Meeting a microbe in the morning or in the evening: is it all the same?
Does the time of day matter when our body is infected by a parasite? According to new research from 平特五不中, it matters a great deal.
Our body works differently at different times of the day following our internal clocks. Researchers from 平特五不中 and the Douglas Mental Health University Institute have now established that parasitic infections are also controlled by these clocks. The severity of a microbe鈥檚 infection will thus vary whether it is encountered during the day or at night, a discovery that scientists believe could pave the way to new treatment and prevention strategies for parasitic infections.
Nicolas Cermakian, a professor at 平特五不中鈥檚 Department of Psychiatry and researcher at the Douglas Institute, made the discovery using Leishmania, a parasite that causes leishmaniasis and that is transmitted at night by the female sandfly. Every year, Leishmania infects about 1聽million people, killing thousands and leaving many others with scars. Although the parasite is mostly located in tropical areas, climate change could spread Leishmania far beyond where it is found today. The parasite has already spread to certain parts of southern Europe.
When mice were injected with the parasite, Professor Cermakian鈥檚 team discovered that their immune response varied greatly depending on what time of day the infection occurred.
鈥淥ur previous work showed that our immune system has its own biological clocks. Our body鈥檚 defence mechanisms are more or less active at different times of the day,鈥� says Nicolas Cermakian, lead author of the published in in collaboration with 平特五不中/RI-MUHC Professor Martin Olivier and Professor Nathalie Labrecque of Universit茅 de Montr茅al and Maisonneuve-Rosemont Hospital research centre.
Silke Kiessling, a former postdoctoral student in Professor Cermakian鈥檚 lab, found that Leishmania鈥檚 infection was more effective in the early night, a time when the immune response to the parasite was the strongest.
But why would the parasite be transmitted by a fly that bites at the exact time when our defences are at their strongest? Simply put, the parasite thrives when it elicits a strong immune response, attracting inflammatory cells it uses to multiply (macrophages and neutrophils) to the infection site.
鈥淲e already knew that viral and bacterial infections were controlled by our immune system鈥檚 circadian rhythms, but this is the first time this is shown for a parasitic infection, and for a vector-transmitted infection,鈥� Professor Cermakian adds.
Tools for better treatment and prevention
Professor Cermakian鈥檚 team will now try to better define how Leishmania鈥檚 circadian rhythm is controlled at the molecular and cellular levels. As a first step, they already found that the clock within cells of the immune system is directing the daily rhythm of response to Leishmania.
A better understanding of how the circadian clock controls Leishmania infection could contribute to the development of new therapeutics and better prevention approaches. Working out how time regulation of host-parasite interactions are controlled, Cermakian says, might also be useful in the fight against other diseases transmitted by insects.
Image caption :
In this electron microscope image, a Leishmania parasite (above) is entering a type of immune cell known as a macrophage (below). Image provided by Professor Martin Olivier.
This research was funded by the Canadian Institutes of Health Research
, Silke Kiessling et al.,
