Generation of a ‘mutator’ Plasmodium parasite to understand antimalarial drug resistance

New collaborative research led by new WCAIR PI Prof. Marcus Lee has created a new tool to aid the development of treatments for malaria as well as understand how resistance to them develops. This work is published in Nature Communications.

Many promising antimalarial compounds have been uncovered using whole-cell phenotypic-based screening. However, one challenge with this approach is the lack of information on the molecular target, knowledge of which would facilitate compound optimisation and an understanding of drug mode of action.

One key approach for identifying drug targets is the evolution of drug resistance followed by whole-genome analysis, which can pinpoint targets as well as provide information on resistance liabilities and genetic markers for surveillance of resistance in the field. However, the ability to evolve drug resistance in vitro depends, at least in part, on an inoculum size with sufficient genetic variation. For reasons of technical practicality, experiments to evolve resistance in the lab are typically performed with several orders of magnitude fewer parasites than in an infected human. These selection experiments can take weeks or months, and may fail entirely if the relevant mutant is not present in the culture.

To overcome this bottleneck, research led by the Lee lab, used CRISPR editing to generate a Plasmodium falciparum parasite line with an elevated mutation rate by impairing the proof-reading activity of DNA polymerase. The resulting line had a higher mutation rate and was able to generate resistance more quickly and with a lower inoculum than wild type parasites. Resistance was also generated to a previously ‘irresistible’ compound, yielding mutations in a gene of unknown function. Collectively these results support the potential of this mutator line to drive the identification of new antimalarial targets and understand drug resistance mechanisms.

Research was a collaborative international effort that included the University of Dundee, the Wellcome Sanger Institute, Umeå University, Columbia University, University of California San Diego and the Malaria Drug Accelerator Consortium.

The work was funded by the Bill & Melinda Gates Foundation, Wellcome and Mahidol University.

Shows a transgenic malaria parasite inside a red blood cell. image is in 3 parts :Left hand just the parasite, middle, just the red blood cell, right the combined image
A red blood cell infected with a transgenic Plasmodium falciparum parasite (Green: parasite plasma membrane; Red: endoplasmic reticulum; Blue: nucleus). Credit: Professor Marcus Lee