The circadian system modulates practically all cellular and physiological functions of our body and synchronizes them to the light-dark environmental cycle. In particular, the circadian modulation of the immune response has been widely studied both in basal and pathogen-challenge conditions. A considerable body of research has focused on analysing the relationship between biological clocks, clock genes and the immune system. It has been observed that the circadian regulation of these processes leads to the differentiation, maturation, activation and functioning of different immune cells with clinical relevance. In particular, NK cells, macrophages and lymphocytes, all implied in viral and bacterial response, are under circadian control. Moreover, disruption of the circadian rhythms by genetic or environmental manipulations triggers profound changes in the immune response, both in humans and in experimental models, which are associated with a poor prognosis in several bacterial or virus infectious diseases including the septic response.
Research into the circadian oscillations of the immune functions could account for the daily fluctuation in the symptoms of a lot of pathologies and the severity of many inflammatory processes. For example, the circadian regulation of the levels of Pattern-Recognition Receptors (PRRs) or macrophages profiles modulate the host response to infection. Furthermore, the effectiveness of chrono-modulated therapies depends on the knowledge of the daily pattern of the specific mechanism involved in each treatment. On the other hand, pro-inflammatory cytokines and chemokines, which are well known mediators of host responses to infection, trauma and immune responses, modulate the activity of the hypothalamic central clock. These mechanisms may also be related with the sickness behaviour observed in many infectious diseases.
In the light of these, it would be relevant to study the effect of the circadian regulation on inflammatory processes both in physiological and in pathological conditions. Since the regulation of the immune function depends on the tissue and the specific cell type implied in each process, it is crucial to deepen the research into the circadian modulation of each specific mechanism.
This Frontiers Research Topic therefore welcomes articles focused on the regulatory mechanisms that help us to understand how we can use the circadian clock as a tool to improve the management of infectious diseases. In particular, we welcome manuscripts on the following topics:
• The circadian clock and the immune response interplay during viral infections, including SARS-CoV2: including circadian responses to cytokines, both interferons and proinflammatory molecules, antibodies, and cells such as NK, NKT, ILC, LT cytotoxic and Th1.
• Interplay between bacterial immune response and circadian system, both for pathogenic bacteria or the microbiome: including modulation of cells activation status and levels of receptors of the innate immunity by the clock, and cellular and humoral adaptive immune response to bacterial challenges at different times of day.
• Effect of the circadian disruption or sleep disorders on the progression of infectious diseases and the exacerbation of inflammatory processes.
• Study of the crosstalk between circadian rhythms, metabolic state, and the inflammatory response during bacterial or virus infections diseases.
