Structural basis for human respiratory syncytial virus NS1-mediated modulation of host responses

Human respiratory syncytial virus (hRSV) is a major cause of morbidity and mortality in the pediatric, elderly, and immune compromised populations. A gap in our understanding of hRSVdisease pathology is the interplay between virally encoded immune antagonists and host components that limit hRSV replication. hRSV encodes for non-structural (NS) proteins that are important immune antagonists; however, the role of these proteins in viral pathogenesis is incompletely understood. Here we report the crystal structure of hRSV NS1 protein, which suggests that NS1 is a structural paralog of hRSV matrix (M) protein. Comparative analysis of the shared structural fold with M revealed regions unique to NS1. Studies on NS1 WT or mutant alone or in recombinant RSVs demonstrate that structural regions unique to NS1 contribute to modulation of host responses, including inhibition of type I IFN responses, suppression of dendritic cell maturation, and promotion of inflammatory responses. Transcriptional profiles of A549 cells infected with recombinant RSVs show significant differences in multiple host pathways, suggesting that NS1 may have a greater role in regulating host responses than previously appreciated. These results provide a framework to target NS1 for therapeutic development to limit hRSV associated morbidity and mortality. Overall design: 12 samples where analysed. A549 cell line was infected with mock, hRSV or mutated hRSV virus. Samples are: control mock-infected (2 replicas), hRSV wild-type NS1 infected (3 replicas), hRSV NS1 1-118 infected (3 replicas), hRSV NS1 L132A/L133A infected (2 replicas) and hRSV NS1 Y125A infected (2 replicas). Libraries was prepared for 96 h.p.i.

人类呼吸道合胞病毒（Human respiratory syncytial virus, hRSV）是引发儿科、老年及免疫功能低下人群发病与死亡的主要病原体。目前学界对该病毒致病机制的认知仍存在缺口：病毒编码的免疫拮抗剂与限制病毒复制的宿主因子之间的相互作用尚未被充分阐明。人类呼吸道合胞病毒编码的非结构蛋白（non-structural, NS）是重要的免疫拮抗剂，但此类蛋白在病毒致病过程中的具体作用仍未被完全明确。本研究解析了人类呼吸道合胞病毒NS1蛋白的晶体结构，结果表明NS1是病毒基质蛋白（matrix, M）的结构旁系同源物。通过与M蛋白共享的结构折叠域进行比较分析，我们鉴定出了NS1特有的结构区域。针对NS1野生型（wild-type, WT）或突变体的单独实验，以及基于重组人类呼吸道合胞病毒的相关实验均证实，NS1特有的结构区域可调控宿主免疫应答，具体包括抑制I型干扰素（interferon, IFN）应答、阻滞树突状细胞成熟以及促发炎症反应。对感染重组人类呼吸道合胞病毒的A549细胞进行转录组分析后发现，多条宿主信号通路存在显著差异，这提示NS1在调控宿主免疫应答中的作用比此前认知的更为关键。本研究结果为靶向NS1开发治疗策略以降低人类呼吸道合胞病毒相关的发病与死亡提供了理论依据。实验整体设计：共分析12份样本。将A549细胞系分别以空白对照（mock）、野生型人类呼吸道合胞病毒或突变型人类呼吸道合胞病毒进行感染。样本分组如下：空白对照感染组（2个生物学重复）、野生型NS1人类呼吸道合胞病毒感染组（3个生物学重复）、hRSV NS1 1-118突变体感染组（3个生物学重复）、hRSV NS1 L132A/L133A双突变体感染组（2个生物学重复）以及hRSV NS1 Y125A突变体感染组（2个生物学重复）。于感染后96小时（hours post infection, h.p.i.）制备测序文库。