Jan 2019     Issue 9
Research
Diagnosis of Malaria in Saliva via a new Biomarker: The Activity of Plasmodium Topoisomerase
Prof. Megan Yi-Ping Ho, Department of Biomedical Engineering

Malaria is among the major threats to global health. The main burden of the disease is in rural areas of developing countries where accurate diagnosis, based on non-invasive samples, is in high demand. Malaria-causing Plasmodium parasites are typically hosted by the red blood cells, so blood has been the major sample type for the diagnosis of malaria via rapid diagnostic tests, such as gold standard thick- or thin-smear microscopy, or nucleic acids-based amplification techniques.  Although literature has reported the presence of trace amounts of Plasmodium derived nucleotide sequences and proteins in saliva from infected individuals, there is a lack of validation that the saliva may be a sample candidate for detecting the onset of malaria. 

Continuing our long-term collaboration with our Danish partner, Prof. Birgitta R. Knudsen, from the Department of Molecular Biology and Genetics, Aarhus University, we have developed a platform technology combining (a) a novel enzyme-extraction technique based on droplet microfluidics to handle minute samples and to extract active enzymes more effectively, and (b) a DNA nanosensor to sensitively probe the activity from a class of essential enzymes in malaria-causing parasites.  The proposed platform is extremely sensitive and is therefore able to pick up tiny amounts of targeted enzymatic activity in saliva, allowing the identification of the onset of malaria at an early stage of infection. Furthermore, the assay is tailored for testing in rural areas, given the operation does not require delicate equipment, and the results can be determined directly by the naked eye and documented by quantifying the colour intensity using a standard paper scanner.

Our clinical partner at the Centre de Recherches Médicale de Lambaréné in Gabon, a leading research and training centre in the Central African region, has collected 35 matching blood and saliva samples from malaria patients.  The developed assay has successfully demonstrated positive detection of active Plasmodium enzymes in saliva in all 35 of the malaria-positive individuals, where the positive detection was confirmed by traditional diagnostic approaches using blood samples.  The possibility of using a non-invasive sample type such as saliva as test material for the enzyme-based assay holds great promise for the future.  The assay may be used for diagnosis in areas with a cultural reluctance to give blood, as well as for eradication programmes, which may involve testing a large number of asymptomatic individuals.

The working principle of this assay is patented and serves as the basis of a start-up company, Zymonostics, co-founded by our team and our Danish partners. 



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