Last Updated: 01/03/2024

Development of new in vitro phenotypic assay to detect the artemisinin resistant Plasmodium falciparum


*The details were machine translated from Japanese

The purpose of this research is to improve the ring-stage assay survival (RSA) analysis method, which is a method for detecting parasite resistance to artemisinin, the first-line malaria drug, and to develop a simpler in vitro resistance test method.

Principal Institution

Juntendo University

Principal Investigators / Focal Persons

Mie Ikeda

Rationale and Abstract

At the beginning of this study, RSA suspected a relationship between the pyknotic form produced by artemisinin and resistance. Previous analyzes have revealed that there is no correlation between the presence or absence of artemisinin resistance and the frequency of the pyknotic form, and that the frequency of the pyknotic form changes depending on the culture conditions in the laboratory. Furthermore, the results of an artemisinin epidemiological survey conducted in Uganda using qRSA, an improved method of RSA, show that the frequency of pyknotic forms in samples remains the same as around 2014, and the frequency among artemisinin-resistant and susceptible protozoa in 2022 samples. No big difference was found either. We concluded that there is a weak relationship between the frequency of pyknotic forms and resistance, and that it is difficult to determine the presence or absence of resistance based on the frequency of pyknotic forms.
As a new finding this year, we have discovered the conditions for the appearance of pyknotic forms using cultured protozoa. Using the standard strain 3D7, synchronized culture was repeated twice in a 5% sorbitol solution, and after 96 hours, almost all of the protozoa were successfully converted to the pyknotic form. This is thought to be due to the fact that the protozoa are synchronized and the protozoa density is high. Furthermore, it is highly likely that increasing hematocrit under culture conditions also contributes to pyknotic form formation, although further investigation is required compared to the former. Until now, it has been difficult to stably obtain the pyknotic form, but by using the culture method described above, stable analysis becomes possible.


Apr 2019 — Mar 2024

Total Project Funding


Funding Details
Japan Society for the Promotion of Science (JSPS)

Grant ID: 19K16631
4,290,000 JPY
Project Site



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