Congratulations to recently graduated PhD student Melanie Ridgway for winning the 2023 John Frederick Adrian Sprent Prize for her PhD thesis “Sex specific biology of Plasmodium falciparum”.
Melanie studied Life Sciences as an Excellence-Major Scholar at Université Pierre et Marie Curie in Paris. For her Honours research project supervised by Dr. Adele Lehane and Prof. Kiaran Kirk at the Australian National University (ANU), she investigated ion transport and drug resistance in the malaria parasite Plasmodium falciparum. She joined Prof. Alexander Maier’s lab for her PhD at ANU, where she developed a method to separate male and female P. falciparum gametocytes and subsequently investigated their sex-specific biology.
During her candidature, Melanie investigated three major areas:
Plasmodium lipid dynamics in the mammalian and mosquito host.
Melanie determined the lipid composition of different asexual stages in the human malaria species P. falciparum and the murine malaria species P. berghei. She also looked at the scavenging of host lipids and correlated the lipid profile of the parasite with the available host cell lipids in the different host species (which she also determined). Finally, she compared the lipid composition of the mosquito host to the lipid composition of the transmissible sporozoite stage. Melanie identified essential lipid species that are taken up from the various host environments, which are crucial for the growth and propagation of the parasite. This led to a publication in the ASP’s International Journal for Parasitology (2020)
Development of a novel method to separate male and female gametocytes.
Melanie developed a system that allows the separation of a large numbers of male and female gametocytes. Although morphologically distinct, it was previously not possible to purify pure populations of either sex, which hindered the analysis of sex-specific characteristics. Thanks to Melanie, this is now possible, and several labs are using the system to shed light on the differences between male and female gametocytes. The system is also used for drug screens. Previously, only the effect of drugs on total gametocyte numbers could be assessed. This is less informative given that P. falciparum produces 4 times more female than male gametocytes. Even drugs that selectively kill male gametocytes at very low concentrations (and therefore would be terrific transmission blocking agents) would have been dismissed as poorly acting drugs, since the remaining 80% female gametocytes would have survived. She applied this technique not only to elucidate the sex-specific lipidome of P. falciparum, but also to determine sex specific methylation patterns. This work led to the publication in m-Sphere (2020) and Bio-protocols (2021).
Sex-specific lipid metabolism in P. falciparum gametocytes
When malaria parasites are transmitted from the human to the mosquito host, they encounter completely different environments which is also reflected in the available lipids. By conducting a comprehensive stocktake of the available lipids, Melanie discovered that host sphingomyelin and neutral lipids are essential for the transmission of the parasites and hence interference with their uptake and storage might provide novel intervention strategies to stop transmission of the parasite. These results were published in 2016 Malaria Journal and in 2022 in the Journal of Cell Science.
In addition, during her PhD candidature, Melanie has contributed to a publication on the sensitivity of P. falciparum to the drug ketotifen, which was published in the International Journal for Parasitology Drugs and Drug Resistance (2016).
Melanie is an accomplished science communicator and champion or parasitological research. During her PhD she won multiple Three Minute Thesis prizes and a student presentation prize from the Australian Society for Parasitology and Melanie organised the outreach activities of the ANU parasitology groups for National Science Week in 2016 – 2019 and was a University finalist of the Three Minute thesis competition in 2017 (https://www.youtube.com/watch?v=D4Qbf0TN6Sk ).
Melanie graduated in December 2019 with a thesis entitled: “Sex-specific biology of the malaria parasite Plasmodium falciparum”.
Melanie is an exceptional scientist and has not only made substantial contributions to our understanding of the fundamental biology of malaria parasites, but also identified new leads for intervention strategies. She has also developed much-needed tools that has and will continue to have a significant impact in the years to come.
Melanie Ridgway is a very worthy recipient of the 2023 John Frederick Adrian Sprent Prize.
