Circadian rhythms are known to affect many physiological processes in chickens, and commercial poultry are reared in artificial light-dark periods that are tightly regulated to manipulate the circadian clock, to ensure maximal productivity. In mammals, the circadian clock can influence viral replication, and vaccine immunogenicity, and there is some data to suggest that the time of day of vaccination can influence the immune responses elicited. However, how the circadian rhythm influences infections or vaccinations in poultry remains unknown. In this proposal, we aimed to evaluate whether the circadian oscillations in the expression of the clock gene chBmal1 correlated with avian type I IFN responses and influenced the replication of an avian virus of importance to the UK poultry industry, infectious bursal disease virus (IBDV). We found that in synchronised chicken DF-1 cells, chBmal1 expression oscillated over a 24-hour period, which correlated with type I IFN responses, and inversely correlated with the kinetics of viral replication. These data demonstrate that avian viruses in avian cells are also sensitive to circadian oscillations, implying these pathways evolved before mammals, and could be harnessed to optimize disease control in poultry in the future by optimising the timing of vaccination.
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