New study could help fight malaria

Malaria may be more serious when bitten by a mosquito early in the day, according to a new Montreal study. This work on the chronobiology of the parasitic infection could lead to new means of prevention.

“We have been working for about ten years on the chronobiology of parasitic infections,” explains Nicolas Cermakian, a biologist at the Douglas Institute and McGill University, who is co-author of two studies on the subject, published Monday in the journals ImmunoHorizon And iScience. “With malaria, there is an interaction of the chronobiology of three species, the parasite, the mosquito that transmits it and the human host. It’s a bit like a ménage à trois.”

Malaria, or paludism, is caused by a parasite that is transmitted by mosquitoes. The disease kills more than 600,000 people each year, mostly children and in Africa.

Chronobiology is the study of the interaction between time of day and cellular activity. It’s also called circadian rhythms, or biological clocks. “Different types of cells in the human body have different chronobiologies,” Cermakian says. “We want to know how, in the immune system, these clocks influence how we fight infections and how we respond to vaccines.”

A previous study by Mr. Cermakian in 2019 found that the time of day you get vaccinated influences the effectiveness of the vaccine. Vaccination early in the day works best, several studies seem to show, he says.

Severe neurological form of malaria

Both studies looked at a severe neurological form of malaria, caused by an overreaction of the immune system. One of the studies looked at mouse cell broths, specifically macrophages, the immune system cells responsible for this very strong rapid reaction. The macrophages reacted more strongly at the end of the day, which corresponds to the beginning of the day for humans, because laboratory mice are nocturnal.

The other study involved lab mice and concluded that glucose cycles appear to be important in the immune response to the parasite. “We now need to see whether this cycle is linked to rhythms in the immune system or in other tissues,” says the McGill biologist.

What will be the practical applications of this work? Could people in malaria-affected regions be encouraged to work nights? “It’s hard to predict, because we have different clocks in three species. But we tried to influence the rhythms of the mice to reproduce the experience of night work. To our surprise, there were fewer parasites in these mice.”