Malaria is a leading cause of mortality causing more than 600,000 deaths in 2020. It is caused by parasites of the Plasmodium genus with most deaths due to P. falciparum infection. The control of malaria is complicated by the lack of a widely effective vaccine, the spread of mosquito resistance to insecticides, and Plasmodium parasite resistance to available drugs. Thus, there is an urgent need for novel treatment strategies to continue to combat the devastating effects of malaria globally.
The infection of red blood cells with Plasmodium parasites causes the typical clinical symptoms of malaria. However, before the parasite transitions into this erythrocytic life stage, Plasmodium sporozoites, injected into the human body after the bite of an infected mosquito, first travel from the skin via the bloodstream to the liver where the initial step of malaria infection occurs. The remarkable sporozoite’s journey from the skin to final invasion of hepatocytes in the liver is associated with cell traversal which describes the migration of parasites through host tissue by entering and rupturing host cells. Stopping this step of infection would prevent onward transmission and the development of the malaria disease. However, there is only little knowledge about the molecular interactions involved in this process, specifically about potentially involved host proteins which the parasite may interact with to successfully migrate through a cell.
Here, we established a protocol that combines a whole-genome CRISPR/Cas9 knock-out screen with a newly designed positive selection cell traversal assay to study host factors involved in P. falciparum cell traversal. The first step of this pipeline, a pooled CRISPR screen, identified more than hundred host factors potentially associated with this mechanism. Interestingly, many of these genes are also involved in infection by other pathogens. In a second step, single-gene knockouts were generated to validate the screening results which is currently underway. The identification of essential host factors involved in the first step of the malaria lifecycle would not just provide more leverage for future prophylactic malaria treatments but might also give insights into migration processes of other pathogens that demonstrate similar migratory behaviors.