Division of Infectious Diseases, Department of Medicine, Edison Family Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
PLoS Pathog. 2024 May 3;20(5):e1011961. doi: 10.1371/journal.ppat.1011961. eCollection 2024 May.
Noroviruses (NoVs) are a leading cause of viral gastroenteritis. Despite global clinical relevance, our understanding of how host factors, such as antiviral cytokines interferons (IFNs), modulate NoV population dynamics is limited. Murine NoV (MNoV) is a tractable in vivo model for the study of host regulation of NoV. A persistent strain of MNoV, CR6, establishes a reservoir in intestinal tuft cells for chronic viral shedding in stool. However, the influence of host innate immunity and permissive cell numbers on viral population dynamics is an open question. We generated a pool of 20 different barcoded viruses (CR6BC) by inserting 6-nucleotide barcodes at the 3' position of the NS4 gene and used this pool as our viral inoculum for in vivo infections of different mouse lines. We found that over the course of persistent CR6 infection, shed virus was predominantly colon-derived, and viral barcode richness decreased over time irrespective of host immune status, suggesting that persistent infection involves a series of reinfection events. In mice lacking the IFN-λ receptor, intestinal barcode richness was enhanced, correlating with increased viral intestinal replication. IL-4 treatment, which increases tuft cell numbers, also increased barcode richness, indicating the abundance of permissive tuft cells to be a bottleneck during CR6 infection. In mice lacking type I IFN signaling (Ifnar1-/-) or all IFN signaling (Stat1-/-), barcode diversity at extraintestinal sites was dramatically increased, implicating different IFNs as critical bottlenecks at specific tissue sites. Of interest, extraintestinal barcodes were overlapping but distinct from intestinal barcodes, indicating that disseminated virus represents a distinct viral population than that replicating in the intestine. Barcoded viruses are a valuable tool to explore the influence of host factors on viral diversity in the context of establishment and maintenance of infection as well as dissemination and have provided important insights into how NoV infection proceeds in immunocompetent and immunocompromised hosts.
诺如病毒（NoV）是病毒性肠胃炎的主要病因。尽管具有全球临床相关性，但我们对宿主因素（如抗病毒细胞因子干扰素（IFNs））如何调节 NoV 群体动态的了解有限。鼠诺如病毒（MNoV）是研究宿主对 NoV 调控的可行体内模型。一种持续存在的 MNoV 株 CR6 在肠簇状细胞中建立了一个储库，用于慢性粪便病毒脱落。然而，宿主先天免疫和允许性细胞数量对病毒群体动态的影响仍是一个悬而未决的问题。我们通过在 NS4 基因的 3' 位置插入 6 个核苷酸条形码，生成了一个由 20 种不同条形码病毒（CR6BC）组成的池，并将该池用作体内感染不同小鼠品系的病毒接种物。我们发现，在持续感染 CR6 的过程中，脱落的病毒主要来源于结肠，并且无论宿主免疫状态如何，病毒条形码丰富度随时间降低，这表明持续性感染涉及一系列再感染事件。在缺乏 IFN-λ 受体的小鼠中，肠道条形码丰富度增强，与病毒肠道复制增加相关。增加簇状细胞数量的 IL-4 处理也增加了条形码丰富度，表明在 CR6 感染过程中，允许性簇状细胞的丰度是一个瓶颈。在缺乏 I 型 IFN 信号（Ifnar1-/-）或所有 IFN 信号（Stat1-/-）的小鼠中，肠道外部位的条形码多样性显著增加，这表明不同的 IFN 是特定组织部位的关键瓶颈。有趣的是，肠道外的条形码是重叠但又不同于肠道的条形码，这表明传播的病毒代表了与在肠道中复制的病毒不同的病毒群体。条形码病毒是一种有价值的工具，可以在感染的建立和维持以及传播的背景下，探索宿主因素对病毒多样性的影响，并为了解免疫功能正常和免疫功能低下宿主的 NoV 感染过程提供了重要的见解。
