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VU investigators use magnetism to help isolate malaria biomarker

Jan. 21, 2016, 9:05 AM

by Marilyn Holt

Vanderbilt investigators have developed a way to detect malaria that is faster and more sensitive than current clinical methods — a development that has the potential to make malaria detection significantly less expensive and more stable.

Researchers led by David Wright, Ph.D., Stevenson professor of Chemistry and chair of the department, published the results in the journal Analytical Biochemistry.

Malaria is a mosquito-borne disease endemic to many tropical and subtropical countries, and kills about 600,000 people a year, mostly children in sub-Saharan Africa. The disease is also a huge economic burden, as malaria illness, treatment and other costs reach an estimated $12 billion a year.

One of the biomarkers of malaria is Plasmodium falciparum lactate dehydrogenase (pLDH), and Wright and colleagues developed a test that targets that biomarker.

Though pLDH is a reliable way to detect malaria, there is very little of it in the blood. While scientists have previously used LDH to screen potential antimalarials, their techniques simply weren’t sensitive enough to be diagnostically useful.

“The challenge with pLDH,” Wright said, “is that there’s just not a lot of it in a patient.”
The key was to make the assay more sensitive. To accomplish this, members of the research team both optimized a known pLDH activity assay for sensitivity and added an extra component — magnetism.

“We took antibody-functionalized magnetic particles and used those to pull pLDH out of a lysed whole blood sample, and then we were able to perform the Malstat assay directly on the beads,” said graduate student Christine Markwalter, who worked on the research.

Removing the pLDH from the blood is a little like listening to a soloist instead of a choir — a single voice is easily distinguishable, instead of being overwhelmed by all the other voices.

In the same way, pulling out pLDH provided a huge boost in sensitivity, as that meant the team could detect a much weaker signal without it being overwhelmed by noise from other components of the patient’s blood. These changes doubled the sensitivity of this assay, which now requires only 45 minutes to generate a result — a fifth of the time required for techniques with similar sensitivity.

This assay is also more robust and accessible than many diagnostic assays, which rely on the activity of an expensive, thermally unstable secondary enzyme for the signal.

“Here, we don’t need to worry about that, because the target that’s going to generate the activity is inside the patient,” Wright said. “That additional simplicity is the key to making low-resources diagnostics as robust as they need to be to work every time.”

Further work is needed to develop this assay into a tool that can be used in the clinical setting, work that Wright already said he has in his sights.

“As far as we’re concerned, you don’t solve the problem by coming up with another clever idea in the lab. You solve the problem by showing that your ideas work in the real world,” he said.

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