medical University of South Carolina, Charleston, SC.