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

人类巨细胞病毒（HCMV）通过逃避免疫系统，部分是通过直接的细胞间病毒传播来建立终身持续感染。在实体器官或干细胞移植受者中，HCMV的传播导致可导致死亡的末端器官疾病。在怀孕期间，HCMV传播引起先天性感染，是先天性残疾的主要原因。没有任何治疗方法可以治愈HCMV，也没有疫苗。因此，基于HCMV生物学的新发现，需要新的治疗方法来限制感染。HCMV细胞间传播所需的病毒蛋白是已知的，但参与HCMV细胞间传播的宿主过程却很少受到关注。HCMV临床毒株通过细胞间传播最有效，但HCMV细胞间传播的分子机制——包括宿主代谢机制——在很大程度上是未知的。了解宿主调节细胞间扩散的机制可能会导致对如何减少HCMV感染的新认识。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理解病毒与宿主之间的相互作用，这些相互作用调节了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一种代谢物——犬尿氨酸（KYN）能促进HCMV的传播。除了它的代谢作用，KYN是一个信号信使。KYN信号通过芳烃受体（AhR）传递。我们发现AhR的激活支持HCMV复制。此外，我们发现缺氧诱导因子1α (HIF1α)通过其代谢调节功能，限制KYN的产生，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促进了HCMV细胞间的传播，这种传播被hif α依赖的细胞反应所减弱。拟议的研究将确定kyn代谢物信号增强HCMV感染的分子机制（目标1），并确定病毒与宿主相互作用调节HIF1α抑制HCMV细胞间传播（目标2）。该实验方法将整合病毒分析、CRISPR/Cas9工程和非靶向代谢组学来了解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细胞间传播中的机制理解，以及hif α依赖的宿主反应，该宿主反应以代谢物信号传导为目标，以减少感染。我们的研究将提高我们对HCMV研究不足领域的认识，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一步。

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.