The circadian clock modulates Anopheles gambiae infection with Plasmodium falciparum

Abstract

Key behaviours, physiologies and gene expressions in Anopheles mosquitoes impact the transmission of Plasmodium. Such mosquito factors are rhythmic to closely follow diel rhythms. Here, we set to explore the impact of the mosquito circadian rhythm on the tripartite interaction between the vector, the parasite and the midgut microbiota, and investigate how this may affect the parasite infection outcomes. We assess Plasmodium falciparum infection prevalence and intensity, as a proxy for gametocyte infectivity, in Anopheles gambiae mosquitoes that received a gametocyte-containing bloodfeed and measure the abundance of the midgut microbiota at different times of the mosquito rearing light-dark cycle. Gametocyte infectivity is also compared in mosquitoes reared and maintained under a reversed light-dark regime. The effect of the circadian clock on the infection outcome is also investigated through silencing of the CLOCK gene that is central in the regulation of animal circadian rhythms. The results reveal that the A. gambiae circadian cycle plays a key role in the intensity of infection of P. falciparum gametocytes. We show that parasite gametocytes are more infectious during the night-time, where standard membrane feeding assays (SMFAs) at different time points in the mosquito natural circadian rhythm demonstrate that gametocytes are more infectious when ingested at midnight than midday. When mosquitoes were cultured under a reversed light/dark regime, disrupting their natural physiological homeostasis, and infected with P. falciparum at evening hours, the infection intensity and prevalence were significantly decreased. Similar results were obtained in mosquitoes reared under the standard light/dark regime upon silencing of CLOCK, a key regulator of the circadian rhythm, highlighting the importance of the circadian rhythm for the mosquito vectorial capacity. At that time, the mosquito midgut microbiota load is significantly reduced, while the expression of lysozyme C-1 (LYSC-1) is elevated, which is involved in both the immune response and microbiota digestion. We conclude that the tripartite interactions between the mosquito vector, the malaria parasite and the mosquito gut microbiota are finely tuned to support and maintain malaria transmission. Our data add to the knowledge framework required for designing appropriate and biologically relevant SMFA protocols.

Artificial nighttime lighting impacts Plasmodium falciparum mature stage V gametocytes infectivity in Anopheles stephensi

“…Light acts as a prominent environmental cue to regulate most of the mosquito’s biological processes from gene expression to physiology and behaviour, like for example biting, molecular clock genes, sugar feeding, metabolism or immunity among others [ 9 , 19 , 25 , 26 ]. In the other hand, it has been also described that microbiota present in the mosquitoes as well as the development of Plasmodium are subjected to light:dark rhythms [ 27 ]. Bacteria community in the mosquito shifts during life stage transitions and community structure is associated with dietary regimes as well as mosquito species [ 28 , 29 ].…”

Multiple hosts, multiple impacts: the role of vertebrate host diversity in shaping mosquito life history and pathogen transmission

“…In addition, even though we observed a lower feeding rate of exposed females compared to unexposed females in the following blood meals, all successive blood meals were carried out on membrane feeders and results could be different on wholebody hosts. Fourth, our laboratory setting did not take into account the natural blood foraging rhythm of the vector nor the circadian rhythm of the parasite which have both been shown to influence mosquito and parasite fitness (Schneider et al 2018, O'Donnell et al 2019, Habtewold et al 2022. Fifth, we measured mosquito competence at two time points classically illustrating the non-transmissible and the transmissible parasite stages.…”

Multiple hosts, multiple impacts: the role of vertebrate host diversity in shaping mosquito life history and pathogen transmission

“…defensive behavior (Edman and Scott 1987, Lyimo et al 2012), host availability (Lyimo et al 2013, Fikrig et al 2021), parasite manipulation of host behaviour (Vantaux et al 2021) or female individual experience (Vantaux et al 2014). Fourth, our laboratory setting did not take into account the natural blood foraging rhythm of the vector nor the circadian rhythm of the parasite which have both been shown to influence mosquito and parasite fitness (Schneider et al 2018, O’Donnell et al 2019, Habtewold et al 2022). Fifth, we measured mosquito competence at two time points classically illustrating the non-transmissible and the transmissible parasite stages.…”