Increased sleep promotes survival during a bacterial infection in Drosophila

The relationship between sleep and immune function is not well understood at a functional or molecular level. We therefore used a genetic approach in Drosophila to manipulate sleep and evaluated effects on the ability of flies to fight bacterial infection. Laboratory. Drosophila melanogaster. We used a genetic approach to transiently alter neuronal excitability in the mushroom body, a region in the central brain that is known to regulate sleep. Flies with increased sleep for up to two days prior to a bacterial infection showed increased resistance to the infection and improved survival. These flies also had increased expression levels of a subset of anti-microbial peptide mRNA prior to infection, as well as increased NFκB activity during infection as indicated by in vivo luciferase reporter activity. In contrast, flies that experienced reduced sleep for up to two days prior to infection had no effect on survival or on NFκB activity during infection. However, flies with reduced sleep showed an altered defense mechanism, such that resistance to infection was increased, but at the expense of reduced tolerance. This effect was dependent on environmental condition. Increasing sleep enhanced activity of an NFκB transcription factor, increased resistance to infection, and strongly promoted survival. Together, these findings support the hypothesis that sleep is beneficial to the host by maintaining a robust immune system.