Does the time of day influence leishmania infection?

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New research from McGill University (Montreal, Canada) and Douglas Mental Health University Institute (Verdun, Canada) has suggested that the time of Leishmania infection may influence the extent of infection due to host circadian rhythms. This research could pave the way for new therapeutics or prevention approaches.

It has been well-reported that our body has daily rhythms as a result of Clock genes, in this new study, published recently in Scientific Reports, the researchers investigated the influence of host circadian rhythms on parasitic infection.

The study focused on leishmania – a parasitic infection transmitted nocturnally by the sandfly that affects approximately one million individuals each year. The researchers examined the rhythms of leishmania infection in both macrophages in vitro and mouse models in vivo, discovering that the extent of parasitic infection varied over 24 hour periods in both settings.

Looking at the in vivo experiments, the group noticed that the extent of infection was correlated with rhythmic chemokine expression and time of day-dependent neutrophil and macrophage infiltration to the infection site. Further supporting their findings, when mice with immune cells deficient in clock capabilities were infected all infection-related rhythms were abolished.

The researchers observed infections were more severe in the early night, when the immune response to the parasite was the strongest. Nicolas Cermakian (McGill University) commented: “Our previous work showed that our immune system has its own biological clocks. Our body’s defense mechanisms are more or less active at different times of the day.

“We already knew that viral and bacterial infections were controlled by our immune system’s circadian rhythms, but this is the first time this is shown for a parasitic infection, and for a vector-transmitted infection.”

This is the first study to report the influence of circadian controls on parasitic infection in mammals. Moving forwards, the team are aiming to define how leishmania rhythms are controlled at a molecular and cellular level and hope this could lead to better therapeutics and prevention methods.

Sources: Kiessling S, Dubeau-Laramée G, Ohn H, Labrecque N, Olivier M & Cermakian N. The circadian clock in immune cells controls the magnitude of Leishmania parasite infection. Sci. Rep. 7(10892) doi:10.1038/s41598-017-11297-8 (2017) (Epub); www.mcgill.ca/newsroom/channels/news/meeting-microbe-morning-or-evening-it-all-same-270162

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