Circadian control of enteric virus infection

Project Summary/Abstract Circadian rhythms are 24h oscillations in a variety of processes that are entrained by environmental cues including light. Molecularly, this “clock” is driven by key transcription factors and feedback loops that generate rhythmic expression of thousands of mammalian genes in a variety of tissues. Past work has revealed the impact of circadian rhythms on metabolism and immunity. However, the impact of circadian rhythms on infection, particularly enteric virus infection, is understudied. Preliminary experiments using the enteric virus coxsackievirus B3 (CVB3) revealed a profound circadian effect on infection: Mice orally inoculated with CVB3 in the morning had viral titers 10-100 fold lower than mice inoculated in the evening. Inhibition of viral replication in the morning correlated with increased expression of antiviral proteins at this time. Circadian effects on CVB3 infection were lost in mice lacking certain proteins involved in interferon-mediated antiviral responses, suggesting a possible link between circadian transcriptional control and innate immune responses in the intestine. Indeed, expression of an antiviral protein was lost in mice that lack activity of an important clock transcription factor. Thus, CVB3 infection is under circadian control and rhythmic host interferon responses contribute to these effects. However, several questions remain. In this work we will 1) examine mechanisms by which clock transcription factors control expression of innate immune genes, 2) examine the effect of clock transcription factors on infection with CVB3 and other enteric viruses, and 3) identify and evaluate cell types in the intestine that contribute to circadian control of enteric virus infection. Answering these questions will illuminate key, but unanticipated, aspects of intestinal biology that influence enteric virus infection.