Developing a Nonradioactive Heteroduplex Tracking Assay to Identify Relapsing P. vivax Parasites (2013)

Undergraduates: Matthew Givens, Jessica Lin

Faculty Advisor: Jonathan Juliano
Department: Health Environmental Sciences & Engineering

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Malaria is a devastating global disease causing about 216 million infections and 655,000 deaths worldwide. Five species of Plasmodium parasites cause infection in humans. Compared to the dominant malaria-causing species (P. falciparum) little work has been done on understanding P. vivax, a species that causes extensive morbidity in South Asia and South America. Infected mosquitos inject multiple strains of P. vivax into the human host. The Heteroduplex Tracking Assay (HTA) is the primary molecular tool for detecting this intrahost diversity of P. vivax. The HTA is used to determine differences in nucleotide sequences. A polymorphism in the primary sequence can be detected by running DNA fragments on an electrophoresis gel that separates bands based on the frictional forces that slow the fragment as it migrates through the gel. However, this assay is limited in its usefulness because it uses a radioactive probe and thus is subject to local laws and regulations. This project developed a new non-radioactive, capillary electrophoresis-based HTA to quantify the number of variants in a particular host. The new method is applied to the merozoite surface protein 1 of P. vivax isolated from patient samples from the Anlong Veng district in Northern Cambodia. We found that the number of variants within a host ranged from 1 to 6 with a mean of 2.5 variants. This successful new method will allow HTAs to be exported to endemic countries to be used for clinical and research purposes.