A new study led by researchers from the University of Heidelberg in Germany details the mechanism by which the malaria-causing parasite Plasmodium falciparum remains dormant in the human bloodstream during the dry season. The team was led by Silvia Portugal from the University of Heidelberg in collaboration with Dr. Mario Recker from the University of Exeter. Their findings are published in the journal Nature Medicine.
Dr. Recker, who focused on the mathematical modeling of the study, explained how the parasite can evade the immune system for so long: "We knew that the parasite can prolong infections by continuously altering its appearance to the immune system. What this study shows is that the parasite also adopts another strategy that effectively allows it to hide in plain view by using the spleen to keep its numbers below the immune radar."
As Dr. Recker alludes, the team’s findings point toward the ability of P. falciparum to alter its gene expression throughout the months of the dry season when there are fewer mosquitoes and transmission rates are low. By following individuals in Mali over consecutive dry and rainy seasons, the team determined how infected blood cells are cleared to low levels by the spleen when a change in gene transcription results in a reduced adherence of infected red blood cells to blood vessels.
While they say that more research will be needed in order to understand how environmental changes affect the transcriptional profiles of P. falciparum, their initial findings conclude that the distinct gene transcription patterns are the reason behind the parasite’s disguise.
Malaria continues to be a significant cause of death throughout Africa. In 2018, approximately 405 000 deaths were reported globally, with Africa being disproportionately affected; 93% of malaria cases and 94% of malaria deaths occur within the continent. Children under the age of 5 years old are some of those at the highest risk.