Effect of external cues on clock-driven protection from Influenza A infection

Influenza and other respiratory viral pathogens are leading causes of mortality and morbidity. We previously demonstrated that circadian rhythms confer temporal protection from influenza infection. Here, we investigated whether this protection requires rhythmic function after the initial infection by manipulating environmental cycles. We demonstrate that disrupting environmental lighting cues within a critical window of vulnerability abrogates time-of-day specific protection. This poor outcome is mediated by a dysregulated immune response, evidenced by the accumulation of inflammatory monocytes and CD8 ⁺ cells in the lungs and a transcriptomic profile indicative of an exaggerated immune response. Disruption of the light cycle does not affect outcomes in a clock mutant, indicating that it acts by compromising endogenous timekeeping. Importantly, rhythmic meal timing mitigates the adverse effects of disrupted light cycles, suggesting that external cycling cues, which act through different body clocks, can substitute for each other. Our findings highlight the crucial interplay between environmental factors and endogenous clocks in shaping influenza outcomes, offering significant translational potential for improving the care of critically ill patients with respiratory viral infections.