Metabolite-mediated Signaling in Cell-to-Cell Spread of Human Cytomegalovirus

人巨细胞病毒（HCMV）通过逃避免疫系统，部分通过直接细胞间病毒传播，建立终身持续感染。在实体器官或干细胞移植受者中，HCMV传播导致可导致死亡的终末器官疾病。在怀孕期间，HCMV传播导致先天性感染，是先天性残疾的主要原因。没有HCMV治疗提供治愈，也没有疫苗。因此，需要基于HCMV生物学的新发现的新治疗来限制感染。HCMV细胞间传播所需的病毒蛋白是已知的，但涉及HCMV细胞间传播的宿主过程受到的关注较少。HCMV临床株通过细胞间传播最有效，但HCMV细胞间传播所必需的分子机制（包括宿主代谢机制）在很大程度上尚不清楚。了解宿主调节细胞间传播的机制可能会对如何减少HCMV感染产生新的认识。我们的研究揭示了代谢物信号在促进HCMV传播中的新作用。该项目的总体目标是从机制上了解病毒-宿主相互作用，调节HCMV细胞间传播所必需的代谢物信号。我们发现色氨酸代谢中的代谢产物-犬尿氨酸（KYN）-增强HCMV传播。除了代谢作用外，KYN还是一种信号信使。KYN通过芳香烃受体（AhR）发出信号。我们发现AhR的激活支持HCMV复制。此外，我们发现低氧诱导因子1α（HIF 1 α）通过其代谢调节功能限制KYN的产生并抑制HCMV感染。我们假设，从感染细胞到未感染细胞的代谢物介导的信号传导促进HCMV细胞间传播，而这种传播被HIF 1 α依赖性细胞应答减弱。拟议的研究将确定通过KYN代谢物信号传导增强HCMV感染的分子机制（目的1），并确定调节HCMV细胞间传播的HIF 1 α衰减的病毒-宿主相互作用（目的2）。该实验方法将整合病毒检测，CRISPR/Cas9工程和非靶向代谢组学，以了解HCMV生物学。我们的研究结果将提供代谢物信号传导和AhR活性在促进HCMV细胞间传播和HIF 1 α依赖性宿主反应中的机制性理解，该宿主反应靶向代谢物信号传导以减少感染。我们的研究将推进我们在HCMV研究的未充分研究领域的知识，这将为开发治疗HCMV感染和限制HCMV相关疾病的新策略提供重要的进展。

Human cytomegalovirus (HCMV) establishes a life-long persistent infection by evading the immune system, in part, by direct cell-to-cell viral spread. In solid organ or stem cell transplant recipients, HCMV spread leads to end-organ diseases that can cause death. During pregnancy, HCMV spread causes congenital infection and is a leading cause of congenital disabilities. No HCMV treatment offers a cure, and there is no vaccine. Thus, there is a need for new treatments to limit infection based on novel discoveries in HCMV biology. Viral proteins required for HCMV cell-to-cell spread are known, but the host processes involved in HCMV cell-to-cell spread have received less attention. Clinical strains of HCMV spread most efficiently through cell-to-cell means, but the molecular mechanisms—including host metabolic ones—essential to HCMV cell-to-cell spread are largely unknown. Understanding host mechanisms regulating cell-to-cell spread may lead to new understandings of how to reduce HCMV infection. Our research has uncovered a novel role of metabolite signaling in promoting HCMV spread. This project's overall goal is to mechanistically understand virus-host interactions regulating metabolite signaling essential to HCMV cell-to-cell spread. We found a metabolite in tryptophan metabolism—kynurenine (KYN)—enhances HCMV spread. In addition to its metabolic role, KYN is a signaling messenger. KYN signals through aryl hydrocarbon receptor (AhR). We show that activation of AhR supports HCMV replication. Moreover, we found that hypoxia-inducible factor 1α (HIF1α), through its metabolic regulatory function, limits the production of KYN and suppresses HCMV infection. We hypothesize that metabolite-mediated signaling from infected cells to uninfected cells promotes HCMV cell-to-cell spread, which is attenuated by a HIF1α-dependent cellular response. The proposed research will determine molecular mechanisms involved in the enhancement of HCMV infection by KYN-metabolite signaling (aim 1) and define virus-host interactions regulating HIF1α attenuation of HCMV cell-to-cell spread (aim 2). The experimental approach will integrate virus assays, CRISPR/Cas9 engineering, and untargeted metabolomics to understand HCMV biology. Our findings will provide a mechanistic understanding of metabolite signaling and AhR activity in promoting HCMV cell-to-cell spread and the HIF1α-dependent host-response that targets metabolite signaling to reduce infection. Our studies will advance our knowledge in an understudied area of HCMV research that will provide significant steps-forward in developing novel strategies to treat HCMV infection and limit HCMV-related disease.