Advancing drug resistance testing

Quick DNA test for malaria drug resistance also holds promise for other diseases

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NASHVILLE, Tenn.—One of the keys to quickly diagnosing anti-malarial drug resistance, and potentially saving lives in many cases, lies in testing whole blood instead of extracting DNA, eliminating processing steps that can take hours or days. A team of Vanderbilt University biomedical engineers cracked the code to doing just that and are working on applying the method to help patients with HIV, tuberculosis and a host of other diseases.
But it started with malaria.
As noted by Mindy Leelawong, a research assistant professor of biomedical engineering, the problem of drug-resistant malaria is prevalent in Southeast Asia and may spread to Africa and beyond. Healthcare professionals currently can tell whether powerful malaria drugs will work on someone or not through the use of polymerase chain reaction technology for optical detection of a disease’s biomarkers; however, they formerly had to extract the malaria parasite’s DNA first, which is virtually impossible to do in rural, low-resource areas.
Leelawong and her team took on issues preventing a whole-blood test one at a time until they hit upon two major changes that would work: reinventing dyes typically used in PCR so that they’re more compatible with blood, and adding a different type of DNA to the PCR process that allows people in the field to see individual mutations. In a new study, they have analyzed a single mutation in a malaria parasite from a single drop of whole blood.
“In my global health work, it was frustrating to collect pinprick samples on paper in the field, ship them back to a central laboratory, and then wait,” said Leelawong, who has worked in Zambia and Peru. “There would be hundreds of blood spots stored in a freezer somewhere, awaiting people to sit down and do the DNA extraction process, while patients needed answers. I wanted to eliminate the paper and the bottleneck.”
She worked with Frederick Haselton, a professor of biomedical engineering, and Nicholas Adams, a research assistant professor of biomedical engineering, who are inventors of an adaptive PCR machine that simplifies the DNA extraction process by using left-handed DNA to monitor and control the molecular reactions that take place during PCR. With their shoebox-size machine and Leelawong’s method, detecting malaria drug resistance requires only a tiny sample tube, a laptop and a power source.
“In the past, it was easier to use adaptive PCR on clear bodily fluids, because this is an optical technique,” Haselton said. “What Dr. Leelawong has done is extend this basic technology to blood so that we don’t have to do extraction methods for the molecular materials, where we can see biomarkers of infectious disease encoded in certain DNA segments.”
He noted that the technique can be modified to assess resistance to artemisinin, a common and powerful antimalarial drug, and future drugs.
Their work is outlined in the article “Detection of Single Nucleotide Polymorphism Markers of Antimalarial Drug Resistance Directly from Whole Blood,” which appeared in the July issue of The Journal of Molecular Diagnostics.
Adapted from an article by Heidi Hall of the Vanderbilt Research News Office

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