Calming the Cytokine Storm: Elucidating Mechanisms Contributing to Toxic Inflammatory Responses to Viruses

在细胞感知病毒病原体相关分子模式后，病毒诱导I型干扰素（IFN）。这些IFN由IFN α/IFN β受体（IFNAR）检测，下游信号传导诱导IFN刺激的基因，其通过包括促炎细胞因子分泌的机制促进病毒的清除。虽然这表明缺乏I型IFN信号可能会减少促炎细胞因子，但我们的结果证明了相反的情况。我们开发了一种病毒血症的小鼠模型，其中造血细胞缺乏IFNAR。在这些小鼠静脉注射高度减毒的非致病性水泡性口炎病毒后，它们在18小时内死于大量细胞因子风暴。在评估的26种细胞因子中，25种达到异常高的水平。出乎意料的是，并且本申请的焦点是，与雄性相比，雌性中的细胞因子失调更严重。这是值得注意的，因为在许多炎症介导的疾病的发病率中存在对女性的性别偏见。初步结果表明，中性粒细胞在该模型中可能具有主要的调节作用，因为当这些细胞耗尽时，促炎细胞因子变得更加失调。在密度梯度中分离后，中性粒细胞可细分为两种主要表型。假设这些亚群之一可能在细胞因子应答期间具有抑制作用。男性中性粒细胞的抑制性亚群的定量或定性差异可能赋予对病毒失调的细胞因子应答的抗性。我们还提出了一个模型的细胞信号级联作为蓝图，用于测试第二个假设：干扰素刺激的反应元件的性别依赖性启动子有助于差异调节I型IFN-调节细胞因子对病毒的反应。目的：1.评估男性和女性中性粒细胞亚群免疫调节潜力的定量与定性差异。2.确定其他白细胞，除了中性粒细胞，有助于病毒诱导的细胞因子风暴。3.确定潜在的性别偏见失调的细胞因子反应的机制，包括细胞因子信号通路的细胞内变化，在病毒感染与IFNAR阻断，和宿主因素的作用，可能解释性别差异。在病毒免疫学的跨学科领域培训下一代加拿大生物医学科学家是这项研究的组成部分。科学家们为开发新型冠状病毒病（COVID）-19大流行的解决方案而进行的长期斗争突出了对这种专业知识的需求。这项研究应该提供一个机制的理解，如何性别可以影响之间的联系受损IFNAR介导的信号，细胞因子过度生产，白细胞亚群参与。这与一系列性别偏见的细胞因子紊乱有关，从危及生命的细胞因子风暴到过度炎症。

Viruses induce type I interferons (IFNs) after cells sense viral pathogen-associated molecular patterns. These IFNs are detected by the IFN a/ß receptor (IFNAR), with downstream signaling inducing IFN-stimulated genes that facilitate clearance of viruses through mechanisms that include secretion of pro-inflammatory cytokines. Although this would suggest that a lack of type I IFN signaling might reduce pro-inflammatory cytokines, our results demonstrated the opposite. We developed a murine model of viremia in which hematopoietic cells lacked IFNARs. After these mice received intravenous injections of a highly attenuated, non-pathogenic vesicular stomatitis virus, they succumbed to massive cytokine storms in 18 hours. Out of 26 cytokines that were assessed, 25 reached abnormally high levels. Unexpectedly, and a focus of this application, was that cytokine dysregulation was more exaggerated in females compared to males. This is notable because there is a sex bias towards females in the incidence of many inflammation-mediated diseases. Preliminary results suggested neutrophils may have a predominantly regulatory role in this model, since pro-inflammatory cytokines became more dysregulated when these cells were depleted. Neutrophils can be sub-divided into two major phenotypes after separation in a density gradient. Hypothetically, one of these subsets may have a suppressive role during cytokine responses. Quantitative or qualitative differences in a suppressive subset of male neutrophils may confer resistance to dysregulated cytokine responses to viruses. We also propose a model of cell signaling cascades as a blueprint for testing a second hypothesis: interferon-stimulated response elements in sex-dependent promoters contribute to differential regulation of type I IFN-modulated cytokine responses to viruses. Objectives: 1. Assess quantitative versus qualitative differences in the immunoregulatory potential of subsets of neutrophils from males and females. 2. Identify other leukocytes, beyond neutrophils, that contribute to the virus-induced cytokine storm. 3. Identify mechanisms underlying sex-biased dysregulation of cytokine responses, including intracellular changes in cytokine signaling pathways during viral infection with and without IFNAR-blockade, and the role of host factors that may explain sex differences. Training the next generation of Canadian biomedical scientists in the interdisciplinary field of viral immunology is integral to this research. A need for this expertise has been highlighted by the protracted struggle for scientists to develop solutions for the coronavirus disease (COVID)-19 pandemic. This research should provide a mechanistic understanding of how sex can influence the link between impaired IFNAR-mediated signaling, cytokine overproduction, and the leukocyte subsets that are involved. This has relevance for a spectrum of sex-biased cytokine disorders ranging from life-threatening cytokine storms to excessive inflammation.