UC San Diego

Interferon-alpha (IFN-α) is a major cytokine produced in response to viral infection and clinically important in anti-viral and anti-cancer therapy. Although several key components of the interferon pathway have been characterized, their dynamics in response to repetitive stimulation remain elusive. Here, we studied how IFN-α pretreatment can lead to two contradictory effects: priming and desensitization. We used a microfluidic device to control the dynamics of IFN-α stimulation. Single cell quantification from time-lapse microscopy revealed that 2- and 10-hour pretreatment can lead to increased cellular response while 24-hour pretreatment lead to a decrease cellular response both in STAT1 nuclear translocation and the rate of IRF9 induction. To further investigate the mechanism, we knock-downed ubiquitin specific protease 18 (USP18), a known negative regulator of IFN-α signaling using shRNA, and found that STAT1 nuclear translocation was restored and the rate of IRF9 induction was significantly higher. Intriguingly, we observed heterogeneity in the desensitization among 24-hour-pretreated cells of which expressed low level of USP18. We developed a mathematical model to describe and predict the effect of pulsatile IFN-α stimulation. As expected, a pulsatile treatment of IFN-α led to higher IRF9 induction compared to a sustained treatment. Our results demonstrate that priming and desensitization of IFN-α is duration dependent and controlled by USP18 as a delayed negative feedback. This discovery provides insight information to improve pharmacokinetic of IFN-α delivery for more effective viral-infected disease and cancer therapy.