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，部分通过直接细胞间病毒传播，建立了终身持续感染。在实体器官或干细胞移植接受者中，HCMV的传播会导致可导致死亡的终末性器官疾病。在怀孕期间，人巨细胞病毒传播会引起先天性感染，是导致先天性残疾的主要原因。没有一种巨细胞病毒疗法能提供治愈，也没有疫苗。因此，基于巨细胞病毒生物学的新发现，需要新的治疗方法来限制感染。人巨细胞病毒细胞间传播所需的病毒蛋白是已知的，但人巨细胞病毒细胞间传播所涉及的宿主过程受到的关注较少。HCMV临床毒株通过细胞间传播最有效，但其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导致对如何减少HCMV感染的新理解。我们的研究发现了代谢产物信号在促进HCMV传播中的一个新的作用。该项目的总体目标是从机制上了解病毒与宿主之间的相互作用，调节对巨细胞病毒细胞间传播至关重要的代谢物信号。我们发现色氨酸代谢中的一种代谢物-犬尿氨酸(KYN)-促进了HCMV的传播。除了新陈代谢作用外，Kyn还是一个信号信使。KYN通过芳香烃受体(AhR)传递信号。我们发现AhR的激活支持HCMV的复制。此外，我们还发现，缺氧诱导因子1α(HIF1α)通过其代谢调节功能限制KYN的产生，抑制人巨细胞病毒感染。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巨细胞病毒在细胞之间的传播，这种传播被依赖于HIF1α的细胞反应减弱。这项拟议的研究将确定通过基因代谢物信号转导增强人巨细胞病毒感染的分子机制(目标1)，并确定病毒与宿主之间的相互作用调节人巨细胞病毒细胞间传播的HIF1α减弱(目标2)。该实验方法将结合病毒分析、CRISPR/Cas9工程和非靶向代谢组学来了解HCMV生物学。我们的发现将从机制上理解代谢物信号和AhR活性在促进巨细胞病毒细胞间传播中的作用，以及针对代谢物信号以减少感染的HIF1HIF1依赖α的宿主反应。我们的研究将推进我们在未被充分研究的巨细胞病毒研究领域的知识，这将在开发治疗巨细胞病毒感染和限制巨细胞病毒相关疾病的新策略方面向前迈出重要的一步。

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.