Innate immune responses and IL-27: novel regulatory mechanisms of TLR7 expression and signaling

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Induction of innate immune responses is accomplished by specific cytokines which activate, recruit, and control differentiation of immune cells necessary for control of immune responses. Of the sentinel proteins found on innate immune cells, the Toll-like receptor (TLR) family of pattern recognition receptors binds to molecular patterns present on a variety of pathogens. One family member, TLR7, is responsible for recognizing single-stranded RNA, genetic information for many viruses. The molecular mechanisms induced by cytokines to control TLR7 expression and function during an innate immune response have not been fully elucidated. A recently defined cytokine, IL-27, is involved in the regulation of immune responses however; the role of IL-27 in the innate immune response is poorly understood. Supported by my previous Discovery grant, we showed that IL-27 augmented TLR4 expression, the TLR family member responsible for recognizing bacterial lipopolysaccharide (LPS) and that IL-27 induced cytokine expression as well as enhanced LPS-induced cytokine production (Guzzo et al, JBC 2010; Guzzo et al JI 2012; Petes et al JLB 2016 under revision). Furthermore, we showed that IL-27 induced expression of the anti-viral protein, tetherin (Guzzo et al Sci Rep 2012). Taken together, this work establishes a role for IL-27 in priming immune responses to infection. Herein, we will further explore the role of IL-27 in innate immunity by examining molecular mechanisms regulated by IL-27 to induce TLR7-mediated anti-viral responses. We hypothesize that IL-27 upregulates TLR7 expression and stimulates TLR7 function in myeloid cells. Indeed, our preliminary data demonstrates that IL-27 upregulates TLR7 expression specifically in macrophages. In order to fully address this hypothesis, in vitro experiments will be conducted in primary human cells and cell lines, using state-of-the-art techniques. The following aims will be investigated: 1) Identify IL-27 dependent regulatory mediators that upregulate TLR7 expression 2) Evaluate the mechanism by which IL-27 impacts TLR7-mediated signaling and responses 3) Determine if IL-27 regulates virus infection/replication and innate immune responses Significance: The overarching goal of my research program is to pinpoint novel mechanisms used by cytokines to control innate immunity. We will develop a human in vitro system that can be expanded to other innate sentinel molecules to understand how the innate immune system relies on activation by pattern receptor recognition molecules and initiate immune responses. This work will benefit Canada by providing valuable training to HQP in immunological research, giving our future scientific leaders the technical expertise and experience required for promoting research and development in the natural sciences. HQP training: A total of 2 PhD, 2 MSc, and 5 NSERC-USRA students will be hired to complete this work.