Regulation of Antiviral Responses in Plasmacytoid Dendritic Cells to Chikungunya Virus by the Gut Microbiota

项目摘要 基孔肯雅病毒（Chikungunya virus，CHIKV）是披膜病毒科（Togaviridae）中重新出现的蚊媒甲病毒 导致严重的急性和慢性多关节炎，影响全球数百万人。尽管发病率 与CHIKV感染和大量处于风险中的人群相关，目前还没有批准的疫苗或治疗剂。 可用于预防或治疗CHIKV感染。此外，决定症状严重程度的后天因素 或从急性疾病进展为慢性疾病的认识很少。CHIKV发病机制的小鼠模型具有 强调了I型干扰素（IFN）信号在限制病毒传播和预防致命性疾病方面的关键作用。 CHIKV感染。最近，几项研究表明肠道微生物群在引发全身性IFN应答中起作用 或在远离胃肠道的部位调节病毒发病机制。尽管越来越多的证据表明 肠道微生物群在肠外部位形成抗病毒反应，其在影响宿主免疫力方面的作用， 甲病毒感染尚未被研究。 拟议的项目建立在广泛的初步数据基础上，这些数据表明肠道微生物群 调节全身先天性抗病毒应答以限制CHIKV传播。皮下CHIKV感染 口服抗生素（Abx）治疗或无菌（GF）小鼠导致血液中病毒负荷增加， 远离接种部位的组织。这种增强的病毒传播是由于病毒复制增加 在血液或脾脏的单核细胞中。此外，在CHIKV感染后，微生物菌群耗尽的小鼠表现出 一种通常由循环浆细胞样树突状细胞促进的迟钝的全身I型IFN应答 （pDC）。Abx处理的或GF小鼠的粪便微生物群转移的重新定殖，所述粪便微生物群转移来源于未处理的 Abx初治对照可恢复I型IFN应答并降低血液中的病毒负荷。特别是 引入单一细菌物种（例如，梭菌）或其衍生代谢产物，次级胆汁酸 (BA)去氧胆酸注射到Abx处理的或GF小鼠体内也可以限制病毒在血液中的传播。 我推测，特定的BA-转化细菌物种指示pDC中的I型IFN应答。在 由于缺乏这些微生物因子，pDC不能足够迅速地应答以产生IFN并限制 在一些实施方案中，CHIKV感染导致循环中的单核细胞减少，从而导致病毒传播增强。本提案的目标1 重点是表征肠道微生物群指示pDC功能的免疫途径， CHIKV感染。目标2的重点是识别由以下物质产生的分子成分，特别是BA 特异性梭菌属物种限制单核细胞的CHIKV感染和传播。所有这些 结果将增强我们对肠道微生物群如何塑造先天免疫反应的理解， 甲病毒的感染和发病机制，以及潜在的对单核细胞具有嗜性的其他病毒。

Project Summary Chikungunya virus (CHIKV) is a re-emerging mosquito-transmitted alphavirus in the Togaviridae family that causes severe acute and chronic polyarthritis and affects millions of people globally. Despite the morbidity associated with CHIKV infection and the large population at risk, no approved vaccines or therapeutics are available to prevent or treat CHIKV infection. Moreover, the acquired factors that dictate the severity of symptoms or progression from acute to chronic disease are poorly understood. Mouse models of CHIKV pathogenesis have highlighted a critical role of type I interferon (IFN) signaling in limiting viral dissemination and preventing fatal CHIKV infection. Recently, several studies have implicated the gut microbiota in priming systemic IFN responses or modulating viral pathogenesis at sites distant from the gastrointestinal tract. Despite the growing evidence that the gut microbiota shapes antiviral responses at extra-intestinal sites, its role in influencing host immunity to alphavirus infections has not been explored. The proposed project builds upon extensive preliminary data suggesting that the gut microbiota modulates systemic innate antiviral responses to limit CHIKV dissemination. Subcutaneous CHIKV infection of either oral antibiotic (Abx)-treated or germ-free (GF) mice results in increased viral burden in the blood and in tissues distant from the inoculation site. This enhanced viral dissemination is due to increased viral replication in monocytes of the blood or spleen. Furthermore, upon CHIKV infection, microbiota-depleted mice demonstrate a blunted systemic type I IFN response that normally is promoted by circulating plasmacytoid dendritic cells (pDCs). Re-colonization of either Abx-treated or GF mice with fecal microbiota transfers derived from untreated Abx-naïve controls restores type I IFN responses and decreases viral burden in the blood. Notably, the introduction of a single bacterial species (e.g., Clostridium) or its derived metabolite, the secondary bile acid (BA), deoxycholic acid, into Abx-treated or GF mice also can restrict viral dissemination in the blood. I hypothesize that specific BA-transforming bacterial species instruct type I IFN responses in pDCs. In the absence of these microbial factors, pDCs cannot respond rapidly enough to produce IFNs and restrict monocytes in circulation from CHIKV infection, leading to enhanced viral dissemination. Aim 1 of this proposal focuses on characterizing immune pathways by which the gut microbiota instructs pDC function in response to CHIKV infection. Aim 2 focuses on identifying the molecular components, specifically BAs, generated by specific Clostridium species that restrict CHIKV infection of monocytes and dissemination. Together, these results will enhance our understanding of how the gut microbiota shapes the innate immune response to limit infection and pathogenesis of alphaviruses, and potentially other viruses with a tropism for monocytes.