Xingbin Ai, MassGeneral Hospital for Children, Boston, MA, United States; Caiqi Zhao, MGH, Boston, MA, United States; Yan Bai, MGH, Boston, MA, United States
Associate Professor of Pediatrics MassGeneral Hospital for Children Boston, Massachusetts, United States
Background: Respiratory syncytial virus (RSV) is a major cause of acute respiratory infection and bronchiolitis in children younger than 2 years of age. In contrast, RSV-infected healthy adults often show mild symptoms. Our recent study has identified an impaired STAT3 response to RSV in infant ciliated cells causing apoptosis to facilitate RSV spread in the human bronchial epithelium. In contrast, adult ciliated cells robustly activate STAT3 above an already higher baseline following RSV infection to prevent apoptosis and reduce virus spread. Mechanisms of age in STAT3 activation in response to RSV infection in ciliated cells is unknown. Objective: Our goal is to elucidate how age regulates RSV resistance so that novel therapeutics to treat active RSV infection in young children can be developed. Design/Methods: Leveraging single cell, bulk, and ATAC RNA-sequencing (RNA-seq) datasets of infant and adult bronchial epithelial cells in vivo and in air-liquid interface cultures of basal stem cells (BSCs), we performed bioinformatic analyses to identify age-related changes in the transcriptomic and epigenetic profiles. To link these changes to memory of prior infection and inflammation, we performed similar analyses using specific pathogen-free mouse models of acute respiratory viral infection and human neonatal BSC models of cytokine cocktail treatment to simulate the inflammatory milieu in vivo following infection. We also assessed the role of RSV nonstructural protein 1 (NS1) and 2 (NS2) in the interaction with a host factor, RIG-I, to regulate STAT3 activation and apoptosis in bronchial epithelial cells. Results: An adult age of human bronchial epithelial cells is manifested by enriched inflammatory response gene expression and increased chromatin opening that are found in vivo and maintained in vitro. Similar changes in the transcriptomic and epigenetic profiles of bronchial epithelial cells are induced by acute respiratory viral infection in mice and cytokine cocktail treatment in neonatal BSCs. RIG-I is an unregulated memory protein with age in adult ciliated cell, which is dispensable for the interferon response but is required for STAT3 activation by countering RSV NS2 binding. In contrast, a lower level of RIG-I in infant ciliated cells is insufficient to prevent inactivation by RSV NS2. Age-related RIG-I upregulation requires STAT3 and is possibly facilitated by reduced H3K27me3 at the regulatory element.
Conclusion(s): Prior respiratory infection and inflammation endow BSCs and their progeny cells with inflammatory memory thereby mediating RSV resistance through the RIG-I-RSV NS2 axis.
